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|
//
// Copyright (c) Microsoft. All rights reserved.
// Licensed under the MIT license. See LICENSE file in the project root for full license information.
//
/*XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XX XX
XX OptCSE XX
XX XX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
*/
#include "jitpch.h"
#ifdef _MSC_VER
#pragma hdrstop
#endif
/*****************************************************************************/
#if FEATURE_ANYCSE
/*****************************************************************************/
/* static */
const size_t Compiler::s_optCSEhashSize = EXPSET_SZ*2;
/*****************************************************************************
*
* We've found all the candidates, build the index for easy access.
*/
void Compiler::optCSEstop()
{
if (optCSECandidateCount == 0)
return;
CSEdsc * dsc;
CSEdsc * * ptr;
unsigned cnt;
optCSEtab = new (this, CMK_CSE) CSEdsc*[optCSECandidateCount]();
for (cnt = s_optCSEhashSize, ptr = optCSEhash;
cnt;
cnt--, ptr++)
{
for (dsc = *ptr; dsc; dsc = dsc->csdNextInBucket)
{
if (dsc->csdIndex)
{
noway_assert((unsigned)dsc->csdIndex <= optCSECandidateCount);
if (optCSEtab[dsc->csdIndex-1] == 0)
{
optCSEtab[dsc->csdIndex-1] = dsc;
}
}
}
}
#ifdef DEBUG
for (cnt = 0; cnt < optCSECandidateCount; cnt++)
{
noway_assert(optCSEtab[cnt] != NULL);
}
#endif
}
/*****************************************************************************
*
* Return the descriptor for the CSE with the given index.
*/
inline
Compiler::CSEdsc * Compiler::optCSEfindDsc(unsigned index)
{
noway_assert(index);
noway_assert(index <= optCSECandidateCount);
noway_assert(optCSEtab[index-1]);
return optCSEtab[index-1];
}
/*****************************************************************************
*
* For a previously marked CSE, decrement the use counts and unmark it
*/
void Compiler::optUnmarkCSE(GenTreePtr tree)
{
noway_assert(IS_CSE_INDEX(tree->gtCSEnum));
unsigned CSEnum = GET_CSE_INDEX(tree->gtCSEnum);
CSEdsc * desc;
// make sure it's been initialized
noway_assert(optCSEweight <= BB_MAX_WEIGHT);
/* Is this a CSE use? */
if (IS_CSE_USE(tree->gtCSEnum))
{
desc = optCSEfindDsc(CSEnum);
#ifdef DEBUG
if (verbose)
{
printf("Unmark CSE use #%02d at ", CSEnum);
printTreeID(tree);
printf(": %3d -> %3d\n", desc->csdUseCount, desc->csdUseCount - 1);
}
#endif
/* Reduce the nested CSE's 'use' count */
noway_assert(desc->csdUseCount > 0);
if (desc->csdUseCount > 0)
{
desc->csdUseCount -= 1;
if (desc->csdUseWtCnt < optCSEweight)
desc->csdUseWtCnt = 0;
else
desc->csdUseWtCnt -= optCSEweight;
}
}
else
{
desc = optCSEfindDsc(CSEnum);
#ifdef DEBUG
if (verbose)
{
printf("Unmark CSE def #%02d at ", CSEnum);
printTreeID(tree);
printf(": %3d -> %3d\n", desc->csdDefCount, desc->csdDefCount - 1);
}
#endif
/* Reduce the nested CSE's 'def' count */
noway_assert(desc->csdDefCount > 0);
if (desc->csdDefCount > 0)
{
desc->csdDefCount -= 1;
if (desc->csdDefWtCnt < optCSEweight)
desc->csdDefWtCnt = 0;
else
desc->csdDefWtCnt -= optCSEweight;
}
}
tree->gtCSEnum = NO_CSE;
}
Compiler::fgWalkResult Compiler::optHasNonCSEChild(GenTreePtr * pTree, fgWalkData *data)
{
if (*pTree == data->pCallbackData)
return WALK_CONTINUE;
if ((*pTree)->gtFlags & GTF_DONT_CSE)
{
// Fix 392756 WP7 Crossgen
// Don't propagate the GTF_DONT_CSE flag up from a GT_CNS_INT
//
// During codegen optGetArrayRefScaleAndIndex() makes the assumption that op2 of a GT_MUL node
// is a constant and is not capable of handling CSE'ing the elemSize constant into a lclvar.
// Hence to prevent the constant from becoming a CSE we have marked it as NO_CSE, but this
// should not prevent tree's above the constant from becoming CSE's.
//
if ((*pTree)->gtOper == GT_CNS_INT)
return WALK_SKIP_SUBTREES;
return WALK_ABORT;
}
return WALK_SKIP_SUBTREES;
}
Compiler::fgWalkResult Compiler::optPropagateNonCSE(GenTreePtr *pTree, fgWalkData *data)
{
GenTree *tree = *pTree;
Compiler* comp = data->compiler;
/* Calls get DONT_CSE implicitly */
if (tree->OperGet() == GT_CALL)
{
if (!IsSharedStaticHelper(tree))
tree->gtFlags |= GTF_DONT_CSE;
}
if ((tree->gtFlags & GTF_DONT_CSE) == 0)
{
/* Propagate the DONT_CSE flag from child to parent */
if (comp->fgWalkTreePre(&tree, optHasNonCSEChild, tree) == WALK_ABORT)
tree->gtFlags |= GTF_DONT_CSE;
}
return WALK_CONTINUE;
}
/*****************************************************************************
*
* Helper passed to Compiler::fgWalkAllTreesPre() to unmark nested CSE's.
*/
/* static */
Compiler::fgWalkResult Compiler::optUnmarkCSEs(GenTreePtr *pTree, fgWalkData *data)
{
GenTreePtr tree = *pTree;
Compiler * comp = data->compiler;
GenTreePtr keepList = (GenTreePtr)(data->pCallbackData);
// We may have a non-NULL side effect list that is being kept
//
if (keepList)
{
GenTreePtr keptTree = keepList;
while (keptTree->OperGet() == GT_COMMA)
{
assert(keptTree->OperKind() & GTK_SMPOP);
GenTreePtr op1 = keptTree->gtOp.gtOp1;
GenTreePtr op2 = keptTree->gtGetOp2();
// For the GT_COMMA case the op1 is part of the orginal CSE tree
// that is being kept because it contains some side-effect
//
if (tree == op1)
{
// This tree and all of its sub trees are being kept
// so we skip marking with GTF_DEAD, etc...
return WALK_SKIP_SUBTREES;
}
// For the GT_COMMA case the op2 are the remaining side-effects of the orginal CSE tree
// which can again be another GT_COMMA or the final side-effect part
//
keptTree = op2;
}
if (tree == keptTree)
{
// This tree and all of its sub trees are being kept
// so we skip marking with GTF_DEAD, etc...
return WALK_SKIP_SUBTREES;
}
}
// This node is being removed from the graph of GenTreePtr
// Mark with GTF_DEAD, call optUnmarkCSE and
// decrement the LclVar ref counts.
//
assert((tree->gtFlags & GTF_DEAD) == 0);
tree->gtFlags |= GTF_DEAD;
if (IS_CSE_INDEX(tree->gtCSEnum))
comp->optUnmarkCSE(tree);
/* Look for any local variable references */
if (tree->gtOper == GT_LCL_VAR)
{
unsigned lclNum;
LclVarDsc * varDsc;
/* This variable ref is going away, decrease its ref counts */
lclNum = tree->gtLclVarCommon.gtLclNum;
assert(lclNum < comp->lvaCount);
varDsc = comp->lvaTable + lclNum;
// make sure it's been initialized
assert(comp->optCSEweight <= BB_MAX_WEIGHT);
/* Decrement its lvRefCnt and lvRefCntWtd */
varDsc->decRefCnts(comp->optCSEweight, comp);
}
return WALK_CONTINUE;
}
Compiler::fgWalkResult Compiler::optCSE_MaskHelper(GenTreePtr *pTree, fgWalkData *walkData)
{
GenTree* tree = *pTree;
Compiler* comp = walkData->compiler;
optCSE_MaskData* pUserData = (optCSE_MaskData*)(walkData->pCallbackData);
if (IS_CSE_INDEX(tree->gtCSEnum))
{
unsigned cseIndex = GET_CSE_INDEX(tree->gtCSEnum);
EXPSET_TP cseBit = genCSEnum2bit(cseIndex);
if (IS_CSE_DEF(tree->gtCSEnum))
{
pUserData->CSE_defMask |= cseBit;
}
else
{
pUserData->CSE_useMask |= cseBit;
}
}
return WALK_CONTINUE;
}
// This functions walks all the node for an given tree
// and return the mask of CSE defs and uses for the tree
//
void Compiler::optCSE_GetMaskData(GenTreePtr tree, optCSE_MaskData* pMaskData)
{
pMaskData->CSE_defMask = 0;
pMaskData->CSE_useMask = 0;
fgWalkTreePre(&tree, optCSE_MaskHelper, (void*)pMaskData);
}
// Given a binary tree node return true if it is safe to swap the order of evaluation for op1 and op2
// It only considers the locations of the CSE defs and uses for op1 and op2 to decide this
//
bool Compiler::optCSE_canSwap(GenTreePtr tree)
{
assert((tree->OperKind() & GTK_SMPOP) != 0);
GenTreePtr op1 = tree->gtOp.gtOp1;
GenTreePtr op2 = tree->gtGetOp2();
assert(op1 != nullptr); // We must have a binary treenode with non-null op1 and op2
assert(op2 != nullptr);
bool canSwap = true; // the default result unless proven otherwise.
optCSE_MaskData op1MaskData;
optCSE_MaskData op2MaskData;
optCSE_GetMaskData(op1, &op1MaskData);
optCSE_GetMaskData(op2, &op2MaskData);
// We cannot swap if op1 contains a CSE def that is used by op2
if ((op1MaskData.CSE_defMask & op2MaskData.CSE_useMask) != 0)
{
canSwap = false;
}
else
{
// We also cannot swap if op2 contains a CSE def that is used by op1
if ((op2MaskData.CSE_defMask & op1MaskData.CSE_useMask) != 0)
{
canSwap = false;
}
}
return canSwap;
}
/*****************************************************************************
*
* Compare function passed to qsort() by optLexicalOptimizeCSEs().
*/
/* static */
int __cdecl Compiler::optCSEcostCmpEx(const void *op1, const void *op2)
{
CSEdsc * dsc1 = *(CSEdsc * *)op1;
CSEdsc * dsc2 = *(CSEdsc * *)op2;
GenTreePtr exp1 = dsc1->csdTree;
GenTreePtr exp2 = dsc2->csdTree;
int diff;
diff = (int) (exp2->gtCostEx - exp1->gtCostEx);
if (diff != 0)
return diff;
diff = (int) (dsc2->csdDefWtCnt - dsc1->csdDefWtCnt);
if (diff != 0)
return diff;
diff = (int) (dsc1->csdUseWtCnt - dsc2->csdUseWtCnt);
if (diff != 0)
return diff;
// If order to ensure that we have a stable sort we use the cseIndex
return (int) (dsc1->csdIndex - dsc2->csdIndex);
}
/*****************************************************************************
*
* Compare function passed to qsort() by optLexicalOptimizeCSEs().
*/
/* static */
int __cdecl Compiler::optCSEcostCmpSz(const void *op1, const void *op2)
{
CSEdsc * dsc1 = *(CSEdsc * *)op1;
CSEdsc * dsc2 = *(CSEdsc * *)op2;
GenTreePtr exp1 = dsc1->csdTree;
GenTreePtr exp2 = dsc2->csdTree;
return exp2->gtCostSz - exp1->gtCostSz;
}
/*****************************************************************************/
#if FEATURE_VALNUM_CSE
/*****************************************************************************/
/*****************************************************************************
*
* Initialize the Value Number CSE tracking logic.
*/
void Compiler::optValnumCSE_Init()
{
#ifdef DEBUG
optCSEtab = NULL;
#endif
/* Allocate and clear the hash bucket table */
optCSEhash = new (this, CMK_CSE) CSEdsc*[s_optCSEhashSize]();
optCSECandidateCount = 0;
optDoCSE = false; // Stays false until we find duplicate CSE tree
}
/*****************************************************************************
*
* Assign an index to the given expression (adding it to the lookup table,
* if necessary). Returns the index or 0 if the expression can not be a CSE.
*/
unsigned Compiler::optValnumCSE_Index(GenTreePtr tree, GenTreePtr stmt)
{
unsigned key;
unsigned hash;
unsigned hval;
CSEdsc * hashDsc;
ValueNum vnlib = tree->GetVN(VNK_Liberal);
/* Compute the hash value for the expression */
key = (unsigned) vnlib;
hash = key;
hash *= (unsigned) (s_optCSEhashSize + 1);
hash >>= 7;
hval = hash % s_optCSEhashSize;
/* Look for a matching index in the hash table */
bool newCSE = false;
for (hashDsc = optCSEhash[hval];
hashDsc;
hashDsc = hashDsc->csdNextInBucket)
{
if (hashDsc->csdHashValue == key)
{
treeStmtLstPtr newElem;
/* Have we started the list of matching nodes? */
if (hashDsc->csdTreeList == 0)
{
// Create the new element based upon the matching hashDsc element.
newElem = new (this, CMK_TreeStatementList) treeStmtLst;
newElem->tslTree = hashDsc->csdTree;
newElem->tslStmt = hashDsc->csdStmt;
newElem->tslBlock = hashDsc->csdBlock;
newElem->tslNext = 0;
/* Start the list with the first CSE candidate recorded */
hashDsc->csdTreeList = newElem;
hashDsc->csdTreeLast = newElem;
}
noway_assert(hashDsc->csdTreeList);
/* Append this expression to the end of the list */
newElem = new (this, CMK_TreeStatementList) treeStmtLst;
newElem->tslTree = tree;
newElem->tslStmt = stmt;
newElem->tslBlock = compCurBB;
newElem->tslNext = 0;
hashDsc->csdTreeLast->tslNext = newElem;
hashDsc->csdTreeLast = newElem;
optDoCSE = true; // Found a duplicate CSE tree
/* Have we assigned a CSE index? */
if (hashDsc->csdIndex == 0)
{
newCSE = true;
break;
}
#if 0
// Use this to see if this Value Number base CSE is also a lexical CSE
bool treeMatch = GenTree::Compare(hashDsc->csdTree, tree, true);
#endif
assert(FitsIn<signed char>(hashDsc->csdIndex));
tree->gtCSEnum = ((signed char) hashDsc->csdIndex);
return hashDsc->csdIndex;
}
}
if (!newCSE)
{
/* Not found, create a new entry (unless we have too many already) */
if (optCSECandidateCount < MAX_CSE_CNT)
{
hashDsc = new (this, CMK_CSE) CSEdsc;
hashDsc->csdHashValue = key;
hashDsc->csdIndex = 0;
hashDsc->csdLiveAcrossCall = 0;
hashDsc->csdDefCount = 0;
hashDsc->csdUseCount = 0;
hashDsc->csdDefWtCnt = 0;
hashDsc->csdUseWtCnt = 0;
hashDsc->csdTree = tree;
hashDsc->csdStmt = stmt;
hashDsc->csdBlock = compCurBB;
hashDsc->csdTreeList = 0;
/* Append the entry to the hash bucket */
hashDsc->csdNextInBucket = optCSEhash[hval];
optCSEhash[hval] = hashDsc;
}
return 0;
}
else // newCSE is true
{
/* We get here only after finding a matching CSE */
/* Create a new CSE (unless we have the maximum already) */
if (optCSECandidateCount == MAX_CSE_CNT)
return 0;
C_ASSERT((signed char)MAX_CSE_CNT == MAX_CSE_CNT);
unsigned CSEindex = ++optCSECandidateCount;
EXPSET_TP CSEmask = genCSEnum2bit(CSEindex);
/* Record the new CSE index in the hashDsc */
hashDsc->csdIndex = CSEindex;
/* Update the gtCSEnum field in the original tree */
noway_assert(hashDsc->csdTreeList->tslTree->gtCSEnum == 0);
assert(FitsIn<signed char>(CSEindex));
hashDsc->csdTreeList->tslTree->gtCSEnum = ((signed char) CSEindex);
noway_assert(((unsigned) hashDsc->csdTreeList->tslTree->gtCSEnum) == CSEindex);
tree->gtCSEnum = ((signed char) CSEindex);
#ifdef DEBUG
if (verbose)
{
printf("\nCSE candidate #%02u, vn=", CSEindex);
vnPrint(vnlib, 0);
printf(" cseMask=%s in BB%02u, [cost=%2u, size=%2u]: \n",
genES2str(genCSEnum2bit(CSEindex)), compCurBB->bbNum, tree->gtCostEx, tree->gtCostSz);
gtDispTree(tree);
}
#endif // DEBUG
return CSEindex;
}
}
/*****************************************************************************
*
* Locate CSE candidates and assign indices to them
* return 0 if no CSE candidates were found
* Also initialize bbCseIn, bbCseout and bbCseGen sets for all blocks
*/
unsigned Compiler::optValnumCSE_Locate()
{
// Locate CSE candidates and assign them indices
for (BasicBlock * block = fgFirstBB; block; block = block->bbNext)
{
GenTreePtr stmt;
GenTreePtr tree;
/* Make the block publicly available */
compCurBB = block;
/* Ensure that the BBF_VISITED and BBF_MARKED flag are clear */
/* Everyone who uses these flags are required to clear afterwards */
noway_assert((block->bbFlags & (BBF_VISITED|BBF_MARKED)) == 0);
/* Walk the statement trees in this basic block */
#if JIT_FEATURE_SSA_SKIP_DEFS
for (stmt = block->FirstNonPhiDef(); stmt; stmt = stmt->gtNext)
#else
for (stmt = block->bbTreeList; stmt; stmt = stmt->gtNext)
#endif
{
noway_assert(stmt->gtOper == GT_STMT);
/* We walk the tree in the forwards direction (bottom up) */
for (tree = stmt->gtStmt.gtStmtList; tree; tree = tree->gtNext)
{
if (!optIsCSEcandidate(tree))
continue;
ValueNum vnlib = tree->GetVN(VNK_Liberal);
if (ValueNumStore::isReservedVN(vnlib))
continue;
// Don't CSE constant values, instead let the Value Number
// based Assertion Prop phase handle them.
//
if (vnStore->IsVNConstant(vnlib))
continue;
/* Assign an index to this expression */
unsigned CSEindex = optValnumCSE_Index(tree, stmt);
if (CSEindex != 0)
{
noway_assert(((unsigned) tree->gtCSEnum ) == CSEindex);
}
}
}
}
/* We're done if there were no interesting expressions */
if (!optDoCSE)
return 0;
/* We're finished building the expression lookup table */
optCSEstop();
return 1;
}
/*****************************************************************************
*
* Compute each blocks bbCseGen
* This is the bitset that represents the CSEs that are generated within the block
*/
void Compiler::optValnumCSE_InitDataFlow()
{
for (BasicBlock * block = fgFirstBB; block; block = block->bbNext)
{
GenTreePtr stmt;
GenTreePtr tree;
/* Initialize the blocks's bbCseIn set */
bool init_to_zero = false;
if (block == fgFirstBB)
{
/* Clear bbCseIn for the entry block */
init_to_zero = true;
}
#if !CSE_INTO_HANDLERS
else
{
if (bbIsHandlerBeg(block))
{
/* Clear everything on entry to filters or handlers */
init_to_zero = true;
}
}
#endif
if (init_to_zero)
{
/* Initialize to {ZERO} prior to dataflow */
block->bbCseIn = 0;
}
else
{
/* Initialize to {ALL} prior to dataflow */
block->bbCseIn = EXPSET_ALL;
}
block->bbCseOut = EXPSET_ALL;
/* Initialize to {ZERO} prior to locating the CSE candidates */
block->bbCseGen = 0;
}
// We walk the set of CSE candidates and set the bit corresponsing to the CSEindex
// in the block's bbCseGen bitset
//
for (unsigned cnt = 0; cnt < optCSECandidateCount; cnt++)
{
CSEdsc* dsc = optCSEtab[cnt];
unsigned CSEindex = dsc->csdIndex;
treeStmtLstPtr lst = dsc->csdTreeList; noway_assert(lst);
while (lst != nullptr)
{
BasicBlock* block = lst->tslBlock;
block->bbCseGen |= genCSEnum2bit(CSEindex);
lst = lst->tslNext;
}
}
#ifdef DEBUG
// Dump out the bbCseGen information that we just created
//
if (verbose)
{
bool headerPrinted = false;
for (BasicBlock* block = fgFirstBB; block; block = block->bbNext)
{
if (block->bbCseGen != 0)
{
if (!headerPrinted)
{
printf("\nBlocks that generate CSE def/uses\n");
headerPrinted = true;
}
printf("BB%02u", block->bbNum);
printf(" cseGen = %s\n", genES2str(block->bbCseGen));
}
}
}
fgDebugCheckLinks();
#endif // DEBUG
}
/*****************************************************************************
*
* CSE Dataflow, so that all helper methods for dataflow are in a single place
*
*/
class CSE_DataFlow
{
private:
EXPSET_TP m_preMergeOut;
EXPSET_TP m_postMergeOut;
Compiler* m_pCompiler;
public:
CSE_DataFlow(Compiler* pCompiler)
: m_pCompiler(pCompiler)
{}
Compiler* getCompiler()
{ return m_pCompiler; }
// At the start of the merge function of the dataflow equations, initialize premerge state (to detect changes.)
void StartMerge(BasicBlock* block)
{
m_preMergeOut = block->bbCseOut;
}
// During merge, perform the actual merging of the predecessor's (since this is a forward analysis) dataflow flags.
void Merge(BasicBlock* block, BasicBlock* predBlock, flowList* preds)
{
block->bbCseIn &= predBlock->bbCseOut;
}
// At the end of the merge store results of the dataflow equations, in a postmerge state.
void EndMerge(BasicBlock* block)
{
EXPSET_TP mergeOut = block->bbCseOut & (block->bbCseIn | block->bbCseGen);
m_postMergeOut = mergeOut;
}
// Check if anything changed by comparing premerge and postmerge states.
bool Changed(BasicBlock* block)
{
bool changed = (m_postMergeOut != m_preMergeOut);
return changed;
}
// Finish any updates to the basic blocks after the merge.
DataFlow::UpdateResult Update(BasicBlock* block)
{
block->bbCseOut = m_postMergeOut;
return DataFlow::ContinueAnalysis;
}
};
/*****************************************************************************
*
* Perform a DataFlow forward analysis using the block CSE bitsets:
* Inputs:
* bbCseGen - Exact CSEs that are become available within the block
* bbCseIn - Maximal estimate of CSEs that are/could be available at input to the block
* bbCseOut - Maximal estimate of CSEs that are/could be available at exit to the block
*
* Outputs:
* bbCseIn - Computed CSEs that are available at input to the block
* bbCseOut - Computed CSEs that are available at exit to the block
*/
void Compiler::optValnumCSE_DataFlow()
{
CSE_DataFlow cse(this);
// Modified dataflow algorithm for available expressions.
DataFlow cse_flow(this);
cse_flow.ForwardAnalysis(cse);
#ifdef DEBUG
if (verbose)
{
printf("\nAfter performing DataFlow for ValnumCSE's\n");
for (BasicBlock* block = fgFirstBB; block; block = block->bbNext)
{
printf("BB%02u", block->bbNum);
printf(" cseIn = %s", genES2str(block->bbCseIn ));
printf(" cseOut = %s", genES2str(block->bbCseOut));
printf("\n");
}
printf("\n");
}
#endif // DEBUG
}
/*****************************************************************************
*
* Using the information computed by CSE_DataFlow determine for each
* CSE whether the CSE is a definition (if the CSE was not available)
* or if the CSE is a use (if the CSE was previously made available)
* The implementation iterates of all blocks setting 'available_cses'
* to the CSEs that are available at input to the block.
* When a CSE expression is encountered it is classified as either
* as a definition (if the CSE is not in the 'available_cses' set) or
* as a use (if the CSE is in the 'available_cses' set). If the CSE
* is a definition then it is added to the 'available_cses' set.
* In the Value Number based CSEs we do not need to have kill sets
*/
void Compiler::optValnumCSE_Availablity()
{
#ifdef DEBUG
if (verbose)
{
printf("Labeling the CSEs with Use/Def information\n");
}
#endif
for (BasicBlock * block = fgFirstBB; block; block = block->bbNext)
{
GenTreePtr stmt;
GenTreePtr tree;
/* Make the block publicly available */
compCurBB = block;
EXPSET_TP available_cses = block->bbCseIn;
optCSEweight = block->getBBWeight(this);
/* Walk the statement trees in this basic block */
#if JIT_FEATURE_SSA_SKIP_DEFS
for (stmt = block->FirstNonPhiDef(); stmt; stmt = stmt->gtNext)
#else
for (stmt = block->bbTreeList; stmt; stmt = stmt->gtNext)
#endif
{
noway_assert(stmt->gtOper == GT_STMT);
/* We walk the tree in the forwards direction (bottom up) */
for (tree = stmt->gtStmt.gtStmtList; tree; tree = tree->gtNext)
{
if (IS_CSE_INDEX(tree->gtCSEnum))
{
EXPSET_TP mask = genCSEnum2bit(tree->gtCSEnum);
CSEdsc * desc = optCSEfindDsc(tree->gtCSEnum);
unsigned stmw = block->getBBWeight(this);
/* Is this expression available here? */
if (available_cses & mask)
{
/* This is a CSE use */
desc->csdUseCount += 1;
desc->csdUseWtCnt += stmw;
}
else
{
if (tree->gtFlags & GTF_COLON_COND)
{
// We can't create CSE definitions inside QMARK-COLON trees
tree->gtCSEnum = NO_CSE;
continue;
}
/* This is a CSE def */
desc->csdDefCount += 1;
desc->csdDefWtCnt += stmw;
/* Mark the node as a CSE definition */
tree->gtCSEnum = TO_CSE_DEF(tree->gtCSEnum);
/* This CSE will be available after this def */
available_cses |= mask;
}
#ifdef DEBUG
if (verbose && IS_CSE_INDEX(tree->gtCSEnum))
{
printf("BB%02u ", block->bbNum);
printTreeID(tree);
printf(" %s of CSE #%02u [weight=%s]\n",
IS_CSE_USE(tree->gtCSEnum) ? "Use" : "Def",
GET_CSE_INDEX(tree->gtCSEnum), refCntWtd2str(stmw));
}
#endif
}
}
}
}
}
// The following class handles the CSE heuristics
// we use a complex set of heuristic rules
// to determine if it is likely to be profitable to perform this CSE
//
class CSE_Heuristic
{
Compiler* m_pCompiler;
unsigned m_addCSEcount;
unsigned aggressiveRefCnt;
unsigned moderateRefCnt;
unsigned enregCount; // count of the number of enregisterable variables
bool largeFrame;
bool hugeFrame;
Compiler::codeOptimize codeOptKind;
Compiler::CSEdsc** sortTab;
size_t sortSiz;
public:
CSE_Heuristic(Compiler* pCompiler)
: m_pCompiler(pCompiler)
{
codeOptKind = m_pCompiler->compCodeOpt();
}
Compiler::codeOptimize CodeOptKind() { return codeOptKind; }
// Perform the Initialization step for our CSE Heuristics
// determine the various cut off values to use for
// the aggressive, moderate and conservative CSE promotions
// count the number of enregisterable variables
// determine if the method has a large or huge stack frame.
//
void Initialize()
{
m_addCSEcount = 0; /* Count of the number of LclVars for CSEs that we added */
// Record the weighted ref count of the last "for sure" callee saved LclVar
aggressiveRefCnt = 0;
moderateRefCnt = 0;
enregCount = 0;
largeFrame = false;
hugeFrame = false;
sortTab = nullptr;
sortSiz = 0;
#ifdef _TARGET_XARCH_
if (m_pCompiler->compLongUsed)
{
enregCount++;
}
#endif
unsigned frameSize = 0;
unsigned lclNum;
LclVarDsc * varDsc;
for (lclNum = 0, varDsc = m_pCompiler->lvaTable;
lclNum < m_pCompiler->lvaCount;
lclNum++ , varDsc++)
{
frameSize += m_pCompiler->lvaLclSize(lclNum);
#ifdef _TARGET_XARCH_
if (frameSize > 0x0A0)
{
largeFrame = true;
break;
}
#else // _TARGET_ARM_
if (frameSize > 0x0400)
{
largeFrame = true;
}
if (frameSize > 0x10000)
{
hugeFrame = true;
break;
}
#endif
}
unsigned sortNum = 0;
while (sortNum < m_pCompiler->lvaTrackedCount)
{
LclVarDsc* varDsc = m_pCompiler->lvaRefSorted[sortNum++];
var_types varTyp = varDsc->TypeGet();
if (varDsc->lvDoNotEnregister)
continue;
if (!varTypeIsFloating(varTyp))
{
enregCount += genTypeStSz(varTyp);
}
if ((aggressiveRefCnt == 0) && (enregCount >= CNT_CALLEE_ENREG))
{
if (CodeOptKind() == Compiler::SMALL_CODE)
aggressiveRefCnt = varDsc->lvRefCnt+1;
else
aggressiveRefCnt = varDsc->lvRefCntWtd+1;
}
if ((moderateRefCnt == 0) && (enregCount >= CNT_CALLEE_ENREG*2))
{
if (CodeOptKind() == Compiler::SMALL_CODE)
moderateRefCnt = varDsc->lvRefCnt;
else
moderateRefCnt = varDsc->lvRefCntWtd;
}
}
aggressiveRefCnt = max(BB_UNITY_WEIGHT * 3, aggressiveRefCnt);
moderateRefCnt = max((BB_UNITY_WEIGHT * 3)/2, moderateRefCnt);
#ifdef DEBUG
if (m_pCompiler->verbose)
{
printf("\n");
printf("Aggressive CSE Promotion cutoff is %u\n", aggressiveRefCnt);
printf("Moderate CSE Promotion cutoff is %u\n", moderateRefCnt);
printf("We have a %s frame\n", hugeFrame ? "huge" : (largeFrame ? "large" : "small"));
}
#endif
}
void SortCandidates()
{
/* Create an expression table sorted by decreasing cost */
sortTab = new (m_pCompiler, CMK_CSE) Compiler::CSEdsc*[m_pCompiler->optCSECandidateCount];
sortSiz = m_pCompiler->optCSECandidateCount * sizeof(*sortTab);
memcpy(sortTab, m_pCompiler->optCSEtab, sortSiz);
if (CodeOptKind() == Compiler::SMALL_CODE)
qsort(sortTab, m_pCompiler->optCSECandidateCount, sizeof(*sortTab), m_pCompiler->optCSEcostCmpSz);
else
qsort(sortTab, m_pCompiler->optCSECandidateCount, sizeof(*sortTab), m_pCompiler->optCSEcostCmpEx);
#ifdef DEBUG
if (m_pCompiler->verbose)
{
printf("\nSorted CSE candidates:\n");
/* Print out the CSE candidates */
for (unsigned cnt = 0; cnt < m_pCompiler->optCSECandidateCount; cnt++)
{
Compiler::CSEdsc* dsc = sortTab[cnt];
GenTreePtr expr = dsc->csdTree;
unsigned def;
unsigned use;
if (CodeOptKind() == Compiler::SMALL_CODE)
{
def = dsc->csdDefCount; // def count
use = dsc->csdUseCount; // use count (excluding the implicit uses at defs)
}
else
{
def = dsc->csdDefWtCnt; // weighted def count
use = dsc->csdUseWtCnt; // weighted use count (excluding the implicit uses at defs)
}
printf("CSE #%02u,cseMask=%s,useCnt=%d: [def=%3u, use=%3u", dsc->csdIndex, genES2str(genCSEnum2bit(dsc->csdIndex)), dsc->csdUseCount, def, use);
printf("] :: ");
m_pCompiler->gtDispTree(expr, 0, nullptr, true);
}
printf("\n");
}
#endif // DEBUG
}
// The following class nested within CSE_Heuristic encapsulates the information
// about the current CSE candidate that is under consideration
//
// TODO-Cleanup: This is still very much based upon the old Lexical CSE implementation
// and needs to be reworked for the Value Number based implementation
//
class CSE_Candidate
{
CSE_Heuristic* m_context;
Compiler::CSEdsc* m_CseDsc;
unsigned m_cseIndex;
unsigned m_defCount;
unsigned m_useCount;
unsigned m_Cost;
public:
CSE_Candidate(CSE_Heuristic* context, Compiler::CSEdsc* cseDsc)
: m_context(context)
, m_CseDsc(cseDsc)
{
m_cseIndex = m_CseDsc->csdIndex;
}
Compiler::CSEdsc* CseDsc() { return m_CseDsc; }
unsigned CseIndex() { return m_cseIndex; }
unsigned DefCount() { return m_defCount; }
unsigned UseCount() { return m_useCount; }
// TODO-CQ: With ValNum CSE's the Expr and its cost can vary.
GenTreePtr Expr() { return m_CseDsc->csdTree; }
unsigned Cost() { return m_Cost; }
bool LiveAcrossCall() { return (m_CseDsc->csdLiveAcrossCall != 0); }
void InitializeCounts()
{
if (m_context->CodeOptKind() == Compiler::SMALL_CODE)
{
m_Cost = Expr()->gtCostSz;
m_defCount = m_CseDsc->csdDefCount; // def count
m_useCount = m_CseDsc->csdUseCount; // use count (excluding the implicit uses at defs)
}
else
{
m_Cost = Expr()->gtCostEx;
m_defCount = m_CseDsc->csdDefWtCnt; // weighted def count
m_useCount = m_CseDsc->csdUseWtCnt; // weighted use count (excluding the implicit uses at defs)
}
}
};
// Given a CSE candidate decide whether it passes or fails the profitablity heuristic
// return true if we believe that it is profitable to promote this candidate to a CSE
//
bool PromotionCheck(CSE_Candidate* candidate)
{
bool result = false;
#ifdef DEBUG
if (m_pCompiler->optConfigDisableCSE2())
{
return false; // skip this CSE
}
#endif
/*
Our calculation is based on the following cost estimate formula
Existing costs are:
(def + use) * cost
If we introduce a CSE temp are each definition and
replace the use with a CSE temp then our cost is:
(def * (cost + cse-def-cost)) + (use * cse-use-cost)
We must estimate the values to use for cse-def-cost and cse-use-cost
If we are able to enregister the CSE then the cse-use-cost is one
and cse-def-cost is either zero or one. Zero in the case where
we needed to evaluate the def into a register and we can use that
register as the CSE temp as well.
If we are unable to enregister the CSE then the cse-use-cost is IND_COST
and the cse-def-cost is also IND_COST.
If we want to be conservative we use IND_COST as the the value
for both cse-def-cost and cse-use-cost and then we never introduce
a CSE that could pessimize the execution time of the method.
If we want to be more moderate we use (IND_COST_EX + 1) / 2 as the
values for both cse-def-cost and cse-use-cost.
If we want to be aggressive we use 1 as the values for both
cse-def-cost and cse-use-cost.
If we believe that the CSE very valuable in terms of weighted ref counts
such that it would always be enregistered by the register allocator we choose
the aggressive use def costs.
If we believe that the CSE is somewhat valuable in terms of weighted ref counts
such that it could be likely be enregistered by the register allocator we choose
the moderate use def costs.
otherwise we choose the conservative use def costs.
*/
unsigned cse_def_cost;
unsigned cse_use_cost;
unsigned no_cse_cost = 0;
unsigned yes_cse_cost = 0;
unsigned cseRefCnt = (candidate->DefCount() * 2) + candidate->DefCount();
if (CodeOptKind() == Compiler::SMALL_CODE)
{
if (cseRefCnt >= aggressiveRefCnt)
{
#ifdef DEBUG
if (m_pCompiler->verbose)
{
printf("Aggressive CSE Promotion (%u >= %u)\n", cseRefCnt, aggressiveRefCnt);
}
#endif
cse_def_cost = 1;
cse_use_cost = 1;
if (candidate->LiveAcrossCall() != 0)
{
if (largeFrame)
{
cse_def_cost++;
cse_use_cost++;
}
if (hugeFrame)
{
cse_def_cost++;
cse_use_cost++;
}
}
}
else if (largeFrame)
{
#ifdef DEBUG
if (m_pCompiler->verbose)
{
printf("Codesize CSE Promotion (large frame)\n");
}
#endif
#ifdef _TARGET_XARCH_
/* The following formula is good choice when optimizing CSE for SMALL_CODE */
cse_def_cost = 6; // mov [EBP-0x00001FC],reg
cse_use_cost = 5; // [EBP-0x00001FC]
#else // _TARGET_ARM_
if (hugeFrame)
{
cse_def_cost = 12; // movw/movt r10 and str reg,[sp+r10]
cse_use_cost = 12;
}
else
{
cse_def_cost = 8; // movw r10 and str reg,[sp+r10]
cse_use_cost = 8;
}
#endif
}
else // small frame
{
#ifdef DEBUG
if (m_pCompiler->verbose)
{
printf("Codesize CSE Promotion (small frame)\n");
}
#endif
#ifdef _TARGET_XARCH_
/* The following formula is good choice when optimizing CSE for SMALL_CODE */
cse_def_cost = 3; // mov [EBP-1C],reg
cse_use_cost = 2; // [EBP-1C]
#else // _TARGET_ARM_
cse_def_cost = 2; // str reg,[sp+0x9c]
cse_use_cost = 2; // ldr reg,[sp+0x9c]
#endif
}
}
else // not SMALL_CODE ...
{
if (cseRefCnt >= aggressiveRefCnt)
{
#ifdef DEBUG
if (m_pCompiler->verbose)
{
printf("Aggressive CSE Promotion (%u >= %u)\n", cseRefCnt, aggressiveRefCnt);
}
#endif
cse_def_cost = 1;
cse_use_cost = 1;
}
else if (candidate->LiveAcrossCall() == 0)
{
#ifdef DEBUG
if (m_pCompiler->verbose)
{
printf("Aggressive CSE Promotion (CSE never live at call)\n");
}
#endif
if (cseRefCnt >= moderateRefCnt)
cse_def_cost = 1;
else
cse_def_cost = (IND_COST_EX + 1) / 2;
cse_use_cost = 1;
}
else if (cseRefCnt >= moderateRefCnt)
{
#ifdef DEBUG
if (m_pCompiler->verbose)
{
printf("Moderate CSE Promotion (%u >= %u)\n", cseRefCnt, moderateRefCnt);
}
#endif
cse_def_cost = (IND_COST_EX + 1) / 2;
cse_use_cost = (IND_COST_EX + 1) / 2;
yes_cse_cost = 2; // We might have to spill/restore a caller saved register
}
else
{
#ifdef DEBUG
if (m_pCompiler->verbose)
{
printf("Conservative CSE Promotion (%u < %u)\n", cseRefCnt, moderateRefCnt);
}
#endif
cse_def_cost = IND_COST_EX;
cse_use_cost = IND_COST_EX;
yes_cse_cost = 4; // We might have to spill/restore a caller saved register
// If we have maxed out lvaTrackedCount then this CSE may end up as an untracked variable
if (m_pCompiler->lvaTrackedCount == lclMAX_TRACKED)
{
cse_def_cost++;
cse_use_cost++;
}
}
if (largeFrame)
{
cse_def_cost++;
cse_use_cost++;
}
if (hugeFrame)
{
cse_def_cost++;
cse_use_cost++;
}
}
/* no_cse_cost is the cost estimate when we decide not to make a CSE */
/* yes_cse_cost is the cost estimate when we decide to make a CSE */
no_cse_cost = candidate->UseCount() * candidate->Cost();
yes_cse_cost += (candidate->DefCount() * cse_def_cost) + (candidate->UseCount() * cse_use_cost);
#if CPU_LONG_USES_REGPAIR
if (candidate->Expr()->TypeGet() == TYP_LONG)
{
yes_cse_cost += (candidate->DefCount() * cse_def_cost) + (candidate->UseCount() * cse_use_cost);
}
#endif
#ifdef DEBUG
if (m_pCompiler->verbose)
{
printf("CSE cost savings check (%u >= %u) %s\n",
no_cse_cost, yes_cse_cost,
(no_cse_cost >= yes_cse_cost) ? "passes" : "fails");
}
#endif
/* Does it cost us more to make this expression a CSE? */
if (yes_cse_cost <= no_cse_cost)
{
result = true; // YES_CSE
}
else
{
/* In stress mode we will make some extra CSEs */
if (no_cse_cost > 0)
{
int percentage = (no_cse_cost * 100) / yes_cse_cost;
if (m_pCompiler->compStressCompile(Compiler::STRESS_MAKE_CSE, percentage))
{
result = true; // YES_CSE
}
}
}
return result;
}
// PerformCSE() takes a successful candidate and performs the appropriate replacements:
//
// It will replace all of the CSE defs with assignments to a new "cse0" LclVar
// and will replace all of the CSE uses with reads of the "cse0" LclVar
//
void PerformCSE(CSE_Candidate* successfulCandidate)
{
unsigned cseRefCnt = (successfulCandidate->DefCount() * 2) + successfulCandidate->UseCount();
// As we introduce new LclVars for these CSE we slightly
// increase the cutoffs for aggressive and moderate CSE's
//
if (successfulCandidate->LiveAcrossCall() != 0)
{
int incr = 1;
#if CPU_LONG_USES_REGPAIR
if (successfulCandidate->Expr()->TypeGet() == TYP_LONG)
incr *= 2;
#endif
if (cseRefCnt > aggressiveRefCnt)
aggressiveRefCnt += (2*incr);
if (cseRefCnt > moderateRefCnt)
moderateRefCnt += incr;
}
/* Introduce a new temp for the CSE */
// we will create a long lifetime temp for the new cse LclVar
unsigned cseLclVarNum = m_pCompiler->lvaGrabTemp(false DEBUGARG("ValNumCSE"));
var_types cseLclVarTyp = genActualType(successfulCandidate->Expr()->TypeGet());
m_pCompiler->lvaTable[cseLclVarNum].lvType = cseLclVarTyp;
m_pCompiler->lvaTable[cseLclVarNum].lvIsCSE = true;
m_addCSEcount++; // Record that we created a new LclVar for use as a CSE temp
m_pCompiler->optCSEcount++;
/* Walk all references to this CSE, adding an assignment
to the CSE temp to all defs and changing all refs to
a simple use of the CSE temp.
We also unmark nested CSE's for all uses.
*/
Compiler::treeStmtLstPtr lst; lst = successfulCandidate->CseDsc()->csdTreeList; noway_assert(lst);
#define QQQ_CHECK_CSE_VNS 0
#if QQQ_CHECK_CSE_VNS
assert(lst != NULL);
ValueNum firstVN = lst->tslTree->gtVN;
lst = lst->tslNext;
bool allSame = true;
while (lst != NULL)
{
if (IS_CSE_INDEX(lst->tslTree->gtCSEnum))
{
if (lst->tslTree->gtVN != firstVN)
{
allSame = false;
break;
}
}
lst = lst->tslNext;
}
if (!allSame)
{
lst = dsc->csdTreeList;
GenTreePtr firstTree = lst->tslTree;
printf("In %s, CSE (oper = %s, type = %s) has differing VNs: ", info.compFullName,
GenTree::NodeName(firstTree->OperGet()), varTypeName(firstTree->TypeGet()));
while (lst != NULL) {
if (IS_CSE_INDEX(lst->tslTree->gtCSEnum))
{
printf("0x%x(%s,%d) ", lst->tslTree, IS_CSE_USE(lst->tslTree->gtCSEnum) ? "u" : "d", lst->tslTree->gtVN);
}
lst = lst->tslNext;
}
printf("\n");
}
lst = dsc->csdTreeList;
#endif
do
{
/* Process the next node in the list */
GenTreePtr exp = lst->tslTree;
GenTreePtr stm = lst->tslStmt; noway_assert(stm->gtOper == GT_STMT);
BasicBlock * blk = lst->tslBlock;
/* Advance to the next node in the list */
lst = lst->tslNext;
// Assert if we used DEBUG_DESTROY_NODE on this CSE exp
assert(exp->gtOper != GT_COUNT);
/* Ignore the node if it's part of a removed CSE */
if (exp->gtFlags & GTF_DEAD)
continue;
/* Ignore the node if it's not been marked as a CSE */
if (!IS_CSE_INDEX(exp->gtCSEnum))
continue;
/* Make sure we update the weighted ref count correctly */
m_pCompiler->optCSEweight = blk->getBBWeight(m_pCompiler);
/* Figure out the actual type of the value */
var_types expTyp = genActualType(exp->TypeGet());
noway_assert(expTyp == cseLclVarTyp);
// This will contain the replacement tree for exp
// It will either be the CSE def or CSE ref
//
GenTreePtr cse = nullptr;
bool isDef;
FieldSeqNode* fldSeq = nullptr;
bool hasZeroMapAnnotation = m_pCompiler->GetZeroOffsetFieldMap()->Lookup(exp, &fldSeq);
if (IS_CSE_USE(exp->gtCSEnum))
{
/* This is a use of the CSE */
isDef = false;
#ifdef DEBUG
if (m_pCompiler->verbose)
{
printf("\nCSE #%02u use at ", exp->gtCSEnum);
Compiler::printTreeID(exp);
printf(" replaced in BB%02u with temp use.\n", blk->bbNum);
}
#endif // DEBUG
/* check for and collect any SIDE_EFFECTS */
GenTreePtr sideEffList = NULL;
if (exp->gtFlags & GTF_PERSISTENT_SIDE_EFFECTS)
{
// Extract any side effects from exp
//
m_pCompiler->gtExtractSideEffList(exp, &sideEffList, GTF_PERSISTENT_SIDE_EFFECTS_IN_CSE);
}
// We will replace the CSE ref with a new tree
// this is typically just a simple use of the new CSE LclVar
//
cse = m_pCompiler->gtNewLclvNode(cseLclVarNum, cseLclVarTyp);
cse->gtVNPair = exp->gtVNPair; // assign the proper Value Numbers
#ifdef DEBUG
cse->gtFlags |= GTFD_VAR_CSE_REF;
#endif // DEBUG
// If we have side effects then we need to create a GT_COMMA tree instead
//
if (sideEffList)
{
noway_assert(sideEffList->gtFlags & GTF_SIDE_EFFECT);
#ifdef DEBUG
if (m_pCompiler->verbose)
{
printf("\nThe CSE has side effects! Extracting side effects...\n");
m_pCompiler->gtDispTree(sideEffList); printf("\n");
}
#endif
GenTreePtr cseVal = cse;
GenTreePtr curSideEff = sideEffList;
ValueNumStore* vnStore = m_pCompiler->vnStore;
ValueNumPair exceptions_vnp = ValueNumStore::VNPForEmptyExcSet();
while ((curSideEff->OperGet() == GT_COMMA) || (curSideEff->OperGet() == GT_ASG))
{
GenTreePtr op1 = curSideEff->gtOp.gtOp1;
GenTreePtr op2 = curSideEff->gtOp.gtOp2;
ValueNumPair op1vnp;
ValueNumPair op1Xvnp = ValueNumStore::VNPForEmptyExcSet();
vnStore->VNPUnpackExc(op1->gtVNPair, &op1vnp, &op1Xvnp);
exceptions_vnp = vnStore->VNPExcSetUnion(exceptions_vnp, op1Xvnp);
curSideEff = op2;
}
// We may have inserted a narrowing cast during a previous remorph
// and it will not have a value number.
if ((curSideEff->OperGet() == GT_CAST) && !curSideEff->gtVNPair.BothDefined())
{
// The inserted cast will have no exceptional effects
assert(curSideEff->gtOverflow() == false);
// Process the exception effects from the cast's operand.
curSideEff = curSideEff->gtOp.gtOp1;
}
ValueNumPair op2vnp;
ValueNumPair op2Xvnp = ValueNumStore::VNPForEmptyExcSet();
vnStore->VNPUnpackExc(curSideEff->gtVNPair, &op2vnp, &op2Xvnp);
exceptions_vnp = vnStore->VNPExcSetUnion(exceptions_vnp, op2Xvnp);
op2Xvnp = ValueNumStore::VNPForEmptyExcSet();
vnStore->VNPUnpackExc(cseVal->gtVNPair, &op2vnp, &op2Xvnp);
exceptions_vnp = vnStore->VNPExcSetUnion(exceptions_vnp, op2Xvnp);
/* Create a comma node with the sideEffList as op1 */
cse = m_pCompiler->gtNewOperNode(GT_COMMA, expTyp, sideEffList, cseVal);
cse->gtVNPair = vnStore->VNPWithExc(op2vnp, exceptions_vnp);
}
exp->gtCSEnum = NO_CSE; // clear the gtCSEnum field
/* Unmark any nested CSE's in the sub-operands */
// But we do need to communicate the side effect list to optUnmarkCSEs
// as any part of the 'exp' tree that is in the sideEffList is preserved
// and is not deleted and does not have its ref counts decremented
//
m_pCompiler->optValnumCSE_UnmarkCSEs(exp, sideEffList);
}
else
{
/* This is a def of the CSE */
isDef = true;
#ifdef DEBUG
if (m_pCompiler->verbose)
{
printf("\nCSE #%02u def at ", GET_CSE_INDEX(exp->gtCSEnum));
Compiler::printTreeID(exp);
printf(" replaced in BB%02u with def of V%02u\n",
blk->bbNum, cseLclVarNum);
}
#endif // DEBUG
exp->gtCSEnum = NO_CSE; // clear the gtCSEnum field
GenTreePtr val = exp;
/* Create an assignment of the value to the temp */
GenTreePtr asg = m_pCompiler->gtNewTempAssign(cseLclVarNum, val);
// assign the proper Value Numbers
asg->gtVNPair.SetBoth(ValueNumStore::VNForVoid()); // The GT_ASG node itself is $VN.Void
asg->gtOp.gtOp1->gtVNPair = val->gtVNPair; // The dest op is the same as 'val'
noway_assert(asg->gtOp.gtOp1->gtOper == GT_LCL_VAR);
noway_assert(asg->gtOp.gtOp2 == val);
/* Create a reference to the CSE temp */
GenTreePtr ref = m_pCompiler->gtNewLclvNode(cseLclVarNum, cseLclVarTyp);
ref->gtVNPair = val->gtVNPair; // The new 'ref' is the same as 'val'
// If it has a zero-offset field seq, copy annotation to the ref
if (hasZeroMapAnnotation)
{
m_pCompiler->GetZeroOffsetFieldMap()->Set(ref, fldSeq);
}
/* Create a comma node for the CSE assignment */
cse = m_pCompiler->gtNewOperNode(GT_COMMA, expTyp, asg, ref);
cse->gtVNPair = ref->gtVNPair; // The comma's value is the same as 'val'
// as the assignment to the CSE LclVar
// cannot add any new exceptions
}
// Increment ref count for the CSE ref
m_pCompiler->lvaTable[cseLclVarNum].incRefCnts(blk->getBBWeight(m_pCompiler), m_pCompiler);
if (isDef)
{
// Also increment ref count for the CSE assignment
m_pCompiler->lvaTable[cseLclVarNum].incRefCnts(blk->getBBWeight(m_pCompiler), m_pCompiler);
}
// Walk the statement 'stm' and find the pointer
// in the tree is pointing to 'exp'
//
GenTreePtr * link = m_pCompiler->gtFindLink(stm, exp);
#ifdef DEBUG
if (link == NULL)
{
printf("\ngtFindLink failed: stm=");
Compiler::printTreeID(stm);
printf(", exp=");
Compiler::printTreeID(exp);
printf("\n");
printf("stm =");
m_pCompiler->gtDispTree(stm); printf("\n");
printf("exp =");
m_pCompiler->gtDispTree(exp); printf("\n");
}
#endif // DEBUG
noway_assert(link);
// Mutate this link, thus replacing the old exp with the new cse representation
//
*link = cse;
// If it has a zero-offset field seq, copy annotation.
if (hasZeroMapAnnotation)
{
m_pCompiler->GetZeroOffsetFieldMap()->Set(cse, fldSeq);
}
assert(m_pCompiler->fgRemoveRestOfBlock == false);
/* re-morph the statement */
m_pCompiler->fgMorphBlockStmt(blk, stm DEBUGARG("optValnumCSE"));
}
while (lst != nullptr);
}
// Consider each of the CSE candidates and if the CSE passes
// the PromotionCheck then transform the CSE by calling PerformCSE
//
void ConsiderCandidates()
{
/* Consider each CSE candidate, in order of decreasing cost */
unsigned cnt = m_pCompiler->optCSECandidateCount;
Compiler::CSEdsc* * ptr = sortTab;
for (; (cnt > 0); cnt--, ptr++)
{
Compiler::CSEdsc* dsc = *ptr;
CSE_Candidate candidate(this, dsc);
candidate.InitializeCounts();
if (candidate.UseCount() == 0)
{
#ifdef DEBUG
if (m_pCompiler->verbose)
{
printf("Skipped CSE #%02u because use count is 0\n", candidate.CseIndex());
}
#endif
continue;
}
#ifdef DEBUG
if (m_pCompiler->verbose)
{
printf("\nConsidering CSE #%02u [def=%2u, use=%2u, cost=%2u] CSE Expression:\n",
candidate.CseIndex(), candidate.DefCount(), candidate.UseCount(), candidate.Cost());
m_pCompiler->gtDispTree(candidate.Expr());
printf("\n");
}
#endif
if ((dsc->csdDefCount <= 0) || (dsc->csdUseCount == 0))
{
// If we reach this point, then the CSE def was incorrectly marked or the
// block with this use is unreachable. So skip and go to the next CSE.
// Without the "continue", we'd generate bad code in retail.
// Commented out a noway_assert(false) here due to bug: 3290124.
// The problem is if there is sub-graph that is not reachable from the
// entry point, the CSE flags propagated, would be incorrect for it.
continue;
}
bool doCSE = PromotionCheck(&candidate);
#ifdef DEBUG
if (m_pCompiler->verbose)
{
if (doCSE)
{
printf("\nPromoting CSE:\n");
}
else
{
printf("Did Not promote this CSE\n");
}
}
#endif // DEBUG
if (doCSE)
{
PerformCSE(&candidate);
}
}
}
// Perform the necessary cleanup after our CSE heuristics have run
//
void Cleanup()
{
if (m_addCSEcount > 0)
{
/* We've added new local variables to the lvaTable so note that we need to recreate the sorted table */
m_pCompiler->lvaSortAgain = true;
}
}
};
/*****************************************************************************
*
* Routine for performing the Value Number based CSE using our heuristics
*/
void Compiler::optValnumCSE_Heuristic()
{
#ifdef DEBUG
if (verbose)
{
printf("\n************ Trees at start of optValnumCSE_Heuristic()\n");
fgDumpTrees(fgFirstBB, NULL);
printf("\n");
}
#endif // DEBUG
CSE_Heuristic cse_heuristic(this);
cse_heuristic.Initialize();
cse_heuristic.SortCandidates();
cse_heuristic.ConsiderCandidates();
cse_heuristic.Cleanup();
}
/*****************************************************************************
*
* Routine to unmark any CSEs contained within a tree
* - optionally a 'keepList' vcan be provided to specify a list of trees that will be kept
*
*/
void Compiler::optValnumCSE_UnmarkCSEs(GenTreePtr deadTree, GenTreePtr keepList)
{
assert(optValnumCSE_phase);
// We need to communicate the 'keepList' to optUnmarkCSEs
// as any part of the 'deadTree' tree that is in the keepList is preserved
// and is not deleted and does not have its ref counts decremented
// We communicate this value using the walkData.pCallbackData field
//
fgWalkTreePre(&deadTree, optUnmarkCSEs, (void*)keepList);
}
/*****************************************************************************
*
* Perform common sub-expression elimination.
*/
void Compiler::optOptimizeValnumCSEs()
{
#ifdef DEBUG
if (verbose)
printf("\n*************** In optOptimizeValnumCSEs()\n");
if (optConfigDisableCSE(false))
return; // Disabled by JitNoCSE
#endif
optValnumCSE_phase = true;
/* Initialize the expression tracking logic */
optValnumCSE_Init();
/* Locate interesting expressions and assign indices to them */
if (optValnumCSE_Locate() > 0)
{
optCSECandidateTotal += optCSECandidateCount;
optValnumCSE_InitDataFlow();
optValnumCSE_DataFlow();
optValnumCSE_Availablity();
optValnumCSE_Heuristic();
}
optValnumCSE_phase = false;
}
/*****************************************************************************/
#endif // FEATURE_VALNUM_CSE
/*****************************************************************************/
/*****************************************************************************
*
* The following determines whether the given expression is a worthy CSE
* candidate.
*/
bool Compiler::optIsCSEcandidate(GenTreePtr tree)
{
/* No good if the expression contains side effects or if it was marked as DONT CSE */
if (tree->gtFlags & (GTF_ASG|GTF_DONT_CSE))
{
return false;
}
/* The only reason a TYP_STRUCT tree might occur is as an argument to
GT_ADDR. It will never be actually materialized. So ignore them.
Also TYP_VOIDs */
var_types type = tree->TypeGet();
genTreeOps oper = tree->OperGet();
if (type == TYP_STRUCT || type == TYP_VOID)
return false;
#ifdef _TARGET_X86_
if (type == TYP_FLOAT)
{
// TODO-X86-CQ: Revisit this
// Don't CSE a TYP_FLOAT on x86 as we currently can only enregister doubles
return false;
}
#else
if (oper == GT_CNS_DBL)
{
// TODO-CQ: Revisit this
// Don't try to CSE a GT_CNS_DBL as they can represent both float and doubles
return false;
}
#endif
unsigned cost;
if (compCodeOpt() == SMALL_CODE)
cost = tree->gtCostSz;
else
cost = tree->gtCostEx;
/* Don't bother if the potential savings are very low */
if (cost < MIN_CSE_COST)
{
return false;
}
#if !CSE_CONSTS
/* Don't bother with constants */
if (tree->OperKind() & GTK_CONST)
return false;
#endif
/* Check for some special cases */
switch (oper)
{
case GT_CALL:
// If we have a simple helper call with no other persistent side-effects
// then we allow this tree to be a CSE candidate
//
if (gtTreeHasSideEffects(tree, GTF_PERSISTENT_SIDE_EFFECTS_IN_CSE) == false)
{
return true;
}
else
{
// Calls generally cannot be CSE-ed
return false;
}
case GT_IND:
// TODO-CQ: Review this...
/* We try to cse GT_ARR_ELEM nodes instead of GT_IND(GT_ARR_ELEM).
Doing the first allows cse to also kick in for code like
"GT_IND(GT_ARR_ELEM) = GT_IND(GT_ARR_ELEM) + xyz", whereas doing
the second would not allow it */
return (tree->gtOp.gtOp1->gtOper != GT_ARR_ELEM);
case GT_CNS_INT:
case GT_CNS_LNG:
case GT_CNS_DBL:
case GT_CNS_STR:
return true; // We reach here only when CSE_CONSTS is enabled
case GT_ARR_ELEM:
case GT_ARR_LENGTH:
case GT_CLS_VAR:
case GT_LCL_FLD:
return true;
case GT_LCL_VAR:
return false; // Can't CSE a volatile LCL_VAR
case GT_NEG:
case GT_NOT:
case GT_CAST:
return true; // CSE these Unary Operators
case GT_SUB:
case GT_DIV:
case GT_MOD:
case GT_UDIV:
case GT_UMOD:
case GT_OR:
case GT_AND:
case GT_XOR:
case GT_RSH:
case GT_RSZ:
case GT_ROL:
case GT_ROR:
return true; // CSE these Binary Operators
case GT_ADD: // Check for ADDRMODE flag on these Binary Operators
case GT_MUL:
case GT_LSH:
if ((tree->gtFlags & GTF_ADDRMODE_NO_CSE) != 0)
return false;
case GT_EQ:
case GT_NE:
case GT_LT:
case GT_LE:
case GT_GE:
case GT_GT:
return true; // Also CSE these Comparison Operators
case GT_MATH:
return true; // FP Instrinsics: Round, Sqrt, etc...
case GT_COMMA:
return true; // Allow GT_COMMA nodes to be CSE-ed.
case GT_COLON:
case GT_QMARK:
case GT_NOP:
case GT_RETURN:
return false; // Currently the only special nodes that we hit
// that we know that we don't want to CSE
default:
break; // Any new nodes that we might add later...
}
return false;
}
#ifdef DEBUG
//
// A Debug only method that allows you to control whether the CSE logic is enabled for this method.
//
// If this method returns false then the CSE phase should be performed.
// If the method returns true then the CSE phase should be skipped.
//
bool Compiler::optConfigDisableCSE(bool lexicalCSE)
{
bool enabled = true;
#if VALNUM_CSE_ENABLED
if (lexicalCSE)
return true; // lexical CSE phase is disabled
#else
if (!lexicalCSE)
return true; // valnum CSE phase is disabled
#endif
// Next check if COMPLUS_JitNoCSE is set and applies to this method
//
static ConfigDWORD fJitNoCSE;
unsigned jitNoCSE = fJitNoCSE.val(CLRConfig::INTERNAL_JitNoCSE);
if (jitNoCSE > 0)
{
unsigned methodCount = Compiler::jitTotalMethodCompiled;
if ((jitNoCSE & 0xF000000) == 0xF000000)
{
unsigned methodCountMask = methodCount & 0xFFF;
unsigned bitsZero = (jitNoCSE >> 12) & 0xFFF;
unsigned bitsOne = (jitNoCSE >> 0) & 0xFFF;
if ((( methodCountMask & bitsOne) == bitsOne) &&
((~methodCountMask & bitsZero) == bitsZero) )
{
if (verbose)
printf(" Disabled by JitNoCSE methodCountMask\n");
return true; // The CSE phase for this method is disabled
}
}
else if (jitNoCSE <= (methodCount+1))
{
if (verbose)
printf(" Disabled by JitNoCSE > methodCount\n");
return true; // The CSE phase for this method is disabled
}
}
return false;
}
//
// A Debug only method that allows you to control whether the CSE logic is enabled for
// a particular CSE in a method
//
// If this method returns false then the CSE should be performed.
// If the method returns true then the CSE should be skipped.
//
bool Compiler::optConfigDisableCSE2()
{
static unsigned totalCSEcount = 0;
static ConfigDWORD fNoCSE2;
unsigned jitNoCSE2 = fNoCSE2.val(CLRConfig::INTERNAL_JitNoCSE2);
totalCSEcount++;
if (jitNoCSE2 > 0)
{
if ((jitNoCSE2 & 0xF000000) == 0xF000000)
{
unsigned totalCSEMask = totalCSEcount & 0xFFF;
unsigned bitsZero = (jitNoCSE2 >> 12) & 0xFFF;
unsigned bitsOne = (jitNoCSE2 >> 0) & 0xFFF;
if ((( totalCSEMask & bitsOne) == bitsOne) &&
((~totalCSEMask & bitsZero) == bitsZero) )
{
if (verbose)
printf(" Disabled by jitNoCSE2 Ones/Zeros mask\n");
return true;
}
}
else if ((jitNoCSE2 & 0xF000000) == 0xE000000)
{
unsigned totalCSEMask = totalCSEcount & 0xFFF;
unsigned disableMask = jitNoCSE2 & 0xFFF;
disableMask >>= (totalCSEMask % 12);
if (disableMask & 1)
{
if (verbose)
printf(" Disabled by jitNoCSE2 rotating disable mask\n");
return true;
}
}
else if (jitNoCSE2 <= totalCSEcount)
{
if (verbose)
printf(" Disabled by jitNoCSE2 > totalCSEcount\n");
return true;
}
}
return false;
}
#endif
void Compiler::optOptimizeCSEs()
{
#ifdef DEBUG
if (verbose)
{
printf("\n*************** In optOptimizeCSEs()\n");
printf("Blocks/Trees at start of optOptimizeCSE phase\n");
fgDispBasicBlocks(true);
}
#endif // DEBUG
optCSECandidateCount = 0;
optCSEstart = lvaCount;
#if FEATURE_VALNUM_CSE
INDEBUG(optEnsureClearCSEInfo());
optOptimizeValnumCSEs();
EndPhase(PHASE_OPTIMIZE_VALNUM_CSES);
#endif // FEATURE_VALNUM_CSE
}
/*****************************************************************************
*
* Cleanup after CSE to allow us to run more than once.
*/
void Compiler::optCleanupCSEs()
{
// We must clear the BBF_VISITED and BBF_MARKED flags
//
for (BasicBlock* block = fgFirstBB; block; block = block->bbNext)
{
unsigned blkFlags = block->bbFlags;
// And clear all the "visited" bits on the block
//
block->bbFlags &= ~(BBF_VISITED|BBF_MARKED);
/* Walk the statement trees in this basic block */
GenTreePtr stmt;
// Initialize 'stmt' to the first non-Phi statement
#if JIT_FEATURE_SSA_SKIP_DEFS
stmt = block->FirstNonPhiDef();
#else
stmt = block->bbTreeList;
#endif
for (; stmt; stmt = stmt->gtNext)
{
noway_assert(stmt->gtOper == GT_STMT);
/* We must clear the gtCSEnum field */
for (GenTreePtr tree = stmt->gtStmt.gtStmtExpr; tree; tree = tree->gtPrev)
{
tree->gtCSEnum = NO_CSE;
}
}
}
}
#ifdef DEBUG
/*****************************************************************************
*
* Ensure that all the CSE information in the IR is initialized the way we expect it,
* before running a CSE phase. This is basically an assert that optCleanupCSEs() is not needed.
*/
void Compiler::optEnsureClearCSEInfo()
{
for (BasicBlock* block = fgFirstBB; block; block = block->bbNext)
{
assert((block->bbFlags & (BBF_VISITED|BBF_MARKED)) == 0);
/* Walk the statement trees in this basic block */
GenTreePtr stmt;
// Initialize 'stmt' to the first non-Phi statement
#if JIT_FEATURE_SSA_SKIP_DEFS
stmt = block->FirstNonPhiDef();
#else
stmt = block->bbTreeList;
#endif
for (; stmt; stmt = stmt->gtNext)
{
assert(stmt->gtOper == GT_STMT);
for (GenTreePtr tree = stmt->gtStmt.gtStmtExpr; tree; tree = tree->gtPrev)
{
assert(tree->gtCSEnum == NO_CSE);
}
}
}
}
#endif // DEBUG
/*****************************************************************************/
#endif // FEATURE_ANYCSE
/*****************************************************************************/
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