Add compact entry points for ARM (#11109)

4 files changed, 100 insertions, 1 deletions

diff --git a/src/vm/arm/asmhelpers.S b/src/vm/arm/asmhelpers.S
index 04d7527180..36933f5ea6 100644
--- a/src/vm/arm/asmhelpers.S
+++ b/src/vm/arm/asmhelpers.S
@@ -509,6 +509,24 @@ LOCAL_LABEL(UM2MThunk_WrapperHelper_ArgumentsSetup):
         NESTED_END ThePreStub, _TEXT
 
 // ------------------------------------------------------------------
+        NESTED_ENTRY ThePreStubCompactARM, _TEXT, NoHandler
+
+        // r12 - address of compact entry point + PC_REG_RELATIVE_OFFSET
+
+        PROLOG_WITH_TRANSITION_BLOCK
+
+        mov         r0, r12
+
+        bl          C_FUNC(PreStubGetMethodDescForCompactEntryPoint)
+
+        mov         r12, r0                                          // pMethodDesc
+
+        EPILOG_WITH_TRANSITION_BLOCK_TAILCALL
+
+        b           C_FUNC(ThePreStub)
+
+        NESTED_END ThePreStubCompactARM, _TEXT
+// ------------------------------------------------------------------
 // This method does nothing. It's just a fixed function for the debugger to put a breakpoint on.
         LEAF_ENTRY ThePreStubPatch, _TEXT
         nop
diff --git a/src/vm/arm/asmhelpers.asm b/src/vm/arm/asmhelpers.asm
index 542bdc65cc..e5fd41a513 100644
--- a/src/vm/arm/asmhelpers.asm
+++ b/src/vm/arm/asmhelpers.asm
@@ -24,6 +24,7 @@
     IMPORT UMThunkStubRareDisableWorker
     IMPORT UM2MDoADCallBack
     IMPORT PreStubWorker
+    IMPORT PreStubGetMethodDescForCompactEntryPoint
     IMPORT NDirectImportWorker
     IMPORT ObjIsInstanceOfNoGC
     IMPORT ArrayStoreCheck
@@ -571,6 +572,26 @@ UM2MThunk_WrapperHelper_ArgumentsSetup
         NESTED_END
 
 ; ------------------------------------------------------------------
+
+        NESTED_ENTRY ThePreStubCompactARM
+
+        ; r12 - address of compact entry point + PC_REG_RELATIVE_OFFSET
+
+        PROLOG_WITH_TRANSITION_BLOCK
+
+        mov         r0, r12
+
+        bl          PreStubGetMethodDescForCompactEntryPoint
+
+        mov         r12, r0                                  ; pMethodDesc
+
+        EPILOG_WITH_TRANSITION_BLOCK_TAILCALL
+
+        b          ThePreStub
+
+        NESTED_END
+
+; ------------------------------------------------------------------
 ; This method does nothing. It's just a fixed function for the debugger to put a breakpoint on.
         LEAF_ENTRY ThePreStubPatch
         nop
diff --git a/src/vm/arm/cgencpu.h b/src/vm/arm/cgencpu.h
index 34af8187b2..181d5f10eb 100644
--- a/src/vm/arm/cgencpu.h
+++ b/src/vm/arm/cgencpu.h
@@ -57,7 +57,7 @@ EXTERN_C void checkStack(void);
 #define JUMP_ALLOCATE_SIZE                      8   // # bytes to allocate for a jump instruction
 #define BACK_TO_BACK_JUMP_ALLOCATE_SIZE         8   // # bytes to allocate for a back to back jump instruction
 
-//#define HAS_COMPACT_ENTRYPOINTS                 1
+#define HAS_COMPACT_ENTRYPOINTS                 1
 
 #define HAS_NDIRECT_IMPORT_PRECODE              1
 
@@ -90,6 +90,12 @@ EXTERN_C void setFPReturn(int fpSize, INT64 retVal);
 // this is the offset by which it should be decremented to arrive at the callsite.
 #define STACKWALK_CONTROLPC_ADJUST_OFFSET 2
 
+// Max offset for unconditional thumb branch
+#define MAX_OFFSET_UNCONDITIONAL_BRANCH_THUMB 2048
+
+// Offset of pc register
+#define PC_REG_RELATIVE_OFFSET 4
+
 //=======================================================================
 // IMPORTANT: This value is used to figure out how much to allocate
 // for a fixed array of FieldMarshaler's. That means it must be at least
@@ -236,6 +242,53 @@ void emitCOMStubCall (ComCallMethodDesc *pCOMMethod, PCODE target);
 #endif // FEATURE_COMINTEROP
 
 //------------------------------------------------------------------------
+inline void emitUnconditionalBranchThumb(LPBYTE pBuffer, int16_t offset)
+{
+    LIMITED_METHOD_CONTRACT;
+
+    uint16_t *pInstr = (uint16_t *) pBuffer;
+
+    // offset from -2KB to +2KB
+    _ASSERTE (offset >= - MAX_OFFSET_UNCONDITIONAL_BRANCH_THUMB && offset < MAX_OFFSET_UNCONDITIONAL_BRANCH_THUMB);
+
+    if (offset >= 0)
+    {
+        offset = offset >> 1;
+    }
+    else
+    {
+        offset = ((MAX_OFFSET_UNCONDITIONAL_BRANCH_THUMB + offset) >> 1) | 0x400;
+    }
+
+    *pInstr = 0xE000 | offset;
+}
+
+//------------------------------------------------------------------------
+inline int16_t decodeUnconditionalBranchThumb(LPBYTE pBuffer)
+{
+    LIMITED_METHOD_CONTRACT;
+
+    uint16_t *pInstr = (uint16_t *) pBuffer;
+
+    int16_t offset = (~0xE000) & (*pInstr);
+
+    if ((offset & 0x400) == 0)
+    {
+        offset = offset << 1;
+    }
+    else
+    {
+        offset = (~0x400) & offset;
+        offset = (offset << 1) - MAX_OFFSET_UNCONDITIONAL_BRANCH_THUMB;
+    }
+
+    // offset from -2KB to +2KB
+    _ASSERTE (offset >= - MAX_OFFSET_UNCONDITIONAL_BRANCH_THUMB && offset < MAX_OFFSET_UNCONDITIONAL_BRANCH_THUMB);
+
+    return offset;
+}
+
+//------------------------------------------------------------------------
 inline void emitJump(LPBYTE pBuffer, LPVOID target)
 {
     LIMITED_METHOD_CONTRACT;
diff --git a/src/vm/arm/stubs.cpp b/src/vm/arm/stubs.cpp
index f1ba278ada..3088761f0b 100644
--- a/src/vm/arm/stubs.cpp
+++ b/src/vm/arm/stubs.cpp
@@ -1333,6 +1333,13 @@ BOOL DoesSlotCallPrestub(PCODE pCode)
 {
     PTR_WORD pInstr = dac_cast<PTR_WORD>(PCODEToPINSTR(pCode));
 
+#ifdef HAS_COMPACT_ENTRYPOINTS
+    if (MethodDescChunk::GetMethodDescFromCompactEntryPoint(pCode, TRUE) != NULL)
+    {
+        return TRUE;
+    }
+#endif // HAS_COMPACT_ENTRYPOINTS
+
     // FixupPrecode
     if (pInstr[0] == 0x46fc && // // mov r12, pc
         pInstr[1] == 0xf8df &&