From f163abbd16d35032e4450a09c548cb804cf36a85 Mon Sep 17 00:00:00 2001
From: Andy Ayers <andya@microsoft.com>
Date: Thu, 20 Jun 2019 12:04:54 -0700
Subject: JIT: use register indirect for indirect jumps (#25251)

If we are jumping to another method via an indirection cell, the cell address
may be too far from the jump to address via a RIP-relative indirection. So
instead, load the target address into RAX and jump register indirect.

Fixes #22342.
---
 src/jit/codegencommon.cpp | 28 ++++++++++++++++++++++------
 src/jit/emitxarch.cpp     |  8 ++++----
 2 files changed, 26 insertions(+), 10 deletions(-)

diff --git a/src/jit/codegencommon.cpp b/src/jit/codegencommon.cpp
index bb81361d9b..34be5f7de7 100644
--- a/src/jit/codegencommon.cpp
+++ b/src/jit/codegencommon.cpp
@@ -8905,24 +8905,40 @@ void CodeGen::genFnEpilog(BasicBlock* block)
                 NO_WAY("Unsupported JMP indirection");
             }
 
-            const emitter::EmitCallType callType =
-                (addrInfo.accessType == IAT_VALUE) ? emitter::EC_FUNC_TOKEN : emitter::EC_FUNC_TOKEN_INDIR;
+            // If we have IAT_PVALUE, jump via register indirect, as sometimes the
+            // indirection cell can't be reached by the jump.
 
-            // Simply emit a jump to the methodHnd. This is similar to a call so we can use
-            // the same descriptor with some minor adjustments.
+            emitter::EmitCallType callType;
+            void*                 addr;
+            regNumber             indCallReg;
+
+            if (addrInfo.accessType == IAT_PVALUE)
+            {
+                callType   = emitter::EC_INDIR_ARD;
+                indCallReg = REG_RAX;
+                addr       = nullptr;
+                instGen_Set_Reg_To_Imm(EA_HANDLE_CNS_RELOC, indCallReg, (ssize_t)addrInfo.addr);
+                regSet.verifyRegUsed(indCallReg);
+            }
+            else
+            {
+                callType   = emitter::EC_FUNC_TOKEN;
+                addr       = addrInfo.addr;
+                indCallReg = REG_NA;
+            }
 
             // clang-format off
             getEmitter()->emitIns_Call(callType,
                                        methHnd,
                                        INDEBUG_LDISASM_COMMA(nullptr)
-                                       addrInfo.addr,
+                                       addr,
                                        0,                                                      // argSize
                                        EA_UNKNOWN                                              // retSize
                                        MULTIREG_HAS_SECOND_GC_RET_ONLY_ARG(EA_UNKNOWN),        // secondRetSize
                                        gcInfo.gcVarPtrSetCur,
                                        gcInfo.gcRegGCrefSetCur,
                                        gcInfo.gcRegByrefSetCur,
-                                       BAD_IL_OFFSET, REG_NA, REG_NA, 0, 0,  /* iloffset, ireg, xreg, xmul, disp */
+                                       BAD_IL_OFFSET, indCallReg, REG_NA, 0, 0,  /* iloffset, ireg, xreg, xmul, disp */
                                        true /* isJump */
             );
             // clang-format on
diff --git a/src/jit/emitxarch.cpp b/src/jit/emitxarch.cpp
index 157a57e432..1f529ff694 100644
--- a/src/jit/emitxarch.cpp
+++ b/src/jit/emitxarch.cpp
@@ -7057,7 +7057,7 @@ void emitter::emitIns_Call(EmitCallType          callType,
 
     if (isJump)
     {
-        assert(callType == EC_FUNC_TOKEN || callType == EC_FUNC_TOKEN_INDIR);
+        assert(callType == EC_FUNC_TOKEN || callType == EC_INDIR_ARD);
         if (callType == EC_FUNC_TOKEN)
         {
             ins = INS_l_jmp;
@@ -7853,9 +7853,9 @@ void emitter::emitDispAddrMode(instrDesc* id, bool noDetail)
                 printf("reloc ");
             }
             printf("J_M%03u_DS%02u", Compiler::s_compMethodsCount, id->idDebugOnlyInfo()->idMemCookie);
-        }
 
-        disp -= id->idDebugOnlyInfo()->idMemCookie;
+            disp -= id->idDebugOnlyInfo()->idMemCookie;
+        }
     }
 
     bool frameRef = false;
@@ -8351,7 +8351,7 @@ void emitter::emitDispIns(
             emitDispAddrMode(id, isNew);
             emitDispShift(ins);
 
-            if (ins == INS_call)
+            if ((ins == INS_call) || (ins == INS_i_jmp))
             {
                 assert(id->idInsFmt() == IF_ARD);
 
-- 
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