Changeset 134332 in webkit for trunk/Source/JavaScriptCore/assembler/X86Assembler.h

Timestamp:

Nov 12, 2012, 5:55:42 PM (13 years ago)

Author:

[email protected]

Message:

Patching of jumps to stubs should use jump replacement rather than branch destination overwrite
​https://bugs.webkit.org/show_bug.cgi?id=101909

Reviewed by Geoffrey Garen.

This saves a few instructions in inline cases, on those architectures where it is
easy to figure out where to put the jump replacement. Sub-1% speed-up across the
board.

• assembler/MacroAssemblerARMv7.h:

(MacroAssemblerARMv7):
(JSC::MacroAssemblerARMv7::canJumpReplacePatchableBranchPtrWithPatch):
(JSC::MacroAssemblerARMv7::startOfPatchableBranchPtrWithPatch):
(JSC::MacroAssemblerARMv7::revertJumpReplacementToPatchableBranchPtrWithPatch):

• assembler/MacroAssemblerX86.h:

(JSC::MacroAssemblerX86::canJumpReplacePatchableBranchPtrWithPatch):
(MacroAssemblerX86):
(JSC::MacroAssemblerX86::startOfPatchableBranchPtrWithPatch):
(JSC::MacroAssemblerX86::revertJumpReplacementToPatchableBranchPtrWithPatch):

• assembler/MacroAssemblerX86_64.h:

(JSC::MacroAssemblerX86_64::canJumpReplacePatchableBranchPtrWithPatch):
(MacroAssemblerX86_64):
(JSC::MacroAssemblerX86_64::startOfPatchableBranchPtrWithPatch):
(JSC::MacroAssemblerX86_64::revertJumpReplacementToPatchableBranchPtrWithPatch):

• assembler/RepatchBuffer.h:

(JSC::RepatchBuffer::startOfPatchableBranchPtrWithPatch):
(RepatchBuffer):
(JSC::RepatchBuffer::replaceWithJump):
(JSC::RepatchBuffer::revertJumpReplacementToPatchableBranchPtrWithPatch):

• assembler/X86Assembler.h:

(X86Assembler):
(JSC::X86Assembler::revertJumpTo_movq_i64r):
(JSC::X86Assembler::revertJumpTo_cmpl_im_force32):
(X86InstructionFormatter):

• bytecode/StructureStubInfo.h:
• dfg/DFGRepatch.cpp:

(JSC::DFG::replaceWithJump):
(DFG):
(JSC::DFG::tryCacheGetByID):
(JSC::DFG::tryBuildGetByIDList):
(JSC::DFG::tryBuildGetByIDProtoList):
(JSC::DFG::tryCachePutByID):
(JSC::DFG::dfgResetGetByID):
(JSC::DFG::dfgResetPutByID):

File:

• trunk/Source/JavaScriptCore/assembler/X86Assembler.h (modified) (3 diffs)

trunk/Source/JavaScriptCore/assembler/X86Assembler.h

@@ -1884 +1884 @@
     }
     
+#if CPU(X86_64)
+    static void revertJumpTo_movq_i64r(void* instructionStart, int64_t imm, RegisterID dst)
+    {
+        const int rexBytes = 1;
+        const int opcodeBytes = 1;
+        ASSERT(rexBytes + opcodeBytes <= maxJumpReplacementSize());
+        uint8_t* ptr = reinterpret_cast<uint8_t*>(instructionStart);
+        ptr[0] = PRE_REX | (1 << 3) | (dst >> 3);
+        ptr[1] = OP_MOV_EAXIv | (dst & 7);
+        
+        union {
+            uint64_t asWord;
+            uint8_t asBytes[8];
+        } u;
+        u.asWord = imm;
+        for (unsigned i = rexBytes + opcodeBytes; i < static_cast<unsigned>(maxJumpReplacementSize()); ++i)
+            ptr[i] = u.asBytes[i - rexBytes - opcodeBytes];
+    }
+#endif
+    
+    static void revertJumpTo_cmpl_im_force32(void* instructionStart, int32_t imm, int offset, RegisterID dst)
+    {
+        ASSERT_UNUSED(offset, !offset);
+        const int opcodeBytes = 1;
+        const int modRMBytes = 1;
+        ASSERT(opcodeBytes + modRMBytes <= maxJumpReplacementSize());
+        uint8_t* ptr = reinterpret_cast<uint8_t*>(instructionStart);
+        ptr[0] = OP_GROUP1_EvIz;
+        ptr[1] = (X86InstructionFormatter::ModRmMemoryNoDisp << 6) | (GROUP1_OP_CMP << 3) | dst;
+        union {
+            uint32_t asWord;
+            uint8_t asBytes[4];
+        } u;
+        u.asWord = imm;
+        for (unsigned i = opcodeBytes + modRMBytes; i < static_cast<unsigned>(maxJumpReplacementSize()); ++i)
+            ptr[i] = u.asBytes[i - opcodeBytes - modRMBytes];
+    }
+    
     static void replaceWithLoad(void* instructionStart)
     {
@@ -1982 +2020 @@
 
     public:
+
+        enum ModRmMode {
+            ModRmMemoryNoDisp,
+            ModRmMemoryDisp8,
+            ModRmMemoryDisp32,
+            ModRmRegister,
+        };
 
         // Legacy prefix bytes:
@@ -2353 +2398 @@
 #endif
 
-        enum ModRmMode {
-            ModRmMemoryNoDisp,
-            ModRmMemoryDisp8,
-            ModRmMemoryDisp32,
-            ModRmRegister,
-        };
-
         void putModRm(ModRmMode mode, int reg, RegisterID rm)
         {