[x64] Improve key value sign-extension of dehoisted LoadKeyed/StoreKeyed

src/x64/lithium-codegen-x64.cc

Index: src/x64/lithium-codegen-x64.cc
diff --git a/src/x64/lithium-codegen-x64.cc b/src/x64/lithium-codegen-x64.cc
index 72091c3e4d371e6258e83317f2177b306c25cab3..f9ddf21592bca49057a14364d613b5a4f8d5fcd8 100644
--- a/src/x64/lithium-codegen-x64.cc
+++ b/src/x64/lithium-codegen-x64.cc
@@ -273,6 +273,14 @@ void LCodeGen::GenerateOsrPrologue() {
 }
 
 
+void LCodeGen::GenerateBodyInstructionPost(LInstruction* instr) {
+  if (instr->HasResult() && instr->MustSignExtendResult(chunk())) {
+    Register result_reg = ToRegister(instr->result());

[danno, 2014/03/18 08:21:31]

I think this might be a problem for some HValues that don't guarantee their
result is in a register, e.g. HParameters.

[Weiliang, 2014/03/19 08:55:31]

The testcase shows a HChange between HParameters and Load/StoreKeyed to convert
the tagged value to an integer. Sign extension work on the result of HChange
Done.

+    __ movsxlq(result_reg, result_reg);
+  }
+}
+
+
 bool LCodeGen::GenerateJumpTable() {
   Label needs_frame;
   if (jump_table_.length() > 0) {
@@ -2868,19 +2876,6 @@ void LCodeGen::DoAccessArgumentsAt(LAccessArgumentsAt* instr) {
 void LCodeGen::DoLoadKeyedExternalArray(LLoadKeyed* instr) {
   ElementsKind elements_kind = instr->elements_kind();
   LOperand* key = instr->key();
-  if (!key->IsConstantOperand()) {
-    Register key_reg = ToRegister(key);
-    // Even though the HLoad/StoreKeyed (in this case) instructions force
-    // the input representation for the key to be an integer, the input
-    // gets replaced during bound check elimination with the index argument
-    // to the bounds check, which can be tagged, so that case must be
-    // handled here, too.
-    if (instr->hydrogen()->IsDehoisted()) {
-      // Sign extend key because it could be a 32 bit negative value
-      // and the dehoisted address computation happens in 64 bits
-      __ movsxlq(key_reg, key_reg);
-    }
-  }
   int base_offset = instr->is_fixed_typed_array()
     ? FixedTypedArrayBase::kDataOffset - kHeapObjectTag
     : 0;
@@ -2954,19 +2949,6 @@ void LCodeGen::DoLoadKeyedExternalArray(LLoadKeyed* instr) {
 void LCodeGen::DoLoadKeyedFixedDoubleArray(LLoadKeyed* instr) {
   XMMRegister result(ToDoubleRegister(instr->result()));
   LOperand* key = instr->key();
-  if (!key->IsConstantOperand()) {
-    Register key_reg = ToRegister(key);
-    // Even though the HLoad/StoreKeyed instructions force the input
-    // representation for the key to be an integer, the input gets replaced
-    // during bound check elimination with the index argument to the bounds
-    // check, which can be tagged, so that case must be handled here, too.
-    if (instr->hydrogen()->IsDehoisted()) {
-      // Sign extend key because it could be a 32 bit negative value
-      // and the dehoisted address computation happens in 64 bits
-      __ movsxlq(key_reg, key_reg);
-    }
-  }
-
   if (instr->hydrogen()->RequiresHoleCheck()) {
     int offset = FixedDoubleArray::kHeaderSize - kHeapObjectTag +
         sizeof(kHoleNanLower32);
@@ -2994,20 +2976,6 @@ void LCodeGen::DoLoadKeyedFixedArray(LLoadKeyed* instr) {
   HLoadKeyed* hinstr = instr->hydrogen();
   Register result = ToRegister(instr->result());
   LOperand* key = instr->key();
-  if (!key->IsConstantOperand()) {
-    Register key_reg = ToRegister(key);
-    // Even though the HLoad/StoreKeyedFastElement instructions force
-    // the input representation for the key to be an integer, the input
-    // gets replaced during bound check elimination with the index
-    // argument to the bounds check, which can be tagged, so that
-    // case must be handled here, too.
-    if (hinstr->IsDehoisted()) {
-      // Sign extend key because it could be a 32 bit negative value
-      // and the dehoisted address computation happens in 64 bits
-      __ movsxlq(key_reg, key_reg);
-    }
-  }
-
   bool requires_hole_check = hinstr->RequiresHoleCheck();
   int offset = FixedArray::kHeaderSize - kHeapObjectTag;
   Representation representation = hinstr->representation();
@@ -4067,19 +4035,6 @@ void LCodeGen::DoBoundsCheck(LBoundsCheck* instr) {
 void LCodeGen::DoStoreKeyedExternalArray(LStoreKeyed* instr) {
   ElementsKind elements_kind = instr->elements_kind();
   LOperand* key = instr->key();
-  if (!key->IsConstantOperand()) {
-    Register key_reg = ToRegister(key);
-    // Even though the HLoad/StoreKeyedFastElement instructions force
-    // the input representation for the key to be an integer, the input
-    // gets replaced during bound check elimination with the index
-    // argument to the bounds check, which can be tagged, so that case
-    // must be handled here, too.
-    if (instr->hydrogen()->IsDehoisted()) {
-      // Sign extend key because it could be a 32 bit negative value
-      // and the dehoisted address computation happens in 64 bits
-      __ movsxlq(key_reg, key_reg);
-    }
-  }
   int base_offset = instr->is_fixed_typed_array()
     ? FixedTypedArrayBase::kDataOffset - kHeapObjectTag
     : 0;
@@ -4143,20 +4098,6 @@ void LCodeGen::DoStoreKeyedExternalArray(LStoreKeyed* instr) {
 void LCodeGen::DoStoreKeyedFixedDoubleArray(LStoreKeyed* instr) {
   XMMRegister value = ToDoubleRegister(instr->value());
   LOperand* key = instr->key();
-  if (!key->IsConstantOperand()) {
-    Register key_reg = ToRegister(key);
-    // Even though the HLoad/StoreKeyedFastElement instructions force
-    // the input representation for the key to be an integer, the
-    // input gets replaced during bound check elimination with the index
-    // argument to the bounds check, which can be tagged, so that case
-    // must be handled here, too.
-    if (instr->hydrogen()->IsDehoisted()) {
-      // Sign extend key because it could be a 32 bit negative value
-      // and the dehoisted address computation happens in 64 bits
-      __ movsxlq(key_reg, key_reg);
-    }
-  }
-
   if (instr->NeedsCanonicalization()) {
     Label have_value;
 
@@ -4184,20 +4125,6 @@ void LCodeGen::DoStoreKeyedFixedDoubleArray(LStoreKeyed* instr) {
 void LCodeGen::DoStoreKeyedFixedArray(LStoreKeyed* instr) {
   HStoreKeyed* hinstr = instr->hydrogen();
   LOperand* key = instr->key();
-  if (!key->IsConstantOperand()) {
-    Register key_reg = ToRegister(key);
-    // Even though the HLoad/StoreKeyedFastElement instructions force
-    // the input representation for the key to be an integer, the
-    // input gets replaced during bound check elimination with the index
-    // argument to the bounds check, which can be tagged, so that case
-    // must be handled here, too.
-    if (hinstr->IsDehoisted()) {
-      // Sign extend key because it could be a 32 bit negative value
-      // and the dehoisted address computation happens in 64 bits
-      __ movsxlq(key_reg, key_reg);
-    }
-  }
-
   int offset = FixedArray::kHeaderSize - kHeapObjectTag;
   Representation representation = hinstr->value()->representation();