Improve constant element index access code generation

R=jkummerow@chromium.org

Review URL: https://chromiumcodereview.appspot.com/10831049

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@12232 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/arm/lithium-arm.cc

@@ -1546,7 +1546,7 @@ LInstruction* LChunkBuilder::DoDateField(HDateField* instr) {
 
 
 LInstruction* LChunkBuilder::DoBoundsCheck(HBoundsCheck* instr) {
-  LOperand* value = UseRegisterAtStart(instr->index());
+  LOperand* value = UseRegisterOrConstantAtStart(instr->index());
   LOperand* length = UseRegister(instr->length());
   return AssignEnvironment(new(zone()) LBoundsCheck(value, length));
 }
@@ -1838,7 +1838,7 @@ LInstruction* LChunkBuilder::DoLoadKeyedFastElement(
   ASSERT(instr->key()->representation().IsInteger32() ||
          instr->key()->representation().IsTagged());
   LOperand* obj = UseRegisterAtStart(instr->object());
-  LOperand* key = UseRegisterAtStart(instr->key());
+  LOperand* key = UseRegisterOrConstantAtStart(instr->key());
   LLoadKeyedFastElement* result = new(zone()) LLoadKeyedFastElement(obj, key);
   if (instr->RequiresHoleCheck()) AssignEnvironment(result);
   return DefineAsRegister(result);

src/arm/lithium-codegen-arm.cc

@@ -2779,20 +2779,31 @@ void LCodeGen::DoAccessArgumentsAt(LAccessArgumentsAt* instr) {
 
 void LCodeGen::DoLoadKeyedFastElement(LLoadKeyedFastElement* instr) {
   Register elements = ToRegister(instr->elements());
-  Register key = EmitLoadRegister(instr->key(), scratch0());
   Register result = ToRegister(instr->result());
   Register scratch = scratch0();
 
-  // Load the result.
-  if (instr->hydrogen()->key()->representation().IsTagged()) {
-    __ add(scratch, elements,
-           Operand(key, LSL, kPointerSizeLog2 - kSmiTagSize));
+  if (instr->key()->IsConstantOperand()) {
+    LConstantOperand* const_operand = LConstantOperand::cast(instr->key());
+    int offset =
+        (ToInteger32(const_operand) + instr->additional_index()) * kPointerSize
+        + FixedArray::kHeaderSize;
+    __ ldr(result, FieldMemOperand(elements, offset));
   } else {
-    __ add(scratch, elements, Operand(key, LSL, kPointerSizeLog2));
+    Register key = EmitLoadRegister(instr->key(), scratch0());
+    // Even though the HLoadKeyedFastElement instruction forces 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()->key()->representation().IsTagged()) {
+      __ add(scratch, elements,
+             Operand(key, LSL, kPointerSizeLog2 - kSmiTagSize));
+    } else {
+      __ add(scratch, elements, Operand(key, LSL, kPointerSizeLog2));
+    }
+    uint32_t offset = FixedArray::kHeaderSize +
+        (instr->additional_index() << kPointerSizeLog2);
+    __ ldr(result, FieldMemOperand(scratch, offset));
   }
-  uint32_t offset = FixedArray::kHeaderSize +
-                    (instr->additional_index() << kPointerSizeLog2);
-  __ ldr(result, FieldMemOperand(scratch, offset));
 
   // Check for the hole value.
   if (instr->hydrogen()->RequiresHoleCheck()) {
@@ -3817,7 +3828,18 @@ void LCodeGen::DoStoreNamedGeneric(LStoreNamedGeneric* instr) {
 
 
 void LCodeGen::DoBoundsCheck(LBoundsCheck* instr) {
-  __ cmp(ToRegister(instr->index()), ToRegister(instr->length()));
+  if (instr->index()->IsConstantOperand()) {
+    int constant_index =
+        ToInteger32(LConstantOperand::cast(instr->index()));
+    if (instr->hydrogen()->length()->representation().IsTagged()) {
+      __ mov(ip, Operand(Smi::FromInt(constant_index)));
+    } else {
+      __ mov(ip, Operand(constant_index));
+    }
+    __ cmp(ip, ToRegister(instr->length()));
+  } else {
+    __ cmp(ToRegister(instr->index()), ToRegister(instr->length()));
+  }
   DeoptimizeIf(hs, instr->environment());
 }
 
@@ -3837,18 +3859,19 @@ void LCodeGen::DoStoreKeyedFastElement(LStoreKeyedFastElement* instr) {
         + FixedArray::kHeaderSize;
     __ str(value, FieldMemOperand(elements, offset));
   } else {
+    // Even though the HLoadKeyedFastElement instruction forces 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()->key()->representation().IsTagged()) {
       __ add(scratch, elements,
              Operand(key, LSL, kPointerSizeLog2 - kSmiTagSize));
     } else {
       __ add(scratch, elements, Operand(key, LSL, kPointerSizeLog2));
     }
-    if (instr->additional_index() != 0) {
-      __ add(scratch,
-             scratch,
-             Operand(instr->additional_index() << kPointerSizeLog2));
-    }
-    __ str(value, FieldMemOperand(scratch, FixedArray::kHeaderSize));
+    uint32_t offset = FixedArray::kHeaderSize +
+        (instr->additional_index() << kPointerSizeLog2);
+    __ str(value, FieldMemOperand(scratch, offset));
   }
 
   if (instr->hydrogen()->NeedsWriteBarrier()) {

src/hydrogen-instructions.h

@@ -2776,13 +2776,25 @@ class HBoundsCheck: public HTemplateInstruction<2> {
   }
 
   virtual Representation RequiredInputRepresentation(int arg_index) {
-    if (index()->representation().IsTagged() &&
-        !index()->IsConstant() &&
-        key_mode_ == ALLOW_SMI_KEY) {
-      return Representation::Tagged();
-    } else {
+    if (key_mode_ == DONT_ALLOW_SMI_KEY ||
+        !length()->representation().IsTagged()) {
       return Representation::Integer32();
     }
+    // If the index is tagged and isn't constant, then allow the length
+    // to be tagged, since it is usually already tagged from loading it out of
+    // the length field of a JSArray. This allows for direct comparison without
+    // untagging.
+    if (index()->representation().IsTagged() && !index()->IsConstant()) {
+      return Representation::Tagged();
+    }
+    // Also allow the length to be tagged if the index is constant, because
+    // it can be tagged to allow direct comparison.
+    if (index()->IsConstant() &&
+        index()->representation().IsInteger32() &&
+        arg_index == 1) {
+      return Representation::Tagged();
+    }
+    return Representation::Integer32();
   }
 
   virtual void PrintDataTo(StringStream* stream);

src/hydrogen.cc

@@ -5900,7 +5900,8 @@ HInstruction* HGraphBuilder::BuildUncheckedMonomorphicElementAccess(
   } else {
     length = AddInstruction(new(zone()) HFixedArrayBaseLength(elements));
   }
-  checked_key = AddInstruction(new(zone()) HBoundsCheck(key, length));
+  checked_key = AddInstruction(new(zone()) HBoundsCheck(key, length,
+                                                        ALLOW_SMI_KEY));
   return BuildFastElementAccess(elements, checked_key, val, mapcheck,
                                 map->elements_kind(), is_store);
 }

src/ia32/lithium-codegen-ia32.cc

@@ -2705,6 +2705,10 @@ Operand LCodeGen::BuildFastArrayOperand(
     uint32_t additional_index) {
   Register elements_pointer_reg = ToRegister(elements_pointer);
   int shift_size = ElementsKindToShiftSize(elements_kind);
+  // 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 (key_representation.IsTagged() && (shift_size >= 1)) {
     shift_size -= kSmiTagSize;
   }
@@ -3672,8 +3676,14 @@ void LCodeGen::DoStoreNamedGeneric(LStoreNamedGeneric* instr) {
 
 void LCodeGen::DoBoundsCheck(LBoundsCheck* instr) {
   if (instr->index()->IsConstantOperand()) {
-    __ cmp(ToOperand(instr->length()),
-           Immediate(ToInteger32(LConstantOperand::cast(instr->index()))));
+    int constant_index =
+        ToInteger32(LConstantOperand::cast(instr->index()));
+    if (instr->hydrogen()->length()->representation().IsTagged()) {
+      __ cmp(ToOperand(instr->length()),
+             Immediate(Smi::FromInt(constant_index)));
+    } else {
+      __ cmp(ToOperand(instr->length()), Immediate(constant_index));
+    }
     DeoptimizeIf(below_equal, instr->environment());
   } else {
     __ cmp(ToRegister(instr->index()), ToOperand(instr->length()));

src/x64/lithium-codegen-x64.cc

@@ -2506,6 +2506,10 @@ void LCodeGen::DoLoadKeyedFastElement(LLoadKeyedFastElement* instr) {
   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()->key()->representation().IsTagged()) {
       __ SmiToInteger64(key_reg, key_reg);
     } else if (instr->hydrogen()->IsDehoisted()) {
@@ -2542,6 +2546,10 @@ void LCodeGen::DoLoadKeyedFastDoubleElement(
   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()->key()->representation().IsTagged()) {
       __ SmiToInteger64(key_reg, key_reg);
     } else if (instr->hydrogen()->IsDehoisted()) {
@@ -2606,6 +2614,10 @@ void LCodeGen::DoLoadKeyedSpecializedArrayElement(
   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()->key()->representation().IsTagged()) {
       __ SmiToInteger64(key_reg, key_reg);
     } else if (instr->hydrogen()->IsDehoisted()) {
@@ -3549,6 +3561,10 @@ void LCodeGen::DoStoreKeyedSpecializedArrayElement(
   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()->key()->representation().IsTagged()) {
       __ SmiToInteger64(key_reg, key_reg);
     } else if (instr->hydrogen()->IsDehoisted()) {
@@ -3611,8 +3627,13 @@ void LCodeGen::DoBoundsCheck(LBoundsCheck* instr) {
       __ AbortIfNotZeroExtended(reg);
     }
     if (instr->index()->IsConstantOperand()) {
-      __ cmpq(reg,
-              Immediate(ToInteger32(LConstantOperand::cast(instr->index()))));
+      int constant_index =
+          ToInteger32(LConstantOperand::cast(instr->index()));
+      if (instr->hydrogen()->length()->representation().IsTagged()) {
+        __ Cmp(reg, Smi::FromInt(constant_index));
+      } else {
+        __ cmpq(reg, Immediate(constant_index));
+      }
     } else {
       Register reg2 = ToRegister(instr->index());
       if (FLAG_debug_code &&
@@ -3639,6 +3660,10 @@ void LCodeGen::DoStoreKeyedFastElement(LStoreKeyedFastElement* instr) {
   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()->key()->representation().IsTagged()) {
       __ SmiToInteger64(key_reg, key_reg);
     } else if (instr->hydrogen()->IsDehoisted()) {
@@ -3682,6 +3707,10 @@ void LCodeGen::DoStoreKeyedFastDoubleElement(
   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()->key()->representation().IsTagged()) {
       __ SmiToInteger64(key_reg, key_reg);
     } else if (instr->hydrogen()->IsDehoisted()) {