Implement HChange support for Smis and use it in Load/StoreNameField

src/ia32/lithium-ia32.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
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 // modification, are permitted provided that the following conditions are
 // met:
 //
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@@ skipping 1890 matching lines @@
   // All HForceRepresentation instructions should be eliminated in the
   // representation change phase of Hydrogen.
   UNREACHABLE();
   return NULL;
 }
 
 
 LInstruction* LChunkBuilder::DoChange(HChange* instr) {
   Representation from = instr->from();
   Representation to = instr->to();
+  if (from.IsSmi()) {
+    if (to.IsTagged()) {
+      LOperand* value = UseRegister(instr->value());
+      return DefineSameAsFirst(new(zone()) LDummyUse(value));
+    }
+    from = Representation::Tagged();
+  }
   // Only mark conversions that might need to allocate as calling rather than
   // all changes. This makes simple, non-allocating conversion not have to force
   // building a stack frame.
   if (from.IsTagged()) {
     if (to.IsDouble()) {
       info()->MarkAsDeferredCalling();
       LOperand* value = UseRegister(instr->value());
       // Temp register only necessary for minus zero check.
       LOperand* temp = instr->deoptimize_on_minus_zero()
                        ? TempRegister()
                        : NULL;
       LNumberUntagD* res = new(zone()) LNumberUntagD(value, temp);
       if (CpuFeatures::IsSafeForSnapshot(SSE2)) {
         return AssignEnvironment(DefineAsRegister(res));
       } else {
         return AssignEnvironment(DefineX87TOS(res));
       }
+    } else if (to.IsSmi()) {
+      HValue* val = instr->value();
+      LOperand* value = UseRegisterAtStart(val);
+      return AssignEnvironment(
+          DefineSameAsFirst(new(zone()) LCheckSmi(value)));
     } else {
       ASSERT(to.IsInteger32());
       if (instr->value()->type().IsSmi()) {
         LOperand* value = UseRegister(instr->value());
         return DefineSameAsFirst(new(zone()) LSmiUntag(value, false));
       } else {
         bool truncating = instr->CanTruncateToInt32();
         if (CpuFeatures::IsSafeForSnapshot(SSE2)) {
           LOperand* value = UseRegister(instr->value());
           LOperand* xmm_temp =
@@ skipping 16 matching lines @@
       info()->MarkAsDeferredCalling();
       LOperand* value = CpuFeatures::IsSupported(SSE2)
           ? UseRegisterAtStart(instr->value())
           : UseAtStart(instr->value());
       LOperand* temp = FLAG_inline_new ? TempRegister() : NULL;
 
       // Make sure that temp and result_temp are different registers.
       LUnallocated* result_temp = TempRegister();
       LNumberTagD* result = new(zone()) LNumberTagD(value, temp);
       return AssignPointerMap(Define(result, result_temp));
+    } else if (to.IsSmi()) {
+      LOperand* value = UseRegister(instr->value());
+      return AssignEnvironment(
+          DefineAsRegister(new(zone()) LDoubleToSmi(value)));
     } else {
       ASSERT(to.IsInteger32());
       bool truncating = instr->CanTruncateToInt32();
       bool needs_temp = truncating && !CpuFeatures::IsSupported(SSE3);
       LOperand* value = needs_temp ?
           UseTempRegister(instr->value()) : UseRegister(instr->value());
       LOperand* temp = needs_temp ? TempRegister() : NULL;
       return AssignEnvironment(
           DefineAsRegister(new(zone()) LDoubleToI(value, temp)));
     }
   } else if (from.IsInteger32()) {
     info()->MarkAsDeferredCalling();
     if (to.IsTagged()) {
       HValue* val = instr->value();
       LOperand* value = UseRegister(val);
       if (val->HasRange() && val->range()->IsInSmiRange()) {
         return DefineSameAsFirst(new(zone()) LSmiTag(value));
       } else if (val->CheckFlag(HInstruction::kUint32)) {
         LNumberTagU* result = new(zone()) LNumberTagU(value);
         return AssignEnvironment(AssignPointerMap(DefineSameAsFirst(result)));
       } else {
         LNumberTagI* result = new(zone()) LNumberTagI(value);
         return AssignEnvironment(AssignPointerMap(DefineSameAsFirst(result)));
       }
+    } else if (to.IsSmi()) {
+      HValue* val = instr->value();
+      LOperand* value = UseRegister(val);
+      LInstruction* result =
+          DefineSameAsFirst(new(zone()) LInteger32ToSmi(value));
+      if (val->HasRange() && val->range()->IsInSmiRange()) {
+        return result;
+      }
+      return AssignEnvironment(result);
     } else {
       ASSERT(to.IsDouble());
       if (instr->value()->CheckFlag(HInstruction::kUint32)) {
         LOperand* temp = FixedTemp(xmm1);
         return DefineAsRegister(
             new(zone()) LUint32ToDouble(UseRegister(instr->value()), temp));
       } else {
         return DefineAsRegister(
             new(zone()) LInteger32ToDouble(Use(instr->value())));
       }
@@ skipping 20 matching lines @@
 
 LInstruction* LChunkBuilder::DoCheckPrototypeMaps(HCheckPrototypeMaps* instr) {
   LUnallocated* temp = TempRegister();
   LCheckPrototypeMaps* result = new(zone()) LCheckPrototypeMaps(temp);
   return AssignEnvironment(result);
 }
 
 
 LInstruction* LChunkBuilder::DoCheckSmi(HCheckSmi* instr) {
   LOperand* value = UseAtStart(instr->value());
-  return AssignEnvironment(new(zone()) LCheckSmi(value));
+  return AssignEnvironment(DefineSameAsFirst(new(zone()) LCheckSmi(value)));

[Jakob Kummerow, 2013/05/23 12:49:31]

This change causes unnecessary register pressure, because it makes the register
allocater think that LCheckSmi overwrites its input register.

Also, it is missing from the ARM port of this patch, making --trace-hydrogen
segfault on ARM.

I think we should introduce a separate LCheckSmiAndReturn instruction for the
use case in DoChange() above, and keep the original LCheckSmi unmodified (i.e.
not returning a value).

 }
 
 
 LInstruction* LChunkBuilder::DoCheckSmiOrInt32(HCheckSmiOrInt32* instr) {
   LOperand* value = UseAtStart(instr->value());
-  return AssignEnvironment(new(zone()) LCheckSmi(value));
+  return AssignEnvironment(DefineSameAsFirst(new(zone()) LCheckSmi(value)));
 }
 
 
 LInstruction* LChunkBuilder::DoCheckFunction(HCheckFunction* instr) {
   // If the target is in new space, we'll emit a global cell compare and so
   // want the value in a register.  If the target gets promoted before we
   // emit code, we will still get the register but will do an immediate
   // compare instead of the cell compare.  This is safe.
   LOperand* value = instr->target_in_new_space()
       ? UseRegisterAtStart(instr->value()) : UseAtStart(instr->value());
@@ skipping 714 matching lines @@
 LInstruction* LChunkBuilder::DoLoadFieldByIndex(HLoadFieldByIndex* instr) {
   LOperand* object = UseRegister(instr->object());
   LOperand* index = UseTempRegister(instr->index());
   return DefineSameAsFirst(new(zone()) LLoadFieldByIndex(object, index));
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32