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

src/x64/lithium-gap-resolver-x64.cc

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@@ skipping 180 matching lines @@
       __ movp(dst, kScratchRegister);
     }
 
   } else if (source->IsConstantOperand()) {
     LConstantOperand* constant_source = LConstantOperand::cast(source);
     if (destination->IsRegister()) {
       Register dst = cgen_->ToRegister(destination);
       if (cgen_->IsSmiConstant(constant_source)) {
         __ Move(dst, cgen_->ToSmi(constant_source));
       } else if (cgen_->IsInteger32Constant(constant_source)) {
-        __ Set(dst, static_cast<uint32_t>(cgen_->ToInteger32(constant_source)));
+        int32_t constant = cgen_->ToInteger32(constant_source);
+        if (cgen_->IsDehoistedKeyConstant(constant_source)) {
+          __ Set(dst, constant);
+        } else {
+          __ Set(dst, static_cast<uint32_t>(constant));
+        }
       } else {
         __ Move(dst, cgen_->ToHandle(constant_source));
       }
     } else if (destination->IsDoubleRegister()) {
       double v = cgen_->ToDouble(constant_source);
       uint64_t int_val = BitCast<uint64_t, double>(v);
       XMMRegister dst = cgen_->ToDoubleRegister(destination);
       if (int_val == 0) {
         __ xorps(dst, dst);
       } else {
         __ Set(kScratchRegister, int_val);
         __ movq(dst, kScratchRegister);
       }
     } else {
       ASSERT(destination->IsStackSlot());
       Operand dst = cgen_->ToOperand(destination);
       if (cgen_->IsSmiConstant(constant_source)) {

[danno, 2014/03/21 12:36:36]

Just like you added stack slot support elsewhere, the same must be done for
split ranges in the gap resolver that happen to end up in a stack slot. It may
be tricky to construct a test case, but certainly doable (changing
HConstant::EmitAtUses to always return false will certainly make it easier). 

[Weiliang, 2014/03/23 12:15:42]

Yes, that is possible. Actually the "movp" has already done the sign extension
to store the 32bit imm into 64bit stack slot. The original comment is
misleading, so I refine it and some other comments. Thanks a lot.   

[Weiliang, 2014/03/23 12:15:42]

Done.

         __ Move(dst, cgen_->ToSmi(constant_source));
       } else if (cgen_->IsInteger32Constant(constant_source)) {
         // Zero top 32 bits of a 64 bit spill slot that holds a 32 bit untagged
         // value.
         __ movp(dst, Immediate(cgen_->ToInteger32(constant_source)));
       } else {
         __ Move(kScratchRegister, cgen_->ToHandle(constant_source));
         __ movp(dst, kScratchRegister);
       }
     }
@@ skipping 98 matching lines @@
       moves_[i].set_source(source);
     }
   }
 }
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64