Fix invalid X87 stack depth after LCompareNumericAndBranch.

src/ia32/lithium-codegen-ia32.cc

Index: src/ia32/lithium-codegen-ia32.cc
diff --git a/src/ia32/lithium-codegen-ia32.cc b/src/ia32/lithium-codegen-ia32.cc
index 98a049b64abed3387a1d5f6c380a48c1fed8c78f..1a6efc39455ee14343f479d10f4443e3c35715fc 100644
--- a/src/ia32/lithium-codegen-ia32.cc
+++ b/src/ia32/lithium-codegen-ia32.cc
@@ -561,6 +561,16 @@ void LCodeGen::X87LoadForUsage(X87Register reg) {
 }
 
 
+void LCodeGen::X87LoadForUsage(X87Register reg1, X87Register reg2) {
+  ASSERT(x87_stack_.Contains(reg1));
+  ASSERT(x87_stack_.Contains(reg2));
+  x87_stack_.Fxch(reg1, 1);
+  x87_stack_.Fxch(reg2);
+  x87_stack_.pop();
+  x87_stack_.pop();

[Toon Verwaest, 2013/09/24 09:00:08]

Pretty surprising that you first push values to them immediately pop. Can't we
let FCmp consume these values to avoid direct dependency between these
instructions?

[Benedikt Meurer, 2013/09/24 09:12:30]

As discussed offline, we can fix this once the X87 stack tracking is part of the
macro assembler.

+}
+
+
 void LCodeGen::X87Stack::Fxch(X87Register reg, int other_slot) {
   ASSERT(is_mutable_);
   ASSERT(Contains(reg) && stack_depth_ > other_slot);
@@ -2572,10 +2582,7 @@ void LCodeGen::DoCompareNumericAndBranch(LCompareNumericAndBranch* instr) {
         CpuFeatureScope scope(masm(), SSE2);
         __ ucomisd(ToDoubleRegister(left), ToDoubleRegister(right));
       } else {
-        X87Fxch(ToX87Register(right));
-        X87Fxch(ToX87Register(left), 1);
-        __ fld(0);
-        __ fld(2);
+        X87LoadForUsage(ToX87Register(right), ToX87Register(left));
         __ FCmp();
       }
       // Don't base result on EFLAGS when a NaN is involved. Instead