Fix phis for non-sse2 double values

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 75525ed5be95ee7723968a0084687de7c440c3c7..e6e763e6550f5913e59a9fd2d25bc64173252c55 100644
--- a/src/ia32/lithium-codegen-ia32.cc
+++ b/src/ia32/lithium-codegen-ia32.cc
@@ -359,9 +359,13 @@ bool LCodeGen::GenerateBody() {
 
     instr->CompileToNative(this);
 
-    if (!CpuFeatures::IsSupported(SSE2) &&
-        FLAG_debug_code && FLAG_enable_slow_asserts) {
+    if (!CpuFeatures::IsSupported(SSE2)) {
+      if (instr->IsGoto()) {
+        x87_stack_.LeavingBlock(current_block_, LGoto::cast(instr));
+      } else if (FLAG_debug_code && FLAG_enable_slow_asserts &&
+                 !instr->IsGap() && !instr->IsReturn()) {
         __ VerifyX87StackDepth(x87_stack_.depth());
+      }
     }
   }
   EnsureSpaceForLazyDeopt();
@@ -659,6 +663,18 @@ void LCodeGen::X87Stack::FlushIfNecessary(LInstruction* instr, LCodeGen* cgen) {
       __ fstp(0);
       stack_depth_--;
     }
+    __ VerifyX87StackDepth(0);
+  }
+}
+
+
+void LCodeGen::X87Stack::LeavingBlock(int current_block_id, LGoto* goto_instr) {
+  ASSERT(stack_depth_ <= 1);

[Toon Verwaest, 2013/09/11 12:28:30]

Add comment as discussed. If ever used for other stubs than the binary op stub,
two pairs of doubles could be joined into two phis, causing a stack-depth of 2.
In that case, either the stack is in the same order in both incoming blocks,
requiring no gap; or the values on the stack need to be swapped in one of the
branches.

+  if (current_block_id + 1 != goto_instr->block_id()) {
+    // If we have a value on the x87 stack on leaving a block, it must be a
+    // phi input. If the next block we compile is not the join block, we have
+    // to discard the stack state.
+    stack_depth_ = 0;
   }
 }
 
@@ -2439,6 +2455,10 @@ void LCodeGen::EmitGoto(int block) {
 }
 
 
+void LCodeGen::DoClobberDoubles(LClobberDoubles* instr) {
+}
+
+
 void LCodeGen::DoGoto(LGoto* instr) {
   EmitGoto(instr->block_id());
 }