Reland "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 860646c2fd60417e2fdfe5640eabe15cb61c0211..632ad9783fe95ed300365096a36e34fd4909cf1d 100644
--- a/src/ia32/lithium-codegen-ia32.cc
+++ b/src/ia32/lithium-codegen-ia32.cc
@@ -382,9 +382,13 @@ 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();
@@ -682,6 +686,21 @@ void LCodeGen::X87Stack::FlushIfNecessary(LInstruction* instr, LCodeGen* cgen) {
       __ fstp(0);
       stack_depth_--;
     }
+    if (FLAG_debug_code && FLAG_enable_slow_asserts) __ VerifyX87StackDepth(0);
+  }
+}
+
+
+void LCodeGen::X87Stack::LeavingBlock(int current_block_id, LGoto* goto_instr) {
+  ASSERT(stack_depth_ <= 1);
+  // If ever used for new stubs producing two pairs of doubles joined into two
+  // phis this assert hits. That situation is not handled, since the two stacks
+  // might have st0 and st1 swapped.
+  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;
   }
 }
 
@@ -2486,6 +2505,10 @@ void LCodeGen::EmitGoto(int block) {
 }
 
 
+void LCodeGen::DoClobberDoubles(LClobberDoubles* instr) {
+}
+
+
 void LCodeGen::DoGoto(LGoto* instr) {
   EmitGoto(instr->block_id());
 }