Fix compose-discard crasher from 11524. We can't do a call (to a generic

src/ia32/lithium-codegen-ia32.cc

Index: src/ia32/lithium-codegen-ia32.cc
===================================================================
--- src/ia32/lithium-codegen-ia32.cc	(revision 11535)
+++ src/ia32/lithium-codegen-ia32.cc	(working copy)
@@ -2275,8 +2275,7 @@
 
   int map_count = instr->hydrogen()->types()->length();
   Handle<String> name = instr->hydrogen()->name();
-  if (map_count == 0) {
-    ASSERT(instr->hydrogen()->need_generic());
+  if (map_count == 0 && instr->hydrogen()->need_generic()) {
     __ mov(ecx, name);
     Handle<Code> ic = isolate()->builtins()->LoadIC_Initialize();
     CallCode(ic, RelocInfo::CODE_TARGET, instr);
@@ -2291,20 +2290,28 @@
       __ jmp(&done, Label::kNear);
       __ bind(&next);
     }
-    Handle<Map> map = instr->hydrogen()->types()->last();
-    __ cmp(FieldOperand(object, HeapObject::kMapOffset), map);
     if (instr->hydrogen()->need_generic()) {
-      Label generic;
-      __ j(not_equal, &generic, Label::kNear);
-      EmitLoadFieldOrConstantFunction(result, object, map, name);
-      __ jmp(&done, Label::kNear);
-      __ bind(&generic);
+      if (map_count != 0) {

[Michael Starzinger, 2012/05/10 13:06:01]

It seems as if this condition always holds, otherwise you would have ended up in
the IC case. Can we replace this with an ASSERT(map_count != 0)?

[Erik Corry, 2012/05/10 20:28:36]

No, there are two conditions to get into the IC case now.

+        Handle<Map> map = instr->hydrogen()->types()->last();
+        __ cmp(FieldOperand(object, HeapObject::kMapOffset), map);
+        Label generic;
+        __ j(not_equal, &generic, Label::kNear);
+        EmitLoadFieldOrConstantFunction(result, object, map, name);
+        __ jmp(&done, Label::kNear);
+        __ bind(&generic);
+      }
       __ mov(ecx, name);
       Handle<Code> ic = isolate()->builtins()->LoadIC_Initialize();
       CallCode(ic, RelocInfo::CODE_TARGET, instr);
     } else {
-      DeoptimizeIf(not_equal, instr->environment());
-      EmitLoadFieldOrConstantFunction(result, object, map, name);
+      if (map_count != 0) {

[Michael Starzinger, 2012/05/10 13:06:01]

Then it makes sense to turn this into an "else if" which would simplify the
structure.

[Erik Corry, 2012/05/10 20:28:36]

Same objection.

+        Handle<Map> map = instr->hydrogen()->types()->last();
+        __ cmp(FieldOperand(object, HeapObject::kMapOffset), map);
+        DeoptimizeIf(not_equal, instr->environment());
+        EmitLoadFieldOrConstantFunction(result, object, map, name);
+      } else {
+        DeoptimizeIf(no_condition, instr->environment());
+      }
     }
     __ bind(&done);
   }