Fix GC-unsafe corner case in bit-not on ARM

src/arm/code-stubs-arm.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1908 matching lines @@
 
   // Try to store the result in a heap number.
   __ bind(&try_float);
   if (mode_ == UNARY_NO_OVERWRITE) {
     Label slow_allocate_heapnumber, heapnumber_allocated;
     __ AllocateHeapNumber(r0, r2, r3, r6, &slow_allocate_heapnumber);
     __ jmp(&heapnumber_allocated);
 
     __ bind(&slow_allocate_heapnumber);
     __ EnterInternalFrame();
-    __ push(r1);
-      __ CallRuntime(Runtime::kNumberAlloc, 0);
-    __ pop(r1);
+    __ push(r0);  // Push the heap number, not the untagged int32.

[Lasse Reichstein, 2011/05/25 08:44:49]

Are you sure that AllocateHeapNumber above doesn't clobber r0 if it fails to
allocate? (If so, make a comment to that effect).

+    __ CallRuntime(Runtime::kNumberAlloc, 0);
+    // Get the heap number into r2, now that the new heap number is in r0.
+    __ pop(r2);
     __ LeaveInternalFrame();
 
+    // Convert the heap number in r2 to an untagged integer in r1.
+    // This can't go slow-case because it's the same number we already
+    // converted once again.
+    __ ConvertToInt32(r2, r1, r3, r4, d0, slow);

[Lasse Reichstein, 2011/05/25 08:44:49]

Don't forget to negate the result.
(If this isn't caught by a test, maybe we need one).

+
     __ bind(&heapnumber_allocated);
   }
 
   if (CpuFeatures::IsSupported(VFP3)) {
     // Convert the int32 in r1 to the heap number in r0. r2 is corrupted.
     CpuFeatures::Scope scope(VFP3);
     __ vmov(s0, r1);
     __ vcvt_f64_s32(d0, s0);
     __ sub(r2, r0, Operand(kHeapObjectTag));
     __ vstr(d0, r2, HeapNumber::kValueOffset);

[Lasse Reichstein, 2011/05/25 08:44:49]

Shouldn't this just be 
  __ vstr(d0, r0, HeapNumber::kValueOffset - kHeapObjectTag)?
Or should vstr take a MemOperand?

     __ Ret();
   } else {
     // WriteInt32ToHeapNumberStub does not trigger GC, so we do not
     // have to set up a frame.
     WriteInt32ToHeapNumberStub stub(r1, r0, r2);
     __ Jump(stub.GetCode(), RelocInfo::CODE_TARGET);
   }
 }
 
 
@@ skipping 4435 matching lines @@
   __ mov(result, Operand(0));
   __ Ret();
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM