Fix occasional crash when lithium goes out of vregs.

BUG=
R=ulan@chromium.org

Review URL: https://codereview.chromium.org/14850013

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@14550 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/arm/lithium-arm.cc

@@ -677,7 +677,7 @@ LUnallocated* LChunkBuilder::TempRegister() {
   int vreg = allocator_->GetVirtualRegister();
   if (!allocator_->AllocationOk()) {
     Abort("Out of virtual registers while trying to allocate temp register.");
-    return NULL;
+    vreg = 0;
   }
   operand->set_virtual_register(vreg);
   return operand;

src/ia32/lithium-ia32.cc

@@ -736,7 +736,7 @@ LUnallocated* LChunkBuilder::TempRegister() {
   int vreg = allocator_->GetVirtualRegister();
   if (!allocator_->AllocationOk()) {
     Abort("Out of virtual registers while trying to allocate temp register.");
-    return NULL;
+    vreg = 0;
   }
   operand->set_virtual_register(vreg);
   return operand;

src/mips/lithium-mips.cc

@@ -677,7 +677,7 @@ LUnallocated* LChunkBuilder::TempRegister() {
   int vreg = allocator_->GetVirtualRegister();
   if (!allocator_->AllocationOk()) {
     Abort("Out of virtual registers while trying to allocate temp register.");
-    return NULL;
+    vreg = 0;
   }
   operand->set_virtual_register(vreg);
   return operand;

src/x64/lithium-x64.cc

@@ -685,7 +685,7 @@ LUnallocated* LChunkBuilder::TempRegister() {
   int vreg = allocator_->GetVirtualRegister();
   if (!allocator_->AllocationOk()) {
     Abort("Out of virtual registers while trying to allocate temp register.");
-    return NULL;
+    vreg = 0;
   }
   operand->set_virtual_register(vreg);
   return operand;