MIPS64: Fix allocation folding test failures.

Allocation folding tests are failing in debug mode, since the change
https://codereview.chromium.org/1972553002 (6e15433d) introduced a debug check in
lithium-codegen-mips64.cc, line 5287.

Reason for failure is to be found in https://codereview.chromium.org/1899813003 (61f5fbbb),
which is missing changes calling LFastAllocate in lithium-mips64.cc.

BUG=

Review-Url: https://codereview.chromium.org/1977833002
Cr-Commit-Position: refs/heads/master@{#36246}

src/crankshaft/mips64/lithium-mips64.cc

@@ -2303,13 +2303,18 @@ LInstruction* LChunkBuilder::DoStringCharFromCode(HStringCharFromCode* instr) {
 
 
 LInstruction* LChunkBuilder::DoAllocate(HAllocate* instr) {
-  info()->MarkAsDeferredCalling();
-  LOperand* context = UseAny(instr->context());
   LOperand* size = UseRegisterOrConstant(instr->size());
   LOperand* temp1 = TempRegister();
   LOperand* temp2 = TempRegister();
-  LAllocate* result = new(zone()) LAllocate(context, size, temp1, temp2);
-  return AssignPointerMap(DefineAsRegister(result));
+  if (instr->IsAllocationFolded()) {
+    LFastAllocate* result = new (zone()) LFastAllocate(size, temp1, temp2);
+    return DefineAsRegister(result);
+  } else {
+    info()->MarkAsDeferredCalling();
+    LOperand* context = UseAny(instr->context());
+    LAllocate* result = new (zone()) LAllocate(context, size, temp1, temp2);
+    return AssignPointerMap(DefineAsRegister(result));
+  }
 }