S390: [generators] Store the resume mode in the generator object.

port 2e329666

Original Commit Message:
    ... instead of doing stack magic.  This is a cleanup in preparation for the new
    generators implementation.

R=bmeurer@chromium.org, neis@chromium.org, joransiu@ca.ibm.com, michael_dawson@ca.ibm.com, mbrandy@us.ibm.com, bjaideep@ca.ibm.com
BUG=

Review URL: https://codereview.chromium.org/1882553003

Cr-Commit-Position: refs/heads/master@{#35417}

src/full-codegen/s390/full-codegen-s390.cc

@@ -1758,11 +1758,10 @@ void FullCodeGenerator::VisitYield(Yield* expr) {
 
   __ b(&suspend);
   __ bind(&continuation);
-  // When we arrive here, the stack top is the resume mode and
-  // result_register() holds the input value (the argument given to the
-  // respective resume operation).
+  // When we arrive here, r2 holds the generator object.
   __ RecordGeneratorContinuation();
-  __ pop(r3);
+  __ LoadP(r3, FieldMemOperand(r2, JSGeneratorObject::kResumeModeOffset));
+  __ LoadP(r2, FieldMemOperand(r2, JSGeneratorObject::kInputOffset));
   STATIC_ASSERT(JSGeneratorObject::kNext < JSGeneratorObject::kReturn);
   STATIC_ASSERT(JSGeneratorObject::kThrow > JSGeneratorObject::kReturn);
   __ CmpSmiLiteral(r3, Smi::FromInt(JSGeneratorObject::kReturn), r0);

src/s390/builtins-s390.cc

@@ -708,6 +708,9 @@ void Builtins::Generate_ResumeGeneratorTrampoline(MacroAssembler* masm) {
   __ RecordWriteField(r3, JSGeneratorObject::kInputOffset, r2, r5,
                       kLRHasNotBeenSaved, kDontSaveFPRegs);
 
+  // Store resume mode into generator object.
+  __ StoreP(r4, FieldMemOperand(r3, JSGeneratorObject::kResumeModeOffset));
+
   // Load suspended function and context.
   __ LoadP(cp, FieldMemOperand(r3, JSGeneratorObject::kContextOffset));
   __ LoadP(r6, FieldMemOperand(r3, JSGeneratorObject::kFunctionOffset));
@@ -791,17 +794,11 @@ void Builtins::Generate_ResumeGeneratorTrampoline(MacroAssembler* masm) {
     __ bind(&done_loop);
   }
 
-  // Push resume mode (consumed in continuation).
-  __ Push(r4);
-
   // Reset operand stack so we don't leak.
   __ LoadRoot(ip, Heap::kEmptyFixedArrayRootIndex);
   __ StoreP(ip, FieldMemOperand(r3, JSGeneratorObject::kOperandStackOffset),
             r0);
 
-  // Restore value.
-  __ LoadP(r2, FieldMemOperand(r3, JSGeneratorObject::kInputOffset));
-
   // Resume the generator function at the continuation.
   __ LoadP(r5, FieldMemOperand(r6, JSFunction::kSharedFunctionInfoOffset));
   __ LoadP(r5, FieldMemOperand(r5, SharedFunctionInfo::kCodeOffset));
@@ -814,6 +811,7 @@ void Builtins::Generate_ResumeGeneratorTrampoline(MacroAssembler* masm) {
     __ LoadSmiLiteral(r4, Smi::FromInt(JSGeneratorObject::kGeneratorExecuting));
     __ StoreP(r4, FieldMemOperand(r3, JSGeneratorObject::kContinuationOffset),
               r0);
+    __ LoadRR(r2, r3);  // Continuation expects generator object in r2.
     __ Jump(r5);
   }
 }