[generators] Fix loading of FormalParameterCount on 64bit archs.

BUG=v8:4907

Review-Url: https://codereview.chromium.org/2006653003
Cr-Commit-Position: refs/heads/master@{#36467}

src/arm64/builtins-arm64.cc

@@ -775,9 +775,8 @@ void Builtins::Generate_ResumeGeneratorTrampoline(MacroAssembler* masm) {
   // New-style (ignition/turbofan) generator object
   {
     __ Ldr(x0, FieldMemOperand(x4, JSFunction::kSharedFunctionInfoOffset));
-    __ Ldr(x0,
+    __ Ldr(w0,
          FieldMemOperand(x0, SharedFunctionInfo::kFormalParameterCountOffset));
-    __ SmiUntag(x0);
     // We abuse new.target both to indicate that this is a resume call and to
     // pass in the generator object.  In ordinary calls, new.target is always
     // undefined because generator functions are non-constructable.

src/mips64/builtins-mips64.cc

@@ -763,7 +763,6 @@ void Builtins::Generate_ResumeGeneratorTrampoline(MacroAssembler* masm) {
     __ ld(a0, FieldMemOperand(a4, JSFunction::kSharedFunctionInfoOffset));
     __ lw(a0,
          FieldMemOperand(a0, SharedFunctionInfo::kFormalParameterCountOffset));
-    __ SmiUntag(a0);
     // We abuse new.target both to indicate that this is a resume call and to
     // pass in the generator object.  In ordinary calls, new.target is always
     // undefined because generator functions are non-constructable.

test/mjsunit/mjsunit.status

@@ -530,12 +530,8 @@
   # Issue 3219:
   'getters-on-elements': [PASS, ['gc_stress == True', FAIL]],
 
-  # BUG(v8:4907)
-  'harmony/generators-turbo': [SKIP],
-
   # Ignition.
   'es6/templates': [PASS, ['no_snap and mode == debug', NO_IGNITION]],
-  'harmony/generators': [PASS, ['no_snap and mode == debug', NO_IGNITION]],
   'regress/regress-crbug-364374': [PASS, ['no_snap and mode == debug', NO_IGNITION]],
 }],  # 'arch == arm64 and mode == debug and simulator_run == True'