PPC: [turbofan] Desugar JSUnaryNot(x) to Select(x, false, true).

Port 411c5b7f

Original commit message:
    Also remove the ResultMode from ToBooleanStub and always return true or
    false and use the same mechanism in fullcodegen.  This is in preparation
    for adding ToBoolean hints to TurboFan.

    Drive-by-fix: We can use the power of the ToBooleanIC in TurboFan now
    that the ResultMode is gone (and the runtime always returns true or
    false from the miss handler).

R=bmeurer@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com
BUG=v8:4583
LOG=n

Review URL: https://codereview.chromium.org/1490363003

Cr-Commit-Position: refs/heads/master@{#32531}

src/full-codegen/ppc/full-codegen-ppc.cc

@@ -648,8 +648,8 @@ void FullCodeGenerator::DoTest(Expression* condition, Label* if_true,
                                Label* if_false, Label* fall_through) {
   Handle<Code> ic = ToBooleanStub::GetUninitialized(isolate());
   CallIC(ic, condition->test_id());
-  __ cmpi(result_register(), Operand::Zero());
-  Split(ne, if_true, if_false, fall_through);
+  __ CompareRoot(result_register(), Heap::kTrueValueRootIndex);
+  Split(eq, if_true, if_false, fall_through);
 }
 
 
@@ -2030,8 +2030,8 @@ void FullCodeGenerator::VisitYield(Yield* expr) {
       CallLoadIC(NOT_INSIDE_TYPEOF);  // r0=result.done
       Handle<Code> bool_ic = ToBooleanStub::GetUninitialized(isolate());
       CallIC(bool_ic);
-      __ cmpi(r3, Operand::Zero());
-      __ beq(&l_try);
+      __ CompareRoot(result_register(), Heap::kTrueValueRootIndex);
+      __ bne(&l_try);
 
       // result.value
       __ pop(load_receiver);                                 // result