PPC: [runtime] Unify comparison operator runtime entries.

Port 55b4df73

Original commit message:
    Only use one set of %StrictEquals/%StrictNotEquals and
    %Equals/%NotEquals runtime entries for both the interpreter
    and the old-style CompareICStub. The long-term plan is to
    update the CompareICStub to also return boolean values, and
    even allow some more code sharing with the interpreter there.

R=bmeurer@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com
BUG=

Review URL: https://codereview.chromium.org/1737853002

Cr-Commit-Position: refs/heads/master@{#34306}

src/ppc/code-stubs-ppc.cc

@@ -698,11 +698,19 @@ void CompareICStub::GenerateGeneric(MacroAssembler* masm) {
 
   __ bind(&slow);
 
-  __ Push(lhs, rhs);
-  // Figure out which native to call and setup the arguments.
   if (cc == eq) {
-    __ TailCallRuntime(strict() ? Runtime::kStrictEquals : Runtime::kEquals);
+    {
+      FrameAndConstantPoolScope scope(masm, StackFrame::INTERNAL);
+      __ Push(lhs, rhs);
+      __ CallRuntime(strict() ? Runtime::kStrictEquals : Runtime::kEquals);
+    }
+    // Turn true into 0 and false into some non-zero value.
+    STATIC_ASSERT(EQUAL == 0);
+    __ LoadRoot(r4, Heap::kTrueValueRootIndex);
+    __ sub(r3, r3, r4);
+    __ Ret();
   } else {
+    __ Push(lhs, rhs);
     int ncr;  // NaN compare result
     if (cc == lt || cc == le) {
       ncr = GREATER;