PPC: [ic] Also collect known map for relational comparison.

Port e56f265f

Original commit message:
    Previously we only collected the known map for equality comparisons. But
    if we also collect it for relational comparisons, we can inline a fast
    path of ToPrimitive on the objects, which is especially interesting
    since both sides have the same map.

    For now we only inline a very limited subset of ToPrimitive in
    Crankshaft, which is when the receiver map (and its prototype chain)
    doesn't have @@toPrimitive, and both valueOf and toString are the
    default versions on the %ObjectPrototype%. In this case the relational
    comparison would reduce to a string comparison of "[object CLASS]" with
    itself and so we can reduce that to a boolean constant plus map checks
    on both left and right hand side, plus code dependencies on the
    prototype chain. This repairs the regression on box2d.

R=bmeurer@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com, dstence@us.ibm.com
BUG=chromium:534200
LOG=n

Review URL: https://codereview.chromium.org/1358063005

Cr-Commit-Position: refs/heads/master@{#30869}

src/ppc/code-stubs-ppc.cc

@@ -3893,8 +3893,20 @@ void CompareICStub::GenerateKnownObjects(MacroAssembler* masm) {
   __ cmp(r6, r7);
   __ bne(&miss);
 
-  __ sub(r3, r3, r4);
-  __ Ret();
+  if (Token::IsEqualityOp(op())) {
+    __ sub(r3, r3, r4);
+    __ Ret();
+  } else if (is_strong(strength())) {
+    __ TailCallRuntime(Runtime::kThrowStrongModeImplicitConversion, 0, 1);
+  } else {
+    if (op() == Token::LT || op() == Token::LTE) {
+      __ LoadSmiLiteral(r5, Smi::FromInt(GREATER));
+    } else {
+      __ LoadSmiLiteral(r5, Smi::FromInt(LESS));
+    }
+    __ Push(r4, r3, r5);
+    __ TailCallRuntime(Runtime::kCompare, 3, 1);
+  }
 
   __ bind(&miss);
   GenerateMiss(masm);