X87: [RegisterConfiguration] Streamline access to arch defaults, simplify Registers.

src/x87/code-stubs-x87.h

Index: src/x87/code-stubs-x87.h
diff --git a/src/x87/code-stubs-x87.h b/src/x87/code-stubs-x87.h
index 39a4603626f55301fba1c12c0d5c36f2f791f1ca..6290cfed1c3827e84a34d5de618fa744ef11928e 100644
--- a/src/x87/code-stubs-x87.h
+++ b/src/x87/code-stubs-x87.h
@@ -298,8 +298,8 @@ class RecordWriteStub: public PlatformCodeStub {
                                   Register r2,
                                   Register r3) {
       for (int i = 0; i < Register::kNumRegisters; i++) {
-        Register candidate = Register::from_code(i);
-        if (candidate.IsAllocatable()) {
+        if (RegisterConfiguration::Crankshaft()->IsAllocatableGeneralCode(i)) {
+          Register candidate = Register::from_code(i);
           if (candidate.is(ecx)) continue;
           if (candidate.is(r1)) continue;
           if (candidate.is(r2)) continue;