[turbofan] Refactor the InstructionSelector tests.

src/compiler/arm/instruction-selector-arm.cc

Index: src/compiler/arm/instruction-selector-arm.cc
diff --git a/src/compiler/arm/instruction-selector-arm.cc b/src/compiler/arm/instruction-selector-arm.cc
index 029d6e3b96e9d0c61ca3d9e03301afbfe6ffae56..22af55faeec9a6e04045d8999c15bec9ef8716f5 100644
--- a/src/compiler/arm/instruction-selector-arm.cc
+++ b/src/compiler/arm/instruction-selector-arm.cc
@@ -141,11 +141,22 @@ static bool TryMatchROR(InstructionSelector* selector,
   if (value != mshl.left().node()) return false;
   Node* shift = mshr.right().node();
   Int32Matcher mshift(shift);
-  if (mshift.IsInRange(1, 31) && mshl.right().Is(32 - mshift.Value())) {
-    *opcode_return |= AddressingModeField::encode(kMode_Operand2_R_ROR_I);
-    *value_return = g.UseRegister(value);
-    *shift_return = g.UseImmediate(shift);
-    return true;
+  if (mshift.IsInRange(1, 31)) {
+    if (mshl.right().Is(32 - mshift.Value())) {
+      *opcode_return |= AddressingModeField::encode(kMode_Operand2_R_ROR_I);
+      *value_return = g.UseRegister(value);
+      *shift_return = g.UseImmediate(shift);
+      return true;
+    }
+    if (mshl.right().IsInt32Sub()) {

[Jarin, 2014/08/14 05:34:55]

I am a bit confused - this looks like it is matching "const - const" - should
not constant propagation take care of this case (reducing it to the previous
case)?

Or is it here for users of RawMachineAssembler  (which does not optimize)?

[Benedikt Meurer, 2014/08/14 06:22:46]

As discussed offline, I'll add a Word32/64Ror operator in a follow up CL and
cleanup this stuff.

+      Int32BinopMatcher mshlright(mshl.right().node());
+      if (mshlright.left().Is(32) && mshlright.right().Is(mshift.Value())) {
+        *opcode_return |= AddressingModeField::encode(kMode_Operand2_R_ROR_I);
+        *value_return = g.UseRegister(value);
+        *shift_return = g.UseImmediate(shift);
+        return true;
+      }
+    }
   }
   if (mshl.right().IsInt32Sub()) {
     Int32BinopMatcher mshlright(mshl.right().node());