[PATCH] D17548: AMDGPU: Check cheaper condition before SignBitIsZero

[Matt Arsenault via llvm-commits]

arsenm created this revision.
arsenm added a reviewer: tstellarAMD.
arsenm added a subscriber: llvm-commits.
Herald added a subscriber: arsenm.

Don't do an expensive computeKnownBits call when we
can do the cheap check for legal offsets first.

http://reviews.llvm.org/D17548

Files:
  lib/Target/AMDGPU/AMDGPUISelDAGToDAG.cpp

Index: lib/Target/AMDGPU/AMDGPUISelDAGToDAG.cpp
===================================================================
--- lib/Target/AMDGPU/AMDGPUISelDAGToDAG.cpp
+++ lib/Target/AMDGPU/AMDGPUISelDAGToDAG.cpp
@@ -1063,14 +1063,13 @@
   if (CurDAG->isBaseWithConstantOffset(Addr)) {
     SDValue N0 = Addr.getOperand(0);
     SDValue N1 = Addr.getOperand(1);
+
     // Offsets in vaddr must be positive.
-    if (CurDAG->SignBitIsZero(N0)) {
-      ConstantSDNode *C1 = cast<ConstantSDNode>(N1);
-      if (isLegalMUBUFImmOffset(C1)) {
-        VAddr = N0;
-        ImmOffset = CurDAG->getTargetConstant(C1->getZExtValue(), DL, MVT::i16);
-        return true;
-      }
+    ConstantSDNode *C1 = cast<ConstantSDNode>(N1);
+    if (isLegalMUBUFImmOffset(C1) && CurDAG->SignBitIsZero(N0)) {
+      VAddr = N0;
+      ImmOffset = CurDAG->getTargetConstant(C1->getZExtValue(), DL, MVT::i16);
+      return true;
     }
   }
 


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