only capture mask if ops match. reordered tests

Author: Aidan

llvm/include/llvm/CodeGen/SDPatternMatch.h

@@ -554,9 +554,11 @@ template <typename T0, typename T1> struct SDShuffle_match {
   template <typename MatchContext>
   bool match(const MatchContext &Ctx, SDValue N) {
     if (auto *I = dyn_cast<ShuffleVectorSDNode>(N)) {
-      CapturedMask = I->getMask();
-      return Op1.match(Ctx, I->getOperand(0)) &&
-             Op2.match(Ctx, I->getOperand(1));
+      if (Op1.match(Ctx, I->getOperand(0)) &&
+          Op2.match(Ctx, I->getOperand(1))) {
+        CapturedMask = I->getMask();
+        return true;
+      }
     }
     return false;
   }

llvm/unittests/CodeGen/SelectionDAGPatternMatchTest.cpp

@@ -137,11 +137,12 @@ TEST_F(SelectionDAGPatternMatchTest, matchVecShuffle) {
                        m_Shuffle(m_Value(), m_Value(), CapturedMask)));
   EXPECT_TRUE(sd_match(VecShuffleWithMask,
                        m_ShuffleSpecificMask(m_Value(), m_Value(), MaskData)));
-  EXPECT_TRUE(std::equal(MaskData.begin(), MaskData.end(), CapturedMask.begin(),
-                         CapturedMask.end()));
   EXPECT_FALSE(
       sd_match(VecShuffleWithMask,
                m_ShuffleSpecificMask(m_Value(), m_Value(), otherMaskData)));
+
+  EXPECT_TRUE(std::equal(MaskData.begin(), MaskData.end(), CapturedMask.begin(),
+                         CapturedMask.end()));
   EXPECT_FALSE(std::equal(otherMaskData.begin(), otherMaskData.end(),
                           CapturedMask.begin(), CapturedMask.end()));
 }