[llvm] 7c30c05 - [DAG] visitVECTOR_SHUFFLE - MergeInnerShuffle - reset shuffle ops and reorder early-out and second op matching. NFCI.

[Simon Pilgrim via llvm-commits]

Author: Simon Pilgrim
Date: 2021-01-14T11:55:20Z
New Revision: 7c30c05ff71d062f0b8a05b7c3c12ede2c285371

URL: https://github.com/llvm/llvm-project/commit/7c30c05ff71d062f0b8a05b7c3c12ede2c285371
DIFF: https://github.com/llvm/llvm-project/commit/7c30c05ff71d062f0b8a05b7c3c12ede2c285371.diff

LOG: [DAG] visitVECTOR_SHUFFLE - MergeInnerShuffle - reset shuffle ops and reorder early-out and second op matching. NFCI.

I'm hoping to reuse MergeInnerShuffle in some other folds - so ensure the candidate ops/mask are reset at the start of each run.

Also, move the second op matching before bailing to make it simpler to try to match other things afterward.

Added: 
    

Modified: 
    llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index f4c9b814b806..eaf9ad9ef6e2 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -20835,7 +20835,9 @@ SDValue DAGCombiner::visitVECTOR_SHUFFLE(SDNode *N) {
     if (OtherSVN->isSplat())
       return false;
 
+    SV0 = SV1 = SDValue();
     Mask.clear();
+
     for (unsigned i = 0; i != NumElts; ++i) {
       int Idx = SVN->getMaskElt(i);
       if (Idx < 0) {
@@ -20877,15 +20879,16 @@ SDValue DAGCombiner::visitVECTOR_SHUFFLE(SDNode *N) {
         Mask.push_back(Idx);
         continue;
       }
+      if (!SV1.getNode() || SV1 == CurrentVec) {
+        // Ok. CurrentVec is the right hand side.
+        // Update the mask accordingly.
+        SV1 = CurrentVec;
+        Mask.push_back(Idx + NumElts);
+        continue;
+      }
 
       // Bail out if we cannot convert the shuffle pair into a single shuffle.
-      if (SV1.getNode() && SV1 != CurrentVec)
-        return false;
-
-      // Ok. CurrentVec is the right hand side.
-      // Update the mask accordingly.
-      SV1 = CurrentVec;
-      Mask.push_back(Idx + NumElts);
+      return false;
     }
     return true;
   };