commit fe1f36986b23a67c218d7ca24741d5ebd6886473
author Simon Pilgrim <llvm-dev@redking.me.uk> Tue Aug 11 16:42:37 2020 +0100
committer Simon Pilgrim <llvm-dev@redking.me.uk> Tue Aug 11 17:07:32 2020 +0100
tree 9da942fb8df279821751fdae953180d01faa234c
parent c135744b1df394f51b6a08bc562f99a1236e772c

[X86][SSE] combineShuffleWithHorizOp - avoid unnecessary subtraction. NFCI.

We can safely replace ((M - NumElts) % NumEltsPerLane) with (M % NumEltsPerLane) as the modulo result will be the same.

llvm/lib/Target/X86/X86ISelLowering.cpp

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 1a98c46..3a2dadb 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -35900,7 +35900,7 @@
           (M % NumEltsPerLane) >= NumHalfEltsPerLane)
         M -= NumHalfEltsPerLane;
       if (NumElts <= M && BC1.getOperand(0) == BC1.getOperand(1) &&
-          ((M - NumElts) % NumEltsPerLane) >= NumHalfEltsPerLane)
+          (M % NumEltsPerLane) >= NumHalfEltsPerLane)
         M -= NumHalfEltsPerLane;
     }
   }