[PATCH] D129207: [X86] isTargetShuffleEquivalent - attempt to match SM_SentinelZero shuffle mask elements using known bits

[Sanjay Patel via Phabricator via llvm-commits]

spatel added inline comments.


================
Comment at: llvm/lib/Target/X86/X86ISelLowering.cpp:11818
       continue;
+    if (MaskIdx == SM_SentinelZero && 0 <= ExpectedIdx) {
+      // If we need this expected index to be a zero element, then update the
----------------
What do you think about adding a clause above this and below the first clause like:
    // If the mask is more defined than expected, the shuffles are not the same.
    if (ExpectedIdx == SM_SentinelUndef)
      return false;

I think that would then allow simplifying the later checks (converting to asserts).


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D129207/new/

https://reviews.llvm.org/D129207