[InstCombine] remove trunc user restriction for match of bswap

This does not appear to cause any problems, and it
fixes #50910

Extra tests with a trunc user were added with:
3a239379
...but they don't match either way, so there's an
opportunity to improve the matching further.

1 files changed, 1 insertions, 5 deletions

diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp
index ecad79b..efc5396 100644
--- a/llvm/lib/Transforms/Utils/Local.cpp
+++ b/llvm/lib/Transforms/Utils/Local.cpp
@@ -3147,11 +3147,6 @@ bool llvm::recognizeBSwapOrBitReverseIdiom(
   if (!ITy->isIntOrIntVectorTy() || ITy->getScalarSizeInBits() > 128)
     return false;  // Can't do integer/elements > 128 bits.
 
-  Type *DemandedTy = ITy;
-  if (I->hasOneUse())
-    if (auto *Trunc = dyn_cast<TruncInst>(I->user_back()))
-      DemandedTy = Trunc->getType();
-
   // Try to find all the pieces corresponding to the bswap.
   bool FoundRoot = false;
   std::map<Value *, Optional<BitPart>> BPS;
@@ -3165,6 +3160,7 @@ bool llvm::recognizeBSwapOrBitReverseIdiom(
          "Illegal bit provenance index");
 
   // If the upper bits are zero, then attempt to perform as a truncated op.
+  Type *DemandedTy = ITy;
   if (BitProvenance.back() == BitPart::Unset) {
     while (!BitProvenance.empty() && BitProvenance.back() == BitPart::Unset)
       BitProvenance = BitProvenance.drop_back();