commit 937720e75b4692d6ec394fda3e23675d14449c86
author David Bolvansky <david.bolvansky@gmail.com> Wed Apr 03 08:08:44 2019 +0000
committer David Bolvansky <david.bolvansky@gmail.com> Wed Apr 03 08:08:44 2019 +0000
tree 6af554d14d7ae01dc1378376a798b12d57211a4e
parent 94b867dc7c202162f587fd3345eccdb09bff2a77

[InstCombine] Simplify ctpop with bitreverse/bswap

Summary: Fixes PR41337

Reviewers: spatel

Reviewed By: spatel

Subscribers: llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D60148

llvm-svn: 357564

llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index c250679..afcd878 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -1383,6 +1383,14 @@
   assert(II.getIntrinsicID() == Intrinsic::ctpop &&
          "Expected ctpop intrinsic");
   Value *Op0 = II.getArgOperand(0);
+  Value *X;
+  // ctpop(bitreverse(x)) -> ctpop(x)
+  // ctpop(bswap(x)) -> ctpop(x)
+  if (match(Op0, m_BitReverse(m_Value(X))) || match(Op0, m_BSwap(m_Value(X)))) {
+    II.setOperand(0, X);
+    return ⅈ
+  }
+
   // FIXME: Try to simplify vectors of integers.
   auto *IT = dyn_cast<IntegerType>(Op0->getType());
   if (!IT)