[llvm] 0a241e9 - [NFC][InstCombine] `vector_reduce_xor(?ext(<n x i1>))` --> `?ext(vector_reduce_add(<n x i1>))`

[Roman Lebedev via llvm-commits]

Author: Roman Lebedev
Date: 2021-08-07T17:31:33+03:00
New Revision: 0a241e90d4931a764109da70c2322a0a9386b1a7

URL: https://github.com/llvm/llvm-project/commit/0a241e90d4931a764109da70c2322a0a9386b1a7
DIFF: https://github.com/llvm/llvm-project/commit/0a241e90d4931a764109da70c2322a0a9386b1a7.diff

LOG: [NFC][InstCombine] `vector_reduce_xor(?ext(<n x i1>))` --> `?ext(vector_reduce_add(<n x i1>))`

Instead of expanding it ourselves,
we can just forward to `?ext(vector_reduce_add(<n x i1>))`, as per alive2:
https://alive2.llvm.org/ce/z/ymz7zE (self)
https://alive2.llvm.org/ce/z/eKu2v2 (skipped zext)
https://alive2.llvm.org/ce/z/c3BXgc (skipped sext)

Added: 
    

Modified: 
    llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp

Removed: 
    


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diff  --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index 2ba326d791c2..210652e23377 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -2038,20 +2038,17 @@ Instruction *InstCombinerImpl::visitCallInst(CallInst &CI) {
     if (IID == Intrinsic::vector_reduce_xor) {
       // Exclusive disjunction reduction over the vector with
       // (potentially-extended) i1 element type is actually a
-      // (potentially-extended) parity check:
+      // (potentially-extended) arithmetic `add` reduction over the original
+      // non-extended value:
       //   vector_reduce_xor(?ext(<n x i1>))
       //     -->
-      //   ?ext(trunc(vector_reduce_and(<n x i1>) to i1))
+      //   ?ext(vector_reduce_add(<n x i1>))
       Value *Arg = II->getArgOperand(0);
       Value *Vect;
       if (match(Arg, m_ZExtOrSExtOrSelf(m_Value(Vect)))) {
         if (auto *FTy = dyn_cast<FixedVectorType>(Vect->getType()))
           if (FTy->getElementType() == Builder.getInt1Ty()) {
-            Value *V = Builder.CreateBitCast(
-                Vect, Builder.getIntNTy(FTy->getNumElements()));
-            Value *Res = Builder.CreateUnaryIntrinsic(Intrinsic::ctpop, V);
-            Res = Builder.CreateTrunc(Res,
-                                      IntegerType::get(Res->getContext(), 1));
+            Value *Res = Builder.CreateAddReduce(Vect);
             if (Arg != Vect)
               Res = Builder.CreateCast(cast<CastInst>(Arg)->getOpcode(), Res,
                                        II->getType());