[llvm] [InstCombine] Remove mul of SPF abs fold (PR #88675)

[Nikita Popov via llvm-commits]

https://github.com/nikic created https://github.com/llvm/llvm-project/pull/88675

Remove the fold working on abs in SPF representation now that we canonicalize SPF to intrinsics.

This is not strictly NFC because the SPF fold might fire for non-canonical IR due to multi-use, but given the lack of test coverage, I assume this is not important.

>From 89e26d458edf22d4aff5e9774e43221397ace2cd Mon Sep 17 00:00:00 2001
From: Nikita Popov <npopov at redhat.com>
Date: Mon, 15 Apr 2024 11:39:51 +0900
Subject: [PATCH] [InstCombine] Remove mul of SPF abs fold

Remove the fold working on abs in SPF representation now that we
canonicalize SPF to intrinsics.

This is not strictly NFC because the SPF fold might fire for
non-canonical IR due to multi-use, but given the lack of test
coverage, I assume this is not important.
---
 .../InstCombine/InstCombineMulDivRem.cpp       | 18 ++++++------------
 1 file changed, 6 insertions(+), 12 deletions(-)

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
index 4dc1319f1c437f..ea3443175568c5 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -319,19 +319,13 @@ Instruction *InstCombinerImpl::visitMul(BinaryOperator &I) {
   }
 
   // abs(X) * abs(X) -> X * X
-  // nabs(X) * nabs(X) -> X * X
-  if (Op0 == Op1) {
-    Value *X, *Y;
-    SelectPatternFlavor SPF = matchSelectPattern(Op0, X, Y).Flavor;
-    if (SPF == SPF_ABS || SPF == SPF_NABS)
-      return BinaryOperator::CreateMul(X, X);
-
-    if (match(Op0, m_Intrinsic<Intrinsic::abs>(m_Value(X))))
-      return BinaryOperator::CreateMul(X, X);
-  }
+  Value *X;
+  if (Op0 == Op1 &&
+      match(Op0, m_Intrinsic<Intrinsic::abs>(m_Value(X))))
+    return BinaryOperator::CreateMul(X, X);
 
   {
-    Value *X, *Y;
+    Value *Y;
     // abs(X) * abs(Y) -> abs(X * Y)
     if (I.hasNoSignedWrap() &&
         match(Op0,
@@ -344,7 +338,7 @@ Instruction *InstCombinerImpl::visitMul(BinaryOperator &I) {
   }
 
   // -X * C --> X * -C
-  Value *X, *Y;
+  Value *Y;
   Constant *Op1C;
   if (match(Op0, m_Neg(m_Value(X))) && match(Op1, m_Constant(Op1C)))
     return BinaryOperator::CreateMul(X, ConstantExpr::getNeg(Op1C));