[llvm] [VPlan] Mark unary ops as not having side-effects (NFC). (PR #190554)

[Florian Hahn via llvm-commits]

https://github.com/fhahn created https://github.com/llvm/llvm-project/pull/190554

Mark unary ops (only FNeg current) to neither read nor write memory, similar to binary and cast ops.

Should currently be NFC end-to-end.

>From 8cbd014c1449bfc072244fc0ff21988b00b41728 Mon Sep 17 00:00:00 2001
From: Florian Hahn <flo at fhahn.com>
Date: Sun, 5 Apr 2026 15:13:08 +0100
Subject: [PATCH] [VPlan] Mark unary ops as not having side-effects (NFC).

Mark unary ops (only FNeg current) to neither read nor write
memory, similar to binary and cast ops.

Should currently be NFC end-to-end.
---
 llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp    |  3 ++-
 llvm/unittests/Transforms/Vectorize/VPlanTest.cpp | 10 ++++++++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp b/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
index 8323d0d8562a4..b496278ebd6ec 100644
--- a/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
+++ b/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
@@ -1329,7 +1329,8 @@ void VPInstruction::execute(VPTransformState &State) {
 }
 
 bool VPInstruction::opcodeMayReadOrWriteFromMemory() const {
-  if (Instruction::isBinaryOp(getOpcode()) || Instruction::isCast(getOpcode()))
+  if (Instruction::isBinaryOp(getOpcode()) ||
+      Instruction::isUnaryOp(getOpcode()) || Instruction::isCast(getOpcode()))
     return false;
   switch (getOpcode()) {
   case Instruction::GetElementPtr:
diff --git a/llvm/unittests/Transforms/Vectorize/VPlanTest.cpp b/llvm/unittests/Transforms/Vectorize/VPlanTest.cpp
index ec9c904a08b2c..017aa6dab705e 100644
--- a/llvm/unittests/Transforms/Vectorize/VPlanTest.cpp
+++ b/llvm/unittests/Transforms/Vectorize/VPlanTest.cpp
@@ -1441,6 +1441,16 @@ TEST_F(VPRecipeTest, MayHaveSideEffectsAndMayReadWriteMemory) {
     EXPECT_FALSE(Recipe.mayWriteToMemory());
     EXPECT_FALSE(Recipe.mayReadOrWriteMemory());
   }
+  {
+    VPValue *Op1 = Plan.getConstantInt(Int32, 1);
+    VPInstruction VPInst(Instruction::FNeg, {Op1},
+                         VPIRFlags::getDefaultFlags(Instruction::FNeg));
+    VPRecipeBase &Recipe = VPInst;
+    EXPECT_FALSE(Recipe.mayHaveSideEffects());
+    EXPECT_FALSE(Recipe.mayReadFromMemory());
+    EXPECT_FALSE(Recipe.mayWriteToMemory());
+    EXPECT_FALSE(Recipe.mayReadOrWriteMemory());
+  }
   {
     VPValue *Op1 = Plan.getOrAddLiveIn(ConstantInt::get(Int32, 1));
     VPPredInstPHIRecipe Recipe(Op1, {});