[llvm] [EarlyCSE] Rematerialize alignment assumption. (PR #109131)

[Florian Hahn via llvm-commits]

https://github.com/fhahn created https://github.com/llvm/llvm-project/pull/109131

None

>From 415832b3a30ac6674f747852ed5b95f1689bde3c Mon Sep 17 00:00:00 2001
From: Florian Hahn <flo at fhahn.com>
Date: Wed, 18 Sep 2024 13:38:52 +0100
Subject: [PATCH] [EarlyCSE] Rematerialize alignment assumption.

---
 llvm/lib/Transforms/Scalar/EarlyCSE.cpp | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/llvm/lib/Transforms/Scalar/EarlyCSE.cpp b/llvm/lib/Transforms/Scalar/EarlyCSE.cpp
index cf11f5bc885a75..b6a68067070917 100644
--- a/llvm/lib/Transforms/Scalar/EarlyCSE.cpp
+++ b/llvm/lib/Transforms/Scalar/EarlyCSE.cpp
@@ -31,6 +31,7 @@
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/Dominators.h"
 #include "llvm/IR/Function.h"
+#include "llvm/IR/IRBuilder.h"
 #include "llvm/IR/InstrTypes.h"
 #include "llvm/IR/Instruction.h"
 #include "llvm/IR/Instructions.h"
@@ -1588,6 +1589,14 @@ bool EarlyCSE::processNode(DomTreeNode *Node) {
         if (InVal.IsLoad)
           if (auto *I = dyn_cast<Instruction>(Op))
             combineMetadataForCSE(I, &Inst, false);
+        if (auto *AlignMD = Inst.getMetadata(LLVMContext::MD_align)) {
+          auto *A = mdconst::extract<ConstantInt>(AlignMD->getOperand(0));
+          if (Op->getPointerAlignment(SQ.DL).value() % A->getZExtValue() != 0) {
+            IRBuilder B(&Inst);
+            B.CreateAlignmentAssumption(SQ.DL, Op, A);
+          }
+        }
+
         if (!Inst.use_empty())
           Inst.replaceAllUsesWith(Op);
         salvageKnowledge(&Inst, &AC);