[llvm] [SelectionDAG] Remove pointer from MMO for VP strided load/store. (PR #82667)

[Craig Topper via llvm-commits]

https://github.com/topperc created https://github.com/llvm/llvm-project/pull/82667

MachineIR alias analysis assumes that only bytes after the pointer will be accessed. This is incorrect if the stride is negative.

This is causing miscompiles in our downstream after SLP started making strided loads.

>From 56ed060a823fee79b935ac50aabd3743940de3f9 Mon Sep 17 00:00:00 2001
From: Craig Topper <craig.topper at sifive.com>
Date: Thu, 22 Feb 2024 10:07:05 -0800
Subject: [PATCH] [SelectionDAG] Remove pointer from MMO for VP strided
 load/store.

MachineIR alias analysis assumes that only bytes after the pointer
will be accessed. This is incorrect if the stride is negative.
---
 llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index e893a5b616d33e..3e53f3318a374a 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -8017,8 +8017,9 @@ void SelectionDAGBuilder::visitVPStridedLoad(
   MemoryLocation ML = MemoryLocation::getAfter(PtrOperand, AAInfo);
   bool AddToChain = !AA || !AA->pointsToConstantMemory(ML);
   SDValue InChain = AddToChain ? DAG.getRoot() : DAG.getEntryNode();
+  unsigned AS = PtrOperand->getPointerAddressSpace();
   MachineMemOperand *MMO = DAG.getMachineFunction().getMachineMemOperand(
-      MachinePointerInfo(PtrOperand), MachineMemOperand::MOLoad,
+      MachinePointerInfo(AS), MachineMemOperand::MOLoad,
       MemoryLocation::UnknownSize, *Alignment, AAInfo, Ranges);
 
   SDValue LD = DAG.getStridedLoadVP(VT, DL, InChain, OpValues[0], OpValues[1],
@@ -8039,8 +8040,9 @@ void SelectionDAGBuilder::visitVPStridedStore(
   if (!Alignment)
     Alignment = DAG.getEVTAlign(VT.getScalarType());
   AAMDNodes AAInfo = VPIntrin.getAAMetadata();
+  unsigned AS = PtrOperand->getPointerAddressSpace();
   MachineMemOperand *MMO = DAG.getMachineFunction().getMachineMemOperand(
-      MachinePointerInfo(PtrOperand), MachineMemOperand::MOStore,
+      MachinePointerInfo(AS), MachineMemOperand::MOStore,
       MemoryLocation::UnknownSize, *Alignment, AAInfo);
 
   SDValue ST = DAG.getStridedStoreVP(