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

Fixes #82657

Author: topperc

llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

@@ -8030,8 +8030,9 @@ 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->getType()->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],
@@ -8052,8 +8053,9 @@ void SelectionDAGBuilder::visitVPStridedStore(
   if (!Alignment)
     Alignment = DAG.getEVTAlign(VT.getScalarType());
   AAMDNodes AAInfo = VPIntrin.getAAMetadata();
+  unsigned AS = PtrOperand->getType()->getPointerAddressSpace();
   MachineMemOperand *MMO = DAG.getMachineFunction().getMachineMemOperand(
-      MachinePointerInfo(PtrOperand), MachineMemOperand::MOStore,
+      MachinePointerInfo(AS), MachineMemOperand::MOStore,
       MemoryLocation::UnknownSize, *Alignment, AAInfo);
 
   SDValue ST = DAG.getStridedStoreVP(

llvm/test/CodeGen/RISCV/rvv/strided-vpload-vpstore-output.ll

@@ -0,0 +1,46 @@
+; NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py UTC_ARGS: --version 4
+; RUN: llc -mtriple=riscv64 -mattr=+v -stop-after=finalize-isel %s -o - | FileCheck %s
+
+; Test makes sure we don't store a pointer in the MachineMemOperand created for
+; these instructions. MachineMemOperand handling can't currently deal with a
+; negative stride that would allow memory before the pointer to be read.
+
+declare <vscale x 1 x i8> @llvm.experimental.vp.strided.load.nxv1i8.p0.i8(ptr, i8, <vscale x 1 x i1>, i32)
+
+define <vscale x 1 x i8> @strided_vpload_nxv1i8_i8(ptr %ptr, i8 signext %stride, <vscale x 1 x i1> %m, i32 zeroext %evl) {
+  ; CHECK-LABEL: name: strided_vpload_nxv1i8_i8
+  ; CHECK: bb.0 (%ir-block.0):
+  ; CHECK-NEXT:   liveins: $x10, $x11, $v0, $x12
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT:   [[COPY:%[0-9]+]]:gprnox0 = COPY $x12
+  ; CHECK-NEXT:   [[COPY1:%[0-9]+]]:vr = COPY $v0
+  ; CHECK-NEXT:   [[COPY2:%[0-9]+]]:gpr = COPY $x11
+  ; CHECK-NEXT:   [[COPY3:%[0-9]+]]:gpr = COPY $x10
+  ; CHECK-NEXT:   $v0 = COPY [[COPY1]]
+  ; CHECK-NEXT:   [[PseudoVLSE8_V_MF8_MASK:%[0-9]+]]:vrnov0 = PseudoVLSE8_V_MF8_MASK $noreg, [[COPY3]], [[COPY2]], $v0, [[COPY]], 3 /* e8 */, 1 /* ta, mu */ :: (load unknown-size, align 1)
+  ; CHECK-NEXT:   $v8 = COPY [[PseudoVLSE8_V_MF8_MASK]]
+  ; CHECK-NEXT:   PseudoRET implicit $v8
+  %load = call <vscale x 1 x i8> @llvm.experimental.vp.strided.load.nxv1i8.p0.i8(ptr %ptr, i8 %stride, <vscale x 1 x i1> %m, i32 %evl)
+  ret <vscale x 1 x i8> %load
+}
+
+declare void @llvm.experimental.vp.strided.store.nxv1i8.p0.i8(<vscale x 1 x i8>, ptr, i8, <vscale x 1 x i1>, i32)
+
+define void @strided_vpstore_nxv1i8_i8(<vscale x 1 x i8> %val, ptr %ptr, i8 signext %stride, <vscale x 1 x i1> %m, i32 zeroext %evl) {
+  ; CHECK-LABEL: name: strided_vpstore_nxv1i8_i8
+  ; CHECK: bb.0 (%ir-block.0):
+  ; CHECK-NEXT:   liveins: $v8, $x10, $x11, $v0, $x12
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT:   [[COPY:%[0-9]+]]:gprnox0 = COPY $x12
+  ; CHECK-NEXT:   [[COPY1:%[0-9]+]]:vr = COPY $v0
+  ; CHECK-NEXT:   [[COPY2:%[0-9]+]]:gpr = COPY $x11
+  ; CHECK-NEXT:   [[COPY3:%[0-9]+]]:gpr = COPY $x10
+  ; CHECK-NEXT:   [[COPY4:%[0-9]+]]:vr = COPY $v8
+  ; CHECK-NEXT:   $v0 = COPY [[COPY1]]
+  ; CHECK-NEXT:   PseudoVSSE8_V_MF8_MASK [[COPY4]], [[COPY3]], [[COPY2]], $v0, [[COPY]], 3 /* e8 */ :: (store unknown-size, align 1)
+  ; CHECK-NEXT:   PseudoRET
+  call void @llvm.experimental.vp.strided.store.nxv1i8.p0.i8(<vscale x 1 x i8> %val, ptr %ptr, i8 %stride, <vscale x 1 x i1> %m, i32 %evl)
+  ret void
+}
+;; NOTE: These prefixes are unused and the list is autogenerated. Do not add tests below this line:
+; CHECK: {{.*}}