[AArch64][GlobalISel] Add support for widening vector store elements to s8.

Reviewers: topperc, arsenm, davemgreen

Reviewed By: arsenm

Pull Request: #121170

Author: aemerson

llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp

@@ -3022,8 +3022,19 @@ LegalizerHelper::widenScalar(MachineInstr &MI, unsigned TypeIdx, LLT WideTy) {
       return UnableToLegalize;
 
     LLT Ty = MRI.getType(MI.getOperand(0).getReg());
-    if (!Ty.isScalar())
-      return UnableToLegalize;
+    assert(!Ty.isPointerOrPointerVector() && "Can't widen type");
+    if (!Ty.isScalar()) {
+      // We need to widen the vector element type.
+      Observer.changingInstr(MI);
+      widenScalarSrc(MI, WideTy, 0, TargetOpcode::G_ANYEXT);
+      // We also need to adjust the MMO to turn this into a truncating store.
+      MachineMemOperand &MMO = **MI.memoperands_begin();
+      MachineFunction &MF = MIRBuilder.getMF();
+      auto *NewMMO = MF.getMachineMemOperand(&MMO, MMO.getPointerInfo(), Ty);
+      MI.setMemRefs(MF, {NewMMO});
+      Observer.changedInstr(MI);
+      return Legalized;
+    }
 
     Observer.changingInstr(MI);
 

llvm/lib/Target/AArch64/GISel/AArch64LegalizerInfo.cpp

@@ -454,6 +454,7 @@ AArch64LegalizerInfo::AArch64LegalizerInfo(const AArch64Subtarget &ST)
           {nxv2s64, p0, nxv2s64, 8},
       })
       .clampScalar(0, s8, s64)
+      .minScalarOrElt(0, s8)
       .lowerIf([=](const LegalityQuery &Query) {
         return Query.Types[0].isScalar() &&
                Query.Types[0] != Query.MMODescrs[0].MemoryTy;

llvm/test/CodeGen/AArch64/GlobalISel/legalize-store-vector-bools.mir

@@ -0,0 +1,32 @@
+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py UTC_ARGS: --version 5
+# RUN: llc -O0 -mtriple=aarch64 -run-pass=legalizer -global-isel-abort=2 %s -o - | FileCheck %s
+# This test currently is expected to fall back after reaching truncstore of <8 x s8> as <8 x s1>.
+---
+name:            store_8xs1
+tracksRegLiveness: true
+body:             |
+  bb.1:
+    liveins: $q0, $q1, $x0
+    ; CHECK-LABEL: name: store_8xs1
+    ; CHECK: liveins: $q0, $q1, $x0
+    ; CHECK-NEXT: {{  $}}
+    ; CHECK-NEXT: [[COPY:%[0-9]+]]:_(<4 x s32>) = COPY $q0
+    ; CHECK-NEXT: [[COPY1:%[0-9]+]]:_(<4 x s32>) = COPY $q1
+    ; CHECK-NEXT: %ptr:_(p0) = COPY $x0
+    ; CHECK-NEXT: [[CONCAT_VECTORS:%[0-9]+]]:_(<8 x s32>) = G_CONCAT_VECTORS [[COPY]](<4 x s32>), [[COPY1]](<4 x s32>)
+    ; CHECK-NEXT: [[C:%[0-9]+]]:_(s32) = G_CONSTANT i32 0
+    ; CHECK-NEXT: [[BUILD_VECTOR:%[0-9]+]]:_(<8 x s32>) = G_BUILD_VECTOR [[C]](s32), [[C]](s32), [[C]](s32), [[C]](s32), [[C]](s32), [[C]](s32), [[C]](s32), [[C]](s32)
+    ; CHECK-NEXT: [[ICMP:%[0-9]+]]:_(<8 x s1>) = G_ICMP intpred(slt), [[CONCAT_VECTORS]](<8 x s32>), [[BUILD_VECTOR]]
+    ; CHECK-NEXT: [[ANYEXT:%[0-9]+]]:_(<8 x s8>) = G_ANYEXT [[ICMP]](<8 x s1>)
+    ; CHECK-NEXT: G_STORE [[ANYEXT]](<8 x s8>), %ptr(p0) :: (store (<8 x s1>))
+    ; CHECK-NEXT: RET_ReallyLR
+    %1:_(<4 x s32>) = COPY $q0
+    %2:_(<4 x s32>) = COPY $q1
+    %ptr:_(p0) = COPY $x0
+    %0:_(<8 x s32>) = G_CONCAT_VECTORS %1(<4 x s32>), %2(<4 x s32>)
+    %4:_(s32) = G_CONSTANT i32 0
+    %3:_(<8 x s32>) = G_BUILD_VECTOR %4(s32), %4(s32), %4(s32), %4(s32), %4(s32), %4(s32), %4(s32), %4(s32)
+    %5:_(<8 x s1>) = G_ICMP intpred(slt), %0(<8 x s32>), %3
+    G_STORE %5(<8 x s1>), %ptr(p0) :: (store (<8 x s1>))
+    RET_ReallyLR
+...