[AArch64][GlobalISel] Don't crash when legalising vector G_SHL

Author: cofibrant

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

@@ -216,15 +216,15 @@ AArch64LegalizerInfo::AArch64LegalizerInfo(const AArch64Subtarget &ST)
       .widenScalarToNextPow2(0)
       .clampScalar(1, s32, s64)
       .clampScalar(0, s32, s64)
+      .minScalarSameAs(1, 0)
+      .minScalarEltSameAsIf(isVector(0), 1, 0)
+      .maxScalarEltSameAsIf(isVector(0), 1, 0)
       .clampNumElements(0, v8s8, v16s8)
       .clampNumElements(0, v4s16, v8s16)
       .clampNumElements(0, v2s32, v4s32)
       .clampNumElements(0, v2s64, v2s64)
       .moreElementsToNextPow2(0)
-      .minScalarSameAs(1, 0)
-      .scalarizeIf(scalarOrEltWiderThan(0, 64), 0)
-      .minScalarEltSameAsIf(isVector(0), 1, 0)
-      .maxScalarEltSameAsIf(isVector(0), 1, 0);
+      .scalarizeIf(scalarOrEltWiderThan(0, 64), 0);
 
   getActionDefinitionsBuilder(G_PTR_ADD)
       .legalFor({{p0, s64}, {v2p0, v2s64}})

llvm/test/CodeGen/AArch64/GlobalISel/legalize-shl-crash.ll

@@ -0,0 +1,29 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 6
+; RUN: llc -global-isel -o - %s | FileCheck %s
+
+target triple = "aarch64-unknown-unknown"
+
+; Check we don't crash here.
+
+define <2 x i8> @test() {
+; CHECK-LABEL: test:
+; CHECK:       // %bb.0: // %entry
+; CHECK-NEXT:    mov w8, #1 // =0x1
+; CHECK-NEXT:    mov w9, #0 // =0x0
+; CHECK-NEXT:    fmov s0, w8
+; CHECK-NEXT:    fmov s1, w9
+; CHECK-NEXT:    mov v0.b[1], w8
+; CHECK-NEXT:    mov v1.b[1], w9
+; CHECK-NEXT:    ushl v0.8b, v0.8b, v1.8b
+; CHECK-NEXT:    umov w8, v0.b[0]
+; CHECK-NEXT:    umov w9, v0.b[1]
+; CHECK-NEXT:    fmov s0, w8
+; CHECK-NEXT:    mov v0.s[1], w9
+; CHECK-NEXT:    // kill: def $d0 killed $d0 killed $q0
+; CHECK-NEXT:    ret
+entry:
+  %zeroes = zext <2 x i1> zeroinitializer to <2 x i32>
+  %ones = shl <2 x i32> splat (i32 1), %zeroes
+  %ones.trunc = trunc <2 x i32> %ones to <2 x i8>
+  ret <2 x i8> %ones.trunc
+}