[llvm] b5f7058 - [AArch64][GlobalISel] Don't crash when legalising vector G_SHL (#168848)

[via llvm-commits]

Author: Nathan Corbyn
Date: 2025-12-02T07:57:47Z
New Revision: b5f7058e9114bffccadba520eca9d83891782cde

URL: https://github.com/llvm/llvm-project/commit/b5f7058e9114bffccadba520eca9d83891782cde
DIFF: https://github.com/llvm/llvm-project/commit/b5f7058e9114bffccadba520eca9d83891782cde.diff

LOG: [AArch64][GlobalISel] Don't crash when legalising vector G_SHL (#168848)

Added: 
    

Modified: 
    llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
    llvm/test/CodeGen/AArch64/shift.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
index 120c38ab8404c..1aa1d465d8da6 100644
--- a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
@@ -6684,13 +6684,24 @@ LegalizerHelper::moreElementsVector(MachineInstr &MI, unsigned TypeIdx,
   case TargetOpcode::G_FMAXIMUMNUM:
   case TargetOpcode::G_STRICT_FADD:
   case TargetOpcode::G_STRICT_FSUB:
-  case TargetOpcode::G_STRICT_FMUL:
+  case TargetOpcode::G_STRICT_FMUL: {
+    Observer.changingInstr(MI);
+    moreElementsVectorSrc(MI, MoreTy, 1);
+    moreElementsVectorSrc(MI, MoreTy, 2);
+    moreElementsVectorDst(MI, MoreTy, 0);
+    Observer.changedInstr(MI);
+    return Legalized;
+  }
   case TargetOpcode::G_SHL:
   case TargetOpcode::G_ASHR:
   case TargetOpcode::G_LSHR: {
     Observer.changingInstr(MI);
     moreElementsVectorSrc(MI, MoreTy, 1);
-    moreElementsVectorSrc(MI, MoreTy, 2);
+    // The shift operand may have a 
diff erent scalar type from the source and
+    // destination operands.
+    LLT ShiftMoreTy = MoreTy.changeElementType(
+        MRI.getType(MI.getOperand(2).getReg()).getElementType());
+    moreElementsVectorSrc(MI, ShiftMoreTy, 2);
     moreElementsVectorDst(MI, MoreTy, 0);
     Observer.changedInstr(MI);
     return Legalized;
@@ -6806,12 +6817,10 @@ LegalizerHelper::moreElementsVector(MachineInstr &MI, unsigned TypeIdx,
     LLT DstExtTy;
     if (TypeIdx == 0) {
       DstExtTy = MoreTy;
-      SrcExtTy = LLT::fixed_vector(
-          MoreTy.getNumElements(),
+      SrcExtTy = MoreTy.changeElementType(
           MRI.getType(MI.getOperand(1).getReg()).getElementType());
     } else {
-      DstExtTy = LLT::fixed_vector(
-          MoreTy.getNumElements(),
+      DstExtTy = MoreTy.changeElementType(
           MRI.getType(MI.getOperand(0).getReg()).getElementType());
       SrcExtTy = MoreTy;
     }

diff  --git a/llvm/test/CodeGen/AArch64/shift.ll b/llvm/test/CodeGen/AArch64/shift.ll
index 9827cb3526f99..98c7f673ecd01 100644
--- a/llvm/test/CodeGen/AArch64/shift.ll
+++ b/llvm/test/CodeGen/AArch64/shift.ll
@@ -1033,6 +1033,37 @@ define <2 x i128> @lshr_v2i128(<2 x i128> %0, <2 x i128> %1){
     ret <2 x i128> %3
 }
 
+define <2 x i8> @pr168848(<2 x i1> %shift) {
+; CHECK-SD-LABEL: pr168848:
+; CHECK-SD:       // %bb.0: // %entry
+; CHECK-SD-NEXT:    movi v1.2s, #1
+; CHECK-SD-NEXT:    and v0.8b, v0.8b, v1.8b
+; CHECK-SD-NEXT:    ushl v0.2s, v1.2s, v0.2s
+; CHECK-SD-NEXT:    ret
+;
+; CHECK-GI-LABEL: pr168848:
+; CHECK-GI:       // %bb.0: // %entry
+; CHECK-GI-NEXT:    movi v1.2s, #1
+; CHECK-GI-NEXT:    mov w8, #1 // =0x1
+; CHECK-GI-NEXT:    and v0.8b, v0.8b, v1.8b
+; CHECK-GI-NEXT:    fmov s1, w8
+; CHECK-GI-NEXT:    uzp1 v0.4h, v0.4h, v0.4h
+; CHECK-GI-NEXT:    mov v1.b[1], w8
+; CHECK-GI-NEXT:    uzp1 v0.8b, v0.8b, v0.8b
+; CHECK-GI-NEXT:    ushl v0.8b, v1.8b, v0.8b
+; CHECK-GI-NEXT:    umov w8, v0.b[0]
+; CHECK-GI-NEXT:    umov w9, v0.b[1]
+; CHECK-GI-NEXT:    fmov s0, w8
+; CHECK-GI-NEXT:    mov v0.s[1], w9
+; CHECK-GI-NEXT:    // kill: def $d0 killed $d0 killed $q0
+; CHECK-GI-NEXT:    ret
+entry:
+  %shift.zext = zext <2 x i1> %shift to <2 x i32>
+  %ones = shl <2 x i32> splat (i32 1), %shift.zext
+  %ones.trunc = trunc <2 x i32> %ones to <2 x i8>
+  ret <2 x i8> %ones.trunc
+}
+
 ; ===== Vector with Non-Pow 2 Width =====
 
 define <3 x i8> @shl_v3i8(<3 x i8> %0, <3 x i8> %1){