[llvm] 2377b97 - [DAG] SimplifyShift - shift i1/vXi1 X, Y --> X (any non-zero shift amount is undefined).

[Simon Pilgrim via llvm-commits]

Author: Simon Pilgrim
Date: 2024-03-19T20:18:37Z
New Revision: 2377b9773d40d2daa249ac20fe452f041bb6a88c

URL: https://github.com/llvm/llvm-project/commit/2377b9773d40d2daa249ac20fe452f041bb6a88c
DIFF: https://github.com/llvm/llvm-project/commit/2377b9773d40d2daa249ac20fe452f041bb6a88c.diff

LOG: [DAG] SimplifyShift - shift i1/vXi1 X, Y --> X (any non-zero shift amount is undefined).

Alive2: https://alive2.llvm.org/ce/z/SdESbg

Fixes #85681

Added: 
    llvm/test/CodeGen/X86/pr85681.ll

Modified: 
    llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 6f6ed4bd45027b..9d73a42df2a479 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -9595,6 +9595,10 @@ SDValue SelectionDAG::simplifyShift(SDValue X, SDValue Y) {
   if (ISD::matchUnaryPredicate(Y, isShiftTooBig, true))
     return getUNDEF(X.getValueType());
 
+  // shift i1/vXi1 X, Y --> X (any non-zero shift amount is undefined).
+  if (X.getValueType().getScalarType() == MVT::i1)
+    return X;
+
   return SDValue();
 }
 

diff  --git a/llvm/test/CodeGen/X86/pr85681.ll b/llvm/test/CodeGen/X86/pr85681.ll
new file mode 100644
index 00000000000000..3b27a0257ab43d
--- /dev/null
+++ b/llvm/test/CodeGen/X86/pr85681.ll
@@ -0,0 +1,41 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 4
+; RUN: llc < %s -mtriple=x86_64-- -mcpu=emeraldrapids | FileCheck %s
+; RUN: llc < %s -mtriple=x86_64-- -mcpu=x86-64    | FileCheck %s
+; RUN: llc < %s -mtriple=x86_64-- -mcpu=x86-64-v2 | FileCheck %s
+; RUN: llc < %s -mtriple=x86_64-- -mcpu=x86-64-v3 | FileCheck %s
+; RUN: llc < %s -mtriple=x86_64-- -mcpu=x86-64-v4 | FileCheck %s
+
+; PR85681 - shift i1/vXi1 X, Y -> X as only Y==0 is defined
+
+define i32 @shl(i32 %a0) {
+; CHECK-LABEL: shl:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    movl $-1, %eax
+; CHECK-NEXT:    retq
+  %v0 = bitcast i32 %a0 to <32 x i1>
+  %s = shl <32 x i1> <i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true>, %v0
+  %r = bitcast <32 x i1> %s to i32
+  ret i32 %r
+}
+
+define i32 @lshr(i32 %a0) {
+; CHECK-LABEL: lshr:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    movl $-1, %eax
+; CHECK-NEXT:    retq
+  %v0 = bitcast i32 %a0 to <32 x i1>
+  %s = lshr <32 x i1> <i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true>, %v0
+  %r = bitcast <32 x i1> %s to i32
+  ret i32 %r
+}
+
+define i32 @ashr(i32 %a0) {
+; CHECK-LABEL: ashr:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    movl $-1, %eax
+; CHECK-NEXT:    retq
+  %v0 = bitcast i32 %a0 to <32 x i1>
+  %s = ashr <32 x i1> <i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true>, %v0
+  %r = bitcast <32 x i1> %s to i32
+  ret i32 %r
+}