[InstCombine] Fix evaluation order dependent fold

Make sure the function arguments are evaluated in a predictable order.
llvm · Aug 14, 2023 · 2827aa9 · 2827aa9
1 parent 4192c41
commit 2827aa9
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Showing 2 changed files with 12 additions and 8 deletions.
diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -926,13 +926,17 @@ InstCombinerImpl::foldBinOpOfSelectAndCastOfSelectCondition(BinaryOperator &I) {
 
   // If the value used in the zext/sext is the select condition, or the negated
   // of the select condition, the binop can be simplified.
-  if (CondVal == A)
-    return SelectInst::Create(CondVal, NewFoldedConst(false, TrueVal),
+  if (CondVal == A) {
+    Value *NewTrueVal = NewFoldedConst(false, TrueVal);
+    return SelectInst::Create(CondVal, NewTrueVal,
                               NewFoldedConst(true, FalseVal));
+  }
 
-  if (match(A, m_Not(m_Specific(CondVal))))
-    return SelectInst::Create(CondVal, NewFoldedConst(true, TrueVal),
+  if (match(A, m_Not(m_Specific(CondVal)))) {
+    Value *NewTrueVal = NewFoldedConst(true, TrueVal);
+    return SelectInst::Create(CondVal, NewTrueVal,
                               NewFoldedConst(false, FalseVal));
+  }
 
   return nullptr;
 }

diff --git a/llvm/test/Transforms/InstCombine/binop-select-cast-of-select-cond.ll b/llvm/test/Transforms/InstCombine/binop-select-cast-of-select-cond.ll
@@ -187,8 +187,8 @@ define i64 @select_non_const_sides(i1 %c, i64 %arg1, i64 %arg2) {
 define i6 @sub_select_sext_op_swapped_non_const_args(i1 %c, i6 %argT, i6 %argF) {
 ; CHECK-LABEL: define i6 @sub_select_sext_op_swapped_non_const_args
 ; CHECK-SAME: (i1 [[C:%.*]], i6 [[ARGT:%.*]], i6 [[ARGF:%.*]]) {
-; CHECK-DAG:     [[TMP1:%.*]] = xor i6 [[ARGT]], -1
-; CHECK-DAG:     [[TMP2:%.*]] = sub i6 0, [[ARGF]]
+; CHECK-NEXT:    [[TMP1:%.*]] = xor i6 [[ARGT]], -1
+; CHECK-NEXT:    [[TMP2:%.*]] = sub i6 0, [[ARGF]]
 ; CHECK-NEXT:    [[SUB:%.*]] = select i1 [[C]], i6 [[TMP1]], i6 [[TMP2]]
 ; CHECK-NEXT:    ret i6 [[SUB]]
 ;
@@ -201,8 +201,8 @@ define i6 @sub_select_sext_op_swapped_non_const_args(i1 %c, i6 %argT, i6 %argF)
 define i6 @sub_select_zext_op_swapped_non_const_args(i1 %c, i6 %argT, i6 %argF) {
 ; CHECK-LABEL: define i6 @sub_select_zext_op_swapped_non_const_args
 ; CHECK-SAME: (i1 [[C:%.*]], i6 [[ARGT:%.*]], i6 [[ARGF:%.*]]) {
-; CHECK-DAG:     [[TMP1:%.*]] = sub i6 1, [[ARGT]]
-; CHECK-DAG:     [[TMP2:%.*]] = sub i6 0, [[ARGF]]
+; CHECK-NEXT:    [[TMP1:%.*]] = sub i6 1, [[ARGT]]
+; CHECK-NEXT:    [[TMP2:%.*]] = sub i6 0, [[ARGF]]
 ; CHECK-NEXT:    [[SUB:%.*]] = select i1 [[C]], i6 [[TMP1]], i6 [[TMP2]]
 ; CHECK-NEXT:    ret i6 [[SUB]]
 ;