[llvm] [InstCombine] Fold (sub (xor X, (sext C)), (sext C)) => (select C (neg X), X) (PR #79417)
Nikita Popov via llvm-commits
llvm-commits at lists.llvm.org
Wed Jan 31 04:01:37 PST 2024
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@@ -0,0 +1,114 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 4
+; RUN: opt < %s -passes=instcombine -S | FileCheck %s
+
+define i64 @foo(i64 %a, i1 %b) {
+; CHECK-LABEL: define i64 @foo(
+; CHECK-SAME: i64 [[A:%.*]], i1 [[B:%.*]]) {
+; CHECK-NEXT: [[TMP1:%.*]] = sub i64 0, [[A]]
+; CHECK-NEXT: [[R:%.*]] = select i1 [[B]], i64 [[TMP1]], i64 [[A]]
+; CHECK-NEXT: ret i64 [[R]]
+;
+ %c = sext i1 %b to i64
+ %d = xor i64 %a, %c
+ %r = sub i64 %d, %c
+ ret i64 %r
+}
+
+define i64 @bar(i64 %a, i1 %b) {
+; CHECK-LABEL: define i64 @bar(
+; CHECK-SAME: i64 [[A:%.*]], i1 [[B:%.*]]) {
+; CHECK-NEXT: [[TMP1:%.*]] = sub i64 0, [[A]]
+; CHECK-NEXT: [[R:%.*]] = select i1 [[B]], i64 [[A]], i64 [[TMP1]]
+; CHECK-NEXT: ret i64 [[R]]
+;
+ %c = sext i1 %b to i64
+ %d = xor i64 %a, %c
+ %r = sub i64 %c, %d
+ ret i64 %r
+}
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nikic wrote:
Unless I overlooked it, you're missing a commuted test for the xor operands.
https://github.com/llvm/llvm-project/pull/79417
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