[llvm] [InstCombine] fold `(a == 1 && b != 0) || (a != 0 && b == 0))` to `(a ==0) != (b == 0)` (PR #94915)

[Nikita Popov via llvm-commits]

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@@ -0,0 +1,108 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt < %s -S -passes=instcombine | FileCheck %s
+
+declare void @use(i1)
+
+define void @a_or_b(i32 %a, i32 %b)  {
+; CHECK-LABEL: define void @a_or_b(
+; CHECK-SAME: i32 [[A:%.*]], i32 [[B:%.*]]) {
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp eq i32 [[A]], 0
+; CHECK-NEXT:    [[TMP2:%.*]] = icmp eq i32 [[B]], 0
+; CHECK-NEXT:    [[OR:%.*]] = xor i1 [[TMP1]], [[TMP2]]
+; CHECK-NEXT:    call void @use(i1 [[OR]])
+; CHECK-NEXT:    ret void
+;
+  %a_eq_zero = icmp eq i32 %a, 0
+  %b_ne_zero = icmp ne i32 %b, 0
+  %and.1 = and i1 %a_eq_zero, %b_ne_zero
+  %a_ne_zero = icmp ne i32 %a, 0
+  %b_eq_zero = icmp eq i32 %b, 0
+  %and.2 = and i1 %a_ne_zero, %b_eq_zero
+  %or = or i1 %and.1, %and.2
+  call void @use(i1 %or)
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nikic wrote:

Only use `@use()` for multiple-use tests. Simply return the value in normal tests.

https://github.com/llvm/llvm-project/pull/94915