[llvm] [InstCombine] Fold (X == 0 ? Y : 0) | X to X == 0 ? Y : X (PR #138373)

[Sergei Barannikov via llvm-commits]

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@@ -0,0 +1,177 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -passes=instcombine -S | FileCheck %s
+
+; Basic functional test
+define i32 @basic(i32 %a, i32 %b) {
+; CHECK-LABEL: define i32 @basic(
+; CHECK-SAME: i32 [[A:%.*]], i32 [[B:%.*]]) {
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i32 [[A]], 0
+; CHECK-NEXT:    [[RES:%.*]] = select i1 [[CMP]], i32 [[B]], i32 [[A]]
+; CHECK-NEXT:    ret i32 [[RES]]
+;
+  %cmp = icmp eq i32 %a, 0
+  %sel = select i1 %cmp, i32 %b, i32 0
+  %or = or i32 %sel, %a
+  ret i32 %or
+}
+
+; Operand order swap test
+define i32 @swap_operand_order(i32 %x, i32 %y) {
+; CHECK-LABEL: define i32 @swap_operand_order(
+; CHECK-SAME: i32 [[X:%.*]], i32 [[Y:%.*]]) {
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i32 [[X]], 0
+; CHECK-NEXT:    [[RES:%.*]] = select i1 [[CMP]], i32 [[Y]], i32 [[X]]
+; CHECK-NEXT:    ret i32 [[RES]]
+;
+  %cmp = icmp eq i32 %x, 0
+  %sel = select i1 %cmp, i32 %y, i32 0
+  %or = or i32 %x, %sel
+  ret i32 %or
+}
+
+; Negative test: Non-zero false value in select
+define i32 @negative_non_zero_false_val(i32 %a, i32 %b) {
+; CHECK-LABEL: define i32 @negative_non_zero_false_val(
+; CHECK-SAME: i32 [[A:%.*]], i32 [[B:%.*]]) {
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i32 [[A]], 0
+; CHECK-NEXT:    [[TMP1:%.*]] = or i32 [[A]], 1
+; CHECK-NEXT:    [[OR:%.*]] = select i1 [[CMP]], i32 [[B]], i32 [[TMP1]]
+; CHECK-NEXT:    ret i32 [[OR]]
+;
+  %cmp = icmp eq i32 %a, 0
+  %sel = select i1 %cmp, i32 %b, i32 1
+  %or = or i32 %sel, %a
+  ret i32 %or
+}
+
+; Negative test: Incorrect comparison predicate (NE)
+define i32 @negative_wrong_predicate(i32 %a, i32 %b) {
+; CHECK-LABEL: define i32 @negative_wrong_predicate(
+; CHECK-SAME: i32 [[A:%.*]], i32 [[B:%.*]]) {
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i32 [[A]], 0
+; CHECK-NEXT:    [[TMP1:%.*]] = or i32 [[B]], [[A]]
+; CHECK-NEXT:    [[OR:%.*]] = select i1 [[CMP]], i32 0, i32 [[TMP1]]
+; CHECK-NEXT:    ret i32 [[OR]]
+;
+  %cmp = icmp ne i32 %a, 0
+  %sel = select i1 %cmp, i32 %b, i32 0
+  %or = or i32 %sel, %a
+  ret i32 %or
+}
+
+; Comparison direction swap test (0 == X)
+define i32 @cmp_swapped(i32 %x, i32 %y) {
+; CHECK-LABEL: define i32 @cmp_swapped(
+; CHECK-SAME: i32 [[X:%.*]], i32 [[Y:%.*]]) {
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i32 [[X]], 0
+; CHECK-NEXT:    [[RES:%.*]] = select i1 [[CMP]], i32 [[Y]], i32 [[X]]
+; CHECK-NEXT:    ret i32 [[RES]]
+;
+  %cmp = icmp eq i32 0, %x
+  %sel = select i1 %cmp, i32 %y, i32 0
+  %or = or i32 %x, %sel
+  ret i32 %or
+}
+
+; Complex expression test
+define i32 @complex_expression(i32 %a, i32 %b) {
+; CHECK-LABEL: define i32 @complex_expression(
+; CHECK-SAME: i32 [[A:%.*]], i32 [[B:%.*]]) {
+; CHECK-NEXT:    [[X:%.*]] = add i32 [[A]], 1
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i32 [[X]], 0
+; CHECK-NEXT:    [[RES:%.*]] = select i1 [[CMP]], i32 [[B]], i32 [[X]]
+; CHECK-NEXT:    ret i32 [[RES]]
+;
+  %x = add i32 %a, 1
+  %cmp = icmp eq i32 %x, 0
+  %sel = select i1 %cmp, i32 %b, i32 0
+  %or = or i32 %sel, %x
+  ret i32 %or
+}
+
+; zext test
+define i32 @zext_cond(i8 %a, i32 %b) {
+; CHECK-LABEL: define i32 @zext_cond(
+; CHECK-SAME: i8 [[A:%.*]], i32 [[B:%.*]]) {
+; CHECK-NEXT:    [[Z:%.*]] = zext i8 [[A]] to i32
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i8 [[A]], 0
+; CHECK-NEXT:    [[OR:%.*]] = select i1 [[CMP]], i32 [[B]], i32 [[Z]]
+; CHECK-NEXT:    ret i32 [[OR]]
+;
+  %z = zext i8 %a to i32
+  %cmp = icmp eq i8 %a, 0
+  %sel = select i1 %cmp, i32 %b, i32 0
+  %or = or i32 %sel, %z
+  ret i32 %or
+}
+
+; sext test
+define i32 @sext_cond(i8 %a, i32 %b) {
+; CHECK-LABEL: define i32 @sext_cond(
+; CHECK-SAME: i8 [[A:%.*]], i32 [[B:%.*]]) {
+; CHECK-NEXT:    [[S:%.*]] = sext i8 [[A]] to i32
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i8 [[A]], 0
+; CHECK-NEXT:    [[OR:%.*]] = select i1 [[CMP]], i32 [[B]], i32 [[S]]
+; CHECK-NEXT:    ret i32 [[OR]]
+;
+  %s = sext i8 %a to i32
+  %cmp = icmp eq i8 %a, 0
+  %sel = select i1 %cmp, i32 %b, i32 0
+  %or = or i32 %sel, %s
+  ret i32 %or
+}
+
+; Vector type test
+define <2 x i32> @vector_type(<2 x i32> %a, <2 x i32> %b) {
+; CHECK-LABEL: define <2 x i32> @vector_type(
+; CHECK-SAME: <2 x i32> [[A:%.*]], <2 x i32> [[B:%.*]]) {
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq <2 x i32> [[A]], zeroinitializer
+; CHECK-NEXT:    [[RES:%.*]] = select <2 x i1> [[CMP]], <2 x i32> [[B]], <2 x i32> [[A]]
+; CHECK-NEXT:    ret <2 x i32> [[RES]]
+;
+  %cmp = icmp eq <2 x i32> %a, zeroinitializer
+  %sel = select <2 x i1> %cmp, <2 x i32> %b, <2 x i32> zeroinitializer
+  %or = or <2 x i32> %sel, %a
+  ret <2 x i32> %or
+}
+
+; Pointer type test (should not trigger optimization)
+define ptr @pointer_type(ptr %p, ptr %q) {
+; CHECK-LABEL: define ptr @pointer_type(
+; CHECK-SAME: ptr [[P:%.*]], ptr [[Q:%.*]]) {
+; CHECK-NEXT:    [[A:%.*]] = ptrtoint ptr [[P]] to i64
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq ptr [[P]], null
+; CHECK-NEXT:    [[SEL:%.*]] = select i1 [[CMP]], ptr [[Q]], ptr null
+; CHECK-NEXT:    [[SEL_INT:%.*]] = ptrtoint ptr [[SEL]] to i64
+; CHECK-NEXT:    [[OR:%.*]] = or i64 [[A]], [[SEL_INT]]
+; CHECK-NEXT:    [[RET:%.*]] = inttoptr i64 [[OR]] to ptr
+; CHECK-NEXT:    ret ptr [[RET]]
+;
+  %a = ptrtoint ptr %p to i64
+  %cmp = icmp eq i64 %a, 0
+  %sel = select i1 %cmp, ptr %q, ptr null
+  %sel_int = ptrtoint ptr %sel to i64
+  %or_val = or i64 %a, %sel_int
+  %ret = inttoptr i64 %or_val to ptr
+  ret ptr %ret
+}
+
+; Multi-use test (should not trigger optimization)
+define i32 @multi_use_test(i32 %x, i32 %m) {
+; CHECK-LABEL: define i32 @multi_use_test(
+; CHECK-SAME: i32 [[X:%.*]], i32 [[M:%.*]]) {
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i32 [[X]], 0
+; CHECK-NEXT:    [[SEL:%.*]] = select i1 [[CMP]], i32 [[M]], i32 0
+; CHECK-NEXT:    [[OR:%.*]] = or i32 [[SEL]], [[X]]
+; CHECK-NEXT:    [[ADD:%.*]] = add i32 [[SEL]], [[X]]
+; CHECK-NEXT:    [[O2:%.*]] = sub i32 [[OR]], [[ADD]]
+; CHECK-NEXT:    ret i32 [[O2]]
+;
+  %cmp = icmp eq i32 %x, 0
+  %sel = select i1 %cmp, i32 %m, i32 0
+  %or = or i32 %sel, %x
+  %add = add i32 %sel, %x
----------------
s-barannikov wrote:

https://alive2.llvm.org/ce/z/PoxZtr

https://github.com/llvm/llvm-project/pull/138373