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llvm-project/llvm/test/Transforms/InstCombine/select-cmp-eq-op-fold.ll
Yingwei Zheng 5e2dcfe42c
[InstCombine] Avoid infinite loop in foldSelectValueEquivalence (#142754) 
Before this patch, InstCombine hung because it replaced a value with a
more complex one:
```
%sel = select i1 %cmp, i32 %smax, i32 0 ->
%sel = select i1 %cmp, i32 %masked, i32 0 ->
%sel = select i1 %cmp, i32 %smax, i32 0 ->
...
```
This patch makes this replacement more conservative. It only performs
the replacement iff the new value is one of the operands of the original
value.

Closes https://github.com/llvm/llvm-project/issues/142405.
2025-06-04 19:42:56 +08:00

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; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -passes=instcombine -S | FileCheck %s
declare void @use.i1(i1)
declare void @use.i8(i8)
define i8 @replace_with_y_noundef(i8 %x, i8 noundef %y, i8 %z) {
; CHECK-LABEL: @replace_with_y_noundef(
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP]], i8 [[Y]], i8 [[Z:%.*]]
; CHECK-NEXT: ret i8 [[SEL]]
;
%cmp = icmp eq i8 %x, %y
%and = and i8 %x, %y
%sel = select i1 %cmp, i8 %and, i8 %z
ret i8 %sel
}
define i8 @replace_with_x_noundef(i8 noundef %x, i8 %y, i8 %z) {
; CHECK-LABEL: @replace_with_x_noundef(
; CHECK-NEXT: [[CMP:%.*]] = icmp ne i8 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: call void @use.i1(i1 [[CMP]])
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP]], i8 [[Z:%.*]], i8 [[X]]
; CHECK-NEXT: ret i8 [[SEL]]
;
%cmp = icmp ne i8 %x, %y
call void @use.i1(i1 %cmp)
%and = or i8 %x, %y
%sel = select i1 %cmp, i8 %z, i8 %and
ret i8 %sel
}
define i8 @replace_with_x_maybe_undef_fail(i8 %x, i8 %y, i8 %z) {
; CHECK-LABEL: @replace_with_x_maybe_undef_fail(
; CHECK-NEXT: [[CMP:%.*]] = icmp ne i8 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: call void @use.i1(i1 [[CMP]])
; CHECK-NEXT: [[AND:%.*]] = or i8 [[X]], [[Y]]
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP]], i8 [[Z:%.*]], i8 [[AND]]
; CHECK-NEXT: ret i8 [[SEL]]
;
%cmp = icmp ne i8 %x, %y
call void @use.i1(i1 %cmp)
%and = or i8 %x, %y
%sel = select i1 %cmp, i8 %z, i8 %and
ret i8 %sel
}
define i8 @replace_with_y_for_new_oneuse(i8 noundef %xx, i8 noundef %y, i8 %z) {
; CHECK-LABEL: @replace_with_y_for_new_oneuse(
; CHECK-NEXT: [[X:%.*]] = mul i8 [[XX:%.*]], 13
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[X]], [[Y:%.*]]
; CHECK-NEXT: [[ADD:%.*]] = add nuw i8 [[X]], [[Y]]
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP]], i8 [[ADD]], i8 [[Z:%.*]]
; CHECK-NEXT: ret i8 [[SEL]]
;
%x = mul i8 %xx, 13
%cmp = icmp eq i8 %x, %y
%add = add nuw i8 %x, %y
%sel = select i1 %cmp, i8 %add, i8 %z
ret i8 %sel
}
define i8 @replace_with_y_for_new_oneuse2(i8 %xx, i8 noundef %y, i8 %z, i8 %q) {
; CHECK-LABEL: @replace_with_y_for_new_oneuse2(
; CHECK-NEXT: [[X:%.*]] = mul i8 [[XX:%.*]], 13
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[X]], [[Y:%.*]]
; CHECK-NEXT: [[ADD:%.*]] = add nuw i8 [[X]], [[Q:%.*]]
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP]], i8 [[ADD]], i8 [[Z:%.*]]
; CHECK-NEXT: ret i8 [[SEL]]
;
%x = mul i8 %xx, 13
%cmp = icmp eq i8 %x, %y
%add = add nuw i8 %x, %q
%sel = select i1 %cmp, i8 %add, i8 %z
ret i8 %sel
}
define i8 @replace_with_x_for_new_oneuse(i8 noundef %xx, i8 noundef %yy, i8 %z, i8 %w) {
; CHECK-LABEL: @replace_with_x_for_new_oneuse(
; CHECK-NEXT: [[X:%.*]] = mul i8 [[XX:%.*]], 13
; CHECK-NEXT: [[Y:%.*]] = add i8 [[YY:%.*]], [[W:%.*]]
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[X]], [[Y]]
; CHECK-NEXT: [[MUL:%.*]] = mul i8 [[X]], [[Y]]
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP]], i8 [[MUL]], i8 [[Z:%.*]]
; CHECK-NEXT: ret i8 [[SEL]]
;
%x = mul i8 %xx, 13
%y = add i8 %yy, %w
%cmp = icmp eq i8 %x, %y
%mul = mul i8 %x, %y
%sel = select i1 %cmp, i8 %mul, i8 %z
ret i8 %sel
}
define i8 @replace_with_x_for_new_oneuse2(i8 noundef %xx, i8 %yy, i8 %z, i8 %w, i8 %q) {
; CHECK-LABEL: @replace_with_x_for_new_oneuse2(
; CHECK-NEXT: [[X:%.*]] = mul i8 [[XX:%.*]], 13
; CHECK-NEXT: [[Y:%.*]] = add i8 [[YY:%.*]], [[W:%.*]]
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[X]], [[Y]]
; CHECK-NEXT: [[MUL:%.*]] = mul i8 [[Q:%.*]], [[Y]]
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP]], i8 [[MUL]], i8 [[Z:%.*]]
; CHECK-NEXT: ret i8 [[SEL]]
;
%x = mul i8 %xx, 13
%y = add i8 %yy, %w
%cmp = icmp eq i8 %x, %y
%mul = mul i8 %q, %y
%sel = select i1 %cmp, i8 %mul, i8 %z
ret i8 %sel
}
define i8 @replace_with_x_for_simple_binop(i8 noundef %xx, i8 %yy, i8 %z, i8 %w) {
; CHECK-LABEL: @replace_with_x_for_simple_binop(
; CHECK-NEXT: [[X:%.*]] = mul i8 [[XX:%.*]], 13
; CHECK-NEXT: [[Y:%.*]] = add i8 [[YY:%.*]], [[W:%.*]]
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[X]], [[Y]]
; CHECK-NEXT: [[MUL:%.*]] = mul i8 [[X]], [[Y]]
; CHECK-NEXT: call void @use.i8(i8 [[Y]])
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP]], i8 [[MUL]], i8 [[Z:%.*]]
; CHECK-NEXT: ret i8 [[SEL]]
;
%x = mul i8 %xx, 13
%y = add i8 %yy, %w
%cmp = icmp eq i8 %x, %y
%mul = mul i8 %x, %y
call void @use.i8(i8 %y)
%sel = select i1 %cmp, i8 %mul, i8 %z
ret i8 %sel
}
define i8 @replace_with_none_for_new_oneuse_fail_maybe_undef(i8 %xx, i8 %y, i8 %z) {
; CHECK-LABEL: @replace_with_none_for_new_oneuse_fail_maybe_undef(
; CHECK-NEXT: [[X:%.*]] = mul i8 [[XX:%.*]], 13
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[X]], [[Y:%.*]]
; CHECK-NEXT: [[MUL:%.*]] = mul i8 [[X]], [[Y]]
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP]], i8 [[MUL]], i8 [[Z:%.*]]
; CHECK-NEXT: ret i8 [[SEL]]
;
%x = mul i8 %xx, 13
%cmp = icmp eq i8 %x, %y
%mul = mul i8 %x, %y
%sel = select i1 %cmp, i8 %mul, i8 %z
ret i8 %sel
}
define i8 @replace_with_y_for_simple_binop(i8 %x, i8 noundef %y, i8 %z) {
; CHECK-LABEL: @replace_with_y_for_simple_binop(
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[MUL:%.*]] = mul nsw i8 [[X]], [[Y]]
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP]], i8 [[MUL]], i8 [[Z:%.*]]
; CHECK-NEXT: ret i8 [[SEL]]
;
%cmp = icmp eq i8 %x, %y
%mul = mul nsw i8 %x, %y
%sel = select i1 %cmp, i8 %mul, i8 %z
ret i8 %sel
}
define i8 @replace_with_y_for_simple_binop_fail_multiuse(i8 %x, i8 noundef %y, i8 %z) {
; CHECK-LABEL: @replace_with_y_for_simple_binop_fail_multiuse(
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[MUL:%.*]] = mul nsw i8 [[X]], [[Y]]
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP]], i8 [[MUL]], i8 [[Z:%.*]]
; CHECK-NEXT: call void @use.i8(i8 [[MUL]])
; CHECK-NEXT: ret i8 [[SEL]]
;
%cmp = icmp eq i8 %x, %y
%mul = mul nsw i8 %x, %y
%sel = select i1 %cmp, i8 %mul, i8 %z
call void @use.i8(i8 %mul)
ret i8 %sel
}
define i8 @replace_with_y_for_simple_binop_fail(i8 %x, i8 noundef %y, i8 %z, i8 %q) {
; CHECK-LABEL: @replace_with_y_for_simple_binop_fail(
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[MUL:%.*]] = mul nsw i8 [[X]], [[Q:%.*]]
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP]], i8 [[MUL]], i8 [[Z:%.*]]
; CHECK-NEXT: ret i8 [[SEL]]
;
%cmp = icmp eq i8 %x, %y
%mul = mul nsw i8 %x, %q
%sel = select i1 %cmp, i8 %mul, i8 %z
ret i8 %sel
}
; Make sure we don't run into an infinite loop.
define i32 @pr142405(i32 noundef %x) {
; CHECK-LABEL: @pr142405(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[SMAX:%.*]] = call i32 @llvm.smax.i32(i32 [[X:%.*]], i32 0)
; CHECK-NEXT: [[MASKED:%.*]] = and i32 [[SMAX]], 65535
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 [[X]], [[MASKED]]
; CHECK-NEXT: [[TMP0:%.*]] = and i32 [[SMAX]], 1
; CHECK-NEXT: [[AND:%.*]] = select i1 [[CMP]], i32 [[TMP0]], i32 0
; CHECK-NEXT: ret i32 [[AND]]
;
entry:
%smax = call i32 @llvm.smax.i32(i32 %x, i32 0)
%masked = and i32 %smax, 65535
%cmp = icmp eq i32 %x, %masked
%sel = select i1 %cmp, i32 %smax, i32 0
%and = and i32 %sel, 1
ret i32 %and
}
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