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[InstCombine] add test for miscompile from select value equivalence; NFC 

The new test is reduced from:
https://llvm.org/PR49832
...but we already show a potential miscompile in the existing test too.
This commit is contained in:
Sanjay Patel 2021-04-05 12:03:50 -04:00
parent 62a94b725c
commit c0b0da4684
1 changed files with 14 additions and 0 deletions
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14
llvm/test/Transforms/InstCombine/select-binop-cmp.ll
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@ -551,6 +551,8 @@ define i32 @select_xor_icmp_bad_6(i32 %x, i32 %y, i32 %z) {
ret i32 %C
}
; FIXME: Value equivalence substitution is all-or-nothing, so needs a scalar compare.
define <2 x i8> @select_xor_icmp_vec_bad(<2 x i8> %x, <2 x i8> %y, <2 x i8> %z) {
; CHECK-LABEL: @select_xor_icmp_vec_bad(
; CHECK-NEXT: [[A:%.*]] = icmp eq <2 x i8> [[X:%.*]], <i8 5, i8 3>
@ -564,6 +566,18 @@ define <2 x i8> @select_xor_icmp_vec_bad(<2 x i8> %x, <2 x i8> %y, <2 x i8> %z)
ret <2 x i8> %C
}
; FIXME: Value equivalence substitution is all-or-nothing, so needs a scalar compare.
define <2 x i32> @vec_select_no_equivalence(<2 x i32> %x) {
; CHECK-LABEL: @vec_select_no_equivalence(
; CHECK-NEXT: ret <2 x i32> [[X:%.*]]
;
%x10 = shufflevector <2 x i32> %x, <2 x i32> undef, <2 x i32> <i32 1, i32 0>
%cond = icmp eq <2 x i32> %x, zeroinitializer
%s = select <2 x i1> %cond, <2 x i32> %x10, <2 x i32> %x
ret <2 x i32> %s
}
; Folding this would only be legal if we sanitized undef to 0.
define <2 x i8> @select_xor_icmp_vec_undef(<2 x i8> %x, <2 x i8> %y, <2 x i8> %z) {
; CHECK-LABEL: @select_xor_icmp_vec_undef(