https://bugs.llvm.org/show_bug.cgi?id=44383
Bug ID: 44383
Summary: Instcombine: incorrect transformation 'x > (x &
undef)' -> 'x > undef'
Product: libraries
Version: trunk
Hardware: All
OS: All
Status: NEW
Keywords: miscompilation
Severity: normal
Priority: P
Component: Scalar Optimizations
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected], [email protected],
[email protected], [email protected]
The following transformation in
Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-sgt-to-icmp-sgt.ll
is incorrect:
define <3 x i1> @p3_vec_splat_undef() {
%x = call <3 x i8> @gen3x8()
%tmp0 = and <3 x i8> %x, { 3, undef, 3 }
%ret = icmp sgt <3 x i8> %x, %tmp0
ret <3 x i1> %ret
}
=>
define <3 x i1> @p3_vec_splat_undef() {
%x = call <3 x i8> @gen3x8()
%1 = icmp sgt <3 x i8> %x, { 3, undef, 3 }
ret <3 x i1> %1
}
Transformation doesn't verify!
ERROR: Value mismatch
Example:
Source:
<3 x i8> %x = < poison, #x00 (0), poison >
<3 x i8> %tmp0 = < poison, #x00 (0), poison >
<3 x i1> %ret = < poison, #x0 (0), poison >
Target:
<3 x i8> %x = < poison, #x00 (0), poison >
<3 x i1> %1 = < poison, #x1 (1), poison >
Source value: < poison, #x0 (0), poison >
Target value: < poison, #x1 (1), poison >
The transformation does 'x > (x & undef)' -> 'x > undef'.
Take x=0, undef=-1, and we get '0 > 0' -> '0 > -1'.
--
You are receiving this mail because:
You are on the CC list for the bug._______________________________________________
llvm-bugs mailing list
[email protected]
https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-bugs
