https://bugs.llvm.org/show_bug.cgi?id=40891
Bug ID: 40891
Summary: [X86] DAG combine infinite loop caused by
combineTruncatedArithmetic trying to truncate a
bitcast of a build vector of constants
Product: libraries
Version: trunk
Hardware: PC
OS: Windows NT
Status: NEW
Severity: enhancement
Priority: P
Component: Backend: X86
Assignee: unassignedb...@nondot.org
Reporter: craig.top...@gmail.com
CC: craig.top...@gmail.com, llvm-bugs@lists.llvm.org,
llvm-...@redking.me.uk, spatel+l...@rotateright.com
The following test case causes a DAG combine infinite loop when compiled for
avx2 in 32-bit mode
define <8 x i32> @foo(<8 x i64> %x, <4 x i64> %y) {
%a = shufflevector <4 x i64> %y, <4 x i64> <i64 12345, i64 67890, i64 13579,
i64 24680>, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
%b = and <8 x i64> %x, %a
%c = trunc <8 x i64> %b to <8 x i32>
ret <8 x i32> %c
}
We get in a fight between combienTruncatedArithmetic and
hoistLogicOpWithSameOpcodeHands.
Candidate patch here https://reviews.llvm.org/D58705
Filing this bug so that ISPC which found the bug has something to point to. And
because I probably need to request an 8.0 merge
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