https://bugs.llvm.org/show_bug.cgi?id=45772
Bug ID: 45772
Summary: [SimplifyCFG] Alignment mismatch prevents sinking
Product: libraries
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: Scalar Optimizations
Assignee: unassignedb...@nondot.org
Reporter: nikita....@gmail.com
CC: llvm-bugs@lists.llvm.org
opt -S -simplifycfg -sink-common-insts
define void @test(i1 %c, i32* %p1, i32* %p2) {
br i1 %c, label %if1, label %if2
if1:
store i32 0, i32* %p1, align 4
br label %end
if2:
store i32 0, i32* %p2, align 8
br label %end
end:
ret void
}
will not sink the stores into end, because the alignment of the stores differs.
Using align 4 on both stores will sink.
This is because SimplifyCFG checks isSameOperationAs() without the
CompareIgnoringAlignment flag. I believe it should be setting the flag and then
picking the minimum alignment for load/store (possibly by extending andIRFlags
to do that).
Noticed this as an unexpected improvement when inferring less alignment
information.
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