https://bugs.llvm.org/show_bug.cgi?id=51476
Bug ID: 51476
Summary: [AArch64] Peephole pass incorrectly removes comparison
Product: libraries
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: Backend: AArch64
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected],
[email protected], [email protected],
[email protected]
Blocks: 51236
target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
target triple = "aarch64-unknown-linux-gnu"
define void @test(i8 %arg) {
%tmp = alloca i8
%cmp1 = icmp ne i8 %arg, 1
%zext = zext i1 %cmp1 to i8
store i8 %zext, i8* %tmp
%zext2 = load i8, i8* %tmp
%cmp2 = icmp eq i8 %zext2, 3
br i1 %cmp2, label %exit, label %do_call
do_call:
call void @unknown(i8 %zext2)
ret void
exit:
ret void
}
declare void @unknown(i8)
Running through llc produces:
// %bb.0:
str x30, [sp, #-16]! // 8-byte Folded Spill
.cfi_def_cfa_offset 16
.cfi_offset w30, -16
and w8, w0, #0xff
cmp w8, #1
cset w0, ne
strb w0, [sp, #12]
b.ne .LBB0_2
// %bb.1: // %do_call
bl unknown
.LBB0_2: // %common.ret
ldr x30, [sp], #16 // 8-byte Folded Reload
ret
Note how the final comparison to #3 has now reuses the result of the comparison
to #1.
This is caused by the new optimization introduced in
https://reviews.llvm.org/D98564. From a cursory reading, this optimization was
written under the assumption that CmpValue==1 means that the comparison is
against #1, while analyzeCompare() canonicalizes the comparison such that
CmpValue==1 indicates a comparison against any non-zero value.
Referenced Bugs:
https://bugs.llvm.org/show_bug.cgi?id=51236
[Bug 51236] [meta] 13.0.0 Release Blockers
--
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
