https://bugs.llvm.org/show_bug.cgi?id=47697
Bug ID: 47697
Summary: MemCpyOpt: uses sext instead of zext for memcpy/memset
size subtraction
Product: libraries
Version: trunk
Hardware: All
OS: All
Status: NEW
Keywords: miscompilation
Severity: normal
Priority: P
Component: Scalar Optimizations
Assignee: unassignedb...@nondot.org
Reporter: nunoplo...@sapo.pt
CC: ah...@bougacha.org, benny....@gmail.com,
florian_h...@apple.com, juneyoung....@sf.snu.ac.kr,
llvm-bugs@lists.llvm.org
Test: Transforms/MemCpyOpt/memset-memcpy-redundant-memset.ll
MemCpyOpt sign-extends the difference between memcpy/memset sizes instead of
zero-extending them.
https://alive2.llvm.org/ce/z/RgKeyt
----------------------------------------
define void @src(* %dst, * %src, i8 %dst_size, i8 %src_size, i8 %c) {
memset * %dst align 1, i8 %c, i8 %dst_size
memcpy * %dst align 1, * %src align 1, i8 %src_size
ret void
}
=>
define void @src(* %dst, * %src, i8 %dst_size, i8 %src_size, i8 %c) {
%1 = usub_sat i8 %dst_size, %src_size
%2 = sext i8 %src_size to i64
%3 = gep * %dst, 1 x i64 %2
memset * %3 align 1, i8 %c, i8 %1
memcpy * %dst align 1, * %src align 1, i8 %src_size
ret void
}
Transformation doesn't verify!
ERROR: Source is more defined than target
Example:
* %dst = pointer(non-local, block_id=1, offset=96)
* %src = pointer(non-local, block_id=1, offset=9007199254741152)
i8 %dst_size = #x83 (131, -125)
i8 %src_size = #x82 (130, -126)
i8 %c = any
Source:
SOURCE MEMORY STATE
===================
NON-LOCAL BLOCKS:
Block 0 > size: 0 align: 1 alloc type: 0
Block 1 > size: 2305843009213693952 align: 2 alloc type: 0
Block 2 > align: 2 alloc type: 0
Target:
i8 %1 = #x01 (1)
i64 %2 = #xffffffffffffff82 (18446744073709551490, -126)
* %3 = pointer(non-local, block_id=1, offset=-30)
Summary:
0 correct transformations
1 incorrect transformations
0 Alive2 errors
https://web.ist.utl.pt/nuno.lopes/alive2/index.php?hash=1546033e6d866cfc&test=Transforms%2FMemCpyOpt%2Fmemset-memcpy-redundant-memset.ll
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