Extended Description

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