Create rewriter for x86 strcpy chain #1272
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Many x86 binaries contanains strcpy(<dst>, <src>) compiled as
scasb/movsd/movsb sequence:
```
mov edi,<src>
mov edx,<dst>
or ecx,0FFh
xor eax,eax
repne scasb
not ecx
sub edi,ecx
mov esi,edi
mov eax,ecx
mov edi,edx
shr ecx,2h
rep movsd
mov ecx,eax
and ecx,3h
rep movsb
ret
```
Allow DeadCodeEliminator to delete it.
uxmal
reviewed
Jul 25, 2023
| var stms = block.Statements.ToArray(); | ||
| for (int i = 0; i < stms.Length - 1; i++) | ||
| { | ||
| if (TryRewriteStrcpy(subject, stms[i], stms[i + 1])) |
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What if there is another non-related statement between stms[i] and stms[i+1]? Would it be better to "chase" the definition-uses in the SsaState to get more accurate results?
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This code excecutes after expression coalescing, so there is not statements between two memcpy calls normally. And it is unsafe to reorder statements in common case.
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Add support for any 2^n aligmnent intead of using magic number 4.
|
Looks good. Thanks for the contribution! |
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Many x86 binaries contanains strcpy(
<dst>,<src>) compiled asscasb/movsd/movsb sequence: