Questions tagged [compiler-optimization]
The compiler-optimization tag has no usage guidance.
11
questions
0
votes
1
answer
69
views
Tool to analyze .obj files (not COFF) created with /LTCG
This Microsoft article states that:
When building with LTCG, the compiler front end doesn't invoke the
back end. Instead, it emits an OBJ file with IL in it. It bears
repeating: this IL is not the ...
- 1,550
1
vote
1
answer
83
views
What was the original math operation after optimizing compiler?
I'm pretty sure that original code was much simpler:
(((x + 16) >> 31) ^ abs(x + 16) & 3) + 4 * ((y + 16) % 4) - ((x + 16) >> 31)
Looks like division with remainder... Any ideas what ...
- 33
1
vote
0
answers
60
views
Philosophical and procedural question - Process for using x64 inline assembly in recovering source code
I am assuming this should place be appropriate for what I want to ask. I want to ask more of a philosophical and procedural question because I don't want to try things that have been tried and spend ...
- 773
1
vote
1
answer
186
views
Decompilation of CIL code into some high level code - do I need to introduce new variables during data flow analysis?
I'm writing a compiler from .NET CIL code to some high level language. Process is similar to decompilation. I have done some control flow analysis - detecting loops, ifs, and so on. In terms of data ...
- 13
2
votes
1
answer
169
views
ARM multiply compiler optimization
I need help interpreting this compiler optimization:
;R12 = 0x88888889;
UMULL LR, R2, R12, R3 ; R3 * 0x88888889;
MOV R2, R2,LSR#3 ; ((R3 * 0x88888889 << 32) >&...
- 21
0
votes
1
answer
502
views
Why do those useless instruction are in Rust final binary?
I am currently reversing RUST binaries, and I often come across this block of instruction :
.text:000055F4BFB943F2 db 2Eh
.text:000055F4BFB943F2 nop word ptr [rax+rax+00000000h]
.text:...
- 72
2
votes
1
answer
103
views
Way to check if two assembly programs (one possibly compiled with optimizations) come from the same C source code?
Let's suppose I have two programs in assembly code. And I want to check if they both came from the same source code, but one was compiled with optimizations. Is there a tool that can do this? Or some ...
- 133
4
votes
1
answer
469
views
Can somebody explain this weird alignment/optimisation done when zeroing out a buffer?
I have the following disassembly which looks like a buffer being populated with zeros in a loop, however, I'm confused at why the alignment is needed here (if a jump will always be 4-bytes, why does ...
- 163
2
votes
1
answer
282
views
There is something else than a "DllMain" in a module for its initialization?
All right, Actually I am manually mapping a module into a process, actually my mapper calls DllEntryPoint from standard struct IMAGE_NT_HEADERS thus IMAGE_NT_HEADERS::OptionalHeader::...
- 197
2
votes
1
answer
1k
views
What does this magic number do? [duplicate]
I've opened a 64 bit DLL file in IDA. One function has this pseudocode:
unsigned __int64 output;
ULONG input;
output = (unsigned __int64)(input * (unsigned __int128)0xE38E38E38E38E38Fui64 >> 64)...
- 1,559
0
votes
3
answers
914
views
Explain struct access in assembly?
I am having trouble understanding working with structs in assembly from disassembly.
can you please explain the code below. Disassembly below:
Source code:
- 81