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...ne knows which function gives the information that for 32 unrolled steps it is possible to optimize but not for smaller numbers? I also would like to see why the "XOR A, -1" is not turned into a NOT, any hints on that are welcome. Thanks, Daniel Nicacio 2011/7/26 Daniel Nicácio <dnicacios at gmail.com> > Hi Duncan, > > when I run "opt -std-compile-opts" on the original source code it has the > same output of O3. > when I run "opt -std-compile-opts" on the -O3 optimized code, things get > even more weird, it outputs the following code: >...

2011/7/26 Daniel Nicácio <dnicacios at gmail.com>: > > I also would like to see why the "XOR  A,  -1" is not turned into a NOT, any > Probably because NOT (like NEG) doesn't exist :) <http://llvm.org/docs/LangRef.html#instref> I assume the decision was made that it wasn't worth adding the extra...

Hey guys, I still think there is no optimization doing what I want. When the loop is unrolled 32 times, llvm is able to identify that the loop is working on a whole word, it finds some constants and propagate them, resulting in the folded XOR instruction. However, when the loop operates on some bits of the word, llvm is still not able to fold those XOR, even when the operated bits does not

Hi Duncan, when I run "opt -std-compile-opts" on the original source code it has the same output of O3. when I run "opt -std-compile-opts" on the -O3 optimized code, things get even more weird, it outputs the following code: while.body: ; preds = %while.body, %entry %indvar = phi i32 [ 0, %entry ], [ %indvar.next.3, %while.body ] %tmp

Hi Daniel, > Precisely. The code generated by unrolling can be folded into a single XOR and > SHL. And even if it was not inside a loop, it can still be optimized. What I > want to know is: is there any optimization supposed to optimize this code, but > for some reason it thinks it is not possible, or there is no optimization for > that situation at all? it could be a phase

"The fact that the loop is unrolled explains why the XORs, SHLs, and ORs are not folded into 1." I dont see why the unrolling explains it. "I think he is trying to say this expression generated by unrolling by a factor of 4 can indeed be folded into a single XOR, SHL and OR. " Precisely. The code generated by unrolling can be folded into a single XOR and SHL. And even if it

Hi folks, I couldn't find a specific XOR (OR and AND) optimization on llvm, and therefore I am about to implement it. But first I would like to check with you guys that it really does not exist. For a simple loop like this: nbits = 128; bit_addr = 0; while(nbits--) { bindex=bit_addr>>5; /* Index is number /32 */ bitnumb=bit_addr % 32; /* Bit number in longword */

Hi folks, I am going to submit a project to Google Summer of Code, the Project is below to anyone it might interest. Any critics and suggestions are welcome. If anyone is interested mentoring this project please contact me. Building and Executing Traces on LLVM Daniel Nicacio IC-UNICAMP, Brazil April 5, 2011 1 Objective The objective of this project is to augment LLVM with dynamic pro ling