Displaying 3 results from an estimated 3 matches for "speculativelyexecutebb".
2013 Nov 11
1
[LLVMdev] if-conversion
Hi,
>
> Sorry to dig up an old thread but I wondered what the status of
> if-conversion in LLVM is. Has any work been done towards handling this as a
> transform pass on the IR?
>
As far as I know, some if-conversion is done in SimplifyCFG: Have a look at
the SpeculativelyExecuteBB function in lib/Transforms/Utils/SimplifyCFG.cpp.
Cheers,
Jonas
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2016 Aug 12
3
AutoFDO sample profiles v. SelectInst,
...version to disastrous results.
If we compile -O0 for training, and then use the profile now with
accurate branch weights, the program runs in 149.5
seconds. Unfortunately, of course, the training program runs in 501.4
seconds.
Alternately, if we disable the original select conversion performed in
SpeculativelyExecuteBB in SimplifyCFG.cpp so the original control is
visible to sampling, the training program now runs in 229.7 seconds and
the optimized program runs in 151.5, so we recover essentially all of
lost information.
Of course both if these options are unfortunate because they alter the
workflow where it wou...
2012 Mar 29
1
[LLVMdev] Problem recognizing nested select operations
Hello all,
I just noticed that LLVM has trouble recognizing nested simple select
operations.
My testcase is as follows:
-------------------------- snip ------------------------------
#include <stdio.h>
int main(int argc, char **argv)
{
int a;
scanf("%d", &a);
a = a > 255 ? 255 : a < 0 ? 0 : a;
printf("A: %d\n", a);
return 0;
}