Hello.
I am trying to create my own LoopVectorize.cpp pass as a separate pass from
the LLVM
trunk, as described in
http://llvm.org/docs/CMake.html#embedding-llvm-in-your-project. Did
anybody try something like this?
I added close to the end of the .cpp file:
/* this line seems to be required - it allows to run this pass
as an embedded pass by giving opt -my-loop-vectorize */
static RegisterPass<LoopVectorize> Z("my-loop-vectorize",
"Write comments in source
file.");
Note that I did NOT register my new pass in
llvm/lib/Transforms/IPO/PassManagerBuilder.cpp - the original LoopVectorize
module is
registered there.
However, when I give:
opt -debug -load NewLoopVectorize.so -my-loop-vectorize test.c
it does not vectorize a loop that was normally vectorized by the original
LoopVectorize module in LLVM. My module gives:
<<loop not vectorized: loop control flow is not understood by
vectorizer
LV: Not vectorizing: Cannot prove legality.>>
So I tried to explicitly run a few more passes before my new LoopVectorize
to help it
(I think the most important one is -loop-simplify, which canonicalizes the
loop):
opt -debug -loop-simplify -mem2reg -lcssa -load NewLoopVectorize.so
-my-loop-vectorize test.c
However, I do not see any line in the output of opt starting with
"LoopSimplify"
(when I have success, when I give opt -O3, I get "LoopSimplify: Creating
pre-header
for.body.preheader; LoopSimplify: Creating dedicated exit block
for.end.loopexit" before
LoopVectorize) and my LoopVectorize still does not vectorize the loop.
Can anybody help me run explicitly the LoopSimplify pass (before my
LoopVectorize pass)?
Thank you. And wish you happy Easter holidays!
Alex
Hi.
I managed to find the reason why my own LoopVectorize pass does not
vectorize.
Actually, the loop-simplify pass was getting executed, but because it did
not run the
passes loop-rotate and licm before it did not generate a proper loop preheader
and the
loops were not valid for vectorization.
To make my own LoopVectorize pass vectorize I got inspired from the
arguments
displayed on stdout of:
opt -debug-pass=Arguments -O3 ...
and looked at what other passes are being executed before and after
-loop-vectorize .
So I chose the following:
opt -mem2reg -loop-rotate -licm -loop-unswitch -simplifycfg -domtree
-basicaa -aa
-instcombine -loops -loop-simplify \
-force-vector-width=128 -load MyLoopVectorize.so -my-loop-vectorize \
-loop-simplify -scalar-evolution -aa -loop-accesses -loop-load-elim
-basicaa
-aa -instcombine -scalar-evolution -demanded-bits -slp-vectorizer
Best regards,
Alex
On 4/14/2017 11:04 PM, Alex Susu wrote:> Hello.
> I am trying to create my own LoopVectorize.cpp pass as a separate pass
from the LLVM
> trunk, as described in
http://llvm.org/docs/CMake.html#embedding-llvm-in-your-project. Did
> anybody try something like this?
> I added close to the end of the .cpp file:
> /* this line seems to be required - it allows to run this pass
> as an embedded pass by giving opt -my-loop-vectorize */
> static RegisterPass<LoopVectorize>
Z("my-loop-vectorize",
> "Write comments in source
file.");
>
> Note that I did NOT register my new pass in
> llvm/lib/Transforms/IPO/PassManagerBuilder.cpp - the original LoopVectorize
module is
> registered there.
>
> However, when I give:
> opt -debug -load NewLoopVectorize.so -my-loop-vectorize test.c
> it does not vectorize a loop that was normally vectorized by the
original
> LoopVectorize module in LLVM. My module gives:
> <<loop not vectorized: loop control flow is not understood by
vectorizer
> LV: Not vectorizing: Cannot prove legality.>>
>
> So I tried to explicitly run a few more passes before my new
LoopVectorize to help it
> (I think the most important one is -loop-simplify, which canonicalizes the
loop):
> opt -debug -loop-simplify -mem2reg -lcssa -load NewLoopVectorize.so
> -my-loop-vectorize test.c
> However, I do not see any line in the output of opt starting with
"LoopSimplify" (when
> I have success, when I give opt -O3, I get "LoopSimplify: Creating
pre-header
> for.body.preheader; LoopSimplify: Creating dedicated exit block
for.end.loopexit" before
> LoopVectorize) and my LoopVectorize still does not vectorize the loop.
>
> Can anybody help me run explicitly the LoopSimplify pass (before my
LoopVectorize pass)?
>
> Thank you. And wish you happy Easter holidays!
> Alex
Hello.
I come back to this thread because I still have issues with my separate
LoopVectorize
(same code, but without relying on PassManagerBuilder and -O3) LLVM pass.
More exactly, my LoopVectorize pass, when given the following reduction
code:
short SumReduce(short *C, short N) {
short sum = 0;
for (short i = 0; i < N; ++i) {
sum += C[i];
}
return sum;
}
I get on the standard error of opt:
LV: Checking a loop in "SumReduce" from test.c:15:3
LV: Loop hints: force=? width=128 unroll=0
LV: Found a loop: for.body
LoopVectorize::canVectorizeInstrs(): PhiScev =
{0,+,1}<nuw><nsw><%for.body>
LoopVectorize::canVectorizeInstrs(): AR =
{0,+,1}<nuw><nsw><%for.body>
LV: Found an induction variable.
LoopVectorize::canVectorizeInstrs(): PhiScev = %sum.02
LV: PHI is not a poly recurrence.
LV: PHI is not a poly recurrence.
remark: <unknown>:0:0: loop not vectorized: value that could not be
identified as
reduction is used outside the loop
LV: Found an unidentified PHI. %sum.02 = phi i32 [ %add, %for.body ], [
0,
%for.body.preheader ]
LV: Can't vectorize the instructions or CFG
LV: Not vectorizing: Cannot prove legality.
Exiting LoopVectorize::runOnFunction()
Does anybody know what pass would be helpful for this issue (e.g. "PHI
is not a poly
recurrence."), besides the passes presented below already.?
Thank you very much,
Alex
On 4/17/2017 1:01 PM, Alex Susu wrote:> Hi.
> I managed to find the reason why my own LoopVectorize pass does not
vectorize.
> Actually, the loop-simplify pass was getting executed, but because it
did not run the
> passes loop-rotate and licm before it did not generate a proper loop
preheader and the
> loops were not valid for vectorization.
>
> To make my own LoopVectorize pass vectorize I got inspired from the
arguments
> displayed on stdout of:
> opt -debug-pass=Arguments -O3 ...
> and looked at what other passes are being executed before and after
-loop-vectorize .
>
> So I chose the following:
> opt -mem2reg -loop-rotate -licm -loop-unswitch -simplifycfg -domtree
-basicaa -aa
> -instcombine -loops -loop-simplify \
> -force-vector-width=128 -load MyLoopVectorize.so
-my-loop-vectorize \
> -loop-simplify -scalar-evolution -aa -loop-accesses
-loop-load-elim -basicaa -aa
> -instcombine -scalar-evolution -demanded-bits -slp-vectorizer
>
>
> Best regards,
> Alex
>
> On 4/14/2017 11:04 PM, Alex Susu wrote:
>> Hello.
>> I am trying to create my own LoopVectorize.cpp pass as a separate
pass from the LLVM
>> trunk, as described in
http://llvm.org/docs/CMake.html#embedding-llvm-in-your-project. Did
>> anybody try something like this?
>> I added close to the end of the .cpp file:
>> /* this line seems to be required - it allows to run this pass
>> as an embedded pass by giving opt -my-loop-vectorize */
>> static RegisterPass<LoopVectorize>
Z("my-loop-vectorize",
>> "Write comments in source
file.");
>>
>> Note that I did NOT register my new pass in
>> llvm/lib/Transforms/IPO/PassManagerBuilder.cpp - the original
LoopVectorize module is
>> registered there.
>>
>> However, when I give:
>> opt -debug -load NewLoopVectorize.so -my-loop-vectorize test.c
>> it does not vectorize a loop that was normally vectorized by the
original
>> LoopVectorize module in LLVM. My module gives:
>> <<loop not vectorized: loop control flow is not
understood by vectorizer
>> LV: Not vectorizing: Cannot prove legality.>>
>>
>> So I tried to explicitly run a few more passes before my new
LoopVectorize to help it
>> (I think the most important one is -loop-simplify, which canonicalizes
the loop):
>> opt -debug -loop-simplify -mem2reg -lcssa -load
NewLoopVectorize.so
>> -my-loop-vectorize test.c
>> However, I do not see any line in the output of opt starting with
"LoopSimplify" (when
>> I have success, when I give opt -O3, I get "LoopSimplify: Creating
pre-header
>> for.body.preheader; LoopSimplify: Creating dedicated exit block
for.end.loopexit" before
>> LoopVectorize) and my LoopVectorize still does not vectorize the loop.
>>
>> Can anybody help me run explicitly the LoopSimplify pass (before my
LoopVectorize
>> pass)?
>>
>> Thank you. And wish you happy Easter holidays!
>> Alex