[LLVMdev] How to make Polly ignore some non-affine memory accesses

[Marcello Maggioni]

Mmm, this code seems to kill polly:

#include <stdio.h>
#include <stdlib.h>

int main()
{
        char *B;
	int i,j,k,h;
	const int x = 0, y=0;
	B = (char *)malloc(sizeof(char)*1024*1024);

	for (i = 1; i < 1024; i++)
		for (j = 1; j < 1024; j++)
		{
			if (i+j > 1000)
				B[j] = i; 	
}
	printf("Random Value: %d", B[rand() % 1024*1024]);

	return 0;
}

running:

opt -load ${PATH_TO_POLLY_LIB}/LLVMPolly.dylib -polly-scops -analyze
code.preopt.ll

I get:

Printing analysis 'Polly - Create polyhedral description of Scops' for
region: 'for.body3 => for.inc.single_exit' in function 'main':
Invalid Scop!
0  libLLVM-3.1svn.dylib 0x0000000103fab905 _ZL15PrintStackTracePv + 53
1  libLLVM-3.1svn.dylib 0x0000000103fabf79 _ZL13SignalHandleri + 361
2  libsystem_c.dylib    0x00007fff94c8acfa _sigtramp + 26
3  libLLVM-3.1svn.dylib 0x0000000103526810
llvm::SmallVectorTemplateCommon<llvm::SCEV
const*>::operator[](unsigned int) + 128
4  LLVMPolly.dylib      0x0000000106867af8
SCEVAffinator::getLoopDepth(llvm::Loop const*) + 72
5  LLVMPolly.dylib      0x00000001068676c7
SCEVAffinator::visitAddRecExpr(llvm::SCEVAddRecExpr const*) + 247
6  LLVMPolly.dylib      0x000000010686710b
llvm::SCEVVisitor<SCEVAffinator, isl_pw_aff*>::visit(llvm::SCEV
const*) + 283
7  LLVMPolly.dylib      0x0000000106866f71
SCEVAffinator::visit(llvm::SCEV const*) + 449
8  LLVMPolly.dylib      0x000000010686766c
SCEVAffinator::visitAddRecExpr(llvm::SCEVAddRecExpr const*) + 156
9  LLVMPolly.dylib      0x000000010686710b
llvm::SCEVVisitor<SCEVAffinator, isl_pw_aff*>::visit(llvm::SCEV
const*) + 283
10 LLVMPolly.dylib      0x0000000106866f71
SCEVAffinator::visit(llvm::SCEV const*) + 449
11 LLVMPolly.dylib      0x000000010685fd49
SCEVAffinator::getPwAff(polly::ScopStmt const*, llvm::SCEV const*,
llvm::Value const*) + 57
12 LLVMPolly.dylib      0x000000010685d076
polly::ScopStmt::buildConditionSet(polly::Comparison const&) const +
54
13 LLVMPolly.dylib      0x000000010685d414
polly::ScopStmt::addConditionsToDomain(isl_set*, polly::TempScop&,
llvm::Region const&) const + 196
14 LLVMPolly.dylib      0x000000010685d519
polly::ScopStmt::buildDomain(polly::TempScop&, llvm::Region const&)
const + 169
15 LLVMPolly.dylib      0x000000010685d90d
polly::ScopStmt::ScopStmt(polly::Scop&, polly::TempScop&, llvm::Region
const&, llvm::BasicBlock&, llvm::SmallVectorImpl<llvm::Loop*>&,
llvm::SmallVectorImpl<unsigned int>&) + 861
16 LLVMPolly.dylib      0x000000010685d59d
polly::ScopStmt::ScopStmt(polly::Scop&, polly::TempScop&, llvm::Region
const&, llvm::BasicBlock&, llvm::SmallVectorImpl<llvm::Loop*>&,
llvm::SmallVectorImpl<unsigned int>&) + 77
17 LLVMPolly.dylib      0x000000010685ef60
polly::Scop::buildScop(polly::TempScop&, llvm::Region const&,
llvm::SmallVectorImpl<llvm::Loop*>&, llvm::SmallVectorImpl<unsigned
int>&, llvm::LoopInfo&) + 624
18 LLVMPolly.dylib      0x000000010685eeab
polly::Scop::buildScop(polly::TempScop&, llvm::Region const&,
llvm::SmallVectorImpl<llvm::Loop*>&, llvm::SmallVectorImpl<unsigned
int>&, llvm::LoopInfo&) + 443
19 LLVMPolly.dylib      0x000000010685ebee
polly::Scop::Scop(polly::TempScop&, llvm::LoopInfo&,
llvm::ScalarEvolution&, isl_ctx*) + 462
20 LLVMPolly.dylib      0x000000010685ea15
polly::Scop::Scop(polly::TempScop&, llvm::LoopInfo&,
llvm::ScalarEvolution&, isl_ctx*) + 53
21 LLVMPolly.dylib      0x000000010685f8f3
polly::ScopInfo::runOnRegion(llvm::Region*, llvm::RGPassManager&) +
227
22 libLLVM-3.1svn.dylib 0x00000001034f4dc1
llvm::RGPassManager::runOnFunction(llvm::Function&) + 1185
23 libLLVM-3.1svn.dylib 0x0000000103a0f261
llvm::FPPassManager::runOnFunction(llvm::Function&) + 497
24 libLLVM-3.1svn.dylib 0x0000000103a0f5cd
llvm::FPPassManager::runOnModule(llvm::Module&) + 125
25 libLLVM-3.1svn.dylib 0x0000000103a0f855
llvm::MPPassManager::runOnModule(llvm::Module&) + 549
26 libLLVM-3.1svn.dylib 0x0000000103a0ffac
llvm::PassManagerImpl::run(llvm::Module&) + 172
27 libLLVM-3.1svn.dylib 0x0000000103a10491
llvm::PassManager::run(llvm::Module&) + 33
28 opt                  0x00000001032dbb76 main + 6966
29 opt                  0x00000001032ca5a4 start + 52
Stack dump:
0.	Program arguments: opt -load
/Users/Kariddi/Documents/Sviluppo/Tesi/git-prefix/lib//LLVMPolly.dylib
-polly-scops -analyze strange_pointer.preopt.ll
1.	Running pass 'Function Pass Manager' on module 'strange_pointer.preopt.ll'.
2.	Running pass 'Region Pass Manager' on function '@main'
3.	Running pass 'Polly - Create polyhedral description of Scops' on
basic block '%for.body3.single_entry'
./compile_ex.sh: line 9: 36824 Segmentation fault: 11  opt -load
${PATH_TO_POLLY_LIB}/LLVMPolly.dylib -polly-scops -analyze
$1.preopt.ll

Also I want to ask:

Why Bitcast instructions make polly discard scops?

Thanks
Marcello

2011/10/27 Marcello Maggioni <hayarms at gmail.com>:
> Perfect, thank you very much :)
>
> 2011/10/26 Tobias Grosser <tobias at grosser.es>:
>> On 10/24/2011 11:32 PM, Marcello Maggioni wrote:
>>>
>>> Strange , with --enable-shared (I use auto tool by the way ...) it gives:
>>>
>>> MacBook-Pro-di-Marcello:examples Kariddi$ ./compile_ex.sh
>>> not_so_simple_loop
>>> clang (LLVM option parsing): Unknown command line argument
>>> '-enable-polly-viewer'.  Try: 'clang (LLVM option parsing) -help'
>>> clang (LLVM option parsing): Did you mean '-enable-polly-vector'?
>>>
>>> Seems like it doesn't compile the viewer option ...
>>
>> This error message is because the option name was changed. Try -polly-show.
>>
>> Furthermore, I plan to commit the change to clang, that solves the failure
>> when loading clang. Though it will probably take a day until it gets through
>> review.
>>
>> Cheers
>> Tobi
>>
>