Skip to content
This repository has been archived by the owner on Jul 1, 2023. It is now read-only.

Missing info on assumptions/limitations #5

Closed
amonakov opened this issue Jun 20, 2018 · 2 comments
Closed

Missing info on assumptions/limitations #5

amonakov opened this issue Jun 20, 2018 · 2 comments
Assignees
@maksfb

Comments

@amonakov
Copy link

The tool consumes post-link binaries. In general, even finding instruction boundaries on x86 isn't exactly solvable, let alone deciding basic block boundaries, safety of reordering, etc. Thus, the tool obviously makes a lot of assumptions about input, or, in other words, has limitations w.r.t which programs can be correctly transformed.

The EuroLLVM'2016 presentation on BOLT has a brief enumeration of (some?) limitations, so evidently the issues were realized, but unfortunately neither the README nor the initial Facebook article make no mention of them.

It would be nice to have a description of the class of programs to which BOLT may be applied safely.

Also, if BOLT implementation has built-in safeguards for deciding "can't touch this code", it would be nice to know how they operate, too.
@maksfb maksfb self-assigned this Jun 20, 2018
@maksfb
Copy link
Contributor

maksfb commented Jun 20, 2018

It's a really good suggestion. Thank you. We'll add the detailed requirements.

@dstogov dstogov mentioned this issue Jun 20, 2018
Open
@suresh-srinivas suresh-srinivas mentioned this issue Jun 21, 2018
Closed
@danielcdh danielcdh mentioned this issue Jun 21, 2018
Open
@tmsri tmsri mentioned this issue Jul 2, 2018
Closed
@maksfb
Copy link
Contributor

maksfb commented Jan 2, 2019

The README now lists general input binary requirements. If you have specific questions please let me know.

@maksfb maksfb closed this as completed Jan 2, 2019
@railkar railkar mentioned this issue Jul 22, 2019
Closed
@derek-zhang derek-zhang mentioned this issue Aug 1, 2019
Open
@uttampawar uttampawar mentioned this issue Feb 14, 2020
Closed
@ghost ghost mentioned this issue Oct 18, 2020
Closed
@zpget zpget mentioned this issue Nov 10, 2020
Open
@dongAxis dongAxis mentioned this issue Apr 20, 2021
Closed
@ccx1225 ccx1225 mentioned this issue Aug 24, 2021
Open
@mgrice mgrice mentioned this issue Sep 17, 2021
Open
@nadavrot nadavrot mentioned this issue Oct 27, 2021
Closed
@valuenumbering valuenumbering mentioned this issue Dec 13, 2021
Closed
aaupov pushed a commit that referenced this issue Dec 24, 2021
@joker-eph
Revert "[MLIR] rewrite AffineStructures and Presburger tests to use t…
6963be1 
…he parser"

This reverts commit b0e8667.

ASAN/UBSAN bot is broken with this trace:

[ RUN      ] FlatAffineConstraintsTest.FindSampleTest
llvm-project/mlir/include/mlir/Support/MathExtras.h:27:15: runtime error: signed integer overflow: 1229996100002 * 809999700000 cannot be represented in type 'long'
    #0 0x7f63ace960e4 in mlir::ceilDiv(long, long) llvm-project/mlir/include/mlir/Support/MathExtras.h:27:15
    #1 0x7f63ace8587e in ceil llvm-project/mlir/include/mlir/Analysis/Presburger/Fraction.h:57:42
    #2 0x7f63ace8587e in operator* llvm-project/llvm/include/llvm/ADT/STLExtras.h:347:42
    #3 0x7f63ace8587e in uninitialized_copy<llvm::mapped_iterator<mlir::Fraction *, long (*)(mlir::Fraction), long>, long *> include/c++/v1/__memory/uninitialized_algorithms.h:36:62
    #4 0x7f63ace8587e in uninitialized_copy<llvm::mapped_iterator<mlir::Fraction *, long (*)(mlir::Fraction), long>, long *> llvm-project/llvm/include/llvm/ADT/SmallVector.h:490:5
    #5 0x7f63ace8587e in append<llvm::mapped_iterator<mlir::Fraction *, long (*)(mlir::Fraction), long>, void> llvm-project/llvm/include/llvm/ADT/SmallVector.h:662:5
    #6 0x7f63ace8587e in SmallVector<llvm::mapped_iterator<mlir::Fraction *, long (*)(mlir::Fraction), long> > llvm-project/llvm/include/llvm/ADT/SmallVector.h:1204:11
    #7 0x7f63ace8587e in mlir::FlatAffineConstraints::findIntegerSample() const llvm-project/mlir/lib/Analysis/AffineStructures.cpp:1171:27
    #8 0x7f63ae95a84d in mlir::checkSample(bool, mlir::FlatAffineConstraints const&, mlir::TestFunction) llvm-project/mlir/unittests/Analysis/AffineStructuresTest.cpp:37:23
    #9 0x7f63ae957545 in mlir::FlatAffineConstraintsTest_FindSampleTest_Test::TestBody() llvm-project/mlir/unittests/Analysis/AffineStructuresTest.cpp:222:3
@dafoerx dafoerx mentioned this issue Jan 4, 2022
Open
maksfb pushed a commit that referenced this issue Jan 10, 2022
@RitanyaB @chichunchen
SIGSEGV in ompt_tsan_dependences with for-ordered
378b0ac 
Segmentation fault in ompt_tsan_dependences function due to an unchecked NULL pointer dereference is as follows:

```
ThreadSanitizer:DEADLYSIGNAL
	==140865==ERROR: ThreadSanitizer: SEGV on unknown address 0x000000000050 (pc 0x7f217c2d3652 bp 0x7ffe8cfc7e00 sp 0x7ffe8cfc7d90 T140865)
	==140865==The signal is caused by a READ memory access.
	==140865==Hint: address points to the zero page.
	/usr/bin/addr2line: DWARF error: could not find variable specification at offset 1012a
	/usr/bin/addr2line: DWARF error: could not find variable specification at offset 133b5
	/usr/bin/addr2line: DWARF error: could not find variable specification at offset 1371a
	/usr/bin/addr2line: DWARF error: could not find variable specification at offset 13a58
	#0 ompt_tsan_dependences(ompt_data_t*, ompt_dependence_t const*, int) /ptmp/bhararit/llvm-project/openmp/tools/archer/ompt-tsan.cpp:1004 (libarcher.so+0x15652)
	#1 __kmpc_doacross_post /ptmp/bhararit/llvm-project/openmp/runtime/src/kmp_csupport.cpp:4280 (libomp.so+0x74d98)
	#2 .omp_outlined. for_ordered_01.c:? (for_ordered_01.exe+0x5186cb)
	#3 __kmp_invoke_microtask /ptmp/bhararit/llvm-project/openmp/runtime/src/z_Linux_asm.S:1166 (libomp.so+0x14e592)
	#4 __kmp_invoke_task_func /ptmp/bhararit/llvm-project/openmp/runtime/src/kmp_runtime.cpp:7556 (libomp.so+0x909ad)
	#5 __kmp_fork_call /ptmp/bhararit/llvm-project/openmp/runtime/src/kmp_runtime.cpp:2284 (libomp.so+0x8461a)
	#6 __kmpc_fork_call /ptmp/bhararit/llvm-project/openmp/runtime/src/kmp_csupport.cpp:308 (libomp.so+0x6db55)
	#7 main ??:? (for_ordered_01.exe+0x51828f)
	#8 __libc_start_main ??:? (libc.so.6+0x24349)
	#9 _start /home/abuild/rpmbuild/BUILD/glibc-2.26/csu/../sysdeps/x86_64/start.S:120 (for_ordered_01.exe+0x4214e9)

	ThreadSanitizer can not provide additional info.
	SUMMARY: ThreadSanitizer: SEGV /ptmp/bhararit/llvm-project/openmp/tools/archer/ompt-tsan.cpp:1004 in ompt_tsan_dependences(ompt_data_t*, ompt_dependence_t const*, int)
	==140865==ABORTING
```

	To reproduce the error, use the following openmp code snippet:

```
/* initialise  testMatrixInt Matrix, cols, r and c */
	  #pragma omp parallel private(r,c) shared(testMatrixInt)
	    {
	      #pragma omp for ordered(2)
	      for (r=1; r < rows; r++) {
	        for (c=1; c < cols; c++) {
	          #pragma omp ordered depend(sink:r-1, c+1) depend(sink:r-1,c-1)
	          testMatrixInt[r][c] = (testMatrixInt[r-1][c] + testMatrixInt[r-1][c-1]) % cols ;
	          #pragma omp ordered depend (source)
	        }
	      }
	    }
```

	Compilation:
```
clang -g -stdlib=libc++ -fsanitize=thread -fopenmp -larcher test_case.c
```

	It seems like the changes introduced by the commit https://reviews.llvm.org/D114005 causes this particular SEGV while using Archer.

Reviewed By: protze.joachim

Differential Revision: https://reviews.llvm.org/D115328
@DreamTeamWangbowen DreamTeamWangbowen mentioned this issue Mar 3, 2022
Open
@dongjianqiang2 dongjianqiang2 mentioned this issue Mar 22, 2022
Closed
Sign up for free to subscribe to this conversation on GitHub. Already have an account? Sign in.
Assignees

@maksfb maksfb

Labels
None yet
Projects
None yet
Milestone
No milestone
Development

No branches or pull requests
2 participants
@amonakov @maksfb