Commit Graph

6 Commits

Author SHA1 Message Date
Fangrui Song 8fdac7cb7a Revert D71539 "Recommit "[SCEV] Look through single value PHIs.""
This reverts commit 11dccf8d3a.

A bootstrapped clang crashes (due to ArrayRef::front called on an empty
ArrayRef) when compiling some files.  Very strangely, this only reproduces with
modules.

```
13 0x0000564d3349e968 llvm::ArrayRef<llvm::BasicBlock*>::front() const /proc/self/cwd/llvm/include/llvm/ADT/ArrayRef.h:160:7
14 0x0000564d3349e896 llvm::LoopBase<llvm::BasicBlock, llvm::Loop>::getHeader() const /proc/self/cwd/llvm/include/llvm/Analysis/LoopInfo.h:104:50
15 0x0000564d3349fd9d llvm::LoopBase<llvm::BasicBlock, llvm::Loop>::getLoopLatch() const /proc/self/cwd/llvm/include/llvm/Analysis/LoopInfoImpl.h:210:11
16 0x0000564d33593c8a llvm::ScalarEvolution::computeBackedgeTakenCount(llvm::Loop const*, bool) /proc/self/cwd/llvm/lib/Analysis/ScalarEvolution.cpp:6933:15
17 0x0000564d33592ebc llvm::ScalarEvolution::getBackedgeTakenInfo(llvm::Loop const*) /proc/self/cwd/llvm/lib/Analysis/ScalarEvolution.cpp:0:30
18 0x0000564d33593a54 llvm::ScalarEvolution::getBackedgeTakenCount(llvm::Loop const*, llvm::ScalarEvolution::ExitCountKind) /proc/self/cwd/llvm/lib/Analysis/ScalarEvolution.cpp:6487:36
19 0x0000564d32be2402 llvm::ScalarEvolution::getConstantMaxBackedgeTakenCount(llvm::Loop const*) /proc/self/cwd/llvm/include/llvm/Analysis/ScalarEvolution.h:768:5
20 0x0000564d33590807 llvm::ScalarEvolution::getRangeRef(llvm::SCEV const*, llvm::ScalarEvolution::RangeSignHint) /proc/self/cwd/llvm/lib/Analysis/ScalarEvolution.cpp:5495:19
21 0x0000564d320abab7 llvm::ScalarEvolution::getSignedRange(llvm::SCEV const*) /proc/self/cwd/llvm/include/llvm/Analysis/ScalarEvolution.h:840:12
22 0x0000564d335a03aa llvm::ScalarEvolution::isKnownPredicateViaConstantRanges(llvm::CmpInst::Predicate, llvm::SCEV const*, llvm::SCEV const*) /proc/self/cwd/llvm/lib/Analysis/ScalarEvolution.cpp:9239:60
23 0x0000564d33586a80 llvm::ScalarEvolution::isKnownViaNonRecursiveReasoning(llvm::CmpInst::Predicate, llvm::SCEV const*, llvm::SCEV const*) /proc/self/cwd/llvm/lib/Analysis/ScalarEvolution.cpp:10284:60
```
2020-09-21 17:21:43 -07:00
Florian Hahn 11dccf8d3a Recommit "[SCEV] Look through single value PHIs."
This commit was originally because it was suspected to cause a crash,
but a reproducer did not surface.

A crash that was exposed by this change was fixed in 1d8f2e5292.

This reverts the revert commit 0581c0b0ee.
2020-09-21 11:59:50 +01:00
Ali Tamur 0581c0b0ee Revert "[SCEV] Look through single value PHIs."
This reverts commit e441b7a7a0.

This patch causes a compile error in tensorflow opensource project. The stack trace looks like:

Point of crash:
llvm/include/llvm/Analysis/LoopInfoImpl.h : line 35

(gdb) ptype *this
type = const class llvm::LoopBase<llvm::BasicBlock, llvm::Loop> [with BlockT = llvm::BasicBlock, LoopT = llvm::Loop]

(gdb) p *this
$1 = {ParentLoop = 0x0, SubLoops = std::vector of length 0, capacity 0, Blocks = std::vector of length 0, capacity 1,
  DenseBlockSet = {<llvm::SmallPtrSetImpl<llvm::BasicBlock const*>> = {<llvm::SmallPtrSetImplBase> = {<llvm::DebugEpochBase> = {Epoch = 3}, SmallArray = 0x1b2bf6c8, CurArray = 0x1b2bf6c8,
        CurArraySize = 8, NumNonEmpty = 0, NumTombstones = 0}, <No data fields>}, SmallStorage = {0xfffffffffffffffe, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0}}, IsInvalid = true}

(gdb) p *this->DenseBlockSet->CurArray
$2 = (const void *) 0xfffffffffffffffe

I will try to get a case from tensorflow or use creduce to get a small case.
2020-08-12 23:13:24 -07:00
Florian Hahn e441b7a7a0 [SCEV] Look through single value PHIs.
Now that SCEVExpander can preserve LCSSA form,
we do not have to worry about LCSSA form when
trying to look through PHIs. SCEVExpander will take
care of inserting LCSSA PHI nodes as required.

This increases precision of the analysis in some cases.

Reviewed By: mkazantsev, bmahjour

Differential Revision: https://reviews.llvm.org/D71539
2020-08-12 10:03:42 +01:00
Arthur Eubanks 9adbb5cb3a [SCEV] Fix ScalarEvolution tests under NPM
Many tests use opt's -analyze feature, which does not translate well to
NPM and has better alternatives. The alternative here is to explicitly
add a pass that calls ScalarEvolution::print().

The legacy pass manager RUNs aren't changing, but they are now pinned to
the legacy pass manager.  For each legacy pass manager RUN, I added a
corresponding NPM RUN using the 'print<scalar-evolution>' pass. For
compatibility with update_analyze_test_checks.py and existing test
CHECKs, 'print<scalar-evolution>' now prints what -analyze prints per
function.

This was generated by the following Python script and failures were
manually fixed up:

import sys
for i in sys.argv:
    with open(i, 'r') as f:
        s = f.read()
    with open(i, 'w') as f:
        for l in s.splitlines():
            if "RUN:" in l and ' -analyze ' in l and '\\' not in l:
                f.write(l.replace(' -analyze ', ' -analyze -enable-new-pm=0 '))
                f.write('\n')
                f.write(l.replace(' -analyze ', ' -disable-output ').replace(' -scalar-evolution ', ' "-passes=print<scalar-evolution>" ').replace(" | ", " 2>&1 | "))
                f.write('\n')
            else:
                f.write(l)

There are a couple failures still in ScalarEvolution under NPM, but
those are due to other unrelated naming conflicts.

Reviewed By: asbirlea

Differential Revision: https://reviews.llvm.org/D83798
2020-07-16 11:24:07 -07:00
Krzysztof Parzyszek 90f3249ce2 [SCEV] Properly solve quadratic equations
Differential Revision: https://reviews.llvm.org/D48283

llvm-svn: 338758
2018-08-02 19:13:35 +00:00