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llvm-project/llvm/test/Transforms/IndVarSimplify
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Roman Lebedev b2df961231
[IndVarSimplify][LoopUtils] Avoid TOCTOU/ordering issues (PR45835) 
Summary:
Currently, `rewriteLoopExitValues()`'s logic is roughly as following:
> Loop over each incoming value in each PHI node.
> Query whether the SCEV for that incoming value is high-cost.
> Expand the SCEV.
> Perform sanity check (`isValidRewrite()`, D51582)
> Record the info
> Afterwards, see if we can drop the loop given replacements.
> Maybe perform replacements.

The problem is that we interleave SCEV cost checking and expansion.
This is A Problem, because `isHighCostExpansion()` takes special care
to not bill for the expansions that were already expanded, and we can reuse.

While it makes sense in general - if we know that we will expand some SCEV,
all the other SCEV's costs should account for that, which might cause
some of them to become non-high-cost too, and cause chain reaction.

But that isn't what we are doing here. We expand *all* SCEV's, unconditionally.
So every next SCEV's cost will be affected by the already-performed expansions
for previous SCEV's. Even if we are not planning on keeping
some of the expansions we performed.

Worse yet, this current "bonus" depends on the exact PHI node
incoming value processing order. This is completely wrong.

As an example of an issue, see @dmajor's `pr45835.ll` - if we happen to have
a PHI node with two(!) identical high-cost incoming values for the same basic blocks,
we would decide first time around that it is high-cost, expand it,
and immediately decide that it is not high-cost because we have an expansion
that we could reuse (because we expanded it right before, temporarily),
and replace the second incoming value but not the first one;
thus resulting in a broken PHI.

What we instead should do for now, is not perform any expansions
until after we've queried all the costs.

Later, in particular after `isValidRewrite()` is an assertion (D51582)
we could improve upon that, but in a more coherent fashion.

See [[ https://bugs.llvm.org/show_bug.cgi?id=45835 | PR45835 ]]

Reviewers: dmajor, reames, mkazantsev, fhahn, efriedma

Reviewed By: dmajor, mkazantsev

Subscribers: smeenai, nikic, hiraditya, javed.absar, llvm-commits, dmajor

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D79787
 		2020-05-21 13:05:55 +03:00
..
AMDGPU Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
ARM Revert "[SCEV] rewriteLoopExitValues(): even if have hard uses, still rewrite if cheap (PR44668)" 2020-04-03 20:15:04 +03:00
NVPTX Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
X86 [NFC] Create X86 subdirectory for indvar tests 2020-03-26 12:24:45 +00:00
2002-09-09-PointerIndVar.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
2003-04-16-ExprAnalysis.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
2003-09-23-NotAtTop.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
2003-12-10-RemoveInstrCrash.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
2003-12-15-Crash.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
2004-03-10-PHIInsertionBug.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
2004-04-05-InvokeCastCrash.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
2004-04-07-ScalarEvolutionCrash.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
2005-02-11-InvokeCrash.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
2005-02-17-TruncateExprCrash.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
2005-02-26-ExitValueCompute.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
2005-06-15-InstMoveCrash.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
2005-11-18-Crash.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
2006-03-31-NegativeStride.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
2006-06-16-Indvar-LCSSA-Crash.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
2006-09-20-LFTR-Crash.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
2006-12-10-BitCast.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
2007-01-06-TripCount.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
2007-06-06-DeleteDanglesPtr.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
2007-11-23-BitcastCrash.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
2008-06-15-SCEVExpanderBug.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
2008-09-02-IVType.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
2008-10-03-CouldNotCompute.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
2008-11-25-APFloatAssert.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
2009-04-22-IndvarCrash.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
2009-04-27-Floating.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
2009-05-24-useafterfree.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
2011-09-10-widen-nsw.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
2011-09-19-vectoriv.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
2011-09-27-hoistsext.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
2011-10-27-lftrnull.ll Fix a bug w/inbounds invalidation in LFTR (recommit) 2019-06-17 20:32:22 +00:00
2011-11-01-lftrptr.ll [LFTR] Use SCEVExpander for the pointer limit case instead of manual IR gen 2019-07-03 20:03:46 +00:00
2011-11-17-selfphi.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
2012-10-19-congruent-constant.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
2014-06-21-congruent-constant.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
ada-loops.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
ashr-tripcount.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
avoid-i0.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
backedge-on-min-max.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
bec-cmp.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
canonicalize-cmp.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
casted-argument.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
const_phi.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
constant-fold.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
constant_result.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
crash.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
dangling-use.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
divide-pointer.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
dont-recompute.ll Revert "[SCEV] rewriteLoopExitValues(): even if have hard uses, still rewrite if cheap (PR44668)" 2020-04-03 20:15:04 +03:00
drop-exact.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
elim-extend.ll Revert "[SCEV] rewriteLoopExitValues(): even if have hard uses, still rewrite if cheap (PR44668)" 2020-04-03 20:15:04 +03:00
eliminate-comparison.ll [SCEV] SCEVExpander::isHighCostExpansionHelper(): cost-model min/max (PR44668) 2020-02-25 23:05:59 +03:00
eliminate-exit-no-dl.ll [IndVars] Fix a subtle bug in optimizeLoopExits 2019-07-23 17:45:11 +00:00
eliminate-exit.ll [IndVars] Fix sort comparator. 2020-02-27 17:25:18 -08:00
eliminate-max.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
eliminate-rem.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
eliminate-sat.ll [SimplifyIndVar] Simplify non-overflowing saturating add/sub 2019-06-15 08:48:52 +00:00
exit_value_test2.ll [SCEV] SCEVExpander::isHighCostExpansionHelper(): cost-model add/mul 2020-02-25 23:05:58 +03:00
exit_value_test3.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
exit_value_tests.ll [LoopPred] Enable new transformation by default 2019-11-06 15:41:57 -08:00
floating-point-iv.ll [Tests] Add a few more tests for idioms with FP induction variables 2019-10-14 19:10:39 +00:00
full_widening.ll [SCEV] SCEVExpander::isHighCostExpansionHelper(): cost-model min/max (PR44668) 2020-02-25 23:05:59 +03:00
indirectbr.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
infer-poison-flags.ll [Tests] Add poison inference tests for indvars showing both existing transforms, and some room for improvement 2019-06-05 18:00:59 +00:00
interesting-invoke-use.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
iterationCount_zext_or_trunc.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
iv-fold.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
iv-sext.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
iv-widen-elim-ext.ll [IndVarSimplify] Extend previous special case for load use instruction to any narrow type loop variant to avoid extra trunc instruction 2020-03-05 16:27:59 -05:00
iv-zext.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
lcssa-preservation.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
lftr-address-space-pointers.ll [LFTR] Use SCEVExpander for the pointer limit case instead of manual IR gen 2019-07-03 20:03:46 +00:00
lftr-dead-ivs.ll [LoopPred] Selectively disable to preserve test cases 2019-11-06 15:41:57 -08:00
lftr-multi-exit.ll [SCEV] SCEVExpander::isHighCostExpansionHelper(): cost-model min/max (PR44668) 2020-02-25 23:05:59 +03:00
lftr-pr20680.ll [LoopPred] Selectively disable to preserve test cases 2019-11-06 15:41:57 -08:00
lftr-pr31181.ll [IndVarSimplify] Fixup nowrap flags during LFTR (PR31181) 2019-06-01 09:40:18 +00:00
lftr-pr41998.ll [LFTR] Use SCEVExpander for the pointer limit case instead of manual IR gen 2019-07-03 20:03:46 +00:00
lftr-promote.ll [IndVarSimplify] Generate full checks for some LFTR tests; NFC 2019-04-20 12:05:53 +00:00
lftr-reuse.ll [SCEV] SCEVExpander::isHighCostExpansionHelper(): cost-model min/max (PR44668) 2020-02-25 23:05:59 +03:00
lftr.ll [HardwareLoops] llvm.loop.decrement.reg definition 2020-05-21 10:48:16 +01:00
lftr_disabled.ll [IndVarSimplify] Generate full checks for some LFTR tests; NFC 2019-04-20 12:05:53 +00:00
loop-predication.ll [IndVars] Eliminate loop exits with equivalent exit counts 2019-10-20 23:38:02 +00:00
loop_evaluate7.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
loop_evaluate8.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
loop_evaluate9.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
loop_evaluate11.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
loop_evaluate_1.ll [SimplifyCFG] FoldTwoEntryPHINode(): consider *total* speculation cost, not per-BB cost 2019-09-16 16:18:24 +00:00
loop_evaluate_2.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
loop_evaluate_3.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
loop_evaluate_4.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
loop_evaluate_5.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
loop_evaluate_6.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
lrev-existing-umin.ll Revert "[SCEV] rewriteLoopExitValues(): even if have hard uses, still rewrite if cheap (PR44668)" 2020-04-03 20:15:04 +03:00
masked-iv.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
no-iv-rewrite.ll [LoopPred] Selectively disable to preserve test cases 2019-11-06 15:41:57 -08:00
phi-uses-value-multiple-times.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
post-inc-range.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
pr18223.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
pr22222.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
pr24783.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
pr24952.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
pr25060.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
pr25578.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
pr26974.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
pr28705.ll Revert "[SCEV] rewriteLoopExitValues(): even if have hard uses, still rewrite if cheap (PR44668)" 2020-04-03 20:15:04 +03:00
pr32045.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
pr38674.ll [LoopPred] Selectively disable to preserve test cases 2019-11-06 15:41:57 -08:00
pr38855.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
pr39673.ll Revert "[SCEV] rewriteLoopExitValues(): even if have hard uses, still rewrite if cheap (PR44668)" 2020-04-03 20:15:04 +03:00
pr40454.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
pr45835.ll [IndVarSimplify][LoopUtils] Avoid TOCTOU/ordering issues (PR45835) 2020-05-21 13:05:55 +03:00
preserve-memoryssa.ll [IndVarSimplify] Fix for MemorySSA preserve. 2020-01-23 11:06:16 -08:00
preserve-signed-wrap.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
promote-iv-to-eliminate-casts.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
replace-loop-exit-folds.ll [LoopPred] Selectively disable to preserve test cases 2019-11-06 15:41:57 -08:00
replace-sdiv-by-udiv.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
replace-srem-by-urem.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
rewrite-loop-exit-value.ll [IndVars] Extend reasoning about loop invariant exits to non-header blocks 2019-05-14 17:20:10 +00:00
rlev-add-me.ll [IndVars] Fix a bug noticed by inspection 2019-08-23 04:03:23 +00:00
scevexpander-phi-base-case.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
sharpen-range.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
shrunk-constant.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
signed-trip-count.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
single-element-range.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
sink-alloca.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
sink-from-preheader.ll [LoopPred] Selectively disable to preserve test cases 2019-11-06 15:41:57 -08:00
sink-trapping.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
strengthen-overflow.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
tripcount_compute.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
tripcount_infinite.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
udiv-invariant-but-traps.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
udiv.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
ult-sub-to-eq.ll [LFTR] Hoist extend expressions outside of loops w/o waiting for LICM 2019-07-03 18:18:36 +00:00
use-range-metadata.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
variable-stride-ivs-0.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00
widen-loop-comp.ll [SCEV] SCEVExpander::isHighCostExpansionHelper(): cost-model min/max (PR44668) 2020-02-25 23:05:59 +03:00
zext-nuw.ll Revert "Temporarily Revert "Add basic loop fusion pass."" 2019-04-17 04:52:47 +00:00