Fangrui Song adddf2a5ad Revert D71539 "Recommit "[SCEV] Look through single value PHIs."" ... This reverts commit 11dccf8d3aa5d55210f8b886fb21926c7a8353ca. 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
..
AArch64	Mark FMOV constant materialization as being as cheap as a move.	2020-09-10 16:38:59 +00:00
AMDGPU	Migrate function attribute "no-frame-pointer-elim" to "frame-pointer"="all" as cleanups after D56351	2019-12-24 15:57:33 -08:00
ARM	[LSR][ARM] Add new TTI hook to mark some LSR chains as profitable	2020-05-13 14:18:28 +01:00
NVPTX
Power	[SCEV] don't query getSCEV() for incomplete phis	2020-08-01 02:38:54 -04:00
X86	[LoopIdiom,LSR] Add additional tests for SCEVExpander cleanups.	2020-08-21 13:48:31 +01:00
2005-08-15-AddRecIV.ll
2005-08-17-OutOfLoopVariant.ll
2005-09-12-UsesOutOutsideOfLoop.ll
2007-04-23-UseIterator.ll
2008-08-13-CmpStride.ll
2008-09-09-Overflow.ll
2009-01-13-nonconstant-stride-outside-loop.ll
2009-04-28-no-reduce-mul.ll
2011-07-19-CritEdgeBreakCrash.ll
2011-10-03-CritEdgeMerge.ll
2011-10-06-ReusePhi.ll	[SCEV] Use NoWrapFlags when expanding a simple mul	2019-06-17 10:05:18 +00:00
2011-10-13-SCEVChain.ll
2011-10-14-IntPtr.ll
2011-12-19-PostincQuadratic.ll
2012-01-02-nopreheader.ll
2012-01-16-nopreheader.ll
2012-03-15-nopreheader.ll
2012-03-26-constexpr.ll
2012-07-13-ExpandUDiv.ll
2012-07-18-LimitReassociate.ll
2013-01-05-IndBr.ll
2013-01-14-ReuseCast.ll
addrec-gep-address-space.ll
addrec-gep.ll
address-space-loop.ll
count-to-zero.ll
dead-phi.ll
different-type-ivs.ll
dominate-assert.ll
dont_insert_redundant_ops.ll
dont_reduce_bytes.ll
dont_reverse.ll
dont-hoist-simple-loop-constants.ll
ephemeral.ll
exit_compare_live_range.ll
funclet.ll	Revert D71539 "Recommit "[SCEV] Look through single value PHIs.""	2020-09-21 17:21:43 -07:00
gnarly-setupcost.ll
hoist-parent-preheader.ll
illegal-addr-modes.ll
invariant_value_first_arg.ll
invariant_value_first.ll
ivchain.ll	[NewPM][LSR] Rename strength-reduce -> loop-reduce	2020-07-02 11:15:29 -07:00
lsr-comp-time.ll
lsr-overflow.ll
missing-phi-operand-update.ll
negative-scale.ll
nested-reduce.ll
nonintegral.ll
nonlinear-postinc.ll
ops_after_indvar.ll
phi_node_update_multiple_preds.ll
post-inc-icmpzero.ll	[SCEV] Use NoWrapFlags when expanding a simple mul	2019-06-17 10:05:18 +00:00
post-inc-optsize.ll
pr2537.ll
pr2570.ll	[NFC][LSR] Avoid undefined grep in pr2570.ll	2019-06-19 16:02:54 +00:00
pr3086.ll
pr3399.ll
pr3571.ll
pr12018.ll
pr12048.ll
pr12691.ll
pr18165.ll	Migrate function attribute "no-frame-pointer-elim" to "frame-pointer"="all" as cleanups after D56351	2019-12-24 15:57:33 -08:00
pr25541.ll
pr27056.ll	[SCEVExpander] Avoid re-using existing casts if it means updating users.	2020-08-09 13:25:17 +01:00
pr31627.ll
preserve-gep-loop-variant.ll
related_indvars.ll
remove_indvar.ll
scaling_factor_cost_crash.ll
scev-after-loopinstsimplify.ll
scev-expander-lcssa.ll	[SCEV] Add additional tests.	2020-07-28 16:15:57 +01:00
scev-insertpt-bug.ll
sext-ind-var.ll
share_code_in_preheader.ll
share_ivs.ll
shl.ll
two-combinations-bug.ll	Migrate function attribute "no-frame-pointer-elim"="false" to "frame-pointer"="none" as cleanups after D56351	2019-12-24 16:27:51 -08:00
uglygep-address-space.ll
uglygep.ll
use_postinc_value_outside_loop.ll
var_stride_used_by_compare.ll
variable_stride.ll