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Revert Fix a bug w/inbounds invalidation in LFTR 

Reverting because it breaks a green dragon build:
    http://green.lab.llvm.org/green/job/clang-stage2-Rthinlto/18208

This reverts r363289 (git commit eb88badff9)

llvm-svn: 363427
This commit is contained in:
Florian Hahn 2019-06-14 17:23:09 +00:00
parent a19809045c
commit dcdd12b68c
5 changed files with 22 additions and 96 deletions
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94
llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
View File

@ -31,7 +31,6 @@
#include "llvm/ADT/None.h"
#include "llvm/ADT/Optional.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
@ -43,7 +42,6 @@
#include "llvm/Analysis/ScalarEvolutionExpressions.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/Constant.h"
@ -2079,48 +2077,6 @@ static bool needsLFTR(Loop *L, BasicBlock *ExitingBB) {
return Phi != getLoopPhiForCounter(IncV, L);
}
/// Return true if undefined behavior would provable be executed on the path to
/// OnPathTo if Root produced a posion result. Note that this doesn't say
/// anything about whether OnPathTo is actually executed or whether Root is
/// actually poison. This can be used to assess whether a new use of Root can
/// be added at a location which is control equivalent with OnPathTo (such as
/// immediately before it) without introducing UB which didn't previously
/// exist. Note that a false result conveys no information.
static bool mustExecuteUBIfPoisonOnPathTo(Instruction *Root,
Instruction *OnPathTo,
DominatorTree *DT) {
// Basic approach is to assume Root is poison, propagate poison forward
// through all users we can easily track, and then check whether any of those
// users are provable UB and must execute before out exiting block might
// exit.
// The set of all recursive users we've visited (which are assumed to all be
// poison because of said visit)
SmallSet<const Value *, 16> KnownPoison;
SmallVector<const Instruction*, 16> Worklist;
Worklist.push_back(Root);
while (!Worklist.empty()) {
const Instruction *I = Worklist.pop_back_val();
// If we know this must trigger UB on a path leading our target.
if (mustTriggerUB(I, KnownPoison) && DT->dominates(I, OnPathTo))
return true;
// If we can't analyze propagation through this instruction, just skip it
// and transitive users. Safe as false is a conservative result.
if (!propagatesFullPoison(I) && I != Root)
continue;
if (KnownPoison.insert(I).second)
for (const User *User : I->users())
Worklist.push_back(cast<Instruction>(User));
}
// Might be non-UB, or might have a path we couldn't prove must execute on
// way to exiting bb.
return false;
}
/// Recursive helper for hasConcreteDef(). Unfortunately, this currently boils
/// down to checking that all operands are constant and listing instructions
/// that may hide undef.
@ -2209,8 +2165,7 @@ static bool isLoopCounter(PHINode* Phi, Loop *L,
/// valid count without scaling the address stride, so it remains a pointer
/// expression as far as SCEV is concerned.
static PHINode *FindLoopCounter(Loop *L, BasicBlock *ExitingBB,
const SCEV *BECount,
ScalarEvolution *SE, DominatorTree *DT) {
const SCEV *BECount, ScalarEvolution *SE) {
uint64_t BCWidth = SE->getTypeSizeInBits(BECount->getType());
Value *Cond = cast<BranchInst>(ExitingBB->getTerminator())->getCondition();
@ -2255,18 +2210,6 @@ static PHINode *FindLoopCounter(Loop *L, BasicBlock *ExitingBB,
continue;
}
// Avoid introducing undefined behavior due to poison which didn't exist in
// the original program. (Annoyingly, the rules for poison and undef
// propagation are distinct, so this does NOT cover the undef case above.)
// We have to ensure that we don't introduce UB by introducing a use on an
// iteration where said IV produces poison. Our strategy here differs for
// pointers and integer IVs. For integers, we strip and reinfer as needed,
// see code in linearFunctionTestReplace. For pointers, we restrict
// transforms as there is no good way to reinfer inbounds once lost.
if (!Phi->getType()->isIntegerTy() &&
!mustExecuteUBIfPoisonOnPathTo(Phi, ExitingBB->getTerminator(), DT))
continue;
const SCEV *Init = AR->getStart();
if (BestPhi && !AlmostDeadIV(BestPhi, LatchBlock, Cond)) {
@ -2395,30 +2338,15 @@ linearFunctionTestReplace(Loop *L, BasicBlock *ExitingBB,
// compare against the post-incremented value, otherwise we must compare
// against the preincremented value.
if (ExitingBB == L->getLoopLatch()) {
bool SafeToPostInc = IndVar->getType()->isIntegerTy();
if (!SafeToPostInc) {
// For pointer IVs, we chose to not strip inbounds which requires us not
// to add a potentially UB introducing use. We need to either a) show
// the loop test we're modifying is already in post-inc form, or b) show
// that adding a use must not introduce UB.
Instruction *Inc =
cast<Instruction>(IndVar->getIncomingValueForBlock(L->getLoopLatch()));
ICmpInst *LoopTest = getLoopTest(L, ExitingBB);
SafeToPostInc = LoopTest->getOperand(0) == Inc ||
LoopTest->getOperand(1) == Inc ||
mustExecuteUBIfPoisonOnPathTo(Inc, ExitingBB->getTerminator(), DT);
}
if (SafeToPostInc) {
// Add one to the "backedge-taken" count to get the trip count.
// This addition may overflow, which is valid as long as the comparison
// is truncated to BackedgeTakenCount->getType().
IVCount = SE->getAddExpr(BackedgeTakenCount,
SE->getOne(BackedgeTakenCount->getType()));
// The BackedgeTaken expression contains the number of times that the
// backedge branches to the loop header. This is one less than the
// number of times the loop executes, so use the incremented indvar.
CmpIndVar = IndVar->getIncomingValueForBlock(ExitingBB);
}
// Add one to the "backedge-taken" count to get the trip count.
// This addition may overflow, which is valid as long as the comparison is
// truncated to BackedgeTakenCount->getType().
IVCount = SE->getAddExpr(BackedgeTakenCount,
SE->getOne(BackedgeTakenCount->getType()));
// The BackedgeTaken expression contains the number of times that the
// backedge branches to the loop header. This is one less than the
// number of times the loop executes, so use the incremented indvar.
CmpIndVar = IndVar->getIncomingValueForBlock(ExitingBB);
}
// It may be necessary to drop nowrap flags on the incrementing instruction
@ -2718,7 +2646,7 @@ bool IndVarSimplify::run(Loop *L) {
if (BETakenCount->isZero())
continue;
PHINode *IndVar = FindLoopCounter(L, ExitingBB, BETakenCount, SE, DT);
PHINode *IndVar = FindLoopCounter(L, ExitingBB, BETakenCount, SE);
if (!IndVar)
continue;

4
llvm/test/Transforms/IndVarSimplify/2011-10-27-lftrnull.ll
View File

@ -28,15 +28,13 @@ define void @test() nounwind {
; CHECK-NEXT: br label [[FOR_BODY21_I:%.*]]
; CHECK: for.body21.i:
; CHECK-NEXT: [[DESTYPIXELPTR_010_I:%.*]] = phi i8* [ null, [[FOR_BODY21_LR_PH_I]] ], [ [[INCDEC_PTR_I:%.*]], [[IF_END_I126:%.*]] ]
; CHECK-NEXT: [[X_09_I:%.*]] = phi i32 [ 0, [[FOR_BODY21_LR_PH_I]] ], [ [[INC_I125:%.*]], [[IF_END_I126]] ]
; CHECK-NEXT: br i1 undef, label [[IF_END_I126]], label [[IF_ELSE_I124:%.*]]
; CHECK: if.else.i124:
; CHECK-NEXT: store i8 undef, i8* [[DESTYPIXELPTR_010_I]], align 1
; CHECK-NEXT: br label [[IF_END_I126]]
; CHECK: if.end.i126:
; CHECK-NEXT: [[INCDEC_PTR_I]] = getelementptr inbounds i8, i8* [[DESTYPIXELPTR_010_I]], i32 1
; CHECK-NEXT: [[INC_I125]] = add nuw i32 [[X_09_I]], 1
; CHECK-NEXT: [[EXITCOND:%.*]] = icmp ne i32 [[INC_I125]], undef
; CHECK-NEXT: [[EXITCOND:%.*]] = icmp ne i8* [[INCDEC_PTR_I]], null
; CHECK-NEXT: br i1 [[EXITCOND]], label [[FOR_BODY21_I]], label [[FOR_END_I129_LOOPEXIT:%.*]]
; CHECK: for.end.i129.loopexit:
; CHECK-NEXT: br label [[FOR_END_I129]]

10
llvm/test/Transforms/IndVarSimplify/2011-11-01-lftrptr.ll
View File

@ -301,12 +301,13 @@ define void @testnullptr([512 x i8]* %base) nounwind {
; PTR64-NEXT: [[CMP1604192:%.*]] = icmp ult i8* undef, [[ADD_PTR1603]]
; PTR64-NEXT: br i1 [[CMP1604192]], label [[FOR_BODY_PREHEADER:%.*]], label [[FOR_END1609:%.*]]
; PTR64: for.body.preheader:
; PTR64-NEXT: [[SCEVGEP:%.*]] = getelementptr [512 x i8], [512 x i8]* [[BASE]], i64 1, i64 0
; PTR64-NEXT: br label [[FOR_BODY:%.*]]
; PTR64: for.body:
; PTR64-NEXT: [[R_17193:%.*]] = phi i8* [ [[INCDEC_PTR1608:%.*]], [[FOR_BODY]] ], [ null, [[FOR_BODY_PREHEADER]] ]
; PTR64-NEXT: [[INCDEC_PTR1608]] = getelementptr i8, i8* [[R_17193]], i64 1
; PTR64-NEXT: [[CMP1604:%.*]] = icmp ult i8* [[INCDEC_PTR1608]], [[ADD_PTR1603]]
; PTR64-NEXT: br i1 [[CMP1604]], label [[FOR_BODY]], label [[FOR_END1609_LOOPEXIT:%.*]]
; PTR64-NEXT: [[EXITCOND:%.*]] = icmp ne i8* [[INCDEC_PTR1608]], [[SCEVGEP]]
; PTR64-NEXT: br i1 [[EXITCOND]], label [[FOR_BODY]], label [[FOR_END1609_LOOPEXIT:%.*]]
; PTR64: for.end1609.loopexit:
; PTR64-NEXT: br label [[FOR_END1609]]
; PTR64: for.end1609:
@ -320,12 +321,13 @@ define void @testnullptr([512 x i8]* %base) nounwind {
; PTR32-NEXT: [[CMP1604192:%.*]] = icmp ult i8* undef, [[ADD_PTR1603]]
; PTR32-NEXT: br i1 [[CMP1604192]], label [[FOR_BODY_PREHEADER:%.*]], label [[FOR_END1609:%.*]]
; PTR32: for.body.preheader:
; PTR32-NEXT: [[SCEVGEP:%.*]] = getelementptr [512 x i8], [512 x i8]* [[BASE]], i32 1, i32 0
; PTR32-NEXT: br label [[FOR_BODY:%.*]]
; PTR32: for.body:
; PTR32-NEXT: [[R_17193:%.*]] = phi i8* [ [[INCDEC_PTR1608:%.*]], [[FOR_BODY]] ], [ null, [[FOR_BODY_PREHEADER]] ]
; PTR32-NEXT: [[INCDEC_PTR1608]] = getelementptr i8, i8* [[R_17193]], i64 1
; PTR32-NEXT: [[CMP1604:%.*]] = icmp ult i8* [[INCDEC_PTR1608]], [[ADD_PTR1603]]
; PTR32-NEXT: br i1 [[CMP1604]], label [[FOR_BODY]], label [[FOR_END1609_LOOPEXIT:%.*]]
; PTR32-NEXT: [[EXITCOND:%.*]] = icmp ne i8* [[INCDEC_PTR1608]], [[SCEVGEP]]
; PTR32-NEXT: br i1 [[EXITCOND]], label [[FOR_BODY]], label [[FOR_END1609_LOOPEXIT:%.*]]
; PTR32: for.end1609.loopexit:
; PTR32-NEXT: br label [[FOR_END1609]]
; PTR32: for.end1609:

8
llvm/test/Transforms/IndVarSimplify/lftr-dead-ivs.ll
View File

@ -25,16 +25,14 @@ define void @neg_dynamically_dead_inbounds(i1 %always_false) #0 {
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: [[I_0:%.*]] = phi i8 [ 0, [[ENTRY:%.*]] ], [ [[TMP4:%.*]], [[CONT:%.*]] ]
; CHECK-NEXT: [[P_0:%.*]] = phi i8* [ getelementptr inbounds ([240 x i8], [240 x i8]* @data, i64 0, i64 0), [[ENTRY]] ], [ [[TMP3:%.*]], [[CONT]] ]
; CHECK-NEXT: [[P_0:%.*]] = phi i8* [ getelementptr inbounds ([240 x i8], [240 x i8]* @data, i64 0, i64 0), [[ENTRY:%.*]] ], [ [[TMP3:%.*]], [[CONT:%.*]] ]
; CHECK-NEXT: [[TMP3]] = getelementptr inbounds i8, i8* [[P_0]], i64 1
; CHECK-NEXT: br i1 [[ALWAYS_FALSE:%.*]], label [[NEVER_EXECUTED:%.*]], label [[CONT]]
; CHECK: never_executed:
; CHECK-NEXT: store volatile i8 0, i8* [[TMP3]]
; CHECK-NEXT: br label [[CONT]]
; CHECK: cont:
; CHECK-NEXT: [[TMP4]] = add nuw i8 [[I_0]], 1
; CHECK-NEXT: [[EXITCOND:%.*]] = icmp ne i8 [[TMP4]], -10
; CHECK-NEXT: [[EXITCOND:%.*]] = icmp ne i8* [[TMP3]], getelementptr (i8, i8* getelementptr inbounds ([240 x i8], [240 x i8]* @data, i64 0, i64 0), i64 246)
; CHECK-NEXT: br i1 [[EXITCOND]], label [[LOOP]], label [[EXIT:%.*]]
; CHECK: exit:
; CHECK-NEXT: ret void
@ -112,7 +110,7 @@ define void @dom_store_preinc() #0 {
; CHECK-NEXT: [[P_0:%.*]] = phi i8* [ getelementptr inbounds ([240 x i8], [240 x i8]* @data, i64 0, i64 0), [[ENTRY:%.*]] ], [ [[TMP3:%.*]], [[LOOP]] ]
; CHECK-NEXT: store volatile i8 0, i8* [[P_0]]
; CHECK-NEXT: [[TMP3]] = getelementptr inbounds i8, i8* [[P_0]], i64 1
; CHECK-NEXT: [[EXITCOND:%.*]] = icmp ne i8* [[P_0]], getelementptr (i8, i8* getelementptr inbounds ([240 x i8], [240 x i8]* @data, i64 0, i64 0), i64 245)
; CHECK-NEXT: [[EXITCOND:%.*]] = icmp ne i8* [[TMP3]], getelementptr (i8, i8* getelementptr inbounds ([240 x i8], [240 x i8]* @data, i64 0, i64 0), i64 246)
; CHECK-NEXT: br i1 [[EXITCOND]], label [[LOOP]], label [[EXIT:%.*]]
; CHECK: exit:
; CHECK-NEXT: ret void

2
llvm/test/Transforms/IndVarSimplify/lftr.ll
View File

@ -167,7 +167,7 @@ define void @test_zext(i8* %a) #0 {
; CHECK-NEXT: [[TMP2:%.*]] = load i8, i8* [[DOT0]], align 1
; CHECK-NEXT: [[TMP3]] = getelementptr inbounds i8, i8* [[P_0]], i64 1
; CHECK-NEXT: store i8 [[TMP2]], i8* [[P_0]], align 1
; CHECK-NEXT: [[EXITCOND:%.*]] = icmp ne i8* [[P_0]], getelementptr inbounds ([240 x i8], [240 x i8]* @data, i64 0, i64 239)
; CHECK-NEXT: [[EXITCOND:%.*]] = icmp ne i8* [[TMP3]], getelementptr (i8, i8* getelementptr inbounds ([240 x i8], [240 x i8]* @data, i64 0, i64 0), i64 240)
; CHECK-NEXT: br i1 [[EXITCOND]], label [[LOOP]], label [[EXIT:%.*]]
; CHECK: exit:
; CHECK-NEXT: ret void