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LSR: fix IVUsers isSimplifiedLoopNest to perform a full domtree walk

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instead of skipping the current loop.

My prior fix was incomplete because of an overzealous compile-time optimization:
Better fix for: <rdar://problem/11049788> Segmentation fault: 11 in LoopStrengthReduce

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@153131 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Andrew Trick 2012-03-20 21:24:40 +00:00
parent aa7b3df178
commit f9492288bb
2 changed files with 96 additions and 19 deletions
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42
lib/Analysis/IVUsers.cpp
View File

@ -79,22 +79,31 @@ static bool isInteresting(const SCEV *S, const Instruction *I, const Loop *L,
return false;
}
/// Return true if this loop and all loop headers that dominate it are in
/// simplified form.
static bool isSimplifiedLoopNest(Loop *L, const DominatorTree *DT,
const LoopInfo *LI) {
if (!L->isLoopSimplifyForm())
return false;
for (DomTreeNode *Rung = DT->getNode(L->getLoopPreheader());
/// Return true if all loop headers that dominate this block are in simplified
/// form.
static bool isSimplifiedLoopNest(BasicBlock *BB, const DominatorTree *DT,
const LoopInfo *LI,
SmallPtrSet<Loop*,16> &SimpleLoopNests) {
Loop *NearestLoop = 0;
for (DomTreeNode *Rung = DT->getNode(BB);
Rung; Rung = Rung->getIDom()) {
BasicBlock *BB = Rung->getBlock();
const Loop *DomLoop = LI->getLoopFor(BB);
if (DomLoop && DomLoop->getHeader() == BB) {
BasicBlock *DomBB = Rung->getBlock();
Loop *DomLoop = LI->getLoopFor(DomBB);
if (DomLoop && DomLoop->getHeader() == DomBB) {
// If the domtree walk reaches a loop with no preheader, return false.
if (!DomLoop->isLoopSimplifyForm())
return false;
// If we have already checked this loop nest, stop checking.
if (SimpleLoopNests.count(DomLoop))
break;
// If we have not already checked this loop nest, remember the loop
// header nearest to BB. The nearest loop may not contain BB.
if (!NearestLoop)
NearestLoop = DomLoop;
}
}
if (NearestLoop)
SimpleLoopNests.insert(NearestLoop);
return true;
}
@ -137,15 +146,10 @@ bool IVUsers::AddUsersIfInteresting(Instruction *I,
if (isa<PHINode>(User) && Processed.count(User))
continue;
Loop *UserLoop = LI->getLoopFor(User->getParent());
// Only consider IVUsers that are dominated by simplified loop
// headers. Otherwise, SCEVExpander will crash.
if (UserLoop && !SimpleLoopNests.count(UserLoop)) {
if (!isSimplifiedLoopNest(UserLoop, DT, LI))
return false;
SimpleLoopNests.insert(UserLoop);
}
if (!isSimplifiedLoopNest(User->getParent(), DT, LI, SimpleLoopNests))
return false;
// Descend recursively, but not into PHI nodes outside the current loop.
// It's important to see the entire expression outside the loop to get
@ -154,7 +158,7 @@ bool IVUsers::AddUsersIfInteresting(Instruction *I,
// If User is already in Processed, we don't want to recurse into it again,
// but do want to record a second reference in the same instruction.
bool AddUserToIVUsers = false;
if (UserLoop != L) {
if (LI->getLoopFor(User->getParent()) != L) {
if (isa<PHINode>(User) || Processed.count(User) ||
!AddUsersIfInteresting(User, SimpleLoopNests)) {
DEBUG(dbgs() << "FOUND USER in other loop: " << *User << '\n'

73
test/Transforms/LoopStrengthReduce/2012-03-15-nopreheader.ll
View File

@ -48,3 +48,76 @@ for.inc: ; preds = %lor.rhs234, %land.l
return: ; preds = %if.end677, %doshell, %if.then96
ret void
}
define void @nopreheader2() nounwind ssp {
entry:
indirectbr i8* undef, [label %while.cond, label %return]
while.cond: ; preds = %while.cond.backedge, %entry
indirectbr i8* undef, [label %while.cond.backedge, label %lor.rhs]
lor.rhs: ; preds = %while.cond
indirectbr i8* undef, [label %while.cond.backedge, label %while.end]
while.cond.backedge: ; preds = %lor.rhs, %while.cond
indirectbr i8* undef, [label %while.cond]
while.end: ; preds = %lor.rhs
indirectbr i8* undef, [label %if.then18, label %return]
if.then18: ; preds = %while.end
indirectbr i8* undef, [label %if.end35, label %lor.lhs.false]
lor.lhs.false: ; preds = %if.then18
indirectbr i8* undef, [label %if.end35, label %return]
if.end35: ; preds = %lor.lhs.false, %if.then18
indirectbr i8* undef, [label %while.cond36]
while.cond36: ; preds = %while.body49, %if.end35
%0 = phi i64 [ %indvar.next13, %while.body49 ], [ 0, %if.end35 ]
indirectbr i8* undef, [label %while.body49, label %lor.rhs42]
lor.rhs42: ; preds = %while.cond36
indirectbr i8* undef, [label %while.body49, label %while.end52]
while.body49: ; preds = %lor.rhs42, %while.cond36
%indvar.next13 = add i64 %0, 1
indirectbr i8* undef, [label %while.cond36]
while.end52: ; preds = %lor.rhs42
indirectbr i8* undef, [label %land.lhs.true, label %return]
land.lhs.true: ; preds = %while.end52
indirectbr i8* undef, [label %while.cond66.preheader, label %return]
while.cond66.preheader: ; preds = %land.lhs.true
indirectbr i8* undef, [label %while.cond66]
while.cond66: ; preds = %while.body77, %while.cond66.preheader
indirectbr i8* undef, [label %land.rhs, label %while.cond81.preheader]
land.rhs: ; preds = %while.cond66
indirectbr i8* undef, [label %while.body77, label %while.cond81.preheader]
while.cond81.preheader: ; preds = %land.rhs, %while.cond66
%tmp45 = add i64 undef, %0
%tmp46 = add i64 %tmp45, undef
indirectbr i8* undef, [label %while.cond81]
while.body77: ; preds = %land.rhs
indirectbr i8* undef, [label %while.cond66]
while.cond81: ; preds = %while.body94, %while.cond81.preheader
%tmp25 = add i64 %tmp46, undef
indirectbr i8* undef, [label %while.body94, label %lor.rhs87]
lor.rhs87: ; preds = %while.cond81
indirectbr i8* undef, [label %while.body94, label %return]
while.body94: ; preds = %lor.rhs87, %while.cond81
indirectbr i8* undef, [label %while.cond81]
return: ; preds = %if.end216, %land.lhs.true183, %land.lhs.true, %while.end52, %lor.lhs.false, %while.end, %entry
ret void
}