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[LSR] Fix bug - check if loop has preheader before calling isInductionPHI 

Fix bug exposed by https://reviews.llvm.org/D125990
rewriteLoopExitValues calls InductionDescriptor::isInductionPHI which requires
the PHI node to have an incoming edge from the loop preheader. This adds checks
before calling InductionDescriptor::isInductionPHI to see that the loop has a
preheader. Also did some refactoring.

Differential Revision: https://reviews.llvm.org/D129297
This commit is contained in:
Zaara Syeda 2022-07-07 14:29:06 -04:00
parent f67fc3acad
commit 58b9666dc1
2 changed files with 37 additions and 9 deletions
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25
llvm/lib/Transforms/Utils/LoopUtils.cpp
View File

@ -1243,6 +1243,20 @@ static bool canLoopBeDeleted(Loop *L, SmallVector<RewritePhi, 8> &RewritePhiSet)
return true;
}
/// Checks if it is safe to call InductionDescriptor::isInductionPHI for \p Phi,
/// and returns true if this Phi is an induction phi in the loop. When
/// isInductionPHI returns true, \p ID will be also be set by isInductionPHI.
static bool checkIsIndPhi(PHINode *Phi, Loop *L, ScalarEvolution *SE,
InductionDescriptor &ID) {
if (!Phi)
return false;
if (!L->getLoopPreheader())
return false;
if (Phi->getParent() != L->getHeader())
return false;
return InductionDescriptor::isInductionPHI(Phi, L, SE, ID);
}
int llvm::rewriteLoopExitValues(Loop *L, LoopInfo *LI, TargetLibraryInfo *TLI,
ScalarEvolution *SE,
const TargetTransformInfo *TTI,
@ -1303,10 +1317,7 @@ int llvm::rewriteLoopExitValues(Loop *L, LoopInfo *LI, TargetLibraryInfo *TLI,
InductionDescriptor ID;
PHINode *IndPhi = dyn_cast<PHINode>(Inst);
if (IndPhi) {
if (IndPhi->getParent() != L->getHeader())
continue;
// Do not consider non induction phis.
if (!InductionDescriptor::isInductionPHI(IndPhi, L, SE, ID))
if (!checkIsIndPhi(IndPhi, L, SE, ID))
continue;
// This is an induction PHI. Check that the only users are PHI
// nodes, and induction variable update binary operators.
@ -1327,12 +1338,8 @@ int llvm::rewriteLoopExitValues(Loop *L, LoopInfo *LI, TargetLibraryInfo *TLI,
continue;
if (llvm::any_of(Inst->users(), [&](User *U) {
PHINode *Phi = dyn_cast<PHINode>(U);
if (!Phi)
if (Phi != PN && !checkIsIndPhi(Phi, L, SE, ID))
return true;
if (Phi->getParent() == L->getHeader()) {
if (!InductionDescriptor::isInductionPHI(Phi, L, SE, ID))
return true;
}
return false;
}))
continue;

21
llvm/test/Transforms/LoopStrengthReduce/remove_scev_indvars.ll
View File

@ -91,3 +91,24 @@ for.end6730: ; preds = %for.cond6418
dead: ; No predecessors!
br label %for.cond6403
}
; Check that this doesn't crash
define void @kernfs_path_from_node() {
entry:
callbr void asm sideeffect "", "i"(i8* blockaddress(@kernfs_path_from_node, %while.body))
to label %asm.fallthrough [label %while.body]
asm.fallthrough: ; preds = %entry
br label %while.body
while.body: ; preds = %while.body, %asm.fallthrough, %entry
%depth.04 = phi i32 [ %inc, %while.body ], [ 0, %asm.fallthrough ], [ 0, %entry ]
%inc = add i32 %depth.04, 1
br i1 false, label %while.end, label %while.body
while.end: ; preds = %while.body
%inc.lcssa = phi i32 [ %depth.04, %while.body ]
store i32 %inc.lcssa, i32* null, align 4
ret void
}