maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity

[IndVars] Set Changed if rewriteFirstIterationLoopExitValues changes IR. PR38863 

Currently, `rewriteFirstIterationLoopExitValues` does not set Changed flag even if it makes
changes in the IR. There is no clear evidence that it can cause a crash, but it
looks highly suspicious and likely invalid.

Differential Revision: https://reviews.llvm.org/D51779
Reviewed By: skatkov

llvm-svn: 341779
This commit is contained in:
Max Kazantsev 2018-09-10 06:50:16 +00:00
parent 4576a77b80
commit fde88578e5
1 changed files with 6 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
View File

@ -145,7 +145,7 @@ class IndVarSimplify {
bool canLoopBeDeleted(Loop *L, SmallVector<RewritePhi, 8> &RewritePhiSet); bool canLoopBeDeleted(Loop *L, SmallVector<RewritePhi, 8> &RewritePhiSet);
void rewriteLoopExitValues(Loop *L, SCEVExpander &Rewriter); void rewriteLoopExitValues(Loop *L, SCEVExpander &Rewriter);
void rewriteFirstIterationLoopExitValues(Loop *L); bool rewriteFirstIterationLoopExitValues(Loop *L);
Value *linearFunctionTestReplace(Loop *L, const SCEV *BackedgeTakenCount, Value *linearFunctionTestReplace(Loop *L, const SCEV *BackedgeTakenCount,
PHINode *IndVar, SCEVExpander &Rewriter); PHINode *IndVar, SCEVExpander &Rewriter);
@ -707,7 +707,7 @@ void IndVarSimplify::rewriteLoopExitValues(Loop *L, SCEVExpander &Rewriter) {
/// exits. If so, we know that if the exit path is taken, it is at the first /// exits. If so, we know that if the exit path is taken, it is at the first
/// loop iteration. This lets us predict exit values of PHI nodes that live in /// loop iteration. This lets us predict exit values of PHI nodes that live in
/// loop header. /// loop header.
void IndVarSimplify::rewriteFirstIterationLoopExitValues(Loop *L) { bool IndVarSimplify::rewriteFirstIterationLoopExitValues(Loop *L) {
// Verify the input to the pass is already in LCSSA form. // Verify the input to the pass is already in LCSSA form.
assert(L->isLCSSAForm(*DT)); assert(L->isLCSSAForm(*DT));
@ -716,6 +716,7 @@ void IndVarSimplify::rewriteFirstIterationLoopExitValues(Loop *L) {
auto *LoopHeader = L->getHeader(); auto *LoopHeader = L->getHeader();
assert(LoopHeader && "Invalid loop"); assert(LoopHeader && "Invalid loop");
bool MadeAnyChanges = false;
for (auto *ExitBB : ExitBlocks) { for (auto *ExitBB : ExitBlocks) {
// If there are no more PHI nodes in this exit block, then no more // If there are no more PHI nodes in this exit block, then no more
// values defined inside the loop are used on this path. // values defined inside the loop are used on this path.
@ -762,12 +763,14 @@ void IndVarSimplify::rewriteFirstIterationLoopExitValues(Loop *L) {
if (PreheaderIdx != -1) { if (PreheaderIdx != -1) {
assert(ExitVal->getParent() == LoopHeader && assert(ExitVal->getParent() == LoopHeader &&
"ExitVal must be in loop header"); "ExitVal must be in loop header");
MadeAnyChanges = true;
PN.setIncomingValue(IncomingValIdx, PN.setIncomingValue(IncomingValIdx,
ExitVal->getIncomingValue(PreheaderIdx)); ExitVal->getIncomingValue(PreheaderIdx));
} }
} }
} }
} }
return MadeAnyChanges;
} }
/// Check whether it is possible to delete the loop after rewriting exit /// Check whether it is possible to delete the loop after rewriting exit
@ -2658,7 +2661,7 @@ bool IndVarSimplify::run(Loop *L) {
// rewriteFirstIterationLoopExitValues does not rely on the computation of // rewriteFirstIterationLoopExitValues does not rely on the computation of
// trip count and therefore can further simplify exit values in addition to // trip count and therefore can further simplify exit values in addition to
// rewriteLoopExitValues. // rewriteLoopExitValues.
rewriteFirstIterationLoopExitValues(L); Changed |= rewriteFirstIterationLoopExitValues(L);
// Clean up dead instructions. // Clean up dead instructions.
Changed |= DeleteDeadPHIs(L->getHeader(), TLI); Changed |= DeleteDeadPHIs(L->getHeader(), TLI);