[PATCH] D89818: [Compile Time] Make it possible to skip redundant debuginst removal
Christopher Tetreault via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Tue Oct 20 14:05:45 PDT 2020
ctetreau updated this revision to Diff 299466.
ctetreau added a comment.
address code review issues
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D89818/new/
https://reviews.llvm.org/D89818
Files:
llvm/include/llvm/Transforms/Utils/BasicBlockUtils.h
llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
llvm/lib/Transforms/Utils/LoopUnroll.cpp
Index: llvm/lib/Transforms/Utils/LoopUnroll.cpp
===================================================================
--- llvm/lib/Transforms/Utils/LoopUnroll.cpp
+++ llvm/lib/Transforms/Utils/LoopUnroll.cpp
@@ -234,6 +234,7 @@
if (isInstructionTriviallyDead(Inst))
BB->getInstList().erase(Inst);
}
+ RemoveRedundantDbgInstrs(BB);
}
// TODO: after peeling or unrolling, previously loop variant conditions are
@@ -862,7 +863,10 @@
if (Term && Term->isUnconditional()) {
BasicBlock *Dest = Term->getSuccessor(0);
BasicBlock *Fold = Dest->getUniquePredecessor();
- if (MergeBlockIntoPredecessor(Dest, &DTU, LI)) {
+ // Deferring redundant debug value elimination. For sufficiently
+ // complicated loop bodies, this can result in multi-minute compile times.
+ if (MergeBlockIntoPredecessor(Dest, &DTU, LI, nullptr, nullptr, false,
+ true)) {
// Dest has been folded into Fold. Update our worklists accordingly.
std::replace(Latches.begin(), Latches.end(), Dest, Fold);
UnrolledLoopBlocks.erase(std::remove(UnrolledLoopBlocks.begin(),
Index: llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
===================================================================
--- llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
+++ llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
@@ -172,7 +172,8 @@
bool llvm::MergeBlockIntoPredecessor(BasicBlock *BB, DomTreeUpdater *DTU,
LoopInfo *LI, MemorySSAUpdater *MSSAU,
MemoryDependenceResults *MemDep,
- bool PredecessorWithTwoSuccessors) {
+ bool PredecessorWithTwoSuccessors,
+ bool SkipRedundantDebugValElimination) {
if (BB->hasAddressTaken())
return false;
@@ -285,10 +286,12 @@
// Add unreachable to now empty BB.
new UnreachableInst(BB->getContext(), BB);
- // Eliminate duplicate/redundant dbg.values. This seems to be a good place to
- // do that since we might end up with redundant dbg.values describing the
- // entry PHI node post-splice.
- RemoveRedundantDbgInstrs(PredBB);
+ if (!SkipRedundantDebugValElimination) {
+ // Eliminate duplicate/redundant dbg.values. This seems to be a good place
+ // to do that since we might end up with redundant dbg.values describing the
+ // entry PHI node post-splice.
+ RemoveRedundantDbgInstrs(PredBB);
+ }
// Inherit predecessors name if it exists.
if (!PredBB->hasName())
Index: llvm/include/llvm/Transforms/Utils/BasicBlockUtils.h
===================================================================
--- llvm/include/llvm/Transforms/Utils/BasicBlockUtils.h
+++ llvm/include/llvm/Transforms/Utils/BasicBlockUtils.h
@@ -91,11 +91,16 @@
/// if BB's Pred has a branch to BB and to AnotherBB, and BB has a single
/// successor Sing. In this case the branch will be updated with Sing instead of
/// BB, and BB will still be merged into its predecessor and removed.
+///
+/// Pass True to SkipRedundantDebugValElimination in order to skip redundant
+/// debug val elimination. This elimination has O(#instructions) time
+/// complexity, and may result in unreasonably long compile times.
bool MergeBlockIntoPredecessor(BasicBlock *BB, DomTreeUpdater *DTU = nullptr,
LoopInfo *LI = nullptr,
MemorySSAUpdater *MSSAU = nullptr,
MemoryDependenceResults *MemDep = nullptr,
- bool PredecessorWithTwoSuccessors = false);
+ bool PredecessorWithTwoSuccessors = false,
+ bool SkipRedundantDebugValElimination = false);
/// Merge block(s) sucessors, if possible. Return true if at least two
/// of the blocks were merged together.
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