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| author | Max Kazantsev <max.kazantsev@azul.com> | 2017-04-28 06:05:48 +0000 |
|---|---|---|
| committer | Max Kazantsev <max.kazantsev@azul.com> | 2017-04-28 06:05:48 +0000 |
| commit | 0589d9fa0fa27f9f5ffa78329697e8dc0ff34db9 (patch) | |
| tree | 1c09d044ee12bf471b9cc946f8325b932d563df0 /llvm/lib/Transforms | |
| parent | 10c6ba06d4dd8d97d8e022cfcad836882f55ab85 (diff) | |
| download | bcm5719-llvm-0589d9fa0fa27f9f5ffa78329697e8dc0ff34db9.tar.gz bcm5719-llvm-0589d9fa0fa27f9f5ffa78329697e8dc0ff34db9.zip | |
[EarlyCSE] Remove guards with conditions known to be true
If a condition is calculated only once, and there are multiple guards on this condition, we should be able
to remove all guards dominated by the first of them. This patch allows EarlyCSE to try to find the condition
of a guard among the known values, and if it is true, remove the guard. Otherwise we keep the guard and
mark its condition as 'true' for future consideration.
Reviewers: sanjoy, reames, apilipenko, skatkov, anna, dberlin
Reviewed By: reames, sanjoy
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D32476
llvm-svn: 301623
Diffstat (limited to 'llvm/lib/Transforms')
| -rw-r--r-- | llvm/lib/Transforms/Scalar/EarlyCSE.cpp | 21 |
1 files changed, 18 insertions, 3 deletions
diff --git a/llvm/lib/Transforms/Scalar/EarlyCSE.cpp b/llvm/lib/Transforms/Scalar/EarlyCSE.cpp index 04479b6e49a..da33c7aa836 100644 --- a/llvm/lib/Transforms/Scalar/EarlyCSE.cpp +++ b/llvm/lib/Transforms/Scalar/EarlyCSE.cpp @@ -658,10 +658,25 @@ bool EarlyCSE::processNode(DomTreeNode *Node) { if (match(Inst, m_Intrinsic<Intrinsic::experimental_guard>())) { if (auto *CondI = dyn_cast<Instruction>(cast<CallInst>(Inst)->getArgOperand(0))) { - // The condition we're on guarding here is true for all dominated - // locations. - if (SimpleValue::canHandle(CondI)) + if (SimpleValue::canHandle(CondI)) { + // Do we already know the actual value of this condition? + if (auto *KnownCond = AvailableValues.lookup(CondI)) { + // Is the condition known to be true? + if (isa<ConstantInt>(KnownCond) && + cast<ConstantInt>(KnownCond)->isOneValue()) { + DEBUG(dbgs() << "EarlyCSE removing guard: " << *Inst << '\n'); + removeMSSA(Inst); + Inst->eraseFromParent(); + Changed = true; + continue; + } else + // Use the known value if it wasn't true. + cast<CallInst>(Inst)->setArgOperand(0, KnownCond); + } + // The condition we're on guarding here is true for all dominated + // locations. AvailableValues.insert(CondI, ConstantInt::getTrue(BB->getContext())); + } } // Guard intrinsics read all memory, but don't write any memory. |
