[llvm] 0016c1f - [JumpThreading] Factor out common code to update the SSA form (NFC)
Kazu Hirata via llvm-commits
llvm-commits at lists.llvm.org
Tue Nov 5 07:15:56 PST 2019
Author: Kazu Hirata
Date: 2019-11-05T06:15:44-08:00
New Revision: 0016c1f40043e67068230208fd8f34657ad44b99
URL: https://github.com/llvm/llvm-project/commit/0016c1f40043e67068230208fd8f34657ad44b99
DIFF: https://github.com/llvm/llvm-project/commit/0016c1f40043e67068230208fd8f34657ad44b99.diff
LOG: [JumpThreading] Factor out common code to update the SSA form (NFC)
Summary:
This patch factors out common code to update the SSA form in
JumpThreading.cpp -- partly for readability and partly to facilitate
an coming patch of my own.
Reviewers: wmi
Subscribers: hiraditya, jfb, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D69811
Added:
Modified:
llvm/include/llvm/Transforms/Scalar/JumpThreading.h
llvm/lib/Transforms/Scalar/JumpThreading.cpp
Removed:
################################################################################
diff --git a/llvm/include/llvm/Transforms/Scalar/JumpThreading.h b/llvm/include/llvm/Transforms/Scalar/JumpThreading.h
index 0464d40c45e6..3ebbddc8f412 100644
--- a/llvm/include/llvm/Transforms/Scalar/JumpThreading.h
+++ b/llvm/include/llvm/Transforms/Scalar/JumpThreading.h
@@ -109,6 +109,8 @@ class JumpThreadingPass : public PassInfoMixin<JumpThreadingPass> {
void FindLoopHeaders(Function &F);
bool ProcessBlock(BasicBlock *BB);
+ void UpdateSSA(BasicBlock *BB, BasicBlock *NewBB,
+ DenseMap<Instruction *, Value *> &ValueMapping);
bool ThreadEdge(BasicBlock *BB, const SmallVectorImpl<BasicBlock *> &PredBBs,
BasicBlock *SuccBB);
bool DuplicateCondBranchOnPHIIntoPred(
diff --git a/llvm/lib/Transforms/Scalar/JumpThreading.cpp b/llvm/lib/Transforms/Scalar/JumpThreading.cpp
index 0cf00baaa24a..e36c7a4c5125 100644
--- a/llvm/lib/Transforms/Scalar/JumpThreading.cpp
+++ b/llvm/lib/Transforms/Scalar/JumpThreading.cpp
@@ -1920,6 +1920,50 @@ static void AddPHINodeEntriesForMappedBlock(BasicBlock *PHIBB,
}
}
+/// Update the SSA form. NewBB contains instructions that are copied from BB.
+/// ValueMapping maps old values in BB to new ones in NewBB.
+void JumpThreadingPass::UpdateSSA(
+ BasicBlock *BB, BasicBlock *NewBB,
+ DenseMap<Instruction *, Value *> &ValueMapping) {
+ // If there were values defined in BB that are used outside the block, then we
+ // now have to update all uses of the value to use either the original value,
+ // the cloned value, or some PHI derived value. This can require arbitrary
+ // PHI insertion, of which we are prepared to do, clean these up now.
+ SSAUpdater SSAUpdate;
+ SmallVector<Use *, 16> UsesToRename;
+
+ for (Instruction &I : *BB) {
+ // Scan all uses of this instruction to see if it is used outside of its
+ // block, and if so, record them in UsesToRename.
+ for (Use &U : I.uses()) {
+ Instruction *User = cast<Instruction>(U.getUser());
+ if (PHINode *UserPN = dyn_cast<PHINode>(User)) {
+ if (UserPN->getIncomingBlock(U) == BB)
+ continue;
+ } else if (User->getParent() == BB)
+ continue;
+
+ UsesToRename.push_back(&U);
+ }
+
+ // If there are no uses outside the block, we're done with this instruction.
+ if (UsesToRename.empty())
+ continue;
+ LLVM_DEBUG(dbgs() << "JT: Renaming non-local uses of: " << I << "\n");
+
+ // We found a use of I outside of BB. Rename all uses of I that are outside
+ // its block to be uses of the appropriate PHI node etc. See ValuesInBlocks
+ // with the two values we know.
+ SSAUpdate.Initialize(I.getType(), I.getName());
+ SSAUpdate.AddAvailableValue(BB, &I);
+ SSAUpdate.AddAvailableValue(NewBB, ValueMapping[&I]);
+
+ while (!UsesToRename.empty())
+ SSAUpdate.RewriteUse(*UsesToRename.pop_back_val());
+ LLVM_DEBUG(dbgs() << "\n");
+ }
+}
+
/// ThreadEdge - We have decided that it is safe and profitable to factor the
/// blocks in PredBBs to one predecessor, then thread an edge from it to SuccBB
/// across BB. Transform the IR to reflect this change.
@@ -2045,44 +2089,7 @@ bool JumpThreadingPass::ThreadEdge(BasicBlock *BB,
{DominatorTree::Insert, PredBB, NewBB},
{DominatorTree::Delete, PredBB, BB}});
- // If there were values defined in BB that are used outside the block, then we
- // now have to update all uses of the value to use either the original value,
- // the cloned value, or some PHI derived value. This can require arbitrary
- // PHI insertion, of which we are prepared to do, clean these up now.
- SSAUpdater SSAUpdate;
- SmallVector<Use*, 16> UsesToRename;
-
- for (Instruction &I : *BB) {
- // Scan all uses of this instruction to see if their uses are no longer
- // dominated by the previous def and if so, record them in UsesToRename.
- // Also, skip phi operands from PredBB - we'll remove them anyway.
- for (Use &U : I.uses()) {
- Instruction *User = cast<Instruction>(U.getUser());
- if (PHINode *UserPN = dyn_cast<PHINode>(User)) {
- if (UserPN->getIncomingBlock(U) == BB)
- continue;
- } else if (User->getParent() == BB)
- continue;
-
- UsesToRename.push_back(&U);
- }
-
- // If there are no uses outside the block, we're done with this instruction.
- if (UsesToRename.empty())
- continue;
- LLVM_DEBUG(dbgs() << "JT: Renaming non-local uses of: " << I << "\n");
-
- // We found a use of I outside of BB. Rename all uses of I that are outside
- // its block to be uses of the appropriate PHI node etc. See ValuesInBlocks
- // with the two values we know.
- SSAUpdate.Initialize(I.getType(), I.getName());
- SSAUpdate.AddAvailableValue(BB, &I);
- SSAUpdate.AddAvailableValue(NewBB, ValueMapping[&I]);
-
- while (!UsesToRename.empty())
- SSAUpdate.RewriteUse(*UsesToRename.pop_back_val());
- LLVM_DEBUG(dbgs() << "\n");
- }
+ UpdateSSA(BB, NewBB, ValueMapping);
// At this point, the IR is fully up to date and consistent. Do a quick scan
// over the new instructions and zap any that are constants or dead. This
@@ -2366,43 +2373,7 @@ bool JumpThreadingPass::DuplicateCondBranchOnPHIIntoPred(
AddPHINodeEntriesForMappedBlock(BBBranch->getSuccessor(1), BB, PredBB,
ValueMapping);
- // If there were values defined in BB that are used outside the block, then we
- // now have to update all uses of the value to use either the original value,
- // the cloned value, or some PHI derived value. This can require arbitrary
- // PHI insertion, of which we are prepared to do, clean these up now.
- SSAUpdater SSAUpdate;
- SmallVector<Use*, 16> UsesToRename;
- for (Instruction &I : *BB) {
- // Scan all uses of this instruction to see if it is used outside of its
- // block, and if so, record them in UsesToRename.
- for (Use &U : I.uses()) {
- Instruction *User = cast<Instruction>(U.getUser());
- if (PHINode *UserPN = dyn_cast<PHINode>(User)) {
- if (UserPN->getIncomingBlock(U) == BB)
- continue;
- } else if (User->getParent() == BB)
- continue;
-
- UsesToRename.push_back(&U);
- }
-
- // If there are no uses outside the block, we're done with this instruction.
- if (UsesToRename.empty())
- continue;
-
- LLVM_DEBUG(dbgs() << "JT: Renaming non-local uses of: " << I << "\n");
-
- // We found a use of I outside of BB. Rename all uses of I that are outside
- // its block to be uses of the appropriate PHI node etc. See ValuesInBlocks
- // with the two values we know.
- SSAUpdate.Initialize(I.getType(), I.getName());
- SSAUpdate.AddAvailableValue(BB, &I);
- SSAUpdate.AddAvailableValue(PredBB, ValueMapping[&I]);
-
- while (!UsesToRename.empty())
- SSAUpdate.RewriteUse(*UsesToRename.pop_back_val());
- LLVM_DEBUG(dbgs() << "\n");
- }
+ UpdateSSA(BB, PredBB, ValueMapping);
// PredBB no longer jumps to BB, remove entries in the PHI node for the edge
// that we nuked.
More information about the llvm-commits
mailing list