Remove pruning of phi nodes in MemorySSA - it makes updating harder
Reviewers: george.burgess.iv
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D24923
llvm-svn: 282419
diff --git a/llvm/lib/Transforms/Utils/MemorySSA.cpp b/llvm/lib/Transforms/Utils/MemorySSA.cpp
index 151e606..e06b604 100644
--- a/llvm/lib/Transforms/Utils/MemorySSA.cpp
+++ b/llvm/lib/Transforms/Utils/MemorySSA.cpp
@@ -1348,7 +1348,7 @@
// branch of the dominator tree first. This will guarantee this resets on
// the smallest set of blocks.
if (LocInfo.LowerBoundBlock && LocInfo.LowerBoundBlock != BB &&
- !DT->dominates(LocInfo.LowerBoundBlock, BB)){
+ !DT->dominates(LocInfo.LowerBoundBlock, BB)) {
// Reset the lower bound of things to check.
// TODO: Some day we should be able to reset to last kill, rather than
// 0.
@@ -1455,12 +1455,10 @@
}
void MemorySSA::placePHINodes(
- const SmallPtrSetImpl<BasicBlock *> &DefiningBlocks,
- const SmallPtrSetImpl<BasicBlock *> &LiveInBlocks) {
+ const SmallPtrSetImpl<BasicBlock *> &DefiningBlocks) {
// Determine where our MemoryPhi's should go
ForwardIDFCalculator IDFs(*DT);
IDFs.setDefiningBlocks(DefiningBlocks);
- IDFs.setLiveInBlocks(LiveInBlocks);
SmallVector<BasicBlock *, 32> IDFBlocks;
IDFs.calculate(IDFBlocks);
@@ -1511,40 +1509,7 @@
if (Accesses)
DefUseBlocks.insert(&B);
}
-
- // Compute live-in.
- // Live in is normally defined as "all the blocks on the path from each def to
- // each of it's uses".
- // MemoryDef's are implicit uses of previous state, so they are also uses.
- // This means we don't really have def-only instructions. The only
- // MemoryDef's that are not really uses are those that are of the LiveOnEntry
- // variable (because LiveOnEntry can reach anywhere, and every def is a
- // must-kill of LiveOnEntry).
- // In theory, you could precisely compute live-in by using alias-analysis to
- // disambiguate defs and uses to see which really pair up with which.
- // In practice, this would be really expensive and difficult. So we simply
- // assume all defs are also uses that need to be kept live.
- // Because of this, the end result of this live-in computation will be "the
- // entire set of basic blocks that reach any use".
-
- SmallPtrSet<BasicBlock *, 32> LiveInBlocks;
- SmallVector<BasicBlock *, 64> LiveInBlockWorklist(DefUseBlocks.begin(),
- DefUseBlocks.end());
- // Now that we have a set of blocks where a value is live-in, recursively add
- // predecessors until we find the full region the value is live.
- while (!LiveInBlockWorklist.empty()) {
- BasicBlock *BB = LiveInBlockWorklist.pop_back_val();
-
- // The block really is live in here, insert it into the set. If already in
- // the set, then it has already been processed.
- if (!LiveInBlocks.insert(BB).second)
- continue;
-
- // Since the value is live into BB, it is either defined in a predecessor or
- // live into it to.
- LiveInBlockWorklist.append(pred_begin(BB), pred_end(BB));
- }
- placePHINodes(DefiningBlocks, LiveInBlocks);
+ placePHINodes(DefiningBlocks);
// Now do regular SSA renaming on the MemoryDef/MemoryUse. Visited will get
// filled in with all blocks.
@@ -2069,8 +2034,8 @@
char MemorySSAAnalysis::PassID;
-MemorySSAAnalysis::Result
-MemorySSAAnalysis::run(Function &F, FunctionAnalysisManager &AM) {
+MemorySSAAnalysis::Result MemorySSAAnalysis::run(Function &F,
+ FunctionAnalysisManager &AM) {
auto &DT = AM.getResult<DominatorTreeAnalysis>(F);
auto &AA = AM.getResult<AAManager>(F);
return MemorySSAAnalysis::Result(make_unique<MemorySSA>(F, &AA, &DT));