[llvm-commits] [llvm] r123062 - /llvm/trunk/lib/Transforms/Scalar/LoopInstSimplify.cpp
Cameron Zwarich
zwarich at apple.com
Sat Jan 8 07:52:22 PST 2011
Author: zwarich
Date: Sat Jan 8 09:52:22 2011
New Revision: 123062
URL: http://llvm.org/viewvc/llvm-project?rev=123062&view=rev
Log:
Contract subloop bodies. However, it is still important to visit the phis at the
top of subloop headers, as the phi uses logically occur outside of the subloop.
Modified:
llvm/trunk/lib/Transforms/Scalar/LoopInstSimplify.cpp
Modified: llvm/trunk/lib/Transforms/Scalar/LoopInstSimplify.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LoopInstSimplify.cpp?rev=123062&r1=123061&r2=123062&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/LoopInstSimplify.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/LoopInstSimplify.cpp Sat Jan 8 09:52:22 2011
@@ -12,6 +12,7 @@
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "loop-instsimplify"
+#include "llvm/Instructions.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/LoopInfo.h"
@@ -68,7 +69,10 @@
SmallPtrSet<const Instruction*, 8> S1, S2, *ToSimplify = &S1, *Next = &S2;
- SmallVector<BasicBlock*, 16> VisitStack;
+ // The bit we are stealing from the pointer represents whether this basic
+ // block is the header of a subloop, in which case we only process its phis.
+ typedef PointerIntPair<BasicBlock*, 1> WorklistItem;
+ SmallVector<WorklistItem, 16> VisitStack;
SmallPtrSet<BasicBlock*, 32> Visited;
bool Changed = false;
@@ -79,10 +83,12 @@
VisitStack.clear();
Visited.clear();
- VisitStack.push_back(L->getHeader());
+ VisitStack.push_back(WorklistItem(L->getHeader(), false));
while (!VisitStack.empty()) {
- BasicBlock *BB = VisitStack.pop_back_val();
+ WorklistItem Item = VisitStack.pop_back_val();
+ BasicBlock* BB = Item.getPointer();
+ bool IsSubloopHeader = Item.getInt();
// Simplify instructions in the current basic block.
for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE;) {
@@ -109,16 +115,44 @@
}
}
LocalChanged |= RecursivelyDeleteTriviallyDeadInstructions(I);
+
+ if (IsSubloopHeader && !isa<PHINode>(I))
+ break;
}
- // Add all successors to the worklist, except for loop exit blocks.
+ // Add all successors to the worklist, except for loop exit blocks and the
+ // bodies of subloops. We visit the headers of loops so that we can process
+ // their phis, but we contract the rest of the subloop body and only follow
+ // edges leading back to the original loop.
for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE;
++SI) {
BasicBlock *SuccBB = *SI;
+ if (!Visited.insert(SuccBB))
+ continue;
+
+ const Loop *SuccLoop = LI->getLoopFor(SuccBB);
+ if (SuccLoop && SuccLoop->getHeader() == SuccBB
+ && L->contains(SuccLoop)) {
+ VisitStack.push_back(WorklistItem(SuccBB, true));
+
+ SmallVector<BasicBlock*, 8> SubLoopExitBlocks;
+ SuccLoop->getExitBlocks(SubLoopExitBlocks);
+
+ for (unsigned i = 0; i < SubLoopExitBlocks.size(); ++i) {
+ BasicBlock *ExitBB = SubLoopExitBlocks[i];
+ if (LI->getLoopFor(ExitBB) == L && Visited.insert(ExitBB))
+ VisitStack.push_back(WorklistItem(ExitBB, false));
+ }
+
+ continue;
+ }
+
bool IsExitBlock = std::binary_search(ExitBlocks.begin(),
- ExitBlocks.end(), SuccBB);
- if (!IsExitBlock && Visited.insert(SuccBB))
- VisitStack.push_back(SuccBB);
+ ExitBlocks.end(), SuccBB);
+ if (IsExitBlock)
+ continue;
+
+ VisitStack.push_back(WorklistItem(SuccBB, false));
}
}
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