[llvm-commits] [llvm] r112457 - in /llvm/trunk/lib: CodeGen/DwarfEHPrepare.cpp Transforms/Scalar/LICM.cpp
Chris Lattner
sabre at nondot.org
Sun Aug 29 12:54:28 PDT 2010
Author: lattner
Date: Sun Aug 29 14:54:28 2010
New Revision: 112457
URL: http://llvm.org/viewvc/llvm-project?rev=112457&view=rev
Log:
rewrite DwarfEHPrepare to use SSAUpdater to promote its allocas
instead of PromoteMemToReg. This allows it to stop using DF and DT,
eliminating a computation of DT and DF from clang -O3. Clang is now
down to 2 runs of DomFrontier.
Modified:
llvm/trunk/lib/CodeGen/DwarfEHPrepare.cpp
llvm/trunk/lib/Transforms/Scalar/LICM.cpp
Modified: llvm/trunk/lib/CodeGen/DwarfEHPrepare.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/DwarfEHPrepare.cpp?rev=112457&r1=112456&r2=112457&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/DwarfEHPrepare.cpp (original)
+++ llvm/trunk/lib/CodeGen/DwarfEHPrepare.cpp Sun Aug 29 14:54:28 2010
@@ -26,6 +26,7 @@
#include "llvm/Target/TargetLowering.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/PromoteMemToReg.h"
+#include "llvm/Transforms/Utils/SSAUpdater.h"
using namespace llvm;
STATISTIC(NumLandingPadsSplit, "Number of landing pads split");
@@ -33,6 +34,8 @@
STATISTIC(NumExceptionValuesMoved, "Number of eh.exception calls moved");
STATISTIC(NumStackTempsIntroduced, "Number of stack temporaries introduced");
+static void PromoteAlloca(AllocaInst *AI);
+
namespace {
class DwarfEHPrepare : public FunctionPass {
const TargetMachine *TM;
@@ -56,7 +59,6 @@
// Dominator info is used when turning stack temporaries into registers.
DominatorTree *DT;
- DominanceFrontier *DF;
// The function we are running on.
Function *F;
@@ -114,21 +116,17 @@
/// PromoteStoreInst - Perform Mem2Reg on a StoreInst.
bool PromoteStoreInst(StoreInst *SI) {
- if (!SI || !DT || !DF) return false;
-
AllocaInst *AI = dyn_cast<AllocaInst>(SI->getOperand(1));
if (!AI || !isAllocaPromotable(AI)) return false;
- // Turn the alloca into a register.
- std::vector<AllocaInst*> Allocas(1, AI);
- PromoteMemToReg(Allocas, *DT, *DF);
+ PromoteAlloca(AI);
return true;
}
/// PromoteEHPtrStore - Promote the storing of an EH pointer into a
/// register. This should get rid of the store and subsequent loads.
bool PromoteEHPtrStore(IntrinsicInst *II) {
- if (!DT || !DF) return false;
+ if (!CompileFast) return false;
bool Changed = false;
StoreInst *SI;
@@ -141,7 +139,7 @@
if (SI) break;
}
- if (!PromoteStoreInst(SI))
+ if (SI && !PromoteStoreInst(SI))
break;
Changed = true;
@@ -160,14 +158,8 @@
virtual bool runOnFunction(Function &Fn);
- // getAnalysisUsage - We need dominance frontiers for memory promotion.
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
- if (!CompileFast)
- AU.addRequired<DominatorTree>();
AU.addPreserved<DominatorTree>();
- if (!CompileFast)
- AU.addRequired<DominanceFrontier>();
- AU.addPreserved<DominanceFrontier>();
}
const char *getPassName() const {
@@ -183,6 +175,128 @@
return new DwarfEHPrepare(tm, fast);
}
+/// PromoteAlloca - This promotes an alloca to registers when we know that it
+/// only has non-volatile loads and stores to it.
+static void PromoteAlloca(AllocaInst *AI) {
+ assert(isAllocaPromotable(AI));
+
+ // First step: bucket up uses of the pointers by the block they occur in.
+ // This is important because we have to handle multiple defs/uses in a block
+ // ourselves: SSAUpdater is purely for cross-block references.
+ // FIXME: Want a TinyVector<Instruction*> since there is usually 0/1 element.
+ DenseMap<BasicBlock*, std::vector<Instruction*> > UsesByBlock;
+ for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end();
+ UI != E; ++UI) {
+ Instruction *User = cast<Instruction>(*UI);
+ UsesByBlock[User->getParent()].push_back(User);
+ }
+
+ SSAUpdater SSA;
+
+ // It wants to know some value of the same type as what we'll be inserting.
+ Value *SomeValue;
+ if (isa<LoadInst>(*AI->use_begin()))
+ SomeValue = *AI->use_begin();
+ else
+ SomeValue = cast<StoreInst>(*AI->use_begin())->getOperand(0);
+ SSA.Initialize(SomeValue);
+
+ // Okay, now we can iterate over all the blocks in the loop with uses,
+ // processing them. Keep track of which loads are loading a live-in value.
+ SmallVector<LoadInst*, 32> LiveInLoads;
+
+ for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end();
+ UI != E; ++UI) {
+ Instruction *User = cast<Instruction>(*UI);
+ std::vector<Instruction*> &BlockUses = UsesByBlock[User->getParent()];
+
+ // If this block has already been processed, ignore this repeat use.
+ if (BlockUses.empty()) continue;
+
+ // Okay, this is the first use in the block. If this block just has a
+ // single user in it, we can rewrite it trivially.
+ if (BlockUses.size() == 1) {
+ // If it is a store, it is a trivial def of the value in the block.
+ if (isa<StoreInst>(User)) {
+ SSA.AddAvailableValue(User->getParent(),
+ cast<StoreInst>(User)->getOperand(0));
+ } else {
+ // Otherwise it is a load, queue it to rewrite as a live-in load.
+ LiveInLoads.push_back(cast<LoadInst>(User));
+ }
+ BlockUses.clear();
+ continue;
+ }
+
+ // Otherwise, check to see if this block is all loads. If so, we can queue
+ // them all as live in loads.
+ bool HasStore = false;
+ for (unsigned i = 0, e = BlockUses.size(); i != e; ++i) {
+ if (isa<StoreInst>(BlockUses[i])) {
+ HasStore = true;
+ break;
+ }
+ }
+
+ if (!HasStore) {
+ for (unsigned i = 0, e = BlockUses.size(); i != e; ++i)
+ LiveInLoads.push_back(cast<LoadInst>(BlockUses[i]));
+ BlockUses.clear();
+ continue;
+ }
+
+ // Otherwise, we have mixed loads and stores (or just a bunch of stores).
+ // Since SSAUpdater is purely for cross-block values, we need to determine
+ // the order of these instructions in the block. If the first use in the
+ // block is a load, then it uses the live in value. The last store defines
+ // the live out value. We handle this by doing a linear scan of the block.
+ BasicBlock *BB = User->getParent();
+ Value *StoredValue = 0;
+ for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E; ++II) {
+ if (LoadInst *L = dyn_cast<LoadInst>(II)) {
+ // If this is a load to an unrelated pointer, ignore it.
+ if (L->getOperand(0) != AI) continue;
+
+ // If we haven't seen a store yet, this is a live in use, otherwise
+ // use the stored value.
+ if (StoredValue)
+ L->replaceAllUsesWith(StoredValue);
+ else
+ LiveInLoads.push_back(L);
+ continue;
+ }
+
+ if (StoreInst *S = dyn_cast<StoreInst>(II)) {
+ // If this is a store to an unrelated pointer, ignore it.
+ if (S->getOperand(1) != AI) continue;
+
+ // Remember that this is the active value in the block.
+ StoredValue = S->getOperand(0);
+ }
+ }
+
+ // The last stored value that happened is the live-out for the block.
+ assert(StoredValue && "Already checked that there is a store in block");
+ SSA.AddAvailableValue(BB, StoredValue);
+ BlockUses.clear();
+ }
+
+ // Okay, now we rewrite all loads that use live-in values in the loop,
+ // inserting PHI nodes as necessary.
+ for (unsigned i = 0, e = LiveInLoads.size(); i != e; ++i) {
+ LoadInst *ALoad = LiveInLoads[i];
+ ALoad->replaceAllUsesWith(SSA.GetValueInMiddleOfBlock(ALoad->getParent()));
+ }
+
+ // Now that everything is rewritten, delete the old instructions from the body
+ // of the loop. They should all be dead now.
+ for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end();
+ UI != E; ++UI)
+ cast<Instruction>(*UI)->eraseFromParent();
+}
+
+
+
/// HasCatchAllInSelector - Return true if the intrinsic instruction has a
/// catch-all.
bool DwarfEHPrepare::HasCatchAllInSelector(IntrinsicInst *II) {
@@ -525,11 +639,9 @@
// Add a fallthrough from NewBB to the original landing pad.
BranchInst::Create(LPad, NewBB);
- // Now update DominatorTree and DominanceFrontier analysis information.
+ // Now update DominatorTree analysis information if it is around.
if (DT)
DT->splitBlock(NewBB);
- if (DF)
- DF->splitBlock(NewBB);
// Remember the newly constructed landing pad. The original landing pad
// LPad is no longer a landing pad now that all unwind edges have been
@@ -655,10 +767,9 @@
/// PromoteStackTemporaries - Turn any stack temporaries we introduced into
/// registers if possible.
bool DwarfEHPrepare::PromoteStackTemporaries() {
- if (ExceptionValueVar && DT && DF && isAllocaPromotable(ExceptionValueVar)) {
- // Turn the exception temporary into registers and phi nodes if possible.
- std::vector<AllocaInst*> Allocas(1, ExceptionValueVar);
- PromoteMemToReg(Allocas, *DT, *DF);
+ // Turn the exception temporary into registers and phi nodes if possible.
+ if (ExceptionValueVar && isAllocaPromotable(ExceptionValueVar)) {
+ PromoteAlloca(ExceptionValueVar);
return true;
}
return false;
@@ -712,7 +823,6 @@
// Initialize internal state.
DT = getAnalysisIfAvailable<DominatorTree>();
- DF = getAnalysisIfAvailable<DominanceFrontier>();
ExceptionValueVar = 0;
F = &Fn;
@@ -731,7 +841,7 @@
// Initialize any stack temporaries we introduced.
Changed |= FinishStackTemporaries();
- // Turn any stack temporaries into registers if possible.
+ // Turn any stack temporaries into registers.
if (!CompileFast)
Changed |= PromoteStackTemporaries();
Modified: llvm/trunk/lib/Transforms/Scalar/LICM.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LICM.cpp?rev=112457&r1=112456&r2=112457&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/LICM.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/LICM.cpp Sun Aug 29 14:54:28 2010
@@ -793,7 +793,7 @@
}
if (StoreInst *S = dyn_cast<StoreInst>(II)) {
- // If this is a load to an unrelated pointer, ignore it.
+ // If this is a store to an unrelated pointer, ignore it.
if (!PointerMustAliases.count(S->getOperand(1))) continue;
// Remember that this is the active value in the block.
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