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indvars: Added DisableIVRewrite and WidenIVs.

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This adds functionality to remove size/zero extension during indvars
without generating a canonical IV and rewriting all IV users. It's
disabled by default so should have no effect on codegen. Work in progress.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@130829 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Andrew Trick 2011-05-04 02:10:13 +00:00
parent 9f1569a3f7
commit 37da408758
2 changed files with 130 additions and 9 deletions
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15
lib/Analysis/IVUsers.cpp
View File

@ -21,6 +21,7 @@
#include "llvm/Analysis/Dominators.h"
#include "llvm/Analysis/LoopPass.h"
#include "llvm/Analysis/ScalarEvolutionExpressions.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Assembly/Writer.h"
#include "llvm/ADT/STLExtras.h"
@ -38,6 +39,15 @@ INITIALIZE_PASS_DEPENDENCY(ScalarEvolution)
INITIALIZE_PASS_END(IVUsers, "iv-users",
"Induction Variable Users", false, true)
// IVUsers behavior currently depends on this temporary indvars mode. The
// option must be defined upstream from its uses.
namespace llvm {
bool DisableIVRewrite = false;
}
cl::opt<bool, true> DisableIVRewriteOpt(
"disable-iv-rewrite", cl::Hidden, cl::location(llvm::DisableIVRewrite),
cl::desc("Disable canonical induction variable rewriting"));
Pass *llvm::createIVUsersPass() {
return new IVUsers();
}
@ -90,6 +100,11 @@ bool IVUsers::AddUsersIfInteresting(Instruction *I) {
if (Width > 64 || (TD && !TD->isLegalInteger(Width)))
return false;
// We expect Sign/Zero extension to be eliminated from the IR before analyzing
// any downstream uses.
if (DisableIVRewrite && (isa<SExtInst>(I) || isa<ZExtInst>(I)))
return false;
if (!Processed.insert(I))
return true; // Instruction already handled.

124
lib/Transforms/Scalar/IndVarSimplify.cpp
View File

@ -52,33 +52,41 @@
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/LoopPass.h"
#include "llvm/Support/CFG.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Target/TargetData.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/STLExtras.h"
using namespace llvm;
STATISTIC(NumRemoved , "Number of aux indvars removed");
STATISTIC(NumWidened , "Number of indvars widened");
STATISTIC(NumInserted, "Number of canonical indvars added");
STATISTIC(NumReplaced, "Number of exit values replaced");
STATISTIC(NumLFTR , "Number of loop exit tests replaced");
// DisableIVRewrite mode currently affects IVUsers, so is defined in libAnalysis
// and referenced here.
namespace llvm {
extern bool DisableIVRewrite;
}
namespace {
class IndVarSimplify : public LoopPass {
IVUsers *IU;
LoopInfo *LI;
ScalarEvolution *SE;
DominatorTree *DT;
TargetData *TD;
SmallVector<WeakVH, 16> DeadInsts;
bool Changed;
public:
static char ID; // Pass identification, replacement for typeid
IndVarSimplify() : LoopPass(ID) {
IndVarSimplify() : LoopPass(ID), IU(0), LI(0), SE(0), DT(0), TD(0) {
initializeIndVarSimplifyPass(*PassRegistry::getPassRegistry());
}
@ -104,6 +112,7 @@ namespace {
void EliminateIVComparisons();
void EliminateIVRemainders();
void RewriteNonIntegerIVs(Loop *L);
const Type *WidenIVs(Loop *L, SCEVExpander &Rewriter);
bool canExpandBackedgeTakenCount(Loop *L,
const SCEV *BackedgeTakenCount);
@ -111,6 +120,7 @@ namespace {
ICmpInst *LinearFunctionTestReplace(Loop *L, const SCEV *BackedgeTakenCount,
PHINode *IndVar,
SCEVExpander &Rewriter);
void RewriteLoopExitValues(Loop *L, SCEVExpander &Rewriter);
void RewriteIVExpressions(Loop *L, SCEVExpander &Rewriter);
@ -123,7 +133,7 @@ namespace {
char IndVarSimplify::ID = 0;
INITIALIZE_PASS_BEGIN(IndVarSimplify, "indvars",
"Canonicalize Induction Variables", false, false)
"Induction Variable Simplification", false, false)
INITIALIZE_PASS_DEPENDENCY(DominatorTree)
INITIALIZE_PASS_DEPENDENCY(LoopInfo)
INITIALIZE_PASS_DEPENDENCY(ScalarEvolution)
@ -131,7 +141,7 @@ INITIALIZE_PASS_DEPENDENCY(LoopSimplify)
INITIALIZE_PASS_DEPENDENCY(LCSSA)
INITIALIZE_PASS_DEPENDENCY(IVUsers)
INITIALIZE_PASS_END(IndVarSimplify, "indvars",
"Canonicalize Induction Variables", false, false)
"Induction Variable Simplification", false, false)
Pass *llvm::createIndVarSimplifyPass() {
return new IndVarSimplify();
@ -209,7 +219,7 @@ canExpandBackedgeTakenCount(Loop *L,
// rewriting the loop.
if (isa<SCEVUDivExpr>(BackedgeTakenCount)) {
ICmpInst *OrigCond = dyn_cast<ICmpInst>(BI->getCondition());
if (!OrigCond) return 0;
if (!OrigCond) return false;
const SCEV *R = SE->getSCEV(OrigCond->getOperand(1));
R = SE->getMinusSCEV(R, SE->getConstant(R->getType(), 1));
if (R != BackedgeTakenCount) {
@ -549,6 +559,8 @@ bool IndVarSimplify::runOnLoop(Loop *L, LPPassManager &LPM) {
LI = &getAnalysis<LoopInfo>();
SE = &getAnalysis<ScalarEvolution>();
DT = &getAnalysis<DominatorTree>();
TD = getAnalysisIfAvailable<TargetData>();
DeadInsts.clear();
Changed = false;
@ -560,6 +572,13 @@ bool IndVarSimplify::runOnLoop(Loop *L, LPPassManager &LPM) {
// Create a rewriter object which we'll use to transform the code with.
SCEVExpander Rewriter(*SE);
if (DisableIVRewrite)
Rewriter.disableCanonicalMode();
const Type *LargestType = 0;
if (DisableIVRewrite) {
LargestType = WidenIVs(L, Rewriter);
}
// Check to see if this loop has a computable loop-invariant execution count.
// If so, this means that we can compute the final value of any expressions
@ -578,7 +597,6 @@ bool IndVarSimplify::runOnLoop(Loop *L, LPPassManager &LPM) {
// Compute the type of the largest recurrence expression, and decide whether
// a canonical induction variable should be inserted.
const Type *LargestType = 0;
bool NeedCannIV = false;
bool ExpandBECount = canExpandBackedgeTakenCount(L, BackedgeTakenCount);
if (ExpandBECount) {
@ -598,8 +616,19 @@ bool IndVarSimplify::runOnLoop(Loop *L, LPPassManager &LPM) {
SE->getEffectiveSCEVType(I->getOperandValToReplace()->getType());
if (!LargestType ||
SE->getTypeSizeInBits(Ty) >
SE->getTypeSizeInBits(LargestType))
LargestType = SE->getEffectiveSCEVType(Ty);
}
if (!DisableIVRewrite) {
for (IVUsers::const_iterator I = IU->begin(), E = IU->end(); I != E; ++I) {
NeedCannIV = true;
const Type *Ty =
SE->getEffectiveSCEVType(I->getOperandValToReplace()->getType());
if (!LargestType ||
SE->getTypeSizeInBits(Ty) >
SE->getTypeSizeInBits(LargestType))
LargestType = Ty;
LargestType = Ty;
}
}
// Now that we know the largest of the induction variable expressions
@ -647,9 +676,9 @@ bool IndVarSimplify::runOnLoop(Loop *L, LPPassManager &LPM) {
NewICmp = LinearFunctionTestReplace(L, BackedgeTakenCount, IndVar,
Rewriter);
}
// Rewrite IV-derived expressions.
RewriteIVExpressions(L, Rewriter);
if (!DisableIVRewrite)
RewriteIVExpressions(L, Rewriter);
// Clear the rewriter cache, because values that are in the rewriter's cache
// can be deleted in the loop below, causing the AssertingVH in the cache to
@ -721,6 +750,83 @@ static bool isSafe(const SCEV *S, const Loop *L, ScalarEvolution *SE) {
return false;
}
/// Widen the type of any induction variables that are sign/zero extended and
/// remove the [sz]ext uses.
///
/// FIXME: This may currently create extra IVs which could increase regpressure
/// (without LSR to cleanup).
///
/// FIXME: may factor this with RewriteIVExpressions once it stabilizes.
const Type *IndVarSimplify::WidenIVs(Loop *L, SCEVExpander &Rewriter) {
const Type *LargestType = 0;
for (IVUsers::iterator UI = IU->begin(), E = IU->end(); UI != E; ++UI) {
Instruction *ExtInst = UI->getUser();
if (!isa<SExtInst>(ExtInst) && !isa<ZExtInst>(ExtInst))
continue;
const SCEV *AR = SE->getSCEV(ExtInst);
// Only widen this IV is SCEV tells us it's safe.
if (!isa<SCEVAddRecExpr>(AR) && !isa<SCEVAddExpr>(AR))
continue;
if (!L->contains(UI->getUser())) {
const SCEV *ExitVal = SE->getSCEVAtScope(AR, L->getParentLoop());
if (SE->isLoopInvariant(ExitVal, L))
AR = ExitVal;
}
// Only expand affine recurences.
if (!isSafe(AR, L, SE))
continue;
const Type *Ty =
SE->getEffectiveSCEVType(ExtInst->getType());
// Only remove [sz]ext if the wide IV is still a native type.
//
// FIXME: We may be able to remove the copy of this logic in
// IVUsers::AddUsersIfInteresting.
uint64_t Width = SE->getTypeSizeInBits(Ty);
if (Width > 64 || (TD && !TD->isLegalInteger(Width)))
continue;
// Now expand it into actual Instructions and patch it into place.
//
// FIXME: avoid creating a new IV.
Value *NewVal = Rewriter.expandCodeFor(AR, Ty, ExtInst);
DEBUG(dbgs() << "INDVARS: Widened IV '" << *AR << "' " << *ExtInst << '\n'
<< " into = " << *NewVal << "\n");
if (!isValidRewrite(ExtInst, NewVal)) {
DeadInsts.push_back(NewVal);
continue;
}
++NumWidened;
Changed = true;
if (!LargestType ||
SE->getTypeSizeInBits(Ty) >
SE->getTypeSizeInBits(LargestType))
LargestType = Ty;
SE->forgetValue(ExtInst);
// Patch the new value into place.
if (ExtInst->hasName())
NewVal->takeName(ExtInst);
ExtInst->replaceAllUsesWith(NewVal);
// The old value may be dead now.
DeadInsts.push_back(ExtInst);
// UI is a linked list iterator, so AddUsersIfInteresting effectively pushes
// nodes on the worklist.
IU->AddUsersIfInteresting(ExtInst);
}
return LargestType;
}
void IndVarSimplify::RewriteIVExpressions(Loop *L, SCEVExpander &Rewriter) {
// Rewrite all induction variable expressions in terms of the canonical
// induction variable.