diff options
-rw-r--r-- | lib/Analysis/ScalarEvolutionExpander.cpp | 59 | ||||
-rw-r--r-- | lib/Transforms/Scalar/IndVarSimplify.cpp | 95 | ||||
-rw-r--r-- | test/Transforms/IndVarSimplify/2003-09-23-NotAtTop.ll | 2 | ||||
-rw-r--r-- | test/Transforms/IndVarSimplify/masked-iv.ll | 24 |
4 files changed, 100 insertions, 80 deletions
diff --git a/lib/Analysis/ScalarEvolutionExpander.cpp b/lib/Analysis/ScalarEvolutionExpander.cpp index 477d88e..e1f8fa4 100644 --- a/lib/Analysis/ScalarEvolutionExpander.cpp +++ b/lib/Analysis/ScalarEvolutionExpander.cpp @@ -16,6 +16,7 @@ #include "llvm/Analysis/ScalarEvolutionExpander.h" #include "llvm/Analysis/LoopInfo.h" #include "llvm/Target/TargetData.h" +#include "llvm/ADT/STLExtras.h" using namespace llvm; /// InsertCastOfTo - Insert a cast of V to the specified type, doing what @@ -442,6 +443,34 @@ Value *SCEVExpander::visitAddRecExpr(const SCEVAddRecExpr *S) { const Type *Ty = SE.getEffectiveSCEVType(S->getType()); const Loop *L = S->getLoop(); + // First check for an existing canonical IV in a suitable type. + PHINode *CanonicalIV = 0; + if (PHINode *PN = L->getCanonicalInductionVariable()) + if (SE.isSCEVable(PN->getType()) && + isa<IntegerType>(SE.getEffectiveSCEVType(PN->getType())) && + SE.getTypeSizeInBits(PN->getType()) >= SE.getTypeSizeInBits(Ty)) + CanonicalIV = PN; + + // Rewrite an AddRec in terms of the canonical induction variable, if + // its type is more narrow. + if (CanonicalIV && + SE.getTypeSizeInBits(CanonicalIV->getType()) > + SE.getTypeSizeInBits(Ty)) { + SCEVHandle Start = SE.getAnyExtendExpr(S->getStart(), + CanonicalIV->getType()); + SCEVHandle Step = SE.getAnyExtendExpr(S->getStepRecurrence(SE), + CanonicalIV->getType()); + Value *V = expand(SE.getAddRecExpr(Start, Step, S->getLoop())); + BasicBlock::iterator SaveInsertPt = getInsertionPoint(); + BasicBlock::iterator NewInsertPt = + next(BasicBlock::iterator(cast<Instruction>(V))); + while (isa<PHINode>(NewInsertPt)) ++NewInsertPt; + V = expandCodeFor(SE.getTruncateExpr(SE.getUnknown(V), Ty), 0, + NewInsertPt); + setInsertionPoint(SaveInsertPt); + return V; + } + // {X,+,F} --> X + {0,+,F} if (!S->getStart()->isZero()) { std::vector<SCEVHandle> NewOps(S->getOperands()); @@ -475,6 +504,14 @@ Value *SCEVExpander::visitAddRecExpr(const SCEVAddRecExpr *S) { // {0,+,1} --> Insert a canonical induction variable into the loop! if (S->isAffine() && S->getOperand(1) == SE.getIntegerSCEV(1, Ty)) { + // If there's a canonical IV, just use it. + if (CanonicalIV) { + assert(Ty == SE.getEffectiveSCEVType(CanonicalIV->getType()) && + "IVs with types different from the canonical IV should " + "already have been handled!"); + return CanonicalIV; + } + // Create and insert the PHI node for the induction variable in the // specified loop. BasicBlock *Header = L->getHeader(); @@ -502,18 +539,16 @@ Value *SCEVExpander::visitAddRecExpr(const SCEVAddRecExpr *S) { return PN; } + // {0,+,F} --> {0,+,1} * F // Get the canonical induction variable I for this loop. - Value *I = getOrInsertCanonicalInductionVariable(L, Ty); + Value *I = CanonicalIV ? + CanonicalIV : + getOrInsertCanonicalInductionVariable(L, Ty); // If this is a simple linear addrec, emit it now as a special case. if (S->isAffine()) { // {0,+,F} --> i*F Value *F = expandCodeFor(S->getOperand(1), Ty); - - // If the step is by one, just return the inserted IV. - if (ConstantInt *CI = dyn_cast<ConstantInt>(F)) - if (CI->getValue() == 1) - return I; - + // If the insert point is directly inside of the loop, emit the multiply at // the insert point. Otherwise, L is a loop that is a parent of the insert // point loop. If we can, move the multiply to the outer most loop that it @@ -548,9 +583,17 @@ Value *SCEVExpander::visitAddRecExpr(const SCEVAddRecExpr *S) { // into this folder. SCEVHandle IH = SE.getUnknown(I); // Get I as a "symbolic" SCEV. - SCEVHandle V = S->evaluateAtIteration(IH, SE); + // Promote S up to the canonical IV type, if the cast is foldable. + SCEVHandle NewS = S; + SCEVHandle Ext = SE.getNoopOrAnyExtend(S, I->getType()); + if (isa<SCEVAddRecExpr>(Ext)) + NewS = Ext; + + SCEVHandle V = cast<SCEVAddRecExpr>(NewS)->evaluateAtIteration(IH, SE); //cerr << "Evaluated: " << *this << "\n to: " << *V << "\n"; + // Truncate the result down to the original type, if needed. + SCEVHandle T = SE.getTruncateOrNoop(V, Ty); return expand(V); } diff --git a/lib/Transforms/Scalar/IndVarSimplify.cpp b/lib/Transforms/Scalar/IndVarSimplify.cpp index 83503fd..38b1198 100644 --- a/lib/Transforms/Scalar/IndVarSimplify.cpp +++ b/lib/Transforms/Scalar/IndVarSimplify.cpp @@ -168,7 +168,7 @@ ICmpInst *IndVarSimplify::LinearFunctionTestReplace(Loop *L, // Expand the code for the iteration count into the preheader of the loop. BasicBlock *Preheader = L->getLoopPreheader(); - Value *ExitCnt = Rewriter.expandCodeFor(RHS, CmpIndVar->getType(), + Value *ExitCnt = Rewriter.expandCodeFor(RHS, IndVar->getType(), Preheader->getTerminator()); // Insert a new icmp_ne or icmp_eq instruction before the branch. @@ -392,10 +392,31 @@ bool IndVarSimplify::runOnLoop(Loop *L, LPPassManager &LPM) { // in this loop, insert a canonical induction variable of the largest size. Value *IndVar = 0; if (NeedCannIV) { + // Check to see if the loop already has a canonical-looking induction + // variable. If one is present and it's wider than the planned canonical + // induction variable, temporarily remove it, so that the Rewriter + // doesn't attempt to reuse it. + PHINode *OldCannIV = L->getCanonicalInductionVariable(); + if (OldCannIV) { + if (SE->getTypeSizeInBits(OldCannIV->getType()) > + SE->getTypeSizeInBits(LargestType)) + OldCannIV->removeFromParent(); + else + OldCannIV = 0; + } + IndVar = Rewriter.getOrInsertCanonicalInductionVariable(L,LargestType); + ++NumInserted; Changed = true; DOUT << "INDVARS: New CanIV: " << *IndVar; + + // Now that the official induction variable is established, reinsert + // the old canonical-looking variable after it so that the IR remains + // consistent. It will be deleted as part of the dead-PHI deletion at + // the end of the pass. + if (OldCannIV) + OldCannIV->insertAfter(cast<Instruction>(IndVar)); } // If we have a trip count expression, rewrite the loop's exit condition @@ -459,8 +480,8 @@ void IndVarSimplify::RewriteIVExpressions(Loop *L, const Type *LargestType, E = List.end(); UI != E; ++UI) { SCEVHandle Offset = UI->getOffset(); Value *Op = UI->getOperandValToReplace(); + const Type *UseTy = Op->getType(); Instruction *User = UI->getUser(); - bool isSigned = UI->isSigned(); // Compute the final addrec to expand into code. SCEVHandle AR = IU->getReplacementExpr(*UI); @@ -471,7 +492,7 @@ void IndVarSimplify::RewriteIVExpressions(Loop *L, const Type *LargestType, // Expand loop-invariant values in the loop preheader. They will // be sunk to the exit block later, if possible. NewVal = - Rewriter.expandCodeFor(AR, LargestType, + Rewriter.expandCodeFor(AR, UseTy, L->getLoopPreheader()->getTerminator()); Rewriter.setInsertionPoint(I); ++NumReplaced; @@ -485,74 +506,6 @@ void IndVarSimplify::RewriteIVExpressions(Loop *L, const Type *LargestType, if (!Stride->isLoopInvariant(L)) continue; - const Type *IVTy = Offset->getType(); - const Type *UseTy = Op->getType(); - - // Promote the Offset and Stride up to the canonical induction - // variable's bit width. - SCEVHandle PromotedOffset = Offset; - SCEVHandle PromotedStride = Stride; - if (SE->getTypeSizeInBits(IVTy) != SE->getTypeSizeInBits(LargestType)) { - // It doesn't matter for correctness whether zero or sign extension - // is used here, since the value is truncated away below, but if the - // value is signed, sign extension is more likely to be folded. - if (isSigned) { - PromotedOffset = SE->getSignExtendExpr(PromotedOffset, LargestType); - PromotedStride = SE->getSignExtendExpr(PromotedStride, LargestType); - } else { - PromotedOffset = SE->getZeroExtendExpr(PromotedOffset, LargestType); - // If the stride is obviously negative, use sign extension to - // produce things like x-1 instead of x+255. - if (isa<SCEVConstant>(PromotedStride) && - cast<SCEVConstant>(PromotedStride) - ->getValue()->getValue().isNegative()) - PromotedStride = SE->getSignExtendExpr(PromotedStride, - LargestType); - else - PromotedStride = SE->getZeroExtendExpr(PromotedStride, - LargestType); - } - } - - // Create the SCEV representing the offset from the canonical - // induction variable, still in the canonical induction variable's - // type, so that all expanded arithmetic is done in the same type. - SCEVHandle NewAR = SE->getAddRecExpr(SE->getIntegerSCEV(0, LargestType), - PromotedStride, L); - // Add the PromotedOffset as a separate step, because it may not be - // loop-invariant. - NewAR = SE->getAddExpr(NewAR, PromotedOffset); - - // Expand the addrec into instructions. - Value *V = Rewriter.expandCodeFor(NewAR); - - // Insert an explicit cast if necessary to truncate the value - // down to the original stride type. This is done outside of - // SCEVExpander because in SCEV expressions, a truncate of an - // addrec is always folded. - if (LargestType != IVTy) { - if (SE->getTypeSizeInBits(IVTy) != SE->getTypeSizeInBits(LargestType)) - NewAR = SE->getTruncateExpr(NewAR, IVTy); - if (Rewriter.isInsertedExpression(NewAR)) - V = Rewriter.expandCodeFor(NewAR); - else { - V = Rewriter.InsertCastOfTo(CastInst::getCastOpcode(V, false, - IVTy, false), - V, IVTy); - assert(!isa<SExtInst>(V) && !isa<ZExtInst>(V) && - "LargestType wasn't actually the largest type!"); - // Force the rewriter to use this trunc whenever this addrec - // appears so that it doesn't insert new phi nodes or - // arithmetic in a different type. - Rewriter.addInsertedValue(V, NewAR); - } - } - - DOUT << "INDVARS: Made offset-and-trunc IV for offset " - << *IVTy << " " << *Offset << ": "; - DEBUG(WriteAsOperand(*DOUT, V, false)); - DOUT << "\n"; - // Now expand it into actual Instructions and patch it into place. NewVal = Rewriter.expandCodeFor(AR, UseTy); } diff --git a/test/Transforms/IndVarSimplify/2003-09-23-NotAtTop.ll b/test/Transforms/IndVarSimplify/2003-09-23-NotAtTop.ll index d70e604..b4a2c50 100644 --- a/test/Transforms/IndVarSimplify/2003-09-23-NotAtTop.ll +++ b/test/Transforms/IndVarSimplify/2003-09-23-NotAtTop.ll @@ -1,4 +1,4 @@ -; RUN: llvm-as < %s | opt -indvars | llvm-dis | %prcontext Loop: 1 | grep %indvar +; RUN: llvm-as < %s | opt -indvars | llvm-dis | %prcontext ^Loop: 1 | grep %Canonical ; The indvar simplification code should ensure that the first PHI in the block ; is the canonical one! diff --git a/test/Transforms/IndVarSimplify/masked-iv.ll b/test/Transforms/IndVarSimplify/masked-iv.ll new file mode 100644 index 0000000..c7583c9 --- /dev/null +++ b/test/Transforms/IndVarSimplify/masked-iv.ll @@ -0,0 +1,24 @@ +; RUN: llvm-as < %s | opt -indvars | llvm-dis | grep trunc | count 1 + +; Indvars should do the IV arithmetic in the canonical IV type (i64), +; and only use one truncation. + +define void @foo(i64* %A, i64* %B, i64 %n, i64 %a, i64 %s) nounwind { +entry: + %t0 = icmp sgt i64 %n, 0 ; <i1> [#uses=1] + br i1 %t0, label %bb.preheader, label %return + +bb.preheader: ; preds = %entry + br label %bb + +bb: ; preds = %bb, %bb.preheader + %i.01 = phi i64 [ %t6, %bb ], [ %a, %bb.preheader ] ; <i64> [#uses=3] + %t1 = and i64 %i.01, 255 ; <i64> [#uses=1] + %t2 = getelementptr i64* %A, i64 %t1 ; <i64*> [#uses=1] + store i64 %i.01, i64* %t2, align 8 + %t6 = add i64 %i.01, %s ; <i64> [#uses=1] + br label %bb + +return: ; preds = %entry + ret void +} |