[llvm-commits] [llvm] r72366 - in /llvm/trunk: include/llvm/Analysis/ScalarEvolutionExpander.h lib/Analysis/ScalarEvolutionExpander.cpp test/Transforms/IndVarSimplify/addrec-gep.ll test/Transforms/IndVarSimplify/gep-with-mul-base.ll
Howard Su
howard0su at gmail.com
Mon May 25 05:58:50 PDT 2009
SCEVHandle RestArray[1] = Rest;
should change to SCEVHandle RestArray[1] = {Rest}; otherwise MSVC will
complain this.
On Mon, May 25, 2009 at 2:06 AM, Dan Gohman <gohman at apple.com> wrote:
> Author: djg
> Date: Sun May 24 13:06:31 2009
> New Revision: 72366
>
> URL: http://llvm.org/viewvc/llvm-project?rev=72366&view=rev
> Log:
> Generalize SCEVExpander::visitAddRecExpr's GEP persuit, and avoid
> sending SCEVUnknowns to expandAddToGEP. This avoids the need for
> expandAddToGEP to bend the rules and peek into SCEVUnknown
> expressions.
>
> Factor out the code for testing whether a SCEV can be factored by
> a constant for use in a GEP index. This allows it to handle
> SCEVAddRecExprs, by recursing.
>
> As a result, SCEVExpander can now put more things in GEP indices,
> so it emits fewer explicit mul instructions.
>
> Added:
> llvm/trunk/test/Transforms/IndVarSimplify/addrec-gep.ll
> Modified:
> llvm/trunk/include/llvm/Analysis/ScalarEvolutionExpander.h
> llvm/trunk/lib/Analysis/ScalarEvolutionExpander.cpp
> llvm/trunk/test/Transforms/IndVarSimplify/gep-with-mul-base.ll
>
> Modified: llvm/trunk/include/llvm/Analysis/ScalarEvolutionExpander.h
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Analysis/ScalarEvolutionExpander.h?rev=72366&r1=72365&r2=72366&view=diff
>
>
> ==============================================================================
> --- llvm/trunk/include/llvm/Analysis/ScalarEvolutionExpander.h (original)
> +++ llvm/trunk/include/llvm/Analysis/ScalarEvolutionExpander.h Sun May 24
> 13:06:31 2009
> @@ -110,8 +110,8 @@
> private:
> /// expandAddToGEP - Expand a SCEVAddExpr with a pointer type into a
> GEP
> /// instead of using ptrtoint+arithmetic+inttoptr.
> - Value *expandAddToGEP(const SCEVAddExpr *S, const PointerType *PTy,
> - const Type *Ty, Value *V);
> + Value *expandAddToGEP(const SCEVHandle *op_begin, const SCEVHandle
> *op_end,
> + const PointerType *PTy, const Type *Ty, Value
> *V);
>
> Value *expand(const SCEV *S);
>
>
> Modified: llvm/trunk/lib/Analysis/ScalarEvolutionExpander.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ScalarEvolutionExpander.cpp?rev=72366&r1=72365&r2=72366&view=diff
>
>
> ==============================================================================
> --- llvm/trunk/lib/Analysis/ScalarEvolutionExpander.cpp (original)
> +++ llvm/trunk/lib/Analysis/ScalarEvolutionExpander.cpp Sun May 24 13:06:31
> 2009
> @@ -144,17 +144,89 @@
> return BO;
> }
>
> +/// FactorOutConstant - Test if S is evenly divisible by Factor, using
> signed
> +/// division. If so, update S with Factor divided out and return true.
> +/// TODO: When ScalarEvolution gets a SCEVSDivExpr, this can be made
> +/// unnecessary; in its place, just signed-divide Ops[i] by the scale and
> +/// check to see if the divide was folded.
> +static bool FactorOutConstant(SCEVHandle &S,
> + const APInt &Factor,
> + ScalarEvolution &SE) {
> + // Everything is divisible by one.
> + if (Factor == 1)
> + return true;
> +
> + // For a Constant, check for a multiple of the given factor.
> + if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S))
> + if (!C->getValue()->getValue().srem(Factor)) {
> + ConstantInt *CI =
> + ConstantInt::get(C->getValue()->getValue().sdiv(Factor));
> + SCEVHandle Div = SE.getConstant(CI);
> + S = Div;
> + return true;
> + }
> +
> + // In a Mul, check if there is a constant operand which is a multiple
> + // of the given factor.
> + if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(S))
> + if (const SCEVConstant *C = dyn_cast<SCEVConstant>(M->getOperand(0)))
> + if (!C->getValue()->getValue().srem(Factor)) {
> + std::vector<SCEVHandle> NewMulOps(M->getOperands());
> + NewMulOps[0] =
> + SE.getConstant(C->getValue()->getValue().sdiv(Factor));
> + S = SE.getMulExpr(NewMulOps);
> + return true;
> + }
> +
> + // In an AddRec, check if both start and step are divisible.
> + if (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(S)) {
> + SCEVHandle Start = A->getStart();
> + if (!FactorOutConstant(Start, Factor, SE))
> + return false;
> + SCEVHandle Step = A->getStepRecurrence(SE);
> + if (!FactorOutConstant(Step, Factor, SE))
> + return false;
> + S = SE.getAddRecExpr(Start, Step, A->getLoop());
> + return true;
> + }
> +
> + return false;
> +}
> +
> /// expandAddToGEP - Expand a SCEVAddExpr with a pointer type into a GEP
> -/// instead of using ptrtoint+arithmetic+inttoptr.
> -Value *SCEVExpander::expandAddToGEP(const SCEVAddExpr *S,
> +/// instead of using ptrtoint+arithmetic+inttoptr. This helps
> +/// BasicAliasAnalysis analyze the result. However, it suffers from the
> +/// underlying bug described in PR2831. Addition in LLVM currently always
> +/// has two's complement wrapping guaranteed. However, the semantics for
> +/// getelementptr overflow are ambiguous. In the common case though, this
> +/// expansion gets used when a GEP in the original code has been converted
> +/// into integer arithmetic, in which case the resulting code will be no
> +/// more undefined than it was originally.
> +///
> +/// Design note: It might seem desirable for this function to be more
> +/// loop-aware. If some of the indices are loop-invariant while others
> +/// aren't, it might seem desirable to emit multiple GEPs, keeping the
> +/// loop-invariant portions of the overall computation outside the loop.
> +/// However, there are a few reasons this is not done here. Hoisting
> simple
> +/// arithmetic is a low-level optimization that often isn't very
> +/// important until late in the optimization process. In fact, passes
> +/// like InstructionCombining will combine GEPs, even if it means
> +/// pushing loop-invariant computation down into loops, so even if the
> +/// GEPs were split here, the work would quickly be undone. The
> +/// LoopStrengthReduction pass, which is usually run quite late (and
> +/// after the last InstructionCombining pass), takes care of hoisting
> +/// loop-invariant portions of expressions, after considering what
> +/// can be folded using target addressing modes.
> +///
> +Value *SCEVExpander::expandAddToGEP(const SCEVHandle *op_begin,
> + const SCEVHandle *op_end,
> const PointerType *PTy,
> const Type *Ty,
> Value *V) {
> const Type *ElTy = PTy->getElementType();
> SmallVector<Value *, 4> GepIndices;
> - std::vector<SCEVHandle> Ops = S->getOperands();
> + std::vector<SCEVHandle> Ops(op_begin, op_end);
> bool AnyNonZeroIndices = false;
> - Ops.pop_back();
>
> // Decend down the pointer's type and attempt to convert the other
> // operands into GEP indices, at each level. The first index in a GEP
> @@ -167,45 +239,27 @@
> std::vector<SCEVHandle> NewOps;
> std::vector<SCEVHandle> ScaledOps;
> for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
> + // Split AddRecs up into parts as either of the parts may be usable
> + // without the other.
> + if (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(Ops[i]))
> + if (!A->getStart()->isZero()) {
> + SCEVHandle Start = A->getStart();
> + Ops.push_back(SE.getAddRecExpr(SE.getIntegerSCEV(0,
> A->getType()),
> + A->getStepRecurrence(SE),
> + A->getLoop()));
> + Ops[i] = Start;
> + ++e;
> + }
> + // If the scale size is not 0, attempt to factor out a scale.
> if (ElSize != 0) {
> - // For a Constant, check for a multiple of the pointer type's
> - // scale size.
> - if (const SCEVConstant *C = dyn_cast<SCEVConstant>(Ops[i]))
> - if (!C->getValue()->getValue().srem(ElSize)) {
> - ConstantInt *CI =
> - ConstantInt::get(C->getValue()->getValue().sdiv(ElSize));
> - SCEVHandle Div = SE.getConstant(CI);
> - ScaledOps.push_back(Div);
> - continue;
> - }
> - // In a Mul, check if there is a constant operand which is a
> multiple
> - // of the pointer type's scale size.
> - if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(Ops[i]))
> - if (const SCEVConstant *C =
> dyn_cast<SCEVConstant>(M->getOperand(0)))
> - if (!C->getValue()->getValue().srem(ElSize)) {
> - std::vector<SCEVHandle> NewMulOps(M->getOperands());
> - NewMulOps[0] =
> - SE.getConstant(C->getValue()->getValue().sdiv(ElSize));
> - ScaledOps.push_back(SE.getMulExpr(NewMulOps));
> - continue;
> - }
> - // In an Unknown, check if the underlying value is a Mul by a
> constant
> - // which is equal to the pointer type's scale size.
> - if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(Ops[i]))
> - if (BinaryOperator *BO =
> dyn_cast<BinaryOperator>(U->getValue()))
> - if (BO->getOpcode() == Instruction::Mul)
> - if (ConstantInt *CI =
> dyn_cast<ConstantInt>(BO->getOperand(1)))
> - if (CI->getValue() == ElSize) {
> - ScaledOps.push_back(SE.getUnknown(BO->getOperand(0)));
> - continue;
> - }
> - // If the pointer type's scale size is 1, no scaling is necessary
> - // and any value can be used.
> - if (ElSize == 1) {
> - ScaledOps.push_back(Ops[i]);
> + SCEVHandle Op = Ops[i];
> + if (FactorOutConstant(Op, ElSize, SE)) {
> + ScaledOps.push_back(Op); // Op now has ElSize factored out.
> continue;
> }
> }
> + // If the operand was not divisible, add it to the list of operands
> + // we'll scan next iteration.
> NewOps.push_back(Ops[i]);
> }
> Ops = NewOps;
> @@ -292,17 +346,14 @@
> const Type *Ty = SE.getEffectiveSCEVType(S->getType());
> Value *V = expand(S->getOperand(S->getNumOperands()-1));
>
> - // Turn things like ptrtoint+arithmetic+inttoptr into GEP. This helps
> - // BasicAliasAnalysis analyze the result. However, it suffers from the
> - // underlying bug described in PR2831. Addition in LLVM currently always
> - // has two's complement wrapping guaranteed. However, the semantics for
> - // getelementptr overflow are ambiguous. In the common case though, this
> - // expansion gets used when a GEP in the original code has been
> converted
> - // into integer arithmetic, in which case the resulting code will be no
> - // more undefined than it was originally.
> + // Turn things like ptrtoint+arithmetic+inttoptr into GEP. See the
> + // comments on expandAddToGEP for details.
> if (SE.TD <http://se.td/>)
> - if (const PointerType *PTy = dyn_cast<PointerType>(V->getType()))
> - return expandAddToGEP(S, PTy, Ty, V);
> + if (const PointerType *PTy = dyn_cast<PointerType>(V->getType())) {
> + const std::vector<SCEVHandle> &Ops = S->getOperands();
> + return expandAddToGEP(Ops.data(), Ops.data() + Ops.size() - 1,
> + PTy, Ty, V);
> + }
>
> V = InsertNoopCastOfTo(V, Ty);
>
> @@ -357,6 +408,27 @@
> return InsertBinop(Instruction::UDiv, LHS, RHS, InsertPt);
> }
>
> +/// Move parts of Base into Rest to leave Base with the minimal
> +/// expression that provides a pointer operand suitable for a
> +/// GEP expansion.
> +static void ExposePointerBase(SCEVHandle &Base, SCEVHandle &Rest,
> + ScalarEvolution &SE) {
> + while (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(Base)) {
> + Base = A->getStart();
> + Rest = SE.getAddExpr(Rest,
> + SE.getAddRecExpr(SE.getIntegerSCEV(0,
> A->getType()),
> + A->getStepRecurrence(SE),
> + A->getLoop()));
> + }
> + if (const SCEVAddExpr *A = dyn_cast<SCEVAddExpr>(Base)) {
> + Base = A->getOperand(A->getNumOperands()-1);
> + std::vector<SCEVHandle> NewAddOps(A->op_begin(), A->op_end());
> + NewAddOps.back() = Rest;
> + Rest = SE.getAddExpr(NewAddOps);
> + ExposePointerBase(Base, Rest, SE);
> + }
> +}
> +
> Value *SCEVExpander::visitAddRecExpr(const SCEVAddRecExpr *S) {
> const Type *Ty = SE.getEffectiveSCEVType(S->getType());
> const Loop *L = S->getLoop();
> @@ -365,8 +437,25 @@
> if (!S->getStart()->isZero()) {
> std::vector<SCEVHandle> NewOps(S->getOperands());
> NewOps[0] = SE.getIntegerSCEV(0, Ty);
> - Value *Rest = expand(SE.getAddRecExpr(NewOps, L));
> - return expand(SE.getAddExpr(S->getStart(), SE.getUnknown(Rest)));
> + SCEVHandle Rest = SE.getAddRecExpr(NewOps, L);
> +
> + // Turn things like ptrtoint+arithmetic+inttoptr into GEP. See the
> + // comments on expandAddToGEP for details.
> + if (SE.TD <http://se.td/>) {
> + SCEVHandle Base = S->getStart();
> + SCEVHandle RestArray[1] = Rest;
> + // Dig into the expression to find the pointer base for a GEP.
> + ExposePointerBase(Base, RestArray[0], SE);
> + // If we found a pointer, expand the AddRec with a GEP.
> + if (const PointerType *PTy = dyn_cast<PointerType>(Base->getType()))
> {
> + Value *StartV = expand(Base);
> + assert(StartV->getType() == PTy && "Pointer type mismatch for
> GEP!");
> + return expandAddToGEP(RestArray, RestArray+1, PTy, Ty, StartV);
> + }
> + }
> +
> + Value *RestV = expand(Rest);
> + return expand(SE.getAddExpr(S->getStart(), SE.getUnknown(RestV)));
> }
>
> // {0,+,1} --> Insert a canonical induction variable into the loop!
>
> Added: llvm/trunk/test/Transforms/IndVarSimplify/addrec-gep.ll
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/IndVarSimplify/addrec-gep.ll?rev=72366&view=auto
>
>
> ==============================================================================
> --- llvm/trunk/test/Transforms/IndVarSimplify/addrec-gep.ll (added)
> +++ llvm/trunk/test/Transforms/IndVarSimplify/addrec-gep.ll Sun May 24
> 13:06:31 2009
> @@ -0,0 +1,78 @@
> +; RUN: llvm-as < %s | opt -indvars | llvm-dis > %t
> +; RUN: grep getelementptr %t | count 1
> +; RUN: grep {mul .*, 37} %t | count 1
> +; RUN: grep {add .*, 5203} %t | count 1
> +; RUN: not grep cast %t
> +
> +; This test tests several things. The load and store should use the
> +; same address instead of having it computed twice, and SCEVExpander
> should
> +; be able to reconstruct the full getelementptr, despite it having a few
> +; obstacles set in its way.
> +
> +target datalayout = "e-p:64:64:64"
> +
> +define void @foo(i64 %n, i64 %m, i64 %o, i64 %q, double* nocapture %p)
> nounwind {
> +entry:
> + %tmp = icmp sgt i64 %n, 0 ; <i1> [#uses=1]
> + br i1 %tmp, label %bb.nph3, label %return
> +
> +bb.nph: ; preds = %bb2.preheader
> + %tmp1 = mul i64 %tmp16, %i.02 ; <i64> [#uses=1]
> + %tmp2 = mul i64 %tmp19, %i.02 ; <i64> [#uses=1]
> + br label %bb1
> +
> +bb1: ; preds = %bb2, %bb.nph
> + %j.01 = phi i64 [ %tmp9, %bb2 ], [ 0, %bb.nph ] ; <i64>
> [#uses=3]
> + %tmp3 = add i64 %j.01, %tmp1 ; <i64> [#uses=1]
> + %tmp4 = add i64 %j.01, %tmp2 ; <i64> [#uses=1]
> + %z0 = add i64 %tmp4, 5203
> + %tmp5 = getelementptr double* %p, i64 %z0 ; <double*>
> [#uses=1]
> + %tmp6 = load double* %tmp5, align 8 ; <double>
> [#uses=1]
> + %tmp7 = fdiv double %tmp6, 2.100000e+00 ; <double>
> [#uses=1]
> + %z1 = add i64 %tmp4, 5203
> + %tmp8 = getelementptr double* %p, i64 %z1 ; <double*>
> [#uses=1]
> + store double %tmp7, double* %tmp8, align 8
> + %tmp9 = add i64 %j.01, 1 ; <i64> [#uses=2]
> + br label %bb2
> +
> +bb2: ; preds = %bb1
> + %tmp10 = icmp slt i64 %tmp9, %m ; <i1> [#uses=1]
> + br i1 %tmp10, label %bb1, label %bb2.bb3_crit_edge
> +
> +bb2.bb3_crit_edge: ; preds = %bb2
> + br label %bb3
> +
> +bb3: ; preds = %bb2.preheader, %bb2.bb3_crit_edge
> + %tmp11 = add i64 %i.02, 1 ; <i64> [#uses=2]
> + br label %bb4
> +
> +bb4: ; preds = %bb3
> + %tmp12 = icmp slt i64 %tmp11, %n ; <i1> [#uses=1]
> + br i1 %tmp12, label %bb2.preheader, label %bb4.return_crit_edge
> +
> +bb4.return_crit_edge: ; preds = %bb4
> + br label %bb4.return_crit_edge.split
> +
> +bb4.return_crit_edge.split: ; preds = %bb.nph3,
> %bb4.return_crit_edge
> + br label %return
> +
> +bb.nph3: ; preds = %entry
> + %tmp13 = icmp sgt i64 %m, 0 ; <i1> [#uses=1]
> + %tmp14 = mul i64 %n, 37 ; <i64> [#uses=1]
> + %tmp15 = mul i64 %tmp14, %o ; <i64> [#uses=1]
> + %tmp16 = mul i64 %tmp15, %q ; <i64> [#uses=1]
> + %tmp17 = mul i64 %n, 37 ; <i64> [#uses=1]
> + %tmp18 = mul i64 %tmp17, %o ; <i64> [#uses=1]
> + %tmp19 = mul i64 %tmp18, %q ; <i64> [#uses=1]
> + br i1 %tmp13, label %bb.nph3.split, label
> %bb4.return_crit_edge.split
> +
> +bb.nph3.split: ; preds = %bb.nph3
> + br label %bb2.preheader
> +
> +bb2.preheader: ; preds = %bb.nph3.split, %bb4
> + %i.02 = phi i64 [ %tmp11, %bb4 ], [ 0, %bb.nph3.split ] ;
> <i64> [#uses=3]
> + br i1 true, label %bb.nph, label %bb3
> +
> +return: ; preds = %bb4.return_crit_edge.split, %entry
> + ret void
> +}
>
> Modified: llvm/trunk/test/Transforms/IndVarSimplify/gep-with-mul-base.ll
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/IndVarSimplify/gep-with-mul-base.ll?rev=72366&r1=72365&r2=72366&view=diff
>
>
> ==============================================================================
> --- llvm/trunk/test/Transforms/IndVarSimplify/gep-with-mul-base.ll
> (original)
> +++ llvm/trunk/test/Transforms/IndVarSimplify/gep-with-mul-base.ll Sun May
> 24 13:06:31 2009
> @@ -1,6 +1,6 @@
> ; RUN: llvm-as < %s | opt -indvars | llvm-dis > %t
> ; RUN: grep add %t | count 8
> -; RUN: grep mul %t | count 9
> +; RUN: grep mul %t | count 7
>
> define void @foo(i64 %n, i64 %m, i64 %o, double* nocapture %p) nounwind {
> entry:
>
>
> _______________________________________________
> llvm-commits mailing list
> llvm-commits at cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
>
--
-Howard
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