[llvm] r315288 - [SCCP] Propagate integer range info for parameters in IPSCCP.
Bruno Cardoso Lopes via llvm-commits
llvm-commits at lists.llvm.org
Tue Oct 10 09:41:18 PDT 2017
Hi Florian,
I reverted this in r315329 since looks like it broke our stage2 bot:
http://green.lab.llvm.org/green/job/clang-stage2-configure-Rlto/21675/
On Tue, Oct 10, 2017 at 2:32 AM, Florian Hahn via llvm-commits
<llvm-commits at lists.llvm.org> wrote:
> Author: fhahn
> Date: Tue Oct 10 02:32:38 2017
> New Revision: 315288
>
> URL: http://llvm.org/viewvc/llvm-project?rev=315288&view=rev
> Log:
> [SCCP] Propagate integer range info for parameters in IPSCCP.
>
> Summary:
> This updates the SCCP solver to use of the ValueElement lattice for
> parameters, which provides integer range information. The range
> information is used to remove unneeded icmp instructions.
>
> For the following function, f() can be optimized to `ret i32 2` with
> this change
>
> source_filename = "sccp.c"
> target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
> target triple = "x86_64-unknown-linux-gnu"
>
> ; Function Attrs: norecurse nounwind readnone uwtable
> define i32 @main() local_unnamed_addr #0 {
> entry:
> %call = tail call fastcc i32 @f(i32 1)
> %call1 = tail call fastcc i32 @f(i32 47)
> %add3 = add nsw i32 %call, %call1
> ret i32 %add3
> }
>
> ; Function Attrs: noinline norecurse nounwind readnone uwtable
> define internal fastcc i32 @f(i32 %x) unnamed_addr #1 {
> entry:
> %c1 = icmp sle i32 %x, 100
>
> %cmp = icmp sgt i32 %x, 300
> %. = select i1 %cmp, i32 1, i32 2
> ret i32 %.
> }
>
> attributes #1 = { noinline }
>
>
>
> Reviewers: davide, sanjoy, efriedma, dberlin
>
> Reviewed By: davide, dberlin
>
> Subscribers: mcrosier, gberry, mssimpso, dberlin, llvm-commits
>
> Differential Revision: https://reviews.llvm.org/D36656
>
> Added:
> llvm/trunk/test/Transforms/SCCP/ip-constan-ranges.ll
> Modified:
> llvm/trunk/lib/Transforms/Scalar/SCCP.cpp
>
> Modified: llvm/trunk/lib/Transforms/Scalar/SCCP.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/SCCP.cpp?rev=315288&r1=315287&r2=315288&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Transforms/Scalar/SCCP.cpp (original)
> +++ llvm/trunk/lib/Transforms/Scalar/SCCP.cpp Tue Oct 10 02:32:38 2017
> @@ -27,6 +27,7 @@
> #include "llvm/Analysis/ConstantFolding.h"
> #include "llvm/Analysis/GlobalsModRef.h"
> #include "llvm/Analysis/TargetLibraryInfo.h"
> +#include "llvm/Analysis/ValueLattice.h"
> #include "llvm/IR/CallSite.h"
> #include "llvm/IR/Constants.h"
> #include "llvm/IR/DataLayout.h"
> @@ -52,6 +53,8 @@ STATISTIC(NumDeadBlocks , "Number of bas
> STATISTIC(IPNumInstRemoved, "Number of instructions removed by IPSCCP");
> STATISTIC(IPNumArgsElimed ,"Number of arguments constant propagated by IPSCCP");
> STATISTIC(IPNumGlobalConst, "Number of globals found to be constant by IPSCCP");
> +STATISTIC(IPNumRangeInfoUsed, "Number of times constant range info was used by"
> + "IPSCCP");
>
> namespace {
> /// LatticeVal class - This class represents the different lattice values that
> @@ -153,6 +156,14 @@ public:
> Val.setInt(forcedconstant);
> Val.setPointer(V);
> }
> +
> + ValueLatticeElement toValueLattice() const {
> + if (isOverdefined())
> + return ValueLatticeElement::getOverdefined();
> + if (isConstant())
> + return ValueLatticeElement::get(getConstant());
> + return ValueLatticeElement();
> + }
> };
> } // end anonymous namespace.
>
> @@ -169,6 +180,8 @@ class SCCPSolver : public InstVisitor<SC
> const TargetLibraryInfo *TLI;
> SmallPtrSet<BasicBlock*, 8> BBExecutable; // The BBs that are executable.
> DenseMap<Value*, LatticeVal> ValueState; // The state each value is in.
> + // The state each parameter is in.
> + DenseMap<Value *, ValueLatticeElement> ParamState;
>
> /// StructValueState - This maintains ValueState for values that have
> /// StructType, for example for formal arguments, calls, insertelement, etc.
> @@ -290,10 +303,15 @@ public:
> return StructValues;
> }
>
> - LatticeVal getLatticeValueFor(Value *V) const {
> - DenseMap<Value*, LatticeVal>::const_iterator I = ValueState.find(V);
> - assert(I != ValueState.end() && "V is not in valuemap!");
> - return I->second;
> + ValueLatticeElement getLatticeValueFor(Value *V) {
> + if (ParamState.count(V) == 0) {
> + DenseMap<Value *, LatticeVal>::const_iterator I = ValueState.find(V);
> + assert(I != ValueState.end() &&
> + "V not found in ValueState nor Paramstate map!");
> + ParamState[V] = I->second.toValueLattice();
> + }
> +
> + return ParamState[V];
> }
>
> /// getTrackedRetVals - Get the inferred return value map.
> @@ -426,6 +444,15 @@ private:
> return LV;
> }
>
> + ValueLatticeElement &getParamState(Value *V) {
> + assert(!V->getType()->isStructTy() && "Should use getStructValueState");
> +
> + if (ParamState.count(V) == 0)
> + ParamState[V] = getValueState(V).toValueLattice();
> +
> + return ParamState[V];
> + }
> +
> /// getStructValueState - Return the LatticeVal object that corresponds to the
> /// value/field pair. This function handles the case when the value hasn't
> /// been seen yet by properly seeding constants etc.
> @@ -1162,6 +1189,9 @@ CallOverdefined:
> mergeInValue(getStructValueState(&*AI, i), &*AI, CallArg);
> }
> } else {
> + // Most other parts of the Solver still only use the simpler value
> + // lattice, so we propagate changes for parameters to both lattices.
> + getParamState(&*AI).mergeIn(getValueState(*CAI).toValueLattice(), DL);
> mergeInValue(&*AI, getValueState(*CAI));
> }
> }
> @@ -1557,6 +1587,44 @@ bool SCCPSolver::ResolvedUndefsIn(Functi
> return false;
> }
>
> +static bool tryToReplaceWithConstantRange(SCCPSolver &Solver, Value *V) {
> + bool Changed = false;
> + if (!V->getType()->isIntegerTy())
> + return false;
> +
> + const ValueLatticeElement &IV = Solver.getLatticeValueFor(V);
> + if (IV.isOverdefined())
> + return false;
> +
> + // Currently we only use range information for integer values.
> + if (!(V->getType()->isIntegerTy() && IV.isConstantRange()))
> + return false;
> +
> + for (auto &Use : V->uses()) {
> + auto *Icmp = dyn_cast<ICmpInst>(Use.getUser());
> + if (!Icmp)
> + continue;
> +
> + auto A = Solver.getLatticeValueFor(Icmp->getOperand(0));
> + auto B = Solver.getLatticeValueFor(Icmp->getOperand(1));
> + Constant *C = nullptr;
> + if (A.satisfiesPredicate(Icmp->getPredicate(), B))
> + C = ConstantInt::getTrue(Icmp->getType());
> + else if (A.satisfiesPredicate(Icmp->getInversePredicate(), B))
> + C = ConstantInt::getFalse(Icmp->getType());
> +
> + if (C) {
> + Icmp->replaceAllUsesWith(C);
> + DEBUG(dbgs() << "Replacing " << *Icmp << " with " << *C
> + << ", because of range information " << A << " " << B
> + << "\n");
> + Icmp->eraseFromParent();
> + Changed = true;
> + }
> + }
> + return Changed;
> +}
> +
> static bool tryToReplaceWithConstant(SCCPSolver &Solver, Value *V) {
> Constant *Const = nullptr;
> if (V->getType()->isStructTy()) {
> @@ -1573,10 +1641,19 @@ static bool tryToReplaceWithConstant(SCC
> }
> Const = ConstantStruct::get(ST, ConstVals);
> } else {
> - LatticeVal IV = Solver.getLatticeValueFor(V);
> + const ValueLatticeElement &IV = Solver.getLatticeValueFor(V);
> if (IV.isOverdefined())
> return false;
> - Const = IV.isConstant() ? IV.getConstant() : UndefValue::get(V->getType());
> +
> + if (IV.isConstantRange()) {
> + if (IV.getConstantRange().isSingleElement())
> + Const =
> + ConstantInt::get(V->getType(), IV.asConstantInteger().getValue());
> + else
> + return false;
> + } else
> + Const =
> + IV.isConstant() ? IV.getConstant() : UndefValue::get(V->getType());
> }
> assert(Const && "Constant is nullptr here!");
> DEBUG(dbgs() << " Constant: " << *Const << " = " << *V << '\n');
> @@ -1816,12 +1893,17 @@ static bool runIPSCCP(Module &M, const D
> if (F.isDeclaration())
> continue;
>
> - if (Solver.isBlockExecutable(&F.front()))
> + if (Solver.isBlockExecutable(&F.front())) {
> for (Function::arg_iterator AI = F.arg_begin(), E = F.arg_end(); AI != E;
> - ++AI)
> + ++AI) {
> if (!AI->use_empty() && tryToReplaceWithConstant(Solver, &*AI))
> ++IPNumArgsElimed;
>
> + if (!AI->use_empty() && tryToReplaceWithConstantRange(Solver, &*AI))
> + ++IPNumRangeInfoUsed;
> + }
> + }
> +
> for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
> if (!Solver.isBlockExecutable(&*BB)) {
> DEBUG(dbgs() << " BasicBlock Dead:" << *BB);
>
> Added: llvm/trunk/test/Transforms/SCCP/ip-constan-ranges.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SCCP/ip-constan-ranges.ll?rev=315288&view=auto
> ==============================================================================
> --- llvm/trunk/test/Transforms/SCCP/ip-constan-ranges.ll (added)
> +++ llvm/trunk/test/Transforms/SCCP/ip-constan-ranges.ll Tue Oct 10 02:32:38 2017
> @@ -0,0 +1,117 @@
> +; RUN: opt < %s -ipsccp -S | FileCheck %s
> +
> +; Constant range for %a is [1, 48) and for %b is [301, 1000)
> +; CHECK-LABEL: f1
> +; CHECK-NOT: icmp
> +; CHECK: %a.1 = select i1 false, i32 1, i32 2
> +; CHECK: %b.1 = select i1 true, i32 1, i32 2
> +; CHECK: %a.2 = select i1 false, i32 1, i32 2
> +; CHECK: %b.2 = select i1 true, i32 1, i32 2
> +define internal i32 @f1(i32 %a, i32 %b) {
> +entry:
> + %cmp.a = icmp sgt i32 %a, 300
> + %cmp.b = icmp sgt i32 %b, 300
> + %cmp.a2 = icmp ugt i32 %a, 300
> + %cmp.b2 = icmp ugt i32 %b, 300
> +
> + %a.1 = select i1 %cmp.a, i32 1, i32 2
> + %b.1 = select i1 %cmp.b, i32 1, i32 2
> + %a.2 = select i1 %cmp.a2, i32 1, i32 2
> + %b.2 = select i1 %cmp.b2, i32 1, i32 2
> + %res1 = add i32 %a.1, %b.1
> + %res2 = add i32 %a.2, %b.2
> + %res3 = add i32 %res1, %res2
> + ret i32 %res3
> +}
> +
> +; Constant range for %x is [47, 302)
> +; CHECK-LABEL: f2
> +; CHECK: %cmp = icmp sgt i32 %x, 300
> +; CHECK: %res1 = select i1 %cmp, i32 1, i32 2
> +; CHECK-NEXT: %res2 = select i1 true, i32 3, i32 4
> +; CHECK-NEXT: %res3 = select i1 true, i32 5, i32 6
> +; CHECK-NEXT: %res4 = select i1 %cmp4, i32 3, i32 4
> +; CHECK-NEXT: %res5 = select i1 true, i32 5, i32 6
> +define internal i32 @f2(i32 %x) {
> +entry:
> + %cmp = icmp sgt i32 %x, 300
> + %cmp2 = icmp ne i32 %x, 10
> + %cmp3 = icmp sge i32 %x, 47
> + %cmp4 = icmp ugt i32 %x, 300
> + %cmp5 = icmp uge i32 %x, 47
> + %res1 = select i1 %cmp, i32 1, i32 2
> + %res2 = select i1 %cmp2, i32 3, i32 4
> + %res3 = select i1 %cmp3, i32 5, i32 6
> + %res4 = select i1 %cmp4, i32 3, i32 4
> + %res5 = select i1 %cmp5, i32 5, i32 6
> +
> + %res6 = add i32 %res1, %res2
> + %res7 = add i32 %res3, %res4
> + %res = add i32 %res6, %res5
> + ret i32 %res
> +}
> +
> +define i32 @caller1() {
> +entry:
> + %call1 = tail call i32 @f1(i32 1, i32 301)
> + %call2 = tail call i32 @f1(i32 47, i32 999)
> + %call3 = tail call i32 @f2(i32 47)
> + %call4 = tail call i32 @f2(i32 301)
> + %res = add nsw i32 %call1, %call2
> + %res.1 = add nsw i32 %res, %call3
> + %res.2 = add nsw i32 %res.1, %call4
> + ret i32 %res.2
> +}
> +
> +; x is overdefined, because constant ranges are only used for parameter
> +; values.
> +; CHECK-LABEL: f3
> +; CHECK: %cmp = icmp sgt i32 %x, 300
> +; CHECK: %res = select i1 %cmp, i32 1, i32 2
> +; CHECK: ret i32 %res
> +define internal i32 @f3(i32 %x) {
> +entry:
> + %cmp = icmp sgt i32 %x, 300
> + %res = select i1 %cmp, i32 1, i32 2
> + ret i32 %res
> +}
> +
> +; The phi node could be converted in a ConstantRange.
> +define i32 @caller2(i1 %cmp) {
> +entry:
> + br i1 %cmp, label %if.true, label %end
> +
> +if.true:
> + br label %end
> +
> +end:
> + %res = phi i32 [ 0, %entry], [ 1, %if.true ]
> + %call1 = tail call i32 @f3(i32 %res)
> + ret i32 %call1
> +}
> +
> +; CHECK-LABEL: f4
> +; CHECK: %cmp = icmp sgt i32 %x, 300
> +; CHECK: %res = select i1 %cmp, i32 1, i32 2
> +; CHECK: ret i32 %res
> +define internal i32 @f4(i32 %x) {
> +entry:
> + %cmp = icmp sgt i32 %x, 300
> + %res = select i1 %cmp, i32 1, i32 2
> + ret i32 %res
> +}
> +
> +; ICmp could introduce bounds on ConstantRanges.
> +define i32 @caller3(i32 %x) {
> +entry:
> + %cmp = icmp sgt i32 %x, 300
> + br i1 %cmp, label %if.true, label %end
> +
> +if.true:
> + %x.1 = tail call i32 @f4(i32 %x)
> + br label %end
> +
> +end:
> + %res = phi i32 [ 0, %entry], [ %x.1, %if.true ]
> + ret i32 %res
> +}
>
>
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--
Bruno Cardoso Lopes
http://www.brunocardoso.cc
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