Commit 86509e8c authored by Johannes Doerfert's avatar Johannes Doerfert
Browse files

[Attributor] Use assumed information to determine side-effects 

We relied on wouldInstructionBeTriviallyDead before but that functions
does not take assumed information, especially for calls, into account.
The replacement, AAIsDead::isAssumeSideEffectFree, does.

This change makes AAIsDeadCallSiteReturn more complex as we can have
a dead call or only dead users.

The test have been modified to include a side effect where there was
none in order to keep the coverage.

Reviewed By: sstefan1

Differential Revision: https://reviews.llvm.org/D73311
parent 190a1114

llvm/lib/Transforms/IPO/Attributor.cpp

+129 −36
Original line number Diff line number Diff line
@@ -2820,29 +2820,16 @@ struct AAIsDeadValueImpl : public AAIsDead { 


  /// See AAIsDead::isKnownDead(Instruction *I).

  bool isKnownDead(const Instruction *I) const override {

    return I == getCtxI() && getKnown();

    return isAssumedDead(I) && getKnown();

  }



  /// See AbstractAttribute::getAsStr().

  const std::string getAsStr() const override {

    return isAssumedDead() ? "assumed-dead" : "assumed-live";

  }

};



struct AAIsDeadFloating : public AAIsDeadValueImpl {

  AAIsDeadFloating(const IRPosition &IRP) : AAIsDeadValueImpl(IRP) {}



  /// See AbstractAttribute::initialize(...).

  void initialize(Attributor &A) override {

    if (Instruction *I = dyn_cast<Instruction>(&getAssociatedValue()))

      if (!wouldInstructionBeTriviallyDead(I))

        indicatePessimisticFixpoint();

    if (isa<UndefValue>(getAssociatedValue()))

      indicatePessimisticFixpoint();

  }



  /// See AbstractAttribute::updateImpl(...).

  ChangeStatus updateImpl(Attributor &A) override {

  /// Check if all uses are assumed dead.

  bool areAllUsesAssumedDead(Attributor &A) {

    auto UsePred = [&](const Use &U, bool &Follow) {

      Instruction *UserI = cast<Instruction>(U.getUser());

      if (CallSite CS = CallSite(UserI)) {
@@ -2862,7 +2849,53 @@ struct AAIsDeadFloating : public AAIsDeadValueImpl { 
      return wouldInstructionBeTriviallyDead(UserI);

    };



    if (!A.checkForAllUses(UsePred, *this, getAssociatedValue()))

    return A.checkForAllUses(UsePred, *this, getAssociatedValue());

  }



  /// Determine if \p I is assumed to be side-effect free.

  bool isAssumedSideEffectFree(Attributor &A, Instruction *I) {

    if (!I || wouldInstructionBeTriviallyDead(I))

      return true;



    auto *CB = dyn_cast<CallBase>(I);

    if (!CB || isa<IntrinsicInst>(CB))

      return false;



    const IRPosition &CallIRP = IRPosition::callsite_function(*CB);

    const auto &NoUnwindAA = A.getAAFor<AANoUnwind>(*this, CallIRP);

    if (!NoUnwindAA.isAssumedNoUnwind())

      return false;



    const auto &MemBehaviorAA = A.getAAFor<AAMemoryBehavior>(*this, CallIRP);

    if (!MemBehaviorAA.isAssumedReadOnly())

      return false;



    return true;

  }

};



struct AAIsDeadFloating : public AAIsDeadValueImpl {

  AAIsDeadFloating(const IRPosition &IRP) : AAIsDeadValueImpl(IRP) {}



  /// See AbstractAttribute::initialize(...).

  void initialize(Attributor &A) override {

    if (isa<UndefValue>(getAssociatedValue())) {

      indicatePessimisticFixpoint();

      return;

    }



    Instruction *I = dyn_cast<Instruction>(&getAssociatedValue());

    if (!isAssumedSideEffectFree(A, I))

      indicatePessimisticFixpoint();

  }



  /// See AbstractAttribute::updateImpl(...).

  ChangeStatus updateImpl(Attributor &A) override {

    Instruction *I = dyn_cast<Instruction>(&getAssociatedValue());

    if (!isAssumedSideEffectFree(A, I))

      return indicatePessimisticFixpoint();



    if (!areAllUsesAssumedDead(A))

      return indicatePessimisticFixpoint();

    return ChangeStatus::UNCHANGED;

  }
@@ -2870,12 +2903,16 @@ struct AAIsDeadFloating : public AAIsDeadValueImpl { 
  /// See AbstractAttribute::manifest(...).

  ChangeStatus manifest(Attributor &A) override {

    Value &V = getAssociatedValue();

    if (auto *I = dyn_cast<Instruction>(&V))

      if (wouldInstructionBeTriviallyDead(I)) {

    if (auto *I = dyn_cast<Instruction>(&V)) {

      // If we get here we basically know the users are all dead. We check if

      // isAssumedSideEffectFree returns true here again because it might not be

      // the case and only the users are dead but the instruction (=call) is

      // still needed.

      if (isAssumedSideEffectFree(A, I) && !isa<InvokeInst>(I)) {

        A.deleteAfterManifest(*I);

        return ChangeStatus::CHANGED;

      }



    }

    if (V.use_empty())

      return ChangeStatus::UNCHANGED;
@@ -2956,6 +2993,69 @@ struct AAIsDeadCallSiteArgument : public AAIsDeadValueImpl { 
  void trackStatistics() const override { STATS_DECLTRACK_CSARG_ATTR(IsDead) }

};



struct AAIsDeadCallSiteReturned : public AAIsDeadFloating {

  AAIsDeadCallSiteReturned(const IRPosition &IRP)

      : AAIsDeadFloating(IRP), IsAssumedSideEffectFree(true) {}



  /// See AAIsDead::isAssumedDead().

  bool isAssumedDead() const override {

    return AAIsDeadFloating::isAssumedDead() && IsAssumedSideEffectFree;

  }



  /// Return true if all users are assumed dead.

  bool hasOnlyAssumedDeadUses() const { return getAssumed(); }



  /// See AbstractAttribute::initialize(...).

  void initialize(Attributor &A) override {

    if (isa<UndefValue>(getAssociatedValue())) {

      indicatePessimisticFixpoint();

      return;

    }



    // We track this separately as a secondary state.

    IsAssumedSideEffectFree = isAssumedSideEffectFree(A, getCtxI());

  }



  /// See AbstractAttribute::updateImpl(...).

  ChangeStatus updateImpl(Attributor &A) override {

    ChangeStatus Changed = ChangeStatus::UNCHANGED;

    if (IsAssumedSideEffectFree && !isAssumedSideEffectFree(A, getCtxI())) {

      IsAssumedSideEffectFree = false;

      Changed = ChangeStatus::CHANGED;

    }



    if (!areAllUsesAssumedDead(A))

      return indicatePessimisticFixpoint();

    return Changed;

  }



  /// See AbstractAttribute::manifest(...).

  ChangeStatus manifest(Attributor &A) override {

    if (auto *CI = dyn_cast<CallInst>(&getAssociatedValue()))

      if (CI->isMustTailCall())

        return ChangeStatus::UNCHANGED;

    return AAIsDeadFloating::manifest(A);

  }



  /// See AbstractAttribute::trackStatistics()

  void trackStatistics() const override {

    if (IsAssumedSideEffectFree)

      STATS_DECLTRACK_CSRET_ATTR(IsDead)

    else

      STATS_DECLTRACK_CSRET_ATTR(UnusedResult)

  }



  /// See AbstractAttribute::getAsStr().

  const std::string getAsStr() const override {

    return isAssumedDead()

               ? "assumed-dead"

               : (getAssumed() ? "assumed-dead-users" : "assumed-live");

  }



private:

  bool IsAssumedSideEffectFree;

};



struct AAIsDeadReturned : public AAIsDeadValueImpl {

  AAIsDeadReturned(const IRPosition &IRP) : AAIsDeadValueImpl(IRP) {}
@@ -2970,7 +3070,8 @@ struct AAIsDeadReturned : public AAIsDeadValueImpl { 
          IRPosition::callsite_returned(ACS.getCallSite());

      const auto &RetIsDeadAA = A.getAAFor<AAIsDead>(*this, CSRetPos);

      AllKnownDead &= RetIsDeadAA.isKnownDead();

      return RetIsDeadAA.isAssumedDead();

      return static_cast<const AAIsDeadCallSiteReturned &>(RetIsDeadAA)

          .hasOnlyAssumedDeadUses();

    };



    bool AllCallSitesKnown;
@@ -3003,16 +3104,6 @@ struct AAIsDeadReturned : public AAIsDeadValueImpl { 
  void trackStatistics() const override { STATS_DECLTRACK_FNRET_ATTR(IsDead) }

};



struct AAIsDeadCallSiteReturned : public AAIsDeadFloating {

  AAIsDeadCallSiteReturned(const IRPosition &IRP) : AAIsDeadFloating(IRP) {}



  /// See AbstractAttribute::initialize(...).

  void initialize(Attributor &A) override {}



  /// See AbstractAttribute::trackStatistics()

  void trackStatistics() const override { STATS_DECLTRACK_CSRET_ATTR(IsDead) }

};



struct AAIsDeadFunction : public AAIsDead {

  AAIsDeadFunction(const IRPosition &IRP) : AAIsDead(IRP) {}
@@ -7530,6 +7621,12 @@ void Attributor::identifyDefaultAbstractAttributes(Function &F) { 


  auto CallSitePred = [&](Instruction &I) -> bool {

    CallSite CS(&I);

    IRPosition CSRetPos = IRPosition::callsite_returned(CS);



    // Call sites might be dead if they do not have side effects and no live

    // users. The return value might be dead if there are no live users.

    getOrCreateAAFor<AAIsDead>(CSRetPos);



    if (Function *Callee = CS.getCalledFunction()) {

      // Skip declerations except if annotations on their call sites were

      // explicitly requested.
@@ -7541,14 +7638,10 @@ void Attributor::identifyDefaultAbstractAttributes(Function &F) { 


        IRPosition CSRetPos = IRPosition::callsite_returned(CS);



        // Call site return values might be dead.

        getOrCreateAAFor<AAIsDead>(CSRetPos);



        // Call site return integer values might be limited by a constant range.

        if (Callee->getReturnType()->isIntegerTy()) {

        if (Callee->getReturnType()->isIntegerTy())

          getOrCreateAAFor<AAValueConstantRange>(CSRetPos);

      }

      }



      for (int i = 0, e = CS.getNumArgOperands(); i < e; i++) {

llvm/test/Transforms/Attributor/ArgumentPromotion/dbg.ll

+2 −0
Original line number Diff line number Diff line
@@ -21,8 +21,10 @@ define internal void @test(i32** %X) !dbg !2 { 


define internal void @test_byval(%struct.pair* byval %P) {

; CHECK-LABEL: define {{[^@]+}}@test_byval()

; CHECK-NEXT:    call void @sink(i32 0)

; CHECK-NEXT:    ret void

;

  call void @sink(i32 0)

  ret void

}

llvm/test/Transforms/Attributor/ArgumentPromotion/variadic.ll

+4 −0
Original line number Diff line number Diff line
@@ -31,8 +31,12 @@ define internal void @callee_t0f(i8* nocapture readnone %tp13, i8* nocapture rea 
; CHECK-LABEL: define {{[^@]+}}@callee_t0f

; CHECK-SAME: (i8* noalias nocapture nofree nonnull readnone [[TP13:%.*]], i8* noalias nocapture nofree nonnull readnone [[TP14:%.*]], i8* noalias nocapture nofree nonnull readnone [[TP15:%.*]], i8* noalias nocapture nofree nonnull readnone [[TP16:%.*]], i8* noalias nocapture nofree nonnull readnone [[TP17:%.*]], ...)

; CHECK-NEXT:  entry:

; CHECK-NEXT:    call void @sink(i32 0)

; CHECK-NEXT:    ret void

;

entry:

  call void @sink(i32 0)

  ret void

}



declare void @sink(i32)

llvm/test/Transforms/Attributor/IPConstantProp/multiple_callbacks.ll

+0 −3
Original line number Diff line number Diff line
@@ -60,7 +60,6 @@ define internal i32 @cb2(i32 %unknown) { 
; CHECK-LABEL: define {{[^@]+}}@cb2

; CHECK-SAME: (i32 returned [[UNKNOWN:%.*]])

; CHECK-NEXT:  entry:

; CHECK-NEXT:    [[CALL:%.*]] = call i32 @cb0(i32 0)

; CHECK-NEXT:    ret i32 [[UNKNOWN]]

;

entry:
@@ -91,8 +90,6 @@ entry: 
define void @foo() {

; CHECK-LABEL: define {{[^@]+}}@foo()

; CHECK-NEXT:  entry:

; CHECK-NEXT:    [[CALL:%.*]] = call i32 @cb0(i32 0)

; CHECK-NEXT:    [[CALL1:%.*]] = call i32 @cb3(i32 1)

; CHECK-NEXT:    call void @broker(i32 (i32)* nonnull @cb0, i32 (i32)* nonnull @cb1, i32 (i32)* nonnull @cb0, i32 0, i32 1)

; CHECK-NEXT:    call void @broker(i32 (i32)* nonnull @cb1, i32 (i32)* nonnull @cb2, i32 (i32)* nonnull @cb2, i32 0, i32 1)

; CHECK-NEXT:    call void @broker(i32 (i32)* nonnull @cb3, i32 (i32)* nonnull @cb2, i32 (i32)* nonnull @cb3, i32 0, i32 1)

llvm/test/Transforms/Attributor/align.ll

+13 −13
Original line number Diff line number Diff line 
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --function-signature --scrub-attributes --turn off

; RUN: opt -attributor -attributor-manifest-internal -attributor-disable=false -attributor-max-iterations-verify -attributor-annotate-decl-cs -attributor-max-iterations=5 -S < %s | FileCheck %s --check-prefixes=ATTRIBUTOR,ATTRIBUTOR_MODULE

; RUN: opt -attributor-cgscc -attributor-manifest-internal -attributor-disable=false -attributor-annotate-decl-cs -attributor-max-iterations=5 -S < %s | FileCheck %s --check-prefixes=ATTRIBUTOR,ATTRIBUTOR_CGSCC

; RUN: opt -passes=attributor -attributor-manifest-internal -attributor-disable=false -attributor-max-iterations-verify -attributor-annotate-decl-cs -attributor-max-iterations=5 -S < %s | FileCheck %s --check-prefixes=ATTRIBUTOR,ATTRIBUTOR_MODULE

; RUN: opt -passes=attributor-cgscc -attributor-manifest-internal -attributor-disable=false -attributor-annotate-decl-cs -attributor-max-iterations=5 -S < %s | FileCheck %s --check-prefixes=ATTRIBUTOR,ATTRIBUTOR_CGSCC

; RUN: opt -attributor -attributor-manifest-internal -attributor-disable=false -attributor-max-iterations-verify -attributor-annotate-decl-cs -attributor-max-iterations=6 -S < %s | FileCheck %s --check-prefixes=ATTRIBUTOR,ATTRIBUTOR_MODULE

; RUN: opt -attributor-cgscc -attributor-manifest-internal -attributor-disable=false -attributor-annotate-decl-cs -attributor-max-iterations=6 -S < %s | FileCheck %s --check-prefixes=ATTRIBUTOR,ATTRIBUTOR_CGSCC

; RUN: opt -passes=attributor -attributor-manifest-internal -attributor-disable=false -attributor-max-iterations-verify -attributor-annotate-decl-cs -attributor-max-iterations=6 -S < %s | FileCheck %s --check-prefixes=ATTRIBUTOR,ATTRIBUTOR_MODULE

; RUN: opt -passes=attributor-cgscc -attributor-manifest-internal -attributor-disable=false -attributor-annotate-decl-cs -attributor-max-iterations=6 -S < %s | FileCheck %s --check-prefixes=ATTRIBUTOR,ATTRIBUTOR_CGSCC



target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
@@ -137,18 +137,18 @@ define internal i8* @f3(i8* readnone %0) local_unnamed_addr #0 { 


; TEST 7

; Better than IR information

define align 4 i32* @test7(i32* align 32 %p) #0 {

define align 4 i8* @test7() #0 {

; ATTRIBUTOR_MODULE-LABEL: define {{[^@]+}}@test7

; ATTRIBUTOR_MODULE-SAME: (i32* nofree readnone returned align 32 "no-capture-maybe-returned" [[P:%.*]])

; ATTRIBUTOR_MODULE-NEXT:    ret i32* [[P]]

; ATTRIBUTOR_MODULE-NEXT:    [[C:%.*]] = tail call i8* @f1(i8* noalias nofree nonnull readnone align 8 dereferenceable(1) @a1)

; ATTRIBUTOR_MODULE-NEXT:    ret i8* [[C]]

;

; ATTRIBUTOR_CGSCC-LABEL: define {{[^@]+}}@test7

; ATTRIBUTOR_CGSCC-SAME: (i32* nofree readnone returned align 32 "no-capture-maybe-returned" [[P:%.*]])

; ATTRIBUTOR_CGSCC-NEXT:    [[TMP1:%.*]] = tail call i8* @f1(i8* noalias nofree nonnull readnone align 8 dereferenceable(1) @a1)

; ATTRIBUTOR_CGSCC-NEXT:    ret i32* [[P]]

; ATTRIBUTOR_CGSCC-SAME: ()

; ATTRIBUTOR_CGSCC-NEXT:    [[C:%.*]] = tail call nonnull align 8 dereferenceable(1) i8* @f1(i8* noalias nofree nonnull readnone align 8 dereferenceable(1) @a1)

; ATTRIBUTOR_CGSCC-NEXT:    ret i8* [[C]]

;

  tail call i8* @f1(i8* align 8 dereferenceable(1) @a1)

  ret i32* %p

  %c = tail call i8* @f1(i8* align 8 dereferenceable(1) @a1)

  ret i8* %c

}



; TEST 7b
@@ -281,7 +281,7 @@ define void @test8_helper() { 
  ret void

}



declare void @user_i32_ptr(i32*) readnone nounwind

declare void @user_i32_ptr(i32* nocapture readnone) nounwind

define internal void @test8(i32* %a, i32* %b, i32* %c) {

; ATTRIBUTOR_MODULE: define internal void @test8(i32* noalias nocapture readnone align 4 %a, i32* noalias nocapture readnone align 4 %b, i32* noalias nocapture readnone %c)

; ATTRIBUTOR_CGSCC: define internal void @test8(i32* nocapture readnone align 4 %a, i32* nocapture readnone align 4 %b, i32* nocapture readnone %c)