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[SCEV] Use depth limit for trunc analysis 

Summary:
This fixes an extremely long compile time caused by recursive analysis
of truncs, which were not previously subject to any depth limits unlike
some of the other ops. I decided to use the same control used for
sext/zext, since the routines analyzing these are sometimes mutually
recursive with the trunc analysis.

Reviewers: mkazantsev, sanjoy

Subscribers: sanjoy, jdoerfert, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D58994

llvm-svn: 355949
This commit is contained in:
Teresa Johnson 2019-03-12 18:28:05 +00:00
parent 9dc2c1d564
commit 4ab0a9f0a4
3 changed files with 70 additions and 33 deletions
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8
llvm/include/llvm/Analysis/ScalarEvolution.h
View File

@ -537,7 +537,7 @@ public:
const SCEV *getConstant(ConstantInt *V);
const SCEV *getConstant(const APInt &Val);
const SCEV *getConstant(Type *Ty, uint64_t V, bool isSigned = false);
const SCEV *getTruncateExpr(const SCEV *Op, Type *Ty);
const SCEV *getTruncateExpr(const SCEV *Op, Type *Ty, unsigned Depth = 0);
const SCEV *getZeroExtendExpr(const SCEV *Op, Type *Ty, unsigned Depth = 0);
const SCEV *getSignExtendExpr(const SCEV *Op, Type *Ty, unsigned Depth = 0);
const SCEV *getAnyExtendExpr(const SCEV *Op, Type *Ty);
@ -635,11 +635,13 @@ public:
/// Return a SCEV corresponding to a conversion of the input value to the
/// specified type. If the type must be extended, it is zero extended.
const SCEV *getTruncateOrZeroExtend(const SCEV *V, Type *Ty);
const SCEV *getTruncateOrZeroExtend(const SCEV *V, Type *Ty,
unsigned Depth = 0);
/// Return a SCEV corresponding to a conversion of the input value to the
/// specified type. If the type must be extended, it is sign extended.
const SCEV *getTruncateOrSignExtend(const SCEV *V, Type *Ty);
const SCEV *getTruncateOrSignExtend(const SCEV *V, Type *Ty,
unsigned Depth = 0);
/// Return a SCEV corresponding to a conversion of the input value to the
/// specified type. If the type must be extended, it is zero extended. The

65
llvm/lib/Analysis/ScalarEvolution.cpp
View File

@ -202,9 +202,9 @@ static cl::opt<unsigned> MaxConstantEvolvingDepth(
cl::desc("Maximum depth of recursive constant evolving"), cl::init(32));
static cl::opt<unsigned>
MaxExtDepth("scalar-evolution-max-ext-depth", cl::Hidden,
cl::desc("Maximum depth of recursive SExt/ZExt"),
cl::init(8));
MaxCastDepth("scalar-evolution-max-cast-depth", cl::Hidden,
cl::desc("Maximum depth of recursive SExt/ZExt/Trunc"),
cl::init(8));
static cl::opt<unsigned>
MaxAddRecSize("scalar-evolution-max-add-rec-size", cl::Hidden,
@ -1234,8 +1234,8 @@ const SCEV *SCEVAddRecExpr::evaluateAtIteration(const SCEV *It,
// SCEV Expression folder implementations
//===----------------------------------------------------------------------===//
const SCEV *ScalarEvolution::getTruncateExpr(const SCEV *Op,
Type *Ty) {
const SCEV *ScalarEvolution::getTruncateExpr(const SCEV *Op, Type *Ty,
unsigned Depth) {
assert(getTypeSizeInBits(Op->getType()) > getTypeSizeInBits(Ty) &&
"This is not a truncating conversion!");
assert(isSCEVable(Ty) &&
@ -1256,15 +1256,23 @@ const SCEV *ScalarEvolution::getTruncateExpr(const SCEV *Op,
// trunc(trunc(x)) --> trunc(x)
if (const SCEVTruncateExpr *ST = dyn_cast<SCEVTruncateExpr>(Op))
return getTruncateExpr(ST->getOperand(), Ty);
return getTruncateExpr(ST->getOperand(), Ty, Depth + 1);
// trunc(sext(x)) --> sext(x) if widening or trunc(x) if narrowing
if (const SCEVSignExtendExpr *SS = dyn_cast<SCEVSignExtendExpr>(Op))
return getTruncateOrSignExtend(SS->getOperand(), Ty);
return getTruncateOrSignExtend(SS->getOperand(), Ty, Depth + 1);
// trunc(zext(x)) --> zext(x) if widening or trunc(x) if narrowing
if (const SCEVZeroExtendExpr *SZ = dyn_cast<SCEVZeroExtendExpr>(Op))
return getTruncateOrZeroExtend(SZ->getOperand(), Ty);
return getTruncateOrZeroExtend(SZ->getOperand(), Ty, Depth + 1);
if (Depth > MaxCastDepth) {
SCEV *S =
new (SCEVAllocator) SCEVTruncateExpr(ID.Intern(SCEVAllocator), Op, Ty);
UniqueSCEVs.InsertNode(S, IP);
addToLoopUseLists(S);
return S;
}
// trunc(x1 + ... + xN) --> trunc(x1) + ... + trunc(xN) and
// trunc(x1 * ... * xN) --> trunc(x1) * ... * trunc(xN),
@ -1276,7 +1284,7 @@ const SCEV *ScalarEvolution::getTruncateExpr(const SCEV *Op,
unsigned numTruncs = 0;
for (unsigned i = 0, e = CommOp->getNumOperands(); i != e && numTruncs < 2;
++i) {
const SCEV *S = getTruncateExpr(CommOp->getOperand(i), Ty);
const SCEV *S = getTruncateExpr(CommOp->getOperand(i), Ty, Depth + 1);
if (!isa<SCEVCastExpr>(CommOp->getOperand(i)) && isa<SCEVTruncateExpr>(S))
numTruncs++;
Operands.push_back(S);
@ -1300,7 +1308,7 @@ const SCEV *ScalarEvolution::getTruncateExpr(const SCEV *Op,
if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(Op)) {
SmallVector<const SCEV *, 4> Operands;
for (const SCEV *Op : AddRec->operands())
Operands.push_back(getTruncateExpr(Op, Ty));
Operands.push_back(getTruncateExpr(Op, Ty, Depth + 1));
return getAddRecExpr(Operands, AddRec->getLoop(), SCEV::FlagAnyWrap);
}
@ -1634,7 +1642,7 @@ ScalarEvolution::getZeroExtendExpr(const SCEV *Op, Type *Ty, unsigned Depth) {
ID.AddPointer(Ty);
void *IP = nullptr;
if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
if (Depth > MaxExtDepth) {
if (Depth > MaxCastDepth) {
SCEV *S = new (SCEVAllocator) SCEVZeroExtendExpr(ID.Intern(SCEVAllocator),
Op, Ty);
UniqueSCEVs.InsertNode(S, IP);
@ -1652,7 +1660,7 @@ ScalarEvolution::getZeroExtendExpr(const SCEV *Op, Type *Ty, unsigned Depth) {
unsigned NewBits = getTypeSizeInBits(Ty);
if (CR.truncate(TruncBits).zeroExtend(NewBits).contains(
CR.zextOrTrunc(NewBits)))
return getTruncateOrZeroExtend(X, Ty);
return getTruncateOrZeroExtend(X, Ty, Depth);
}
// If the input value is a chrec scev, and we can prove that the value
@ -1694,9 +1702,9 @@ ScalarEvolution::getZeroExtendExpr(const SCEV *Op, Type *Ty, unsigned Depth) {
// Check whether the backedge-taken count can be losslessly casted to
// the addrec's type. The count is always unsigned.
const SCEV *CastedMaxBECount =
getTruncateOrZeroExtend(MaxBECount, Start->getType());
const SCEV *RecastedMaxBECount =
getTruncateOrZeroExtend(CastedMaxBECount, MaxBECount->getType());
getTruncateOrZeroExtend(MaxBECount, Start->getType(), Depth);
const SCEV *RecastedMaxBECount = getTruncateOrZeroExtend(
CastedMaxBECount, MaxBECount->getType(), Depth);
if (MaxBECount == RecastedMaxBECount) {
Type *WideTy = IntegerType::get(getContext(), BitWidth * 2);
// Check whether Start+Step*MaxBECount has no unsigned overflow.
@ -1945,7 +1953,7 @@ ScalarEvolution::getSignExtendExpr(const SCEV *Op, Type *Ty, unsigned Depth) {
void *IP = nullptr;
if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
// Limit recursion depth.
if (Depth > MaxExtDepth) {
if (Depth > MaxCastDepth) {
SCEV *S = new (SCEVAllocator) SCEVSignExtendExpr(ID.Intern(SCEVAllocator),
Op, Ty);
UniqueSCEVs.InsertNode(S, IP);
@ -1963,7 +1971,7 @@ ScalarEvolution::getSignExtendExpr(const SCEV *Op, Type *Ty, unsigned Depth) {
unsigned NewBits = getTypeSizeInBits(Ty);
if (CR.truncate(TruncBits).signExtend(NewBits).contains(
CR.sextOrTrunc(NewBits)))
return getTruncateOrSignExtend(X, Ty);
return getTruncateOrSignExtend(X, Ty, Depth);
}
if (auto *SA = dyn_cast<SCEVAddExpr>(Op)) {
@ -2038,9 +2046,9 @@ ScalarEvolution::getSignExtendExpr(const SCEV *Op, Type *Ty, unsigned Depth) {
// Check whether the backedge-taken count can be losslessly casted to
// the addrec's type. The count is always unsigned.
const SCEV *CastedMaxBECount =
getTruncateOrZeroExtend(MaxBECount, Start->getType());
const SCEV *RecastedMaxBECount =
getTruncateOrZeroExtend(CastedMaxBECount, MaxBECount->getType());
getTruncateOrZeroExtend(MaxBECount, Start->getType(), Depth);
const SCEV *RecastedMaxBECount = getTruncateOrZeroExtend(
CastedMaxBECount, MaxBECount->getType(), Depth);
if (MaxBECount == RecastedMaxBECount) {
Type *WideTy = IntegerType::get(getContext(), BitWidth * 2);
// Check whether Start+Step*MaxBECount has no signed overflow.
@ -4038,29 +4046,28 @@ const SCEV *ScalarEvolution::getMinusSCEV(const SCEV *LHS, const SCEV *RHS,
return getAddExpr(LHS, getNegativeSCEV(RHS, NegFlags), AddFlags, Depth);
}
const SCEV *
ScalarEvolution::getTruncateOrZeroExtend(const SCEV *V, Type *Ty) {
const SCEV *ScalarEvolution::getTruncateOrZeroExtend(const SCEV *V, Type *Ty,
unsigned Depth) {
Type *SrcTy = V->getType();
assert(SrcTy->isIntOrPtrTy() && Ty->isIntOrPtrTy() &&
"Cannot truncate or zero extend with non-integer arguments!");
if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
return V; // No conversion
if (getTypeSizeInBits(SrcTy) > getTypeSizeInBits(Ty))
return getTruncateExpr(V, Ty);
return getZeroExtendExpr(V, Ty);
return getTruncateExpr(V, Ty, Depth);
return getZeroExtendExpr(V, Ty, Depth);
}
const SCEV *
ScalarEvolution::getTruncateOrSignExtend(const SCEV *V,
Type *Ty) {
const SCEV *ScalarEvolution::getTruncateOrSignExtend(const SCEV *V, Type *Ty,
unsigned Depth) {
Type *SrcTy = V->getType();
assert(SrcTy->isIntOrPtrTy() && Ty->isIntOrPtrTy() &&
"Cannot truncate or zero extend with non-integer arguments!");
if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
return V; // No conversion
if (getTypeSizeInBits(SrcTy) > getTypeSizeInBits(Ty))
return getTruncateExpr(V, Ty);
return getSignExtendExpr(V, Ty);
return getTruncateExpr(V, Ty, Depth);
return getSignExtendExpr(V, Ty, Depth);
}
const SCEV *

30
llvm/test/Analysis/ScalarEvolution/limit-depth.ll
View File

@ -1,4 +1,4 @@
; RUN: opt -scalar-evolution-max-arith-depth=0 -scalar-evolution-max-ext-depth=0 -analyze -scalar-evolution < %s | FileCheck %s
; RUN: opt -scalar-evolution-max-arith-depth=0 -scalar-evolution-max-cast-depth=0 -analyze -scalar-evolution < %s | FileCheck %s
; Check that depth set to 0 prevents getAddExpr and getMulExpr from making
; transformations in SCEV. We expect the result to be very straightforward.
@ -98,3 +98,31 @@ exit:
%ze2 = zext i64 %iv2.inc to i128
ret void
}
define void @test_trunc(i32 %a, i32 %b, i32 %c, i32 %d, i32 %e, i32 %f) {
; CHECK-LABEL: @test_trunc
; CHECK: %trunc2 = trunc i64 %iv2.inc to i32
; CHECK-NEXT: --> {(trunc i64 (1 + {7,+,1}<%loop>) to i32),+,1}<%loop2>
entry:
br label %loop
loop:
%iv = phi i128 [ 6, %entry ], [ %iv.inc, %loop ]
%iv.inc = add nsw i128 %iv, 1
%cond = icmp sle i128 %iv.inc, 50
br i1 %cond, label %loop, label %between
between:
%trunc = trunc i128 %iv.inc to i64
br label %loop2
loop2:
%iv2 = phi i64 [ %trunc, %between ], [ %iv2.inc, %loop2 ]
%iv2.inc = add nuw i64 %iv2, 1
%cond2 = icmp sle i64 %iv2.inc, 50
br i1 %cond2, label %loop2, label %exit
exit:
%trunc2 = trunc i64 %iv2.inc to i32
ret void
}