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[SCEV] Check the cache in get{S|U}MaxExpr before doing any work

Summary:
This lets us avoid e.g. checking if A >=s B in getSMaxExpr(A, B) if we've
already established that (A smax B) is the best we can do.

Fixes PR41225.

Reviewers: asbirlea

Subscribers: mcrosier, jlebar, bixia, jdoerfert, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D60010

llvm-svn: 357320
This commit is contained in:
Sanjoy Das 2019-03-29 22:00:12 +00:00
parent 131421fe28
commit 253d7ee41e
3 changed files with 199 additions and 12 deletions

View File

@ -1871,6 +1871,16 @@ private:
/// Assign A and B to LHS and RHS, respectively.
bool matchURem(const SCEV *Expr, const SCEV *&LHS, const SCEV *&RHS);
/// Look for a SCEV expression with type `SCEVType` and operands `Ops` in
/// `UniqueSCEVs`.
///
/// The first component of the returned tuple is the SCEV if found and null
/// otherwise. The second component is the `FoldingSetNodeID` that was
/// constructed to look up the SCEV and the third component is the insertion
/// point.
std::tuple<const SCEV *, FoldingSetNodeID, void *>
findExistingSCEVInCache(int SCEVType, ArrayRef<const SCEV *> Ops);
FoldingSet<SCEV> UniqueSCEVs;
FoldingSet<SCEVPredicate> UniquePreds;
BumpPtrAllocator SCEVAllocator;

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@ -3523,6 +3523,17 @@ const SCEV *ScalarEvolution::getSMaxExpr(const SCEV *LHS,
return getSMaxExpr(Ops);
}
std::tuple<const SCEV *, FoldingSetNodeID, void *>
ScalarEvolution::findExistingSCEVInCache(int SCEVType,
ArrayRef<const SCEV *> Ops) {
FoldingSetNodeID ID;
void *IP = nullptr;
ID.AddInteger(SCEVType);
for (unsigned i = 0, e = Ops.size(); i != e; ++i)
ID.AddPointer(Ops[i]);
return {UniqueSCEVs.FindNodeOrInsertPos(ID, IP), std::move(ID), IP};
}
const SCEV *
ScalarEvolution::getSMaxExpr(SmallVectorImpl<const SCEV *> &Ops) {
assert(!Ops.empty() && "Cannot get empty smax!");
@ -3537,6 +3548,11 @@ ScalarEvolution::getSMaxExpr(SmallVectorImpl<const SCEV *> &Ops) {
// Sort by complexity, this groups all similar expression types together.
GroupByComplexity(Ops, &LI, DT);
// Check if we have created the same SMax expression before.
if (const SCEV *S = std::get<0>(findExistingSCEVInCache(scSMaxExpr, Ops))) {
return S;
}
// If there are any constants, fold them together.
unsigned Idx = 0;
if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
@ -3604,16 +3620,16 @@ ScalarEvolution::getSMaxExpr(SmallVectorImpl<const SCEV *> &Ops) {
// Okay, it looks like we really DO need an smax expr. Check to see if we
// already have one, otherwise create a new one.
const SCEV *ExistingSCEV;
FoldingSetNodeID ID;
ID.AddInteger(scSMaxExpr);
for (unsigned i = 0, e = Ops.size(); i != e; ++i)
ID.AddPointer(Ops[i]);
void *IP = nullptr;
if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
void *IP;
std::tie(ExistingSCEV, ID, IP) = findExistingSCEVInCache(scSMaxExpr, Ops);
if (ExistingSCEV)
return ExistingSCEV;
const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
std::uninitialized_copy(Ops.begin(), Ops.end(), O);
SCEV *S = new (SCEVAllocator) SCEVSMaxExpr(ID.Intern(SCEVAllocator),
O, Ops.size());
SCEV *S =
new (SCEVAllocator) SCEVSMaxExpr(ID.Intern(SCEVAllocator), O, Ops.size());
UniqueSCEVs.InsertNode(S, IP);
addToLoopUseLists(S);
return S;
@ -3639,6 +3655,11 @@ ScalarEvolution::getUMaxExpr(SmallVectorImpl<const SCEV *> &Ops) {
// Sort by complexity, this groups all similar expression types together.
GroupByComplexity(Ops, &LI, DT);
// Check if we have created the same UMax expression before.
if (const SCEV *S = std::get<0>(findExistingSCEVInCache(scUMaxExpr, Ops))) {
return S;
}
// If there are any constants, fold them together.
unsigned Idx = 0;
if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
@ -3707,12 +3728,12 @@ ScalarEvolution::getUMaxExpr(SmallVectorImpl<const SCEV *> &Ops) {
// Okay, it looks like we really DO need a umax expr. Check to see if we
// already have one, otherwise create a new one.
const SCEV *ExistingSCEV;
FoldingSetNodeID ID;
ID.AddInteger(scUMaxExpr);
for (unsigned i = 0, e = Ops.size(); i != e; ++i)
ID.AddPointer(Ops[i]);
void *IP = nullptr;
if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
void *IP;
std::tie(ExistingSCEV, ID, IP) = findExistingSCEVInCache(scUMaxExpr, Ops);
if (ExistingSCEV)
return ExistingSCEV;
const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
std::uninitialized_copy(Ops.begin(), Ops.end(), O);
SCEV *S = new (SCEVAllocator) SCEVUMaxExpr(ID.Intern(SCEVAllocator),

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@ -0,0 +1,156 @@
; RUN: opt < %s -analyze -scalar-evolution | FileCheck %s
; SCEV would take a long time to compute SCEV expressions for this IR. If SCEV
; finishes in < 1 second then the bug is fixed.
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64--linux-gnu"
define void @smax(i32 %tmp3) {
; CHECK-LABEL: Printing analysis 'Scalar Evolution Analysis' for function 'smax'
entry:
br label %bb4
bb4:
%tmp5 = phi i64 [ %tmp62, %bb61 ], [ 0, %entry ]
%tmp6 = trunc i64 %tmp5 to i32
%tmp7 = shl nsw i32 %tmp6, 8
%tmp8 = sub nsw i32 %tmp3, %tmp7
%tmp9 = icmp slt i32 %tmp8, 256
%tmp10 = select i1 %tmp9, i32 %tmp8, i32 256
%tmp11 = add nsw i32 %tmp10, 1
%tmp12 = icmp sgt i32 %tmp8, %tmp11
%tmp13 = select i1 %tmp12, i32 %tmp11, i32 %tmp8
%tmp14 = icmp slt i32 %tmp13, 256
%tmp15 = select i1 %tmp14, i32 %tmp13, i32 256
%tmp16 = add nsw i32 %tmp15, 1
%tmp17 = icmp sgt i32 %tmp8, %tmp16
%tmp18 = select i1 %tmp17, i32 %tmp16, i32 %tmp8
%tmp19 = icmp slt i32 %tmp18, 256
%tmp20 = select i1 %tmp19, i32 %tmp18, i32 256
%tmp21 = add nsw i32 %tmp20, 1
%tmp22 = icmp sgt i32 %tmp8, %tmp21
%tmp23 = select i1 %tmp22, i32 %tmp21, i32 %tmp8
%tmp24 = icmp slt i32 %tmp23, 256
%tmp25 = select i1 %tmp24, i32 %tmp23, i32 256
%tmp26 = add nsw i32 %tmp25, 1
%tmp27 = icmp sgt i32 %tmp8, %tmp26
%tmp28 = select i1 %tmp27, i32 %tmp26, i32 %tmp8
%tmp29 = icmp slt i32 %tmp28, 256
%tmp30 = select i1 %tmp29, i32 %tmp28, i32 256
%tmp31 = add nsw i32 %tmp30, 1
%tmp32 = icmp sgt i32 %tmp8, %tmp31
%tmp33 = select i1 %tmp32, i32 %tmp31, i32 %tmp8
%tmp34 = icmp slt i32 %tmp33, 256
%tmp35 = select i1 %tmp34, i32 %tmp33, i32 256
%tmp36 = add nsw i32 %tmp35, 1
%tmp37 = icmp sgt i32 %tmp8, %tmp36
%tmp38 = select i1 %tmp37, i32 %tmp36, i32 %tmp8
%tmp39 = icmp slt i32 %tmp38, 256
%tmp40 = select i1 %tmp39, i32 %tmp38, i32 256
%tmp41 = add nsw i32 %tmp40, 1
%tmp42 = icmp sgt i32 %tmp8, %tmp41
%tmp43 = select i1 %tmp42, i32 %tmp41, i32 %tmp8
%tmp44 = add nsw i32 %tmp10, 7
%tmp45 = icmp slt i32 %tmp43, 256
%tmp46 = select i1 %tmp45, i32 %tmp43, i32 256
; CHECK: %tmp46 = select i1 %tmp45, i32 %tmp43, i32 256
; CHECK-NEXT: --> (-1 + (-1 * (-257 smax (-1 + (-257 smax (-1 + (-257 smax (-1 + (-257 smax (-1 + (-257 smax (-1 + (-257 smax (-1 + (-257 smax (-1 + (-257 smax {(-1 + (-1 * %tmp3)),+,256}<%bb4>))<nsw> smax {(-1 + (-1 * %tmp3)),+,256}<%bb4>))<nsw> smax {(-1 + (-1 * %tmp3)),+,256}<%bb4>))<nsw> smax {(-1 + (-1 * %tmp3)),+,256}<%bb4>))<nsw> smax {(-1 + (-1 * %tmp3)),+,256}<%bb4>))<nsw> smax {(-1 + (-1 * %tmp3)),+,256}<%bb4>))<nsw> smax {(-1 + (-1 * %tmp3)),+,256}<%bb4>))<nsw> smax {(-1 + (-1 * %tmp3)),+,256}<%bb4>))<nsw>)<nsw>
%tmp47 = icmp sgt i32 %tmp44, %tmp46
%tmp48 = select i1 %tmp47, i32 %tmp44, i32 %tmp46
%tmp49 = ashr i32 %tmp48, 3
%tmp50 = icmp sgt i32 %tmp49, 0
%tmp51 = select i1 %tmp50, i32 %tmp49, i32 0
%tmp52 = zext i32 %tmp51 to i64
br label %bb53
bb53:
%tmp54 = phi i64 [ undef, %bb4 ], [ %tmp59, %bb53 ]
%tmp55 = trunc i64 %tmp54 to i32
%tmp56 = shl nsw i32 %tmp55, 3
%tmp57 = sext i32 %tmp56 to i64
%tmp58 = getelementptr inbounds i8, i8* null, i64 %tmp57
store i8 undef, i8* %tmp58, align 8
%tmp59 = add nsw i64 %tmp54, 1
%tmp60 = icmp eq i64 %tmp59, %tmp52
br i1 %tmp60, label %bb61, label %bb53
bb61:
%tmp62 = add nuw nsw i64 %tmp5, 1
br label %bb4
}
define void @umax(i32 %tmp3) {
; CHECK-LABEL: Printing analysis 'Scalar Evolution Analysis' for function 'umax'
entry:
br label %bb4
bb4:
%tmp5 = phi i64 [ %tmp62, %bb61 ], [ 0, %entry ]
%tmp6 = trunc i64 %tmp5 to i32
%tmp7 = shl nsw i32 %tmp6, 8
%tmp8 = sub nsw i32 %tmp3, %tmp7
%tmp9 = icmp ult i32 %tmp8, 256
%tmp10 = select i1 %tmp9, i32 %tmp8, i32 256
%tmp11 = add nsw i32 %tmp10, 1
%tmp12 = icmp ugt i32 %tmp8, %tmp11
%tmp13 = select i1 %tmp12, i32 %tmp11, i32 %tmp8
%tmp14 = icmp ult i32 %tmp13, 256
%tmp15 = select i1 %tmp14, i32 %tmp13, i32 256
%tmp16 = add nsw i32 %tmp15, 1
%tmp17 = icmp ugt i32 %tmp8, %tmp16
%tmp18 = select i1 %tmp17, i32 %tmp16, i32 %tmp8
%tmp19 = icmp ult i32 %tmp18, 256
%tmp20 = select i1 %tmp19, i32 %tmp18, i32 256
%tmp21 = add nsw i32 %tmp20, 1
%tmp22 = icmp ugt i32 %tmp8, %tmp21
%tmp23 = select i1 %tmp22, i32 %tmp21, i32 %tmp8
%tmp24 = icmp ult i32 %tmp23, 256
%tmp25 = select i1 %tmp24, i32 %tmp23, i32 256
%tmp26 = add nsw i32 %tmp25, 1
%tmp27 = icmp ugt i32 %tmp8, %tmp26
%tmp28 = select i1 %tmp27, i32 %tmp26, i32 %tmp8
%tmp29 = icmp ult i32 %tmp28, 256
%tmp30 = select i1 %tmp29, i32 %tmp28, i32 256
%tmp31 = add nsw i32 %tmp30, 1
%tmp32 = icmp ugt i32 %tmp8, %tmp31
%tmp33 = select i1 %tmp32, i32 %tmp31, i32 %tmp8
%tmp34 = icmp ult i32 %tmp33, 256
%tmp35 = select i1 %tmp34, i32 %tmp33, i32 256
%tmp36 = add nsw i32 %tmp35, 1
%tmp37 = icmp ugt i32 %tmp8, %tmp36
%tmp38 = select i1 %tmp37, i32 %tmp36, i32 %tmp8
%tmp39 = icmp ult i32 %tmp38, 256
%tmp40 = select i1 %tmp39, i32 %tmp38, i32 256
%tmp41 = add nsw i32 %tmp40, 1
%tmp42 = icmp ugt i32 %tmp8, %tmp41
%tmp43 = select i1 %tmp42, i32 %tmp41, i32 %tmp8
%tmp44 = add nsw i32 %tmp10, 7
%tmp45 = icmp ult i32 %tmp43, 256
%tmp46 = select i1 %tmp45, i32 %tmp43, i32 256
; CHECK: %tmp46 = select i1 %tmp45, i32 %tmp43, i32 256
; CHECK-NEXT: --> (-1 + (-1 * (-257 umax (-1 + (-257 umax (-1 + (-257 umax (-1 + (-257 umax (-1 + (-257 umax (-1 + (-257 umax (-1 + (-257 umax (-1 + (-257 umax {(-1 + (-1 * %tmp3)),+,256}<%bb4>))<nsw> umax {(-1 + (-1 * %tmp3)),+,256}<%bb4>))<nsw> umax {(-1 + (-1 * %tmp3)),+,256}<%bb4>))<nsw> umax {(-1 + (-1 * %tmp3)),+,256}<%bb4>))<nsw> umax {(-1 + (-1 * %tmp3)),+,256}<%bb4>))<nsw> umax {(-1 + (-1 * %tmp3)),+,256}<%bb4>))<nsw> umax {(-1 + (-1 * %tmp3)),+,256}<%bb4>))<nsw> umax {(-1 + (-1 * %tmp3)),+,256}<%bb4>))<nsw>)<nsw>
%tmp47 = icmp ugt i32 %tmp44, %tmp46
%tmp48 = select i1 %tmp47, i32 %tmp44, i32 %tmp46
%tmp49 = ashr i32 %tmp48, 3
%tmp50 = icmp ugt i32 %tmp49, 0
%tmp51 = select i1 %tmp50, i32 %tmp49, i32 0
%tmp52 = zext i32 %tmp51 to i64
br label %bb53
bb53:
%tmp54 = phi i64 [ undef, %bb4 ], [ %tmp59, %bb53 ]
%tmp55 = trunc i64 %tmp54 to i32
%tmp56 = shl nsw i32 %tmp55, 3
%tmp57 = sext i32 %tmp56 to i64
%tmp58 = getelementptr inbounds i8, i8* null, i64 %tmp57
store i8 undef, i8* %tmp58, align 8
%tmp59 = add nsw i64 %tmp54, 1
%tmp60 = icmp eq i64 %tmp59, %tmp52
br i1 %tmp60, label %bb61, label %bb53
bb61:
%tmp62 = add nuw nsw i64 %tmp5, 1
br label %bb4
}