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Revert "[ScalarEvolution] Handling for ICmp occuring in the evolution chain." 

This reverts commit r316054.  There was some confusion over the review process:
http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20171016/495884.html

llvm-svn: 316129
This commit is contained in:
Sanjoy Das 2017-10-18 22:00:57 +00:00
parent 306d29977d
commit 2f27456c82
4 changed files with 5 additions and 69 deletions
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3
llvm/include/llvm/Analysis/ScalarEvolution.h
View File

@ -1378,9 +1378,6 @@ private:
/// Helper function called from createNodeForPHI.
const SCEV *createAddRecFromPHI(PHINode *PN);
/// Evaluate ICmpInst to a constant node for special patterns.
const SCEV *evaluateForICmp(ICmpInst *IC);
/// A helper function for createAddRecFromPHI to handle simple cases.
const SCEV *createSimpleAffineAddRec(PHINode *PN, Value *BEValueV,
Value *StartValueV);

45
llvm/lib/Analysis/ScalarEvolution.cpp
View File

@ -4756,26 +4756,11 @@ const SCEV *ScalarEvolution::createAddRecFromPHI(PHINode *PN) {
Ops.push_back(Add->getOperand(i));
const SCEV *Accum = getAddExpr(Ops);
bool InvariantF = isLoopInvariant(Accum, L);
if (!InvariantF && Accum->getSCEVType() == scZeroExtend) {
const SCEV *Op = dyn_cast<SCEVZeroExtendExpr>(Accum)->getOperand();
const SCEVUnknown *Un = dyn_cast<SCEVUnknown>(Op);
if (Un && Un->getValue() && isa<Instruction>(Un->getValue()) &&
dyn_cast<Instruction>(Un->getValue())->getOpcode() ==
Instruction::ICmp) {
const SCEV *ICmpSC = evaluateForICmp(cast<ICmpInst>(Un->getValue()));
bool IsConstSC = ICmpSC->getSCEVType() == scConstant;
Accum =
IsConstSC ? getZeroExtendExpr(ICmpSC, Accum->getType()) : Accum;
InvariantF = IsConstSC ? true : false;
}
}
// This is not a valid addrec if the step amount is varying each
// loop iteration, but is not itself an addrec in this loop.
if (InvariantF || (isa<SCEVAddRecExpr>(Accum) &&
cast<SCEVAddRecExpr>(Accum)->getLoop() == L)) {
if (isLoopInvariant(Accum, L) ||
(isa<SCEVAddRecExpr>(Accum) &&
cast<SCEVAddRecExpr>(Accum)->getLoop() == L)) {
SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap;
if (auto BO = MatchBinaryOp(BEValueV, DT)) {
@ -6458,30 +6443,6 @@ void ScalarEvolution::forgetLoop(const Loop *L) {
}
}
const SCEV *ScalarEvolution::evaluateForICmp(ICmpInst *IC) {
BasicBlock *Latch = nullptr;
const Loop *L = LI.getLoopFor(IC->getParent());
// If compare instruction is same or inverse of the compare in the
// branch of the loop latch, then return a constant evolution
// node. This shall facilitate computations of loop exit counts
// in cases where compare appears in the evolution chain of induction
// variables.
if (L && (Latch = L->getLoopLatch())) {
BranchInst *BI = dyn_cast<BranchInst>(Latch->getTerminator());
if (BI && BI->isConditional() && BI->getCondition() == IC) {
if (BI->getSuccessor(0) != L->getHeader())
return getZero(Type::getInt1Ty(getContext()));
else
return getOne(Type::getInt1Ty(getContext()));
}
}
return getUnknown(IC);
}
void ScalarEvolution::forgetValue(Value *V) {
Instruction *I = dyn_cast<Instruction>(V);
if (!I) return;

7
llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
View File

@ -2969,11 +2969,8 @@ void LSRInstance::CollectChains() {
// Ignore users that are part of a SCEV expression. This way we only
// consider leaf IV Users. This effectively rediscovers a portion of
// IVUsers analysis but in program order this time.
if (SE.isSCEVable(I.getType())) {
const SCEV *SI = SE.getSCEV(&I);
if (!isa<SCEVUnknown>(SI) && !isa<SCEVConstant>(SI))
continue;
}
if (SE.isSCEVable(I.getType()) && !isa<SCEVUnknown>(SE.getSCEV(&I)))
continue;
// Remove this instruction from any NearUsers set it may be in.
for (unsigned ChainIdx = 0, NChains = IVChainVec.size();

19
llvm/test/Analysis/ScalarEvolution/pr34538.ll
View File

@ -1,19 +0,0 @@
; RUN: opt -S -scalar-evolution -loop-deletion -simplifycfg -analyze < %s | FileCheck %s --check-prefix=CHECK-ANALYSIS
define i32 @foo() local_unnamed_addr #0 {
; CHECK-ANALYSIS: Loop %do.body: backedge-taken count is 10000
; CHECK-ANALYSIS: Loop %do.body: max backedge-taken count is 10000
; CHECK-ANALYSIS: Loop %do.body: Predicated backedge-taken count is 10000
entry:
br label %do.body
do.body: ; preds = %do.body, %entry
%start.0 = phi i32 [ 0, %entry ], [ %inc.start.0, %do.body ]
%cmp = icmp slt i32 %start.0, 10000
%inc = zext i1 %cmp to i32
%inc.start.0 = add nsw i32 %start.0, %inc
br i1 %cmp, label %do.body, label %do.end
do.end: ; preds = %do.body
ret i32 0
}