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Fix a case where ScalarEvolution was expanding pointer arithmetic

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to inttoptr/ptrtoint unnecessarily.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@82864 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2009-09-26 16:11:57 +00:00
parent 3548ea8e90
commit c70c37794f
2 changed files with 61 additions and 3 deletions
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23
lib/Analysis/ScalarEvolutionExpander.cpp
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@ -508,20 +508,37 @@ Value *SCEVExpander::expandAddToGEP(const SCEV *const *op_begin,
}
Value *SCEVExpander::visitAddExpr(const SCEVAddExpr *S) {
int NumOperands = S->getNumOperands();
const Type *Ty = SE.getEffectiveSCEVType(S->getType());
Value *V = expand(S->getOperand(S->getNumOperands()-1));
// Find the index of an operand to start with. Choose the operand with
// pointer type, if there is one, or the last operand otherwise.
int PIdx = 0;
for (; PIdx != NumOperands - 1; ++PIdx)
if (isa<PointerType>(S->getOperand(PIdx)->getType())) break;
// Expand code for the operand that we chose.
Value *V = expand(S->getOperand(PIdx));
// Turn things like ptrtoint+arithmetic+inttoptr into GEP. See the
// comments on expandAddToGEP for details.
if (const PointerType *PTy = dyn_cast<PointerType>(V->getType())) {
// Take the operand at PIdx out of the list.
const SmallVectorImpl<const SCEV *> &Ops = S->getOperands();
return expandAddToGEP(&Ops[0], &Ops[Ops.size() - 1], PTy, Ty, V);
SmallVector<const SCEV *, 8> NewOps;
NewOps.insert(NewOps.end(), Ops.begin(), Ops.begin() + PIdx);
NewOps.insert(NewOps.end(), Ops.begin() + PIdx + 1, Ops.end());
// Make a GEP.
return expandAddToGEP(NewOps.begin(), NewOps.end(), PTy, Ty, V);
}
// Otherwise, we'll expand the rest of the SCEVAddExpr as plain integer
// arithmetic.
V = InsertNoopCastOfTo(V, Ty);
// Emit a bunch of add instructions
for (int i = S->getNumOperands()-2; i >= 0; --i) {
for (int i = NumOperands-1; i >= 0; --i) {
if (i == PIdx) continue;
Value *W = expandCodeFor(S->getOperand(i), Ty);
V = InsertBinop(Instruction::Add, V, W);
}

41
test/Transforms/IndVarSimplify/preserve-gep-loop-variant.ll Normal file
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@ -0,0 +1,41 @@
; RUN: opt < %s -indvars -S > %t
; RUN: not grep inttoptr %t
; RUN: not grep ptrtoint %t
; RUN: grep scevgep %t
; Indvars shouldn't need inttoptr/ptrtoint to expand an address here.
define void @foo(i8* %p) nounwind {
entry:
br i1 true, label %bb.nph, label %for.end
for.cond:
%phitmp = icmp slt i64 %inc, 20
br i1 %phitmp, label %for.body, label %for.cond.for.end_crit_edge
for.cond.for.end_crit_edge:
br label %for.end
bb.nph:
br label %for.body
for.body:
%storemerge1 = phi i64 [ %inc, %for.cond ], [ 0, %bb.nph ]
%call = tail call i64 @bar() nounwind
%call2 = tail call i64 @car() nounwind
%conv = trunc i64 %call2 to i8
%conv3 = sext i8 %conv to i64
%add = add nsw i64 %call, %storemerge1
%add4 = add nsw i64 %add, %conv3
%arrayidx = getelementptr inbounds i8* %p, i64 %add4
store i8 0, i8* %arrayidx
%inc = add nsw i64 %storemerge1, 1
br label %for.cond
for.end:
ret void
}
declare i64 @bar()
declare i64 @car()