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Allow the construction of SCEVs with SCEVCouldNotCompute operands, by

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implementing folding. Fixes PR2857.

llvm-svn: 57049
This commit is contained in:
Nick Lewycky 2008-10-04 11:19:07 +00:00
parent 4cc9051fbb
commit 53e751fcba
2 changed files with 99 additions and 0 deletions
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67
lib/Analysis/ScalarEvolution.cpp
View File

@ -676,6 +676,9 @@ SCEVHandle ScalarEvolution::getTruncateExpr(const SCEVHandle &Op, const Type *Ty
return getAddRecExpr(Operands, AddRec->getLoop());
}
if (isa<SCEVCouldNotCompute>(Op))
return new SCEVCouldNotCompute();
SCEVTruncateExpr *&Result = (*SCEVTruncates)[std::make_pair(Op, Ty)];
if (Result == 0) Result = new SCEVTruncateExpr(Op, Ty);
return Result;
@ -691,6 +694,9 @@ SCEVHandle ScalarEvolution::getZeroExtendExpr(const SCEVHandle &Op, const Type *
// operands (often constants). This would allow analysis of something like
// this: for (unsigned char X = 0; X < 100; ++X) { int Y = X; }
if (isa<SCEVCouldNotCompute>(Op))
return new SCEVCouldNotCompute();
SCEVZeroExtendExpr *&Result = (*SCEVZeroExtends)[std::make_pair(Op, Ty)];
if (Result == 0) Result = new SCEVZeroExtendExpr(Op, Ty);
return Result;
@ -706,6 +712,9 @@ SCEVHandle ScalarEvolution::getSignExtendExpr(const SCEVHandle &Op, const Type *
// operands (often constants). This would allow analysis of something like
// this: for (signed char X = 0; X < 100; ++X) { int Y = X; }
if (isa<SCEVCouldNotCompute>(Op))
return new SCEVCouldNotCompute();
SCEVSignExtendExpr *&Result = (*SCEVSignExtends)[std::make_pair(Op, Ty)];
if (Result == 0) Result = new SCEVSignExtendExpr(Op, Ty);
return Result;
@ -734,6 +743,10 @@ SCEVHandle ScalarEvolution::getAddExpr(std::vector<SCEVHandle> &Ops) {
// Sort by complexity, this groups all similar expression types together.
GroupByComplexity(Ops);
// Could not compute plus anything equals could not compute.
if (isa<SCEVCouldNotCompute>(Ops.back()))
return new SCEVCouldNotCompute();
// If there are any constants, fold them together.
unsigned Idx = 0;
if (SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
@ -959,6 +972,21 @@ SCEVHandle ScalarEvolution::getMulExpr(std::vector<SCEVHandle> &Ops) {
// Sort by complexity, this groups all similar expression types together.
GroupByComplexity(Ops);
if (isa<SCEVCouldNotCompute>(Ops.back())) {
// CNC * 0 = 0
for (unsigned i = 0, e = Ops.size() - 1; i != e; ++i) {
if (Ops[i]->getSCEVType() != scConstant)
break;
SCEVConstant *SC = cast<SCEVConstant>(Ops[i]);
if (SC->getValue()->isMinValue(false))
return SC;
}
// Otherwise, we can't compute it.
return new SCEVCouldNotCompute();
}
// If there are any constants, fold them together.
unsigned Idx = 0;
if (SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
@ -1124,6 +1152,9 @@ SCEVHandle ScalarEvolution::getUDivExpr(const SCEVHandle &LHS, const SCEVHandle
// FIXME: implement folding of (X*4)/4 when we know X*4 doesn't overflow.
if (isa<SCEVCouldNotCompute>(LHS) || isa<SCEVCouldNotCompute>(RHS))
return new SCEVCouldNotCompute();
SCEVUDivExpr *&Result = (*SCEVUDivs)[std::make_pair(LHS, RHS)];
if (Result == 0) Result = new SCEVUDivExpr(LHS, RHS);
return Result;
@ -1171,6 +1202,12 @@ SCEVHandle ScalarEvolution::getAddRecExpr(std::vector<SCEVHandle> &Operands,
}
}
// Refuse to build an AddRec out of SCEVCouldNotCompute.
for (unsigned i = 0, e = Operands.size(); i != e; ++i) {
if (isa<SCEVCouldNotCompute>(Operands[i]))
return new SCEVCouldNotCompute();
}
SCEVAddRecExpr *&Result =
(*SCEVAddRecExprs)[std::make_pair(L, std::vector<SCEV*>(Operands.begin(),
Operands.end()))];
@ -1193,6 +1230,21 @@ SCEVHandle ScalarEvolution::getSMaxExpr(std::vector<SCEVHandle> Ops) {
// Sort by complexity, this groups all similar expression types together.
GroupByComplexity(Ops);
if (isa<SCEVCouldNotCompute>(Ops.back())) {
// CNC smax +inf = +inf.
for (unsigned i = 0, e = Ops.size() - 1; i != e; ++i) {
if (Ops[i]->getSCEVType() != scConstant)
break;
SCEVConstant *SC = cast<SCEVConstant>(Ops[i]);
if (SC->getValue()->isMaxValue(true))
return SC;
}
// Otherwise, we can't compute it.
return new SCEVCouldNotCompute();
}
// If there are any constants, fold them together.
unsigned Idx = 0;
if (SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
@ -1273,6 +1325,21 @@ SCEVHandle ScalarEvolution::getUMaxExpr(std::vector<SCEVHandle> Ops) {
// Sort by complexity, this groups all similar expression types together.
GroupByComplexity(Ops);
if (isa<SCEVCouldNotCompute>(Ops[0])) {
// CNC umax inf = inf.
for (unsigned i = 0, e = Ops.size() - 1; i != e; ++i) {
if (Ops[i]->getSCEVType() != scConstant)
break;
SCEVConstant *SC = cast<SCEVConstant>(Ops[i]);
if (SC->getValue()->isMaxValue(false))
return SC;
}
// Otherwise, we can't compute it.
return new SCEVCouldNotCompute();
}
// If there are any constants, fold them together.
unsigned Idx = 0;
if (SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {

32
test/Transforms/IndVarsSimplify/2008-10-03-CouldNotCompute.ll Normal file
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@ -0,0 +1,32 @@
; RUN: llvm-as < %s | opt -indvars
; PR2857
@foo = external global i32 ; <i32*> [#uses=1]
define void @test(i32 %n, i32 %arg) {
entry:
br i1 false, label %bb.nph, label %return
bb.nph: ; preds = %entry
%0 = load i32* @foo, align 4 ; <i32> [#uses=1]
%1 = sext i32 %0 to i64 ; <i64> [#uses=1]
br label %bb
bb: ; preds = %bb, %bb.nph
%.in = phi i32 [ %2, %bb ], [ %n, %bb.nph ] ; <i32> [#uses=1]
%val.02 = phi i64 [ %5, %bb ], [ 0, %bb.nph ] ; <i64> [#uses=2]
%result.01 = phi i64 [ %4, %bb ], [ 0, %bb.nph ] ; <i64> [#uses=1]
%2 = add i32 %.in, -1 ; <i32> [#uses=2]
%3 = mul i64 %1, %val.02 ; <i64> [#uses=1]
%4 = add i64 %3, %result.01 ; <i64> [#uses=2]
%5 = add i64 %val.02, 1 ; <i64> [#uses=1]
%6 = icmp sgt i32 %2, 0 ; <i1> [#uses=1]
br i1 %6, label %bb, label %bb3.bb4_crit_edge
bb3.bb4_crit_edge: ; preds = %bb
%.lcssa = phi i64 [ %4, %bb ] ; <i64> [#uses=0]
ret void
return: ; preds = %entry
ret void
}