RPCSX/llvm
1
0
Fork 0
mirror of https://github.com/RPCSX/llvm.git synced 2024-11-29 14:40:25 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

Handle decrementing loops properly. Fixes PR1533.

Browse Source 
Always pass the constant as the second parameter to HowManyLessThans.

Remove obsolete "isSigned" parameter.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@39893 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nick Lewycky 2007-07-16 02:08:00 +00:00
parent f7b71c64cf
commit eefdebe002
3 changed files with 35 additions and 19 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
include/llvm/Analysis/ScalarEvolutionExpressions.h
View File

@ -475,10 +475,8 @@ namespace llvm {
/// looking at this is that it returns the first iteration number where the
/// value is not in the condition, thus computing the exit count. If the
/// iteration count can't be computed, an instance of SCEVCouldNotCompute is
/// returned. The isSigned parameter indicates whether the ConstantRange
/// should be treated as signed or unsigned.
SCEVHandle getNumIterationsInRange(ConstantRange Range,
bool isSigned) const;
/// returned.
SCEVHandle getNumIterationsInRange(ConstantRange Range) const;
SCEVHandle replaceSymbolicValuesWithConcrete(const SCEVHandle &Sym,
const SCEVHandle &Conc) const;

28
lib/Analysis/ScalarEvolution.cpp
View File

@ -1671,8 +1671,7 @@ SCEVHandle ScalarEvolutionsImpl::ComputeIterationCount(const Loop *L) {
ConstantRange CompRange(
ICmpInst::makeConstantRange(Cond, CompVal->getValue()));
SCEVHandle Ret = AddRec->getNumIterationsInRange(CompRange,
false /*Always treat as unsigned range*/);
SCEVHandle Ret = AddRec->getNumIterationsInRange(CompRange);
if (!isa<SCEVCouldNotCompute>(Ret)) return Ret;
}
}
@ -1696,7 +1695,8 @@ SCEVHandle ScalarEvolutionsImpl::ComputeIterationCount(const Loop *L) {
break;
}
case ICmpInst::ICMP_SGT: {
SCEVHandle TC = HowManyLessThans(RHS, LHS, L);
SCEVHandle TC = HowManyLessThans(SCEV::getNegativeSCEV(LHS),
SCEV::getNegativeSCEV(RHS), L);
if (!isa<SCEVCouldNotCompute>(TC)) return TC;
break;
}
@ -2406,8 +2406,7 @@ HowManyLessThans(SCEV *LHS, SCEV *RHS, const Loop *L) {
/// this is that it returns the first iteration number where the value is not in
/// the condition, thus computing the exit count. If the iteration count can't
/// be computed, an instance of SCEVCouldNotCompute is returned.
SCEVHandle SCEVAddRecExpr::getNumIterationsInRange(ConstantRange Range,
bool isSigned) const {
SCEVHandle SCEVAddRecExpr::getNumIterationsInRange(ConstantRange Range) const {
if (Range.isFullSet()) // Infinite loop.
return new SCEVCouldNotCompute();
@ -2419,7 +2418,7 @@ SCEVHandle SCEVAddRecExpr::getNumIterationsInRange(ConstantRange Range,
SCEVHandle Shifted = SCEVAddRecExpr::get(Operands, getLoop());
if (SCEVAddRecExpr *ShiftedAddRec = dyn_cast<SCEVAddRecExpr>(Shifted))
return ShiftedAddRec->getNumIterationsInRange(
Range.subtract(SC->getValue()->getValue()),isSigned);
Range.subtract(SC->getValue()->getValue()));
// This is strange and shouldn't happen.
return new SCEVCouldNotCompute();
}
@ -2443,17 +2442,16 @@ SCEVHandle SCEVAddRecExpr::getNumIterationsInRange(ConstantRange Range,
// If this is an affine expression then we have this situation:
// Solve {0,+,A} in Range === Ax in Range
// Since we know that zero is in the range, we know that the upper value of
// the range must be the first possible exit value. Also note that we
// already checked for a full range.
const APInt &Upper = Range.getUpper();
APInt A = cast<SCEVConstant>(getOperand(1))->getValue()->getValue();
// We know that zero is in the range. If A is positive then we know that
// the upper value of the range must be the first possible exit value.
// If A is negative then the lower of the range is the last possible loop
// value. Also note that we already checked for a full range.
APInt One(getBitWidth(),1);
APInt A = cast<SCEVConstant>(getOperand(1))->getValue()->getValue();
APInt End = A.sge(One) ? (Range.getUpper() - One) : Range.getLower();
// The exit value should be (Upper+A-1)/A.
APInt ExitVal(Upper);
if (A != One)
ExitVal = (Upper + A - One).sdiv(A);
// The exit value should be (End+A)/A.
APInt ExitVal = (End + A).sdiv(A);
ConstantInt *ExitValue = ConstantInt::get(ExitVal);
// Evaluate at the exit value. If we really did fall out of the valid

20
test/Analysis/ScalarEvolution/2007-07-15-NegativeStride.ll Normal file
View File

@ -0,0 +1,20 @@
; RUN: llvm-as < %s | opt -analyze -scalar-evolution 2>&1 | grep "Loop bb: 100 iterations"
; PR1533
@array = weak global [101 x i32] zeroinitializer, align 32 ; <[100 x i32]*> [#uses=1]
define void @loop(i32 %x) {
entry:
br label %bb
bb: ; preds = %bb, %entry
%i.01.0 = phi i32 [ 100, %entry ], [ %tmp4, %bb ] ; <i32> [#uses=2]
%tmp1 = getelementptr [101 x i32]* @array, i32 0, i32 %i.01.0 ; <i32*> [#uses=1]
store i32 %x, i32* %tmp1
%tmp4 = add i32 %i.01.0, -1 ; <i32> [#uses=2]
%tmp7 = icmp sgt i32 %tmp4, -1 ; <i1> [#uses=1]
br i1 %tmp7, label %bb, label %return
return: ; preds = %bb
ret void
}