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Revert 72493 and replace it with a more conservative fix, for now: don't

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rewrite the comparison if there is any implicit extension or truncation
on the induction variable. I'm planning for IVUsers to eventually take
over some of the work of this code, and for it to be generalized.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@72496 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2009-05-27 21:10:47 +00:00
parent ba2352b066
commit c2695eba57
2 changed files with 33 additions and 7 deletions
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15
lib/Transforms/Scalar/LoopStrengthReduce.cpp
View File

@ -1993,6 +1993,12 @@ ICmpInst *LoopStrengthReduce::ChangeCompareStride(Loop *L, ICmpInst *Cond,
ValidScale(!CommonExprs->isZero(), Scale, UsersToProcess))
continue;
// Avoid rewriting the compare instruction with an iv which has
// implicit extension or truncation built into it.
// TODO: This is over-conservative.
if (SE->getTypeSizeInBits(CondUse->getOffset()->getType()) != TyBits)
continue;
// If scale is negative, use swapped predicate unless it's testing
// for equality.
if (Scale < 0 && !Cond->isEquality())
@ -2005,16 +2011,11 @@ ICmpInst *LoopStrengthReduce::ChangeCompareStride(Loop *L, ICmpInst *Cond,
ConstantInt *CI = ConstantInt::get(NewCmpIntTy, NewCmpVal);
NewCmpRHS = ConstantExpr::getIntToPtr(CI, NewCmpTy);
}
NewOffset = CondUse->getOffset();
if (CondUse->isSigned())
NewOffset = SE->getNoopOrSignExtend(CondUse->getOffset(), NewCmpTy);
else
NewOffset = SE->getNoopOrZeroExtend(CondUse->getOffset(), NewCmpTy);
NewOffset = TyBits == NewTyBits
? SE->getMulExpr(NewOffset,
? SE->getMulExpr(CondUse->getOffset(),
SE->getConstant(ConstantInt::get(CmpTy, Scale)))
: SE->getConstant(ConstantInt::get(NewCmpIntTy,
cast<SCEVConstant>(NewOffset)->getValue()
cast<SCEVConstant>(CondUse->getOffset())->getValue()
->getSExtValue()*Scale));
break;
}

25
test/Transforms/LoopStrengthReduce/change-compare-stride-trickiness-2.ll
View File

@ -31,3 +31,28 @@ if.end52: ; preds = %for.cond.i.preheader
%indvar.next689 = add i64 %indvar688, 1 ; <i64> [#uses=1]
br i1 %phitmp654, label %for.cond.i.preheader, label %if.end
}
define void @promote(%struct.dumperinfo* %di) nounwind {
entry:
br label %if.end
if.end: ; preds = %if.end52, %entry
br label %for.cond.i.preheader
for.cond.i.preheader: ; preds = %if.end52, %if.end
%indvar688 = phi i32 [ 0, %if.end ], [ %indvar.next689, %if.end52 ] ; <i64> [#uses=3]
%tmp690 = shl i32 %indvar688, 12 ; <i64> [#uses=1]
%pa.0642 = add i32 %tmp690, 0 ; <i64> [#uses=1]
%tmp692693 = add i32 %indvar688, 1 ; <i32> [#uses=1]
%phitmp = sext i32 %tmp692693 to i64 ; <i64> [#uses=1]
br i1 false, label %if.end52, label %land.lhs.true.i
land.lhs.true.i: ; preds = %for.cond.i.preheader
%shr2.i = lshr i32 %pa.0642, 18 ; <i64> [#uses=0]
unreachable
if.end52: ; preds = %for.cond.i.preheader
%phitmp654 = icmp ult i64 %phitmp, 512 ; <i1> [#uses=1]
%indvar.next689 = add i32 %indvar688, 1 ; <i64> [#uses=1]
br i1 %phitmp654, label %for.cond.i.preheader, label %if.end
}