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If loop induction variable's start value is less then its exit value then do not split the loop.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@53265 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Devang Patel 2008-07-09 00:12:01 +00:00
parent f877b735ad
commit a5e27f8028
3 changed files with 39 additions and 1 deletions
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13
lib/Transforms/Scalar/LoopIndexSplit.cpp
View File

@ -384,6 +384,19 @@ void LoopIndexSplit::findLoopConditionals() {
BasicBlock *Preheader = L->getLoopPreheader();
StartValue = IndVar->getIncomingValueForBlock(Preheader);
}
// If start value is more then exit value where induction variable
// increments by 1 then we are potentially dealing with an infinite loop.
// Do not index split this loop.
if (ExitCondition) {
ConstantInt *SV = dyn_cast<ConstantInt>(StartValue);
ConstantInt *EV =
dyn_cast<ConstantInt>(ExitCondition->getOperand(ExitValueNum));
if (SV && EV && SV->getSExtValue() > EV->getSExtValue())
ExitCondition = NULL;
else if (EV && EV->isZero())
ExitCondition = NULL;
}
}
/// Find condition inside a loop that is suitable candidate for index split.

2
test/Transforms/LoopIndexSplit/2008-05-19-IndVar.ll
View File

@ -24,7 +24,7 @@ bb4.i: ; preds = %bb.i
br label %bb6.i
bb6.i: ; preds = %bb4.i, %bb.i
%tmp8.i = add i16 %g_2.tmp.0.i, 1 ; <i16> [#uses=3]
%tmp11.i = icmp sgt i16 %tmp8.i, 0 ; <i1> [#uses=1]
%tmp11.i = icmp sgt i16 %tmp8.i, 42 ; <i1> [#uses=1]
br i1 %tmp11.i, label %bb.i, label %return.loopexit.i
return.loopexit.i: ; preds = %bb6.i
%tmp8.i.lcssa = phi i16 [ %tmp8.i, %bb6.i ] ; <i16> [#uses=1]

25
test/Transforms/LoopIndexSplit/2008-07-08-MisCompilation.ll Normal file
View File

@ -0,0 +1,25 @@
; RUN: llvm-as < %s | opt -loop-index-split -stats -disable-output | not grep "1 loop-index-split"
; PR 2487
@g_6 = external global i32 ; <i32*> [#uses=1]
define void @func_1() nounwind {
entry:
br label %bb
bb: ; preds = %bb4, %entry
%l_3.0 = phi i8 [ 0, %entry ], [ %tmp6, %bb4 ] ; <i8> [#uses=2]
%tmp1 = icmp eq i8 %l_3.0, 0 ; <i1> [#uses=1]
br i1 %tmp1, label %bb3, label %bb4
bb3: ; preds = %bb
store i32 1, i32* @g_6, align 4
br label %bb4
bb4: ; preds = %bb3, %bb
%tmp6 = add i8 %l_3.0, 1 ; <i8> [#uses=2]
%tmp9 = icmp sgt i8 %tmp6, -1 ; <i1> [#uses=1]
br i1 %tmp9, label %bb, label %return
return: ; preds = %bb4
ret void
}