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Don't attempt to simplify an non-affine IV expression if it can't

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be simplified to a loop-invariant value. This fixes PR4315.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@72798 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2009-06-03 19:11:31 +00:00
parent 222858256f
commit 68c9344056
3 changed files with 53 additions and 12 deletions
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22
lib/Transforms/Scalar/IndVarSimplify.cpp
View File

@ -465,17 +465,6 @@ void IndVarSimplify::RewriteIVExpressions(Loop *L, const Type *LargestType,
// Compute the final addrec to expand into code.
SCEVHandle AR = IU->getReplacementExpr(*UI);
// FIXME: It is an extremely bad idea to indvar substitute anything more
// complex than affine induction variables. Doing so will put expensive
// polynomial evaluations inside of the loop, and the str reduction pass
// currently can only reduce affine polynomials. For now just disable
// indvar subst on anything more complex than an affine addrec, unless
// it can be expanded to a trivial value.
if (!Stride->isLoopInvariant(L) &&
!isa<SCEVConstant>(AR) &&
L->contains(User->getParent()))
continue;
Value *NewVal = 0;
if (AR->isLoopInvariant(L)) {
BasicBlock::iterator I = Rewriter.getInsertionPoint();
@ -487,6 +476,15 @@ void IndVarSimplify::RewriteIVExpressions(Loop *L, const Type *LargestType,
Rewriter.setInsertionPoint(I);
++NumReplaced;
} else {
// FIXME: It is an extremely bad idea to indvar substitute anything more
// complex than affine induction variables. Doing so will put expensive
// polynomial evaluations inside of the loop, and the str reduction pass
// currently can only reduce affine polynomials. For now just disable
// indvar subst on anything more complex than an affine addrec, unless
// it can be expanded to a trivial value.
if (!Stride->isLoopInvariant(L))
continue;
const Type *IVTy = Offset->getType();
const Type *UseTy = Op->getType();
@ -520,7 +518,7 @@ void IndVarSimplify::RewriteIVExpressions(Loop *L, const Type *LargestType,
// induction variable, still in the canonical induction variable's
// type, so that all expanded arithmetic is done in the same type.
SCEVHandle NewAR = SE->getAddRecExpr(SE->getIntegerSCEV(0, LargestType),
PromotedStride, L);
PromotedStride, L);
// Add the PromotedOffset as a separate step, because it may not be
// loop-invariant.
NewAR = SE->getAddExpr(NewAR, PromotedOffset);

0
test/Transforms/IndVarSimplify/variable-stride-ivs.ll → test/Transforms/IndVarSimplify/variable-stride-ivs-0.ll
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43
test/Transforms/IndVarSimplify/variable-stride-ivs-1.ll Normal file
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@ -0,0 +1,43 @@
; RUN: llvm-as < %s | opt -indvars
; PR4315
target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"
target triple = "x86_64-undermydesk-freebsd8.0"
%struct.mbuf = type <{ %struct.mbuf*, i8*, i32, i8, i8, i8, i8 }>
define i32 @crash(%struct.mbuf* %m) nounwind {
entry:
br label %for.cond
for.cond: ; preds = %if.end, %entry
%i.0 = phi i32 [ 0, %entry ], [ %inc, %if.end ] ; <i32> [#uses=3]
%chksum.0 = phi i8 [ 0, %entry ], [ %conv3, %if.end ] ; <i8> [#uses=3]
%cmp = icmp slt i32 %i.0, 1 ; <i1> [#uses=1]
br i1 %cmp, label %for.body, label %do.body
for.body: ; preds = %for.cond
br i1 undef, label %if.end, label %do.body
if.end: ; preds = %for.body
%i.02 = trunc i32 %i.0 to i8 ; <i8> [#uses=1]
%conv3 = add i8 %chksum.0, %i.02 ; <i8> [#uses=1]
%inc = add i32 %i.0, 1 ; <i32> [#uses=1]
br label %for.cond
do.body: ; preds = %do.cond, %for.body, %for.cond
%chksum.2 = phi i8 [ undef, %do.cond ], [ %chksum.0, %for.body ], [ %chksum.0, %for.cond ] ; <i8> [#uses=1]
br i1 undef, label %do.cond, label %bb.nph
bb.nph: ; preds = %do.body
br label %while.body
while.body: ; preds = %while.body, %bb.nph
%chksum.13 = phi i8 [ undef, %while.body ], [ %chksum.2, %bb.nph ] ; <i8> [#uses=0]
br i1 undef, label %do.cond, label %while.body
do.cond: ; preds = %while.body, %do.body
br i1 false, label %do.end, label %do.body
do.end: ; preds = %do.cond
ret i32 0
}