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Fix PR6497, a bug where we'd fold a load into an addc

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node which has a flag.  That flag in turn was used by an
already-selected adde which turned into an ADC32ri8 which
used a selected load which was chained to the load we
folded.  This flag use caused us to form a cycle.  Fix
this by not ignoring chains in IsLegalToFold even in
cases where the isel thinks it can.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@97791 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2010-03-05 06:19:13 +00:00
parent 1beaf41ef6
commit 18fdabadca
2 changed files with 27 additions and 0 deletions
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7
lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
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@ -1485,7 +1485,14 @@ bool SelectionDAGISel::IsLegalToFold(SDValue N, SDNode *U, SDNode *Root,
break; break;
Root = FU; Root = FU;
VT = Root->getValueType(Root->getNumValues()-1); VT = Root->getValueType(Root->getNumValues()-1);
// If our query node has a flag result with a use, we've walked up it. If
// the user (which has already been selected) has a chain or indirectly uses
// the chain, our WalkChainUsers predicate will not consider it. Because of
// this, we cannot ignore chains in this predicate.
IgnoreChains = false;
} }
SmallPtrSet<SDNode*, 16> Visited; SmallPtrSet<SDNode*, 16> Visited;
return !findNonImmUse(Root, N.getNode(), U, Root, Visited, IgnoreChains); return !findNonImmUse(Root, N.getNode(), U, Root, Visited, IgnoreChains);

20
test/CodeGen/X86/crash.ll Normal file
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@ -0,0 +1,20 @@
; RUN: llc -march=x86 %s -o -
; RUN: llc -march=x86-64 %s -o -
; PR6497
; Chain and flag folding issues.
define i32 @test1() nounwind ssp {
entry:
%tmp5.i = volatile load i32* undef ; <i32> [#uses=1]
%conv.i = zext i32 %tmp5.i to i64 ; <i64> [#uses=1]
%tmp12.i = volatile load i32* undef ; <i32> [#uses=1]
%conv13.i = zext i32 %tmp12.i to i64 ; <i64> [#uses=1]
%shl.i = shl i64 %conv13.i, 32 ; <i64> [#uses=1]
%or.i = or i64 %shl.i, %conv.i ; <i64> [#uses=1]
%add16.i = add i64 %or.i, 256 ; <i64> [#uses=1]
%shr.i = lshr i64 %add16.i, 8 ; <i64> [#uses=1]
%conv19.i = trunc i64 %shr.i to i32 ; <i32> [#uses=1]
volatile store i32 %conv19.i, i32* undef
ret i32 undef
}