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Make ISel ignore dead nodes. The DAGCombiner normally eliminates

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dead nodes, but in this case its missing one. Fixing the DAGCombiner
is desirable, but it's somewhat involved.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@58777 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2008-11-05 22:56:47 +00:00
parent 8ad0919786
commit 33a9cb4f40
2 changed files with 27 additions and 0 deletions
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5
include/llvm/CodeGen/DAGISelHeader.h
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@ -108,6 +108,11 @@ void SelectRoot(SelectionDAG &DAG) {
// node).
while (ISelPosition != CurDAG->allnodes_begin()) {
SDNode *Node = --ISelPosition;
// Skip dead nodes. DAGCombiner is expected to eliminate all dead nodes,
// but there are currently some corner cases that it misses. Also, this
// makes it theoretically possible to disable the DAGCombiner.
if (Node->use_empty())
continue;
#if 0
DAG.setSubgraphColor(Node, "red");
#endif

22
test/CodeGen/PowerPC/delete-node.ll Normal file
View File

@ -0,0 +1,22 @@
; RUN: llvm-as < %s | llc -march=ppc32
; The DAGCombiner leaves behind a dead node in this testcase. Currently
; ISel is ignoring dead nodes, though it would be preferable for
; DAGCombiner to be able to eliminate the dead node.
define void @GrayATo32ARGBTabB(i8* %baseAddr, i16** %cmp, i32 %rowBytes) nounwind {
entry:
br label %bb1
bb1: ; preds = %bb1, %entry
%0 = load i16* null, align 2 ; <i16> [#uses=1]
%1 = ashr i16 %0, 4 ; <i16> [#uses=1]
%2 = sext i16 %1 to i32 ; <i32> [#uses=1]
%3 = getelementptr i8* null, i32 %2 ; <i8*> [#uses=1]
%4 = load i8* %3, align 1 ; <i8> [#uses=1]
%5 = zext i8 %4 to i32 ; <i32> [#uses=1]
%6 = shl i32 %5, 24 ; <i32> [#uses=1]
%7 = or i32 0, %6 ; <i32> [#uses=1]
store i32 %7, i32* null, align 4
br label %bb1
}