Make ISel ignore dead nodes. The DAGCombiner normally eliminates
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
diff --git a/include/llvm/CodeGen/DAGISelHeader.h b/include/llvm/CodeGen/DAGISelHeader.h
index 3b4da66..28b2277 100644
--- a/include/llvm/CodeGen/DAGISelHeader.h
+++ b/include/llvm/CodeGen/DAGISelHeader.h
@@ -108,6 +108,11 @@
// 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
diff --git a/test/CodeGen/PowerPC/delete-node.ll b/test/CodeGen/PowerPC/delete-node.ll
new file mode 100644
index 0000000..0b1d734
--- /dev/null
+++ b/test/CodeGen/PowerPC/delete-node.ll
@@ -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
+}