[llvm-commits] [llvm] r46099 - in /llvm/trunk: lib/CodeGen/SelectionDAG/DAGCombiner.cpp test/CodeGen/X86/2008-01-16-InvalidDAGCombineXform.ll
Evan Cheng
evan.cheng at apple.com
Wed Jan 16 15:11:55 PST 2008
Author: evancheng
Date: Wed Jan 16 17:11:54 2008
New Revision: 46099
URL: http://llvm.org/viewvc/llvm-project?rev=46099&view=rev
Log:
Fixes a nasty dag combiner bug that causes a bunch of tests to fail at -O0.
It's not safe to use the two value CombineTo variant to combine away a dead load.
e.g.
v1, chain2 = load chain1, loc
v2, chain3 = load chain2, loc
v3 = add v2, c
Now we replace use of v1 with undef, use of chain2 with chain1.
ReplaceAllUsesWith() will iterate through uses of the first load and update operands:
v1, chain2 = load chain1, loc
v2, chain3 = load chain1, loc
v3 = add v2, c
Now the second load is the same as the first load, SelectionDAG cse will ensure
the use of second load is replaced with the first load.
v1, chain2 = load chain1, loc
v3 = add v1, c
Then v1 is replaced with undef and bad things happen.
Added:
llvm/trunk/test/CodeGen/X86/2008-01-16-InvalidDAGCombineXform.ll
Modified:
llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
Modified: llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp?rev=46099&r1=46098&r2=46099&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp Wed Jan 16 17:11:54 2008
@@ -4055,16 +4055,54 @@
if (!LD->isVolatile()) {
if (N->getValueType(1) == MVT::Other) {
// Unindexed loads.
- if (N->hasNUsesOfValue(0, 0))
- return CombineTo(N, DAG.getNode(ISD::UNDEF, N->getValueType(0)), Chain);
+ if (N->hasNUsesOfValue(0, 0)) {
+ // It's not safe to use the two value CombineTo variant here. e.g.
+ // v1, chain2 = load chain1, loc
+ // v2, chain3 = load chain2, loc
+ // v3 = add v2, c
+ // Now we replace use of v1 with undef, use of chain2 with chain1.
+ // ReplaceAllUsesWith() will iterate through uses of the first load and
+ // update operands:
+ // v1, chain2 = load chain1, loc
+ // v2, chain3 = load chain1, loc
+ // v3 = add v2, c
+ // Now the second load is the same as the first load, SelectionDAG cse
+ // will ensure the use of second load is replaced with the first load.
+ // v1, chain2 = load chain1, loc
+ // v3 = add v1, c
+ // Then v1 is replaced with undef and bad things happen.
+ std::vector<SDNode*> NowDead;
+ SDOperand Undef = DAG.getNode(ISD::UNDEF, N->getValueType(0));
+ DOUT << "\nReplacing.6 "; DEBUG(N->dump(&DAG));
+ DOUT << "\nWith: "; DEBUG(Undef.Val->dump(&DAG));
+ DOUT << " and 1 other value\n";
+ DAG.ReplaceAllUsesOfValueWith(SDOperand(N, 0), Undef, &NowDead);
+ DAG.ReplaceAllUsesOfValueWith(SDOperand(N, 1), Chain, &NowDead);
+ removeFromWorkList(N);
+ for (unsigned i = 0, e = NowDead.size(); i != e; ++i)
+ removeFromWorkList(NowDead[i]);
+ DAG.DeleteNode(N);
+ return SDOperand(N, 0); // Return N so it doesn't get rechecked!
+ }
} else {
// Indexed loads.
assert(N->getValueType(2) == MVT::Other && "Malformed indexed loads?");
if (N->hasNUsesOfValue(0, 0) && N->hasNUsesOfValue(0, 1)) {
- SDOperand Undef0 = DAG.getNode(ISD::UNDEF, N->getValueType(0));
- SDOperand Undef1 = DAG.getNode(ISD::UNDEF, N->getValueType(1));
- SDOperand To[] = { Undef0, Undef1, Chain };
- return CombineTo(N, To, 3);
+ std::vector<SDNode*> NowDead;
+ SDOperand Undef = DAG.getNode(ISD::UNDEF, N->getValueType(0));
+ DOUT << "\nReplacing.6 "; DEBUG(N->dump(&DAG));
+ DOUT << "\nWith: "; DEBUG(Undef.Val->dump(&DAG));
+ DOUT << " and 2 other values\n";
+ DAG.ReplaceAllUsesOfValueWith(SDOperand(N, 0), Undef, &NowDead);
+ DAG.ReplaceAllUsesOfValueWith(SDOperand(N, 1),
+ DAG.getNode(ISD::UNDEF, N->getValueType(1)),
+ &NowDead);
+ DAG.ReplaceAllUsesOfValueWith(SDOperand(N, 2), Chain, &NowDead);
+ removeFromWorkList(N);
+ for (unsigned i = 0, e = NowDead.size(); i != e; ++i)
+ removeFromWorkList(NowDead[i]);
+ DAG.DeleteNode(N);
+ return SDOperand(N, 0); // Return N so it doesn't get rechecked!
}
}
}
Added: llvm/trunk/test/CodeGen/X86/2008-01-16-InvalidDAGCombineXform.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/2008-01-16-InvalidDAGCombineXform.ll?rev=46099&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/X86/2008-01-16-InvalidDAGCombineXform.ll (added)
+++ llvm/trunk/test/CodeGen/X86/2008-01-16-InvalidDAGCombineXform.ll Wed Jan 16 17:11:54 2008
@@ -0,0 +1,30 @@
+; RUN: llvm-as < %s | llc -march=x86 | not grep IMPLICIT_DEF
+
+ %struct.node_t = type { double*, %struct.node_t*, %struct.node_t**, double**, double*, i32, i32 }
+
+define void @localize_local_bb19_bb(%struct.node_t** %cur_node) {
+newFuncRoot:
+ %tmp1 = load %struct.node_t** %cur_node, align 4 ; <%struct.node_t*> [#uses=1]
+ %tmp2 = getelementptr %struct.node_t* %tmp1, i32 0, i32 4 ; <double**> [#uses=1]
+ %tmp3 = load double** %tmp2, align 4 ; <double*> [#uses=1]
+ %tmp4 = load %struct.node_t** %cur_node, align 4 ; <%struct.node_t*> [#uses=1]
+ %tmp5 = getelementptr %struct.node_t* %tmp4, i32 0, i32 4 ; <double**> [#uses=1]
+ store double* %tmp3, double** %tmp5, align 4
+ %tmp6 = load %struct.node_t** %cur_node, align 4 ; <%struct.node_t*> [#uses=1]
+ %tmp7 = getelementptr %struct.node_t* %tmp6, i32 0, i32 3 ; <double***> [#uses=1]
+ %tmp8 = load double*** %tmp7, align 4 ; <double**> [#uses=1]
+ %tmp9 = load %struct.node_t** %cur_node, align 4 ; <%struct.node_t*> [#uses=1]
+ %tmp10 = getelementptr %struct.node_t* %tmp9, i32 0, i32 3 ; <double***> [#uses=1]
+ store double** %tmp8, double*** %tmp10, align 4
+ %tmp11 = load %struct.node_t** %cur_node, align 4 ; <%struct.node_t*> [#uses=1]
+ %tmp12 = getelementptr %struct.node_t* %tmp11, i32 0, i32 0 ; <double**> [#uses=1]
+ %tmp13 = load double** %tmp12, align 4 ; <double*> [#uses=1]
+ %tmp14 = load %struct.node_t** %cur_node, align 4 ; <%struct.node_t*> [#uses=1]
+ %tmp15 = getelementptr %struct.node_t* %tmp14, i32 0, i32 0 ; <double**> [#uses=1]
+ store double* %tmp13, double** %tmp15, align 4
+ %tmp16 = load %struct.node_t** %cur_node, align 4 ; <%struct.node_t*> [#uses=1]
+ %tmp17 = getelementptr %struct.node_t* %tmp16, i32 0, i32 1 ; <%struct.node_t**> [#uses=1]
+ %tmp18 = load %struct.node_t** %tmp17, align 4 ; <%struct.node_t*> [#uses=1]
+ store %struct.node_t* %tmp18, %struct.node_t** %cur_node, align 4
+ ret void
+}
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