mirror of
https://github.com/RPCS3/llvm-mirror.git
synced 2024-12-05 02:07:56 +00:00
[SelectionDAG] Fix CombineToPreIndexedLoadStore O(n^2) behavior
This patch consists of two parts: a performance fix in DAGCombiner.cpp and a correctness fix in SelectionDAG.cpp. The test case tests the bug that's uncovered by the performance fix, and fixed by the correctness fix. The performance fix keeps the containers required by the hasPredecessorHelper (which is a lazy DFS) and reuse them. Since hasPredecessorHelper is called in a loop, the overall efficiency reduced from O(n^2) to O(n), where n is the number of SDNodes. The correctness fix keeps iterating the neighbor list even if it's time to early return. It will return after finishing adding all neighbors to Worklist, so that no neighbors are discarded due to the original early return. llvm-svn: 259691
This commit is contained in:
parent
0262ca1fce
commit
c6dc619045
@ -9593,6 +9593,10 @@ bool DAGCombiner::CombineToPreIndexedLoadStore(SDNode *N) {
|
||||
return false;
|
||||
}
|
||||
|
||||
// Caches for hasPredecessorHelper.
|
||||
SmallPtrSet<const SDNode *, 32> Visited;
|
||||
SmallVector<const SDNode *, 16> Worklist;
|
||||
|
||||
// If the offset is a constant, there may be other adds of constants that
|
||||
// can be folded with this one. We should do this to avoid having to keep
|
||||
// a copy of the original base pointer.
|
||||
@ -9607,7 +9611,7 @@ bool DAGCombiner::CombineToPreIndexedLoadStore(SDNode *N) {
|
||||
if (Use.getUser() == Ptr.getNode() || Use != BasePtr)
|
||||
continue;
|
||||
|
||||
if (Use.getUser()->isPredecessorOf(N))
|
||||
if (N->hasPredecessorHelper(Use.getUser(), Visited, Worklist))
|
||||
continue;
|
||||
|
||||
if (Use.getUser()->getOpcode() != ISD::ADD &&
|
||||
@ -9637,10 +9641,6 @@ bool DAGCombiner::CombineToPreIndexedLoadStore(SDNode *N) {
|
||||
// Now check for #3 and #4.
|
||||
bool RealUse = false;
|
||||
|
||||
// Caches for hasPredecessorHelper
|
||||
SmallPtrSet<const SDNode *, 32> Visited;
|
||||
SmallVector<const SDNode *, 16> Worklist;
|
||||
|
||||
for (SDNode *Use : Ptr.getNode()->uses()) {
|
||||
if (Use == N)
|
||||
continue;
|
||||
|
@ -6949,13 +6949,16 @@ SDNode::hasPredecessorHelper(const SDNode *N,
|
||||
// Haven't visited N yet. Continue the search.
|
||||
while (!Worklist.empty()) {
|
||||
const SDNode *M = Worklist.pop_back_val();
|
||||
bool Found = false;
|
||||
for (const SDValue &OpV : M->op_values()) {
|
||||
SDNode *Op = OpV.getNode();
|
||||
if (Visited.insert(Op).second)
|
||||
Worklist.push_back(Op);
|
||||
if (Op == N)
|
||||
return true;
|
||||
Found = true;
|
||||
}
|
||||
if (Found)
|
||||
return true;
|
||||
}
|
||||
|
||||
return false;
|
||||
|
25
test/CodeGen/PowerPC/combine-to-pre-index-store-crash.ll
Normal file
25
test/CodeGen/PowerPC/combine-to-pre-index-store-crash.ll
Normal file
@ -0,0 +1,25 @@
|
||||
; RUN: llc -mtriple=powerpc64le-unknown-linux-gnu < %s | FileCheck %s
|
||||
|
||||
; CHECK-LABEL: TestFoo:
|
||||
; CHECK: std
|
||||
; CHECK: bl TestBar
|
||||
; CHECK: stbu
|
||||
; CHECK: std
|
||||
; CHECK: blr
|
||||
|
||||
%StructA = type <{ i64, { i64, i64 }, { i64, i64 } }>
|
||||
|
||||
define void @TestFoo(%StructA* %this) {
|
||||
%tmp = getelementptr inbounds %StructA, %StructA* %this, i64 0, i32 1
|
||||
%tmp11 = getelementptr inbounds %StructA, %StructA* %this, i64 0, i32 1, i32 1
|
||||
%tmp12 = bitcast { i64, i64 }* %tmp to i64**
|
||||
store i64* %tmp11, i64** %tmp12
|
||||
call void @TestBar()
|
||||
%tmp13 = getelementptr inbounds %StructA, %StructA* %this, i64 0, i32 2, i32 1
|
||||
store i64* %tmp13, i64** undef
|
||||
%.cast.i.i.i = bitcast i64* %tmp13 to i8*
|
||||
store i8 0, i8* %.cast.i.i.i
|
||||
ret void
|
||||
}
|
||||
|
||||
declare void @TestBar()
|
Loading…
Reference in New Issue
Block a user