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Add support for CombineTo, allowing the dag combiner to replace nodes with

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multiple results.

Use this support to implement trivial store->load forwarding, implementing
CodeGen/PowerPC/store-load-fwd.ll.  Though this is the most simple case and
can be extended in the future, it is still useful.  For example, it speeds
up 197.parser by 6.2% by avoiding an LSU reject in xalloc:

        stw r6, lo16(l5_end_of_array)(r2)
        addi r2, r5, -4
        stwx r5, r4, r2
-       lwzx r5, r4, r2
-       rlwinm r5, r5, 0, 0, 30
        stwx r5, r4, r2
        lwz r2, -4(r4)
        ori r2, r2, 1


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@23690 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2005-10-10 22:04:48 +00:00
parent e64dfbc10b
commit 01a2202138
1 changed files with 56 additions and 2 deletions
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58
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -23,7 +23,6 @@
// FIXME: select C, pow2, pow2 -> something smart
// FIXME: trunc(select X, Y, Z) -> select X, trunc(Y), trunc(Z)
// FIXME: (select C, load A, load B) -> load (select C, A, B)
// FIXME: store -> load -> forward substitute
// FIXME: Dead stores -> nuke
// FIXME: shr X, (and Y,31) -> shr X, Y
// FIXME: TRUNC (LOAD) -> EXT_LOAD/LOAD(smaller)
@ -36,6 +35,7 @@
// FIXME: divide by zero is currently left unfolded. do we want to turn this
// into an undef?
// FIXME: select ne (select cc, 1, 0), 0, true, false -> select cc, true, false
// FIXME: reassociate (X+C)+Y into (X+Y)+C if the inner expression has one use
//
//===----------------------------------------------------------------------===//
@ -76,6 +76,37 @@ namespace {
WorkList.end());
}
SDOperand CombineTo(SDNode *N, const std::vector<SDOperand> &To) {
DEBUG(std::cerr << "\nReplacing "; N->dump();
std::cerr << "\nWith: "; To[0].Val->dump();
std::cerr << " and " << To.size()-1 << " other values\n");
std::vector<SDNode*> NowDead;
DAG.ReplaceAllUsesWith(N, To, &NowDead);
// Push the new nodes and any users onto the worklist
for (unsigned i = 0, e = To.size(); i != e; ++i) {
WorkList.push_back(To[i].Val);
AddUsersToWorkList(To[i].Val);
}
// Nodes can end up on the worklist more than once. Make sure we do
// not process a node that has been replaced.
removeFromWorkList(N);
for (unsigned i = 0, e = NowDead.size(); i != e; ++i)
removeFromWorkList(NowDead[i]);
// Finally, since the node is now dead, remove it from the graph.
DAG.DeleteNode(N);
return SDOperand(N, 0);
}
SDOperand CombineTo(SDNode *N, SDOperand Res0, SDOperand Res1) {
std::vector<SDOperand> To;
To.push_back(Res0);
To.push_back(Res1);
return CombineTo(N, To);
}
/// visit - call the node-specific routine that knows how to fold each
/// particular type of node.
SDOperand visit(SDNode *N);
@ -84,6 +115,7 @@ namespace {
// node types. The semantics are as follows:
// Return Value:
// SDOperand.Val == 0 - No change was made
// SDOperand.Val == N - N was replaced, is dead, and is already handled.
// otherwise - N should be replaced by the returned Operand.
//
SDOperand visitTokenFactor(SDNode *N);
@ -132,6 +164,8 @@ namespace {
SDOperand visitBR_CC(SDNode *N);
SDOperand visitBRTWOWAY_CC(SDNode *N);
SDOperand visitLOAD(SDNode *N);
SDOperand SimplifySelect(SDOperand N0, SDOperand N1, SDOperand N2);
SDOperand SimplifySelectCC(SDOperand N0, SDOperand N1, SDOperand N2,
SDOperand N3, ISD::CondCode CC);
@ -334,7 +368,8 @@ void DAGCombiner::Run(bool RunningAfterLegalize) {
DEBUG(std::cerr << "\nReplacing "; N->dump();
std::cerr << "\nWith: "; RV.Val->dump();
std::cerr << '\n');
DAG.ReplaceAllUsesWith(N, std::vector<SDOperand>(1, RV));
std::vector<SDNode*> NowDead;
DAG.ReplaceAllUsesWith(N, std::vector<SDOperand>(1, RV), &NowDead);
// Push the new node and any users onto the worklist
WorkList.push_back(RV.Val);
@ -343,6 +378,8 @@ void DAGCombiner::Run(bool RunningAfterLegalize) {
// Nodes can end up on the worklist more than once. Make sure we do
// not process a node that has been replaced.
removeFromWorkList(N);
for (unsigned i = 0, e = NowDead.size(); i != e; ++i)
removeFromWorkList(NowDead[i]);
// Finally, since the node is now dead, remove it from the graph.
DAG.DeleteNode(N);
@ -401,6 +438,7 @@ SDOperand DAGCombiner::visit(SDNode *N) {
case ISD::BRCONDTWOWAY: return visitBRCONDTWOWAY(N);
case ISD::BR_CC: return visitBR_CC(N);
case ISD::BRTWOWAY_CC: return visitBRTWOWAY_CC(N);
case ISD::LOAD: return visitLOAD(N);
}
return SDOperand();
}
@ -1513,6 +1551,22 @@ SDOperand DAGCombiner::visitBRTWOWAY_CC(SDNode *N) {
return SDOperand();
}
SDOperand DAGCombiner::visitLOAD(SDNode *N) {
SDOperand Chain = N->getOperand(0);
SDOperand Ptr = N->getOperand(1);
SDOperand SrcValue = N->getOperand(2);
// If this load is directly stored, replace the load value with the stored
// value.
// TODO: Handle store large -> read small portion.
// TODO: Handle TRUNCSTORE/EXTLOAD
if (Chain.getOpcode() == ISD::STORE && Chain.getOperand(2) == Ptr &&
Chain.getOperand(1).getValueType() == N->getValueType(0))
return CombineTo(N, Chain.getOperand(1), Chain);
return SDOperand();
}
SDOperand DAGCombiner::SimplifySelect(SDOperand N0, SDOperand N1, SDOperand N2){
assert(N0.getOpcode() ==ISD::SETCC && "First argument must be a SetCC node!");