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1) With X86 lowering change, the following can no longer happen since 

the branch's chain is also produced by cmp.
          [ch, r : ld]
             ^ ^
             | |
      [XX]--/   \- [flag : cmp]
       ^             ^
       |             |
       \---[br flag]-

Remove an isel check which prevents loads from being folded into cmp / test
instructions.

2) Whenever possible, delete a selected node to allow more load folding
opportunities. Note not all nodes can be deleted after it has been
selected. Some may have simply morphed; some have not changed at all (e.g.
EntryToken).

llvm-svn: 30242
This commit is contained in:
Evan Cheng 2006-09-11 02:24:43 +00:00
parent 4259a0f654
commit 1ec61ba00a
1 changed files with 16 additions and 19 deletions
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35
llvm/utils/TableGen/DAGISelEmitter.cpp
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@ -2246,24 +2246,6 @@ public:
emitCheck(RootName + ".hasOneUse()");
EmittedUseCheck = true;
if (NodeHasChain) {
// FIXME: Don't fold if 1) the parent node writes a flag, 2) the node
// has a chain use.
// This a workaround for this problem:
//
// [ch, r : ld]
// ^ ^
// | |
// [XX]--/ \- [flag : cmp]
// ^ ^
// | |
// \---[br flag]-
//
// cmp + br should be considered as a single node as they are flagged
// together. So, if the ld is folded into the cmp, the XX node in the
// graph is now both an operand and a use of the ld/cmp/br node.
if (NodeHasProperty(P, SDNodeInfo::SDNPOutFlag, ISE))
emitCheck(ParentName + ".Val->isOnlyUse(" + RootName + ".Val)");
// If the immediate use can somehow reach this node through another
// path, then can't fold it either or it will create a cycle.
// e.g. In the following diagram, XX can reach ld through YY. If
@ -3629,6 +3611,16 @@ OS << " unsigned NumKilled = ISelKilled.size();\n";
OS << " RemoveKilled();\n";
OS << "}\n\n";
OS << "void DeleteNode(SDNode *N) {\n";
OS << " CurDAG->DeleteNode(N);\n";
OS << " for (SDNode::op_iterator I = N->op_begin(), E = N->op_end(); "
<< "I != E; ++I) {\n";
OS << " SDNode *Operand = I->Val;\n";
OS << " if (Operand->use_empty())\n";
OS << " DeleteNode(Operand);\n";
OS << " }\n";
OS << "}\n";
OS << "// SelectRoot - Top level entry to DAG isel.\n";
OS << "SDOperand SelectRoot(SDOperand Root) {\n";
OS << " SelectRootInit();\n";
@ -3649,7 +3641,12 @@ OS << " unsigned NumKilled = ISelKilled.size();\n";
OS << " ISelQueue.pop_back();\n";
OS << " if (!isSelected(Node->getNodeId())) {\n";
OS << " SDNode *ResNode = Select(SDOperand(Node, 0));\n";
OS << " if (ResNode && ResNode != Node) ReplaceUses(Node, ResNode);\n";
OS << " if (ResNode != Node) {\n";
OS << " if (ResNode)\n";
OS << " ReplaceUses(Node, ResNode);\n";
OS << " if (Node->use_empty()) // Don't delete EntryToken, etc.\n";
OS << " DeleteNode(Node);\n";
OS << " }\n";
OS << " }\n";
OS << " }\n";
OS << "\n";