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Prevent folding of a node with multiple uses if the node already folds a load!

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Here is an example where the load ended up being done twice:

%A = global uint 0

uint %test(uint %B, ubyte %C) {
	%tmp = load uint *%A;
	%X = shl uint %tmp, ubyte %C
	%Cv = sub ubyte 32, %C
	%Y = shr uint %B, ubyte %Cv
	%Z = or uint %Y, %X
	store uint %Z, uint* %A
	ret uint %Z
}

==>

	subl $4, %esp
	movl %ebx, (%esp)
	movl 8(%esp), %edx
	movl A, %eax
	movb 12(%esp), %bl
	movb %bl, %cl
	shldl %cl, %edx, %eax
	movb %bl, %cl
	shldl %cl, %edx, A
	movl (%esp), %ebx
	addl $4, %esp
	ret

llvm-svn: 25471
This commit is contained in:
Evan Cheng 2006-01-20 01:11:03 +00:00
parent 40c6c91f56
commit d3713a9b9a
1 changed files with 9 additions and 6 deletions
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7
utils/TableGen/DAGISelEmitter.cpp
View File

@ -1907,18 +1907,21 @@ public:
// Emit code to load the child nodes and match their contents recursively.
unsigned OpNo = 0;
bool HasChain = NodeHasProperty(N, SDNodeInfo::SDNPHasChain, ISE);
bool NodeHasChain = NodeHasProperty(N, SDNodeInfo::SDNPHasChain, ISE);
bool HasChain = PatternHasProperty(N, SDNodeInfo::SDNPHasChain, ISE);
if (HasChain) {
if (NodeHasChain)
OpNo = 1;
if (!isRoot) {
const SDNodeInfo &CInfo = ISE.getSDNodeInfo(N->getOperator());
OS << " if (!" << RootName << ".hasOneUse()) goto P"
<< PatternNo << "Fail; // Multiple uses of actual result?\n";
if (NodeHasChain)
OS << " if (CodeGenMap.count(" << RootName
<< ".getValue(" << CInfo.getNumResults() << "))) goto P"
<< PatternNo << "Fail; // Already selected for a chain use?\n";
}
if (!FoundChain) {
if (NodeHasChain && !FoundChain) {
OS << " SDOperand Chain = " << RootName << ".getOperand(0);\n";
FoundChain = true;
}