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tighten up recursion depth again

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llvm-svn: 37330
This commit is contained in:
Chris Lattner 2007-05-25 02:19:06 +00:00
parent 3eb349409f
commit 5161203d52
1 changed files with 13 additions and 11 deletions
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24
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -353,15 +353,15 @@ CombineTo(SDNode *N, SDOperand Res0, SDOperand Res1) {
/// specified expression for the same cost as the expression itself, or 2 if we
/// can compute the negated form more cheaply than the expression itself.
static char isNegatibleForFree(SDOperand Op, unsigned Depth = 0) {
// Don't recurse exponentially.
if (Depth > 6) return false;
// fneg is removable even if it has multiple uses.
if (Op.getOpcode() == ISD::FNEG) return 2;
// Don't allow anything with multiple uses.
if (!Op.hasOneUse()) return 0;
// Don't recurse exponentially.
if (Depth > 6) return 0;
switch (Op.getOpcode()) {
default: return false;
case ISD::ConstantFP:
@ -401,13 +401,15 @@ static char isNegatibleForFree(SDOperand Op, unsigned Depth = 0) {
/// GetNegatedExpression - If isNegatibleForFree returns true, this function
/// returns the newly negated expression.
static SDOperand GetNegatedExpression(SDOperand Op, SelectionDAG &DAG) {
static SDOperand GetNegatedExpression(SDOperand Op, SelectionDAG &DAG,
unsigned Depth = 0) {
// fneg is removable even if it has multiple uses.
if (Op.getOpcode() == ISD::FNEG) return Op.getOperand(0);
// Don't allow anything with multiple uses.
assert(Op.hasOneUse() && "Unknown reuse!");
assert(Depth <= 6 && "GetNegatedExpression doesn't match isNegatibleForFree");
switch (Op.getOpcode()) {
default: assert(0 && "Unknown code");
case ISD::ConstantFP:
@ -418,13 +420,13 @@ static SDOperand GetNegatedExpression(SDOperand Op, SelectionDAG &DAG) {
assert(UnsafeFPMath);
// -(A+B) -> -A - B
if (isNegatibleForFree(Op.getOperand(0)))
if (isNegatibleForFree(Op.getOperand(0), Depth+1))
return DAG.getNode(ISD::FSUB, Op.getValueType(),
GetNegatedExpression(Op.getOperand(0), DAG),
GetNegatedExpression(Op.getOperand(0), DAG, Depth+1),
Op.getOperand(1));
// -(A+B) -> -B - A
return DAG.getNode(ISD::FSUB, Op.getValueType(),
GetNegatedExpression(Op.getOperand(1), DAG),
GetNegatedExpression(Op.getOperand(1), DAG, Depth+1),
Op.getOperand(0));
case ISD::FSUB:
// We can't turn -(A-B) into B-A when we honor signed zeros.
@ -439,21 +441,21 @@ static SDOperand GetNegatedExpression(SDOperand Op, SelectionDAG &DAG) {
assert(!HonorSignDependentRoundingFPMath());
// -(X*Y) -> -X * Y
if (isNegatibleForFree(Op.getOperand(0)))
if (isNegatibleForFree(Op.getOperand(0), Depth+1))
return DAG.getNode(Op.getOpcode(), Op.getValueType(),
GetNegatedExpression(Op.getOperand(0), DAG),
GetNegatedExpression(Op.getOperand(0), DAG, Depth+1),
Op.getOperand(1));
// -(X*Y) -> X * -Y
return DAG.getNode(Op.getOpcode(), Op.getValueType(),
Op.getOperand(0),
GetNegatedExpression(Op.getOperand(1), DAG));
GetNegatedExpression(Op.getOperand(1), DAG, Depth+1));
case ISD::FP_EXTEND:
case ISD::FP_ROUND:
case ISD::FSIN:
return DAG.getNode(Op.getOpcode(), Op.getValueType(),
GetNegatedExpression(Op.getOperand(0), DAG));
GetNegatedExpression(Op.getOperand(0), DAG, Depth+1));
}
}