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expand count-leading/trailing-zeros; the test 2005-05-11-Popcount-ffs-fls.c

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should now pass (the "LLVM" and "REF" results should be identical)


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@21866 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Duraid Madina 2005-05-11 08:45:08 +00:00
parent 07fc17371b
commit 57ff7e5f64
1 changed files with 32 additions and 19 deletions
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51
lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
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@ -1132,27 +1132,40 @@ SDOperand SelectionDAGLegalize::LegalizeOp(SDOperand Op) {
Result = Tmp1;
break;
}
case ISD::CTTZ:
/* This should be used for targets that support ctpop:
int nlz5(unsigned x) {
int pop(unsigned x);
x = x | (x >> 1);
x = x | (x >> 2);
x = x | (x >> 4);
x = x | (x >> 8);
x = x | (x >>16);
return ctpop(~x);
}
See also: http://www.hackersdelight.org/HDcode/nlz.cc
*/
assert(0 && "Cannot expand this yet!");
case ISD::CTLZ: {
/* for now, we do this:
x = x | (x >> 1);
x = x | (x >> 2);
...
x = x | (x >>16);
x = x | (x >>32); // for 64-bit input
return popcount(~x);
but see also: http://www.hackersdelight.org/HDcode/nlz.cc */
MVT::ValueType VT = Tmp1.getValueType();
MVT::ValueType ShVT = TLI.getShiftAmountTy();
unsigned len = getSizeInBits(VT);
for (unsigned i = 0; (1U << i) <= (len / 2); ++i) {
Tmp3 = DAG.getConstant(1ULL << i, ShVT);
Tmp1 = DAG.getNode(ISD::OR, VT, Tmp1,
DAG.getNode(ISD::SRL, VT, Tmp1, Tmp3));
}
Tmp3 = DAG.getNode(ISD::XOR, VT, Tmp1, DAG.getConstant(~0ULL, VT));
Result = DAG.getNode(ISD::CTPOP, VT, Tmp3);
break;
case ISD::CTLZ:
// See Also: http://www.hackersdelight.org/HDcode/ntz.cc
assert(0 && "Cannot expand this yet!");
}
case ISD::CTTZ: {
// for now, we use: { return popcount(~x & (x - 1)); }
// but see also http://www.hackersdelight.org/HDcode/ntz.cc )
MVT::ValueType VT = Tmp1.getValueType();
Tmp2 = DAG.getConstant(~0ULL, VT);
Tmp3 = DAG.getNode(ISD::AND, VT,
DAG.getNode(ISD::XOR, VT, Tmp1, Tmp2),
DAG.getNode(ISD::SUB, VT, Tmp1,
DAG.getConstant(1, VT)));
Result = DAG.getNode(ISD::CTPOP, VT, Tmp3);
break;
}
default:
assert(0 && "Cannot expand this yet!");
break;