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* if ANDing with a constant of the form:

Browse Source 
0x00000..00FFF..FF
      ^      ^
      ^      ^
    any number of
    0's followed by
    some number of
    1's

    then we use dep.z to just paste zeros over the input. For the special
    cases where this is zxt1/zxt2/zxt4, we use those instructions instead,
    because we're all about readability!!!
    that's what it's about!! readability!

  *twitch* ;D


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@21279 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Duraid Madina 2005-04-13 04:50:54 +00:00
parent 003e68e442
commit c02780eed1
1 changed files with 45 additions and 2 deletions
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47
lib/Target/IA64/IA64ISelPattern.cpp
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@ -445,7 +445,7 @@ void ISel::InstructionSelectBasicBlock(SelectionDAG &DAG) {
/// ExactLog2 - This function solves for (Val == 1 << (N-1)) and returns N. It
/// returns zero when the input is not exactly a power of two.
static uint64_t ExactLog2(uint64_t Val) {
static unsigned ExactLog2(uint64_t Val) {
if (Val == 0 || (Val & (Val-1))) return 0;
unsigned Count = 0;
while (Val != 1) {
@ -455,6 +455,17 @@ static uint64_t ExactLog2(uint64_t Val) {
return Count;
}
/// ExactLog2sub1 - This function solves for (Val == (1 << (N-1))-1)
/// and returns N. It returns 666 if Val is not 2^n -1 for some n.
static unsigned ExactLog2sub1(uint64_t Val) {
unsigned int n;
for(n=0; n<64; n++) {
if(Val==(uint64_t)((1<<n)-1))
return n;
}
return 666;
}
/// ponderIntegerDivisionBy - When handling integer divides, if the divide
/// is by a constant such that we can efficiently codegen it, this
/// function says what to do. Currently, it returns 0 if the division must
@ -474,6 +485,19 @@ static unsigned ponderIntegerDivisionBy(SDOperand N, bool isSigned,
return 0; // fallthrough
}
static unsigned ponderIntegerAndWith(SDOperand N, unsigned& Imm) {
if (N.getOpcode() != ISD::Constant) return 0; // if not ANDing with
// a constant, give up.
int64_t v = (int64_t)cast<ConstantSDNode>(N)->getSignExtended();
if ((Imm = ExactLog2sub1(v))!=666) { // if ANDing with ((2^n)-1) for some n
return 1; // say so
}
return 0; // fallthrough
}
static unsigned ponderIntegerAdditionWith(SDOperand N, unsigned& Imm) {
if (N.getOpcode() != ISD::Constant) return 0; // if not adding a
// constant, give up.
@ -967,15 +991,34 @@ assert(0 && "hmm, ISD::SIGN_EXTEND: shouldn't ever be reached. bad luck!\n");
.addReg(bogusTemp1).addReg(IA64::r0).addReg(IA64::r0).addReg(pTemp);
break;
}
// if not a bool, we just AND away:
case MVT::i8:
case MVT::i16:
case MVT::i32:
case MVT::i64: {
Tmp1 = SelectExpr(N.getOperand(0));
switch (ponderIntegerAndWith(N.getOperand(1), Tmp3)) {
case 1: // ANDing a constant that is 2^n-1 for some n
switch (Tmp3) {
case 8: // if AND 0x00000000000000FF, be quaint and use zxt1
BuildMI(BB, IA64::ZXT1, 1, Result).addReg(Tmp1);
break;
case 16: // if AND 0x000000000000FFFF, be quaint and use zxt2
BuildMI(BB, IA64::ZXT2, 1, Result).addReg(Tmp1);
break;
case 32: // if AND 0x00000000FFFFFFFF, be quaint and use zxt4
BuildMI(BB, IA64::ZXT4, 1, Result).addReg(Tmp1);
break;
default: // otherwise, use dep.z to paste zeros
BuildMI(BB, IA64::DEPZ, 3, Result).addReg(Tmp1)
.addImm(0).addImm(Tmp3);
break;
}
return Result; // early exit
} // fallthrough and emit a simple AND:
Tmp2 = SelectExpr(N.getOperand(1));
BuildMI(BB, IA64::AND, 2, Result).addReg(Tmp1).addReg(Tmp2);
break;
}
}
return Result;