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CNTLZ alternative instructions

This commit is contained in:
Dr. Chat 2015-05-02 00:53:25 -05:00
parent 414e5b2d30
commit c464584e89
1 changed files with 101 additions and 7 deletions
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108
src/xenia/cpu/backend/x64/x64_sequences.cc
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@ -5203,25 +5203,119 @@ EMITTER_OPCODE_TABLE(
// ============================================================================
EMITTER(CNTLZ_I8, MATCH(I<OPCODE_CNTLZ, I8<>, I8<>>)) {
static void Emit(X64Emitter& e, const EmitArgType& i) {
// No 8bit lzcnt, so do 16 and sub 8.
e.movzx(i.dest.reg().cvt16(), i.src1);
e.lzcnt(i.dest.reg().cvt16(), i.dest.reg().cvt16());
e.sub(i.dest, 8);
if (e.cpu()->has(Xbyak::util::Cpu::tLZCNT)) {
// No 8bit lzcnt, so do 16 and sub 8.
e.movzx(i.dest.reg().cvt16(), i.src1);
e.lzcnt(i.dest.reg().cvt16(), i.dest.reg().cvt16());
e.sub(i.dest, 8);
} else {
e.inLocalLabel();
e.cmp(i.src1, 0); // Special case if number is 0
e.jne(".la"); // not 0, use bsr
e.mov(i.src1, 8); // If it's 0, the result should be 8
e.jmp(".lb");
// BSR: searches $2 until MSB 1 found, stores idx (from bit 0) in $1
// if input is 0, results are undefined
e.L(".la");
e.bsr(e.ebx, i.src1);
// sub: $1 = $1 - $2
// sub 7 from e.eax
e.mov(e.eax, 7);
e.sub(e.eax, e.ebx);
e.mov(i.dest, e.eax);
e.L(".lb");
e.outLocalLabel();
}
}
};
EMITTER(CNTLZ_I16, MATCH(I<OPCODE_CNTLZ, I8<>, I16<>>)) {
static void Emit(X64Emitter& e, const EmitArgType& i) {
e.lzcnt(i.dest.reg().cvt32(), i.src1);
if (e.cpu()->has(Xbyak::util::Cpu::tLZCNT)) {
// LZCNT: searches $2 until MSB 1 found, stores idx (from last bit) in $1
e.lzcnt(i.dest.reg().cvt32(), i.src1);
} else {
e.inLocalLabel();
e.cmp(i.src1, 0); // Special case if number is 0
e.jne(".la"); // not 0, use bsr
e.mov(i.src1, 16); // If it's 0, the result should be 16
e.jmp(".lb");
// BSR: searches $2 until MSB 1 found, stores idx (from bit 0) in $1
// if input is 0, results are undefined
e.L(".la");
e.bsr(e.ebx, i.src1);
// sub: $1 = $1 - $2
// sub 16 from e.eax
e.mov(e.eax, 15);
e.sub(e.eax, e.ebx);
e.mov(i.dest, e.eax);
e.L(".lb");
e.outLocalLabel();
}
}
};
EMITTER(CNTLZ_I32, MATCH(I<OPCODE_CNTLZ, I8<>, I32<>>)) {
static void Emit(X64Emitter& e, const EmitArgType& i) {
e.lzcnt(i.dest.reg().cvt32(), i.src1);
if (e.cpu()->has(Xbyak::util::Cpu::tLZCNT)) {
e.lzcnt(i.dest.reg().cvt32(), i.src1);
} else {
e.DebugBreak();
e.inLocalLabel();
e.cmp(i.src1, 0); // Special case if number is 0
e.jne(".la"); // not 0, use bsr
e.mov(i.src1, 32); // If it's 0, the result should be 32
e.jmp(".lb");
// BSR: searches $2 until MSB 1 found, stores idx (from bit 0) in $1
// if input is 0, results are undefined
e.L(".la");
e.bsr(e.ebx, i.src1);
// sub: $1 = $1 - $2
// sub 32 from e.eax
e.mov(e.eax, 31);
e.sub(e.eax, e.ebx);
e.mov(i.dest, e.eax);
e.L(".lb");
e.outLocalLabel();
}
}
};
EMITTER(CNTLZ_I64, MATCH(I<OPCODE_CNTLZ, I8<>, I64<>>)) {
static void Emit(X64Emitter& e, const EmitArgType& i) {
e.lzcnt(i.dest.reg().cvt64(), i.src1);
if (e.cpu()->has(Xbyak::util::Cpu::tLZCNT)) {
e.lzcnt(i.dest.reg().cvt64(), i.src1);
} else {
e.inLocalLabel();
e.cmp(i.src1, 0); // Special case if number is 0
e.jne(".la"); // not 0, use bsr
e.mov(i.src1, 64); // If it's 0, the result should be 64
e.jmp(".lb");
// BSR: searches $2 until MSB 1 found, stores idx (from bit 0) in $1
// if input is 0, results are undefined
e.L(".la");
e.bsr(e.rbx, i.src1);
// sub: $1 = $1 - $2
// sub 64 from e.rax
e.mov(e.rax, 63);
e.sub(e.rax, e.ebx);
e.mov(i.dest, e.rax);
e.L(".lb");
e.outLocalLabel();
}
}
};
EMITTER_OPCODE_TABLE(