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Reimplement I32Clz without relying on LZCNT.

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This commit is contained in:
Nick Lewycky
2019-10-15 12:50:33 -07:00
parent caae21c065
commit cf3d2a830d
2 changed files with 61 additions and 6 deletions
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57
lib/singlepass-backend/src/codegen_x64.rs
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@ -2341,12 +2341,57 @@ impl FunctionCodeGenerator<CodegenError> for X64FunctionCode {
Condition::Equal,
Location::Imm32(0),
),
Operator::I32Clz => Self::emit_xcnt_i32(
a,
&mut self.machine,
&mut self.value_stack,
Assembler::emit_lzcnt,
),
Operator::I32Clz => {
let loc = get_location_released(a, &mut self.machine, self.value_stack.pop().unwrap());
let src = match loc {
Location::Imm32(_) | Location::Memory(_, _) => {
let tmp = self.machine.acquire_temp_gpr().unwrap();
a.emit_mov(Size::S32, loc, Location::GPR(tmp));
tmp
},
Location::GPR(reg) => reg,
_ => unreachable!(),
};
let ret = self.machine.acquire_locations(
a,
&[(WpType::I32, MachineValue::WasmStack(self.value_stack.len()))],
false,
)[0];
self.value_stack.push(ret);
let dst = match ret {
Location::Memory(_, _) => { self.machine.acquire_temp_gpr().unwrap() },
Location::GPR(reg) => reg,
_ => unreachable!(),
};
let zero_path = a.get_label();
let end = a.get_label();
a.emit_test_gpr_64(src);
a.emit_jmp(Condition::Equal, zero_path);
a.emit_bsr(Size::S32, Location::GPR(src), Location::GPR(dst));
a.emit_xor(Size::S32, Location::Imm32(31), Location::GPR(dst));
a.emit_jmp(Condition::None, end);
a.emit_label(zero_path);
a.emit_mov(Size::S32, Location::Imm32(32), Location::GPR(dst));
a.emit_label(end);
match loc {
Location::Imm32(_) | Location::Memory(_, _) => {
self.machine.release_temp_gpr(src);
},
_ => {}
};
match ret {
Location::Memory(_, _) => {
a.emit_mov(Size::S32, Location::GPR(dst), ret);
self.machine.release_temp_gpr(dst);
},
_ => {}
};
},
Operator::I32Ctz => Self::emit_xcnt_i32(
a,
&mut self.machine,