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Merge pull request #257 from arpankapoor/master

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Optimize bitreverse codegen
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antoyo 2023-03-28 17:15:12 -04:00 committed by GitHub
commit ade3739c07
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3 changed files with 40 additions and 125 deletions
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3
example/mini_core_hello_world.rs
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@ -168,6 +168,9 @@ fn main() {
world as Box<dyn SomeTrait>;
assert_eq!(intrinsics::bitreverse(0b10101000u8), 0b00010101u8);
assert_eq!(intrinsics::bitreverse(0xddccu16), 0x33bbu16);
assert_eq!(intrinsics::bitreverse(0xffee_ddccu32), 0x33bb77ffu32);
assert_eq!(intrinsics::bitreverse(0x1234_5678_ffee_ddccu64), 0x33bb77ff1e6a2c48u64);
assert_eq!(intrinsics::bswap(0xabu8), 0xabu8);
assert_eq!(intrinsics::bswap(0xddccu16), 0xccddu16);

1
example/std_example.rs
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@ -58,6 +58,7 @@ fn main() {
assert_eq!(0b0000000000000000000000000010000010000000000000000000000000000000_0000000000100000000000000000000000001000000000000100000000000000u128.leading_zeros(), 26);
assert_eq!(0b0000000000000000000000000010000000000000000000000000000000000000_0000000000000000000000000000000000001000000000000000000010000000u128.trailing_zeros(), 7);
assert_eq!(0x1234_5678_ffee_ddcc_1234_5678_ffee_ddccu128.reverse_bits(), 0x33bb77ff1e6a2c4833bb77ff1e6a2c48u128);
let _d = 0i128.checked_div(2i128);
let _d = 0u128.checked_div(2u128);

161
src/intrinsic/mod.rs
View File

@ -549,141 +549,52 @@ fn bit_reverse(&mut self, width: u64, value: RValue<'gcc>) -> RValue<'gcc> {
let context = &self.cx.context;
let result =
match width {
8 => {
8 | 16 | 32 | 64 => {
let mask = ((1u128 << width) - 1) as u64;
let (m0, m1, m2) = if width > 16 {
(
context.new_rvalue_from_long(typ, (0x5555555555555555u64 & mask) as i64),
context.new_rvalue_from_long(typ, (0x3333333333333333u64 & mask) as i64),
context.new_rvalue_from_long(typ, (0x0f0f0f0f0f0f0f0fu64 & mask) as i64),
)
} else {
(
context.new_rvalue_from_int(typ, (0x5555u64 & mask) as i32),
context.new_rvalue_from_int(typ, (0x3333u64 & mask) as i32),
context.new_rvalue_from_int(typ, (0x0f0fu64 & mask) as i32),
)
};
let one = context.new_rvalue_from_int(typ, 1);
let two = context.new_rvalue_from_int(typ, 2);
let four = context.new_rvalue_from_int(typ, 4);
// First step.
let left = self.and(value, context.new_rvalue_from_int(typ, 0xF0));
let left = self.lshr(left, context.new_rvalue_from_int(typ, 4));
let right = self.and(value, context.new_rvalue_from_int(typ, 0x0F));
let right = self.shl(right, context.new_rvalue_from_int(typ, 4));
let left = self.lshr(value, one);
let left = self.and(left, m0);
let right = self.and(value, m0);
let right = self.shl(right, one);
let step1 = self.or(left, right);
// Second step.
let left = self.and(step1, context.new_rvalue_from_int(typ, 0xCC));
let left = self.lshr(left, context.new_rvalue_from_int(typ, 2));
let right = self.and(step1, context.new_rvalue_from_int(typ, 0x33));
let right = self.shl(right, context.new_rvalue_from_int(typ, 2));
let left = self.lshr(step1, two);
let left = self.and(left, m1);
let right = self.and(step1, m1);
let right = self.shl(right, two);
let step2 = self.or(left, right);
// Third step.
let left = self.and(step2, context.new_rvalue_from_int(typ, 0xAA));
let left = self.lshr(left, context.new_rvalue_from_int(typ, 1));
let right = self.and(step2, context.new_rvalue_from_int(typ, 0x55));
let right = self.shl(right, context.new_rvalue_from_int(typ, 1));
let step3 = self.or(left, right);
step3
},
16 => {
// First step.
let left = self.and(value, context.new_rvalue_from_int(typ, 0x5555));
let left = self.shl(left, context.new_rvalue_from_int(typ, 1));
let right = self.and(value, context.new_rvalue_from_int(typ, 0xAAAA));
let right = self.lshr(right, context.new_rvalue_from_int(typ, 1));
let step1 = self.or(left, right);
// Second step.
let left = self.and(step1, context.new_rvalue_from_int(typ, 0x3333));
let left = self.shl(left, context.new_rvalue_from_int(typ, 2));
let right = self.and(step1, context.new_rvalue_from_int(typ, 0xCCCC));
let right = self.lshr(right, context.new_rvalue_from_int(typ, 2));
let step2 = self.or(left, right);
// Third step.
let left = self.and(step2, context.new_rvalue_from_int(typ, 0x0F0F));
let left = self.shl(left, context.new_rvalue_from_int(typ, 4));
let right = self.and(step2, context.new_rvalue_from_int(typ, 0xF0F0));
let right = self.lshr(right, context.new_rvalue_from_int(typ, 4));
let left = self.lshr(step2, four);
let left = self.and(left, m2);
let right = self.and(step2, m2);
let right = self.shl(right, four);
let step3 = self.or(left, right);
// Fourth step.
let left = self.and(step3, context.new_rvalue_from_int(typ, 0x00FF));
let left = self.shl(left, context.new_rvalue_from_int(typ, 8));
let right = self.and(step3, context.new_rvalue_from_int(typ, 0xFF00));
let right = self.lshr(right, context.new_rvalue_from_int(typ, 8));
let step4 = self.or(left, right);
step4
},
32 => {
// TODO(antoyo): Refactor with other implementations.
// First step.
let left = self.and(value, context.new_rvalue_from_long(typ, 0x55555555));
let left = self.shl(left, context.new_rvalue_from_long(typ, 1));
let right = self.and(value, context.new_rvalue_from_long(typ, 0xAAAAAAAA));
let right = self.lshr(right, context.new_rvalue_from_long(typ, 1));
let step1 = self.or(left, right);
// Second step.
let left = self.and(step1, context.new_rvalue_from_long(typ, 0x33333333));
let left = self.shl(left, context.new_rvalue_from_long(typ, 2));
let right = self.and(step1, context.new_rvalue_from_long(typ, 0xCCCCCCCC));
let right = self.lshr(right, context.new_rvalue_from_long(typ, 2));
let step2 = self.or(left, right);
// Third step.
let left = self.and(step2, context.new_rvalue_from_long(typ, 0x0F0F0F0F));
let left = self.shl(left, context.new_rvalue_from_long(typ, 4));
let right = self.and(step2, context.new_rvalue_from_long(typ, 0xF0F0F0F0));
let right = self.lshr(right, context.new_rvalue_from_long(typ, 4));
let step3 = self.or(left, right);
// Fourth step.
let left = self.and(step3, context.new_rvalue_from_long(typ, 0x00FF00FF));
let left = self.shl(left, context.new_rvalue_from_long(typ, 8));
let right = self.and(step3, context.new_rvalue_from_long(typ, 0xFF00FF00));
let right = self.lshr(right, context.new_rvalue_from_long(typ, 8));
let step4 = self.or(left, right);
// Fifth step.
let left = self.and(step4, context.new_rvalue_from_long(typ, 0x0000FFFF));
let left = self.shl(left, context.new_rvalue_from_long(typ, 16));
let right = self.and(step4, context.new_rvalue_from_long(typ, 0xFFFF0000));
let right = self.lshr(right, context.new_rvalue_from_long(typ, 16));
let step5 = self.or(left, right);
step5
},
64 => {
// First step.
let left = self.shl(value, context.new_rvalue_from_long(typ, 32));
let right = self.lshr(value, context.new_rvalue_from_long(typ, 32));
let step1 = self.or(left, right);
// Second step.
let left = self.and(step1, context.new_rvalue_from_long(typ, 0x0001FFFF0001FFFF));
let left = self.shl(left, context.new_rvalue_from_long(typ, 15));
let right = self.and(step1, context.new_rvalue_from_long(typ, 0xFFFE0000FFFE0000u64 as i64)); // TODO(antoyo): transmute the number instead?
let right = self.lshr(right, context.new_rvalue_from_long(typ, 17));
let step2 = self.or(left, right);
// Third step.
let left = self.lshr(step2, context.new_rvalue_from_long(typ, 10));
let left = self.xor(step2, left);
let temp = self.and(left, context.new_rvalue_from_long(typ, 0x003F801F003F801F));
let left = self.shl(temp, context.new_rvalue_from_long(typ, 10));
let left = self.or(temp, left);
let step3 = self.xor(left, step2);
// Fourth step.
let left = self.lshr(step3, context.new_rvalue_from_long(typ, 4));
let left = self.xor(step3, left);
let temp = self.and(left, context.new_rvalue_from_long(typ, 0x0E0384210E038421));
let left = self.shl(temp, context.new_rvalue_from_long(typ, 4));
let left = self.or(temp, left);
let step4 = self.xor(left, step3);
// Fifth step.
let left = self.lshr(step4, context.new_rvalue_from_long(typ, 2));
let left = self.xor(step4, left);
let temp = self.and(left, context.new_rvalue_from_long(typ, 0x2248884222488842));
let left = self.shl(temp, context.new_rvalue_from_long(typ, 2));
let left = self.or(temp, left);
let step5 = self.xor(left, step4);
step5
if width == 8 {
step3
} else {
self.gcc_bswap(step3, width)
}
},
128 => {
// TODO(antoyo): find a more efficient implementation?