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Change memory to little endian format. #161

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Change memory to little endian format. #161

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515c218
Change memory to little endian format.
Apr 24, 2024
2fbea65
wip
Apr 24, 2024
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12 changes: 6 additions & 6 deletions alu_u32/src/add/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -103,17 +103,17 @@ impl Add32Chip {

let mut carry_1 = 0;
let mut carry_2 = 0;
if b[3] as u32 + c[3] as u32 > 255 {
if b[0] as u32 + c[0] as u32 > 255 {
carry_1 = 1;
cols.carry[0] = F::one();
cols.carry[3] = F::one();
}
if b[2] as u32 + c[2] as u32 + carry_1 > 255 {
if b[1] as u32 + c[1] as u32 + carry_1 > 255 {
carry_2 = 1;
cols.carry[1] = F::one();
}
if b[1] as u32 + c[1] as u32 + carry_2 > 255 {
cols.carry[2] = F::one();
}
if b[2] as u32 + c[2] as u32 + carry_2 > 255 {
cols.carry[1] = F::one();
}
cols.is_real = F::one();
}
}
Expand Down
15 changes: 8 additions & 7 deletions machine/src/core.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -3,7 +3,7 @@ use core::cmp::Ordering;
use core::ops::{Add, BitAnd, BitOr, BitXor, Div, Index, IndexMut, Mul, Shl, Shr, Sub};
use p3_field::{Field, PrimeField};

// Currently stored in big-endian form.
// Stored in little-endian form, to avoid conversion between the compiler and the VM, and to be consistent with our file format.
#[derive(Copy, Clone, Debug, Default)]
pub struct Word<F>(pub [F; MEMORY_CELL_BYTES]);

Expand All @@ -18,6 +18,7 @@ pub fn addr_of_word(addr: u32) -> u32 {
(addr & !3) as u32
}

/// Check that an address is a multiple of 4.
pub fn is_mul_4(addr: u32) -> bool {
addr.rem_euclid(4) == 0
}
Expand All @@ -26,7 +27,7 @@ pub fn is_mul_4(addr: u32) -> bool {
impl Word<u8> {
pub fn from_u8(byte: u8) -> Self {
let mut result = [0; MEMORY_CELL_BYTES];
result[MEMORY_CELL_BYTES - 1] = byte;
result[0] = byte;
Self(result)
}
}
Expand All @@ -35,7 +36,7 @@ impl Word<u8> {
pub fn sign_extend_byte(byte: u8) -> Self {
let sign = byte as i8 >> 7;
let mut result: [u8; MEMORY_CELL_BYTES] = [sign as u8; MEMORY_CELL_BYTES];
result[3] = byte;
result[0] = byte;
Self(result)
}
}
Expand All @@ -56,7 +57,7 @@ impl<F: Copy> Word<F> {
{
let mut result: [T; MEMORY_CELL_BYTES] = [T::default(); MEMORY_CELL_BYTES];
for (i, item) in self.0.iter().enumerate() {
result[i] = f(*item);
result[3 - i] = f(*item);
}
Word(result)
}
Expand All @@ -76,7 +77,7 @@ impl Into<u32> for Word<u8> {
fn into(self) -> u32 {
let mut result = 0u32;
for i in 0..MEMORY_CELL_BYTES {
result += (self[MEMORY_CELL_BYTES - i - 1] as u32) << (i * 8);
result += (self[i] as u32) << (i * 8);
}
result
}
Expand All @@ -86,7 +87,7 @@ impl From<u32> for Word<u8> {
fn from(value: u32) -> Self {
let mut result = Word::<u8>::default();
for i in 0..MEMORY_CELL_BYTES {
result[MEMORY_CELL_BYTES - i - 1] = ((value >> (i * 8)) & 0xFF) as u8;
result[i] = ((value >> (i * 8)) & 0xFF) as u8;
}
result
}
Expand Down Expand Up @@ -272,7 +273,7 @@ impl BitOr for Word<u8> {

impl<F: Field> From<F> for Word<F> {
fn from(bytes: F) -> Self {
Self([F::zero(), F::zero(), F::zero(), bytes])
Self([bytes, F::zero(), F::zero(), F::zero()])
}
}

Expand Down
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