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Jorge Aparicio
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Merge pull request #25 from japaric/udivmoddi4
port udivmoddi4 and __aeabi_uldivmod
2 parents c4142ed + eb20684 commit 4ab4465

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6 files changed

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6 files changed

+392
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‎Cargo.toml

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Original file line numberDiff line numberDiff line change
@@ -2,3 +2,6 @@
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authors = ["Jorge Aparicio <[email protected]>"]
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name = "rustc_builtins"
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version = "0.1.0"
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[dev-dependencies]
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quickcheck = "0.3.1"

‎ci/install.sh

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Original file line numberDiff line numberDiff line change
@@ -49,19 +49,19 @@ install_c_toolchain() {
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;;
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mips-unknown-linux-gnu)
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apt-get install -y --no-install-recommends \
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gcc-mips-linux-gnu libc6-dev-mips-cross
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gcc gcc-mips-linux-gnu libc6-dev libc6-dev-mips-cross
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;;
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mipsel-unknown-linux-gnu)
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apt-get install -y --no-install-recommends \
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gcc-mipsel-linux-gnu libc6-dev-mipsel-cross
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gcc gcc-mipsel-linux-gnu libc6-dev libc6-dev-mipsel-cross
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;;
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powerpc64-unknown-linux-gnu)
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apt-get install -y --no-install-recommends \
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gcc-powerpc64-linux-gnu libc6-dev-ppc64-cross
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gcc gcc-powerpc64-linux-gnu libc6-dev libc6-dev-ppc64-cross
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;;
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powerpc64le-unknown-linux-gnu)
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apt-get install -y --no-install-recommends \
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gcc-powerpc64le-linux-gnu libc6-dev-ppc64el-cross
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gcc gcc-powerpc64le-linux-gnu libc6-dev libc6-dev-ppc64el-cross
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;;
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esac
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}

‎src/arm.rs

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Original file line numberDiff line numberDiff line change
@@ -1,3 +1,37 @@
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use core::intrinsics;
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// NOTE This function and the one below are implemented using assembly because they using a custom
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// calling convention which can't be implemented using a normal Rust function
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// TODO use `global_asm!`
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#[naked]
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#[no_mangle]
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pub unsafe extern "aapcs" fn __aeabi_uidivmod() {
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asm!("push { lr }
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sub sp, sp, #4
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mov r2, sp
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bl __udivmodsi4
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ldr r1, [sp]
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add sp, sp, #4
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pop { pc }");
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intrinsics::unreachable();
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}
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// TODO use `global_asm!`
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#[naked]
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#[no_mangle]
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pub unsafe extern "aapcs" fn __aeabi_uldivmod() {
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asm!("push {r11, lr}
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sub sp, sp, #16
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add r12, sp, #8
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str r12, [sp]
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bl __udivmoddi4
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ldr r2, [sp, #8]
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ldr r3, [sp, #12]
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add sp, sp, #16
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pop {r11, pc}");
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intrinsics::unreachable();
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}
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extern "C" {
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fn memcpy(dest: *mut u8, src: *const u8, n: usize) -> *mut u8;
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fn memmove(dest: *mut u8, src: *const u8, n: usize) -> *mut u8;

‎src/div.rs

+271
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,271 @@
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use {Int, LargeInt, U64};
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/// Returns `n / d`
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#[no_mangle]
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pub extern "C" fn __udivsi3(n: u32, d: u32) -> u32 {
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let u32_bits = u32::bits() as u32;
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// Special cases
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if d == 0 {
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panic!("Division by zero");
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}
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if n == 0 {
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return 0;
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}
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let mut sr = d.leading_zeros().wrapping_sub(n.leading_zeros());
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// d > n
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if sr > u32_bits - 1 {
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return 0;
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}
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// d == 1
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if sr == u32_bits - 1 {
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return n;
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}
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sr = sr + 1;
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// 1 <= sr <= u32_bits - 1
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let mut q = n << (u32_bits - sr);
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let mut r = n >> sr;
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let mut carry = 0;
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for _ in 0..sr {
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// r:q = ((r:q) << 1) | carry
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r = (r << 1) | (q >> (u32_bits - 1));
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q = (q << 1) | carry;
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// carry = 0;
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// if r > d {
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// r -= d;
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// carry = 1;
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// }
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let s = (d.wrapping_sub(r).wrapping_sub(1)) as i32 >> (u32_bits - 1);
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carry = (s & 1) as u32;
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r -= d & s as u32;
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}
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(q << 1) | carry
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}
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/// Returns `n / d` and sets `*rem = n % d`
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#[no_mangle]
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pub extern "C" fn __udivmodsi4(a: u32, b: u32, rem: Option<&mut u32>) -> u32 {
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let d = __udivsi3(a, b);
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if let Some(rem) = rem {
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*rem = a - (d * b);
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}
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return d;
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}
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/// Returns `n / d` and sets `*rem = n % d`
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#[no_mangle]
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pub extern "C" fn __udivmoddi4(n: u64, d: u64, rem: Option<&mut u64>) -> u64 {
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let u32_bits = u32::bits() as u32;
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let u64_bits = u64::bits() as u32;
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// NOTE X is unknown, K != 0
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if n.high() == 0 {
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if d.high() == 0 {
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// 0 X
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// ---
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// 0 X
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if let Some(rem) = rem {
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*rem = u64::from(n.low() % d.low());
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}
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return u64::from(n.low() / d.low());
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} else
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// d.high() != 0
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{
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// 0 X
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// ---
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// K X
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if let Some(rem) = rem {
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*rem = u64::from(n.low());
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}
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return 0;
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};
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}
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let mut sr;
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let mut q = U64 { low: 0, high: 0 };
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let mut r = U64 { low: 0, high: 0 };
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// n.high() != 0
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if d.low() == 0 {
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if d.high() == 0 {
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// K X
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// ---
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// 0 0
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107+
panic!("Division by zero");
108+
}
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// d.high() != 0
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if n.low() == 0 {
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// K 0
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// ---
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// K 0
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116+
if let Some(rem) = rem {
117+
*rem = U64 {
118+
low: 0,
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high: n.high() % d.high(),
120+
}[..];
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}
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return u64::from(n.high() / d.high());
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}
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// n.low() != 0
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// K K
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// ---
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// K 0
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if d.high().is_power_of_two() {
131+
if let Some(rem) = rem {
132+
*rem = U64 {
133+
low: n.low(),
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high: n.high() & (d.high() - 1),
135+
}[..];
136+
}
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138+
return u64::from(n.high() >> d.high().trailing_zeros());
139+
}
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sr = d.high().leading_zeros().wrapping_sub(n.high().leading_zeros());
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// D > N
144+
if sr > u32_bits - 2 {
145+
if let Some(rem) = rem {
146+
*rem = n;
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}
148+
return 0;
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}
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sr = sr + 1;
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// 1 <= sr <= u32_bits - 1
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// q = n << (u64_bits - sr);
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q.low = 0;
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q.high = n.low() << (u32_bits - sr);
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// r = n >> sr
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r.high = n.high() >> sr;
159+
r.low = (n.high() << (u32_bits - sr)) | (n.low() >> sr);
160+
} else
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// d.low() != 0
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{
163+
if d.high() == 0 {
164+
// K X
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// ---
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// 0 K
167+
if d.low().is_power_of_two() {
168+
if let Some(rem) = rem {
169+
*rem = u64::from(n.low() & (d.low() - 1));
170+
}
171+
172+
if d.low() == 1 {
173+
return n;
174+
} else {
175+
let sr = d.low().trailing_zeros();
176+
return U64 {
177+
low: (n.high() << (u32_bits - sr)) | (n.low() >> sr),
178+
high: n.high() >> sr,
179+
}[..];
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};
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}
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sr = 1 + u32_bits + d.low().leading_zeros() - n.high().leading_zeros();
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// 2 <= sr <= u64_bits - 1
186+
// q = n << (u64_bits - sr)
187+
// r = n >> sr;
188+
if sr == u32_bits {
189+
q.low = 0;
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q.high = n.low();
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r.high = 0;
192+
r.low = n.high();
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} else if sr < u32_bits
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// 2 <= sr <= u32_bits - 1
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{
196+
q.low = 0;
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q.high = n.low() << (u32_bits - sr);
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r.high = n.high() >> sr;
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r.low = (n.high() << (u32_bits - sr)) | (n.low() >> sr);
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} else
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// u32_bits + 1 <= sr <= u64_bits - 1
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{
203+
q.low = n.low() << (u64_bits - sr);
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q.high = (n.high() << (u64_bits - sr)) | (n.low() >> (sr - u32_bits));
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r.high = 0;
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r.low = n.high() >> (sr - u32_bits);
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}
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} else
210+
// d.high() != 0
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{
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// K X
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// ---
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// K K
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216+
sr = d.high().leading_zeros().wrapping_sub(n.high().leading_zeros());
217+
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// D > N
219+
if sr > u32_bits - 1 {
220+
if let Some(rem) = rem {
221+
*rem = n;
222+
return 0;
223+
}
224+
}
225+
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sr += 1;
227+
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// 1 <= sr <= u32_bits
229+
// q = n << (u64_bits - sr)
230+
q.low = 0;
231+
if sr == u32_bits {
232+
q.high = n.low();
233+
r.high = 0;
234+
r.low = n.high();
235+
} else {
236+
q.high = n.low() << (u32_bits - sr);
237+
r.high = n.high() >> sr;
238+
r.low = (n.high() << (u32_bits - sr)) | (n.low() >> sr);
239+
}
240+
}
241+
}
242+
243+
// Not a special case
244+
// q and r are initialized with
245+
// q = n << (u64_bits - sr)
246+
// r = n >> sr
247+
// 1 <= sr <= u64_bits - 1
248+
let mut carry = 0;
249+
250+
for _ in 0..sr {
251+
// r:q = ((r:q) << 1) | carry
252+
r[..] = (r[..] << 1) | (q[..] >> 63);
253+
q[..] = (q[..] << 1) | carry as u64;
254+
255+
// carry = 0
256+
// if r >= d {
257+
// r -= d;
258+
// carry = 1;
259+
// }
260+
261+
let s = (d.wrapping_sub(r[..]).wrapping_sub(1)) as i64 >> (u64_bits - 1);
262+
carry = (s & 1) as u32;
263+
r[..] -= d & s as u64;
264+
}
265+
266+
q[..] = (q[..] << 1) | carry as u64;
267+
if let Some(rem) = rem {
268+
*rem = r[..];
269+
}
270+
q[..]
271+
}

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