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Fix invalid 128-bit division on 32-bit target (#41228) #41250

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Merged
merged 1 commit into from
Apr 13, 2017
Merged

Fix invalid 128-bit division on 32-bit target (#41228) #41250

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2 changes: 1 addition & 1 deletion src/libcompiler_builtins/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -180,7 +180,7 @@ pub mod reimpls {
sr = sr.wrapping_add(1);

// 1 <= sr <= u64::bits() - 1
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Actually, is the comment still correct?

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Yes, its consistent with the comment in the c implementation /* 1 <= sr <= n_udword_bits - 1 */.

Its types are defined here and here.

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And the C code is actually assuming it when executing the shift, it sets the low value to 0 because it knows that n gets shifted at least by 65 bits.

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@nikomatsakis The comment is about the range of sr, not the amount of shift, so it is still correct.

q = n.wrapping_shl(64u32.wrapping_sub(sr));
q = n.wrapping_shl(128u32.wrapping_sub(sr));
r = n.wrapping_shr(sr);
} else {
if d.high() == 0 {
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5 changes: 5 additions & 0 deletions src/test/run-pass/i128.rs
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Expand Up @@ -104,4 +104,9 @@ fn main() {
assert_eq!(l.checked_sub(l), Some(0));
assert_eq!(b(1u128).checked_shl(b(127)), Some(1 << 127));
assert_eq!(o.checked_shl(b(128)), None);

// https://github.com/rust-lang/rust/issues/41228
assert_eq!(b(-87559967289969187895646876466835277875_i128) /
b(84285771033834995895337664386045050880_i128),
-1i128);
}
45 changes: 45 additions & 0 deletions src/test/run-pass/u128.rs
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Expand Up @@ -77,4 +77,49 @@ fn main() {
assert_eq!(o.checked_sub(b(18)), None);
assert_eq!(b(1u128).checked_shl(b(127)), Some(1 << 127));
assert_eq!(o.checked_shl(b(128)), None);

// Test cases for all udivmodti4 branches.
// case "0X/0X"
assert_eq!(b(0x69545bd57727c050_u128) /
b(0x3283527a3350d88c_u128),
2u128);
// case "0X/KX"
assert_eq!(b(0x0_8003c9c50b473ae6_u128) /
b(0x1_283e8838c30fa8f4_u128),
0u128);
// case "K0/K0"
assert_eq!(b(0xc43f42a207978720_u128 << 64) /
b(0x098e62b74c23cf1a_u128 << 64),
20u128);
// case "KK/K0" for power-of-two D.
assert_eq!(b(0xa9008fb6c9d81e42_0e25730562a601c8_u128) /
b(1u128 << 120),
169u128);
// case "KK/K0" with N >= D (https://github.com/rust-lang/rust/issues/41228).
assert_eq!(b(0xe4d26e59f0640328_06da5b06efe83a41_u128) /
b(0x330fcb030ea4447c_u128 << 64),
4u128);
assert_eq!(b(3u128 << 64 | 1) /
b(3u128 << 64),
1u128);
// case "KK/K0" with N < D.
assert_eq!(b(0x6655c9fb66ca2884_e2d1dfd470158c62_u128) /
b(0xb35b667cab7e355b_u128 << 64),
0u128);
// case "KX/0K" for power-of-two D.
assert_eq!(b(0x3e49dd84feb2df59_7b2f97d93a253969_u128) /
b(1u128 << 4),
0x03e49dd84feb2df5_97b2f97d93a25396_u128);
// case "KX/0K" in general.
assert_eq!(b(0x299692b3a1dae5bd_6162e6f489d2620e_u128) /
b(0x900b6f027571d6f7_u128),
0x49e95f54b0442578_u128);
// case "KX/KK" with N >= D.
assert_eq!(b(0xc7b889180b67b07d_bc1a3c88783d35b5_u128) /
b(0x1d7e69f53160b9e2_60074771e852f244_u128),
6u128);
// case "KX/KK" with N < D.
assert_eq!(b(0x679289ac23bb334f_36144401cf882172_u128) /
b(0x7b0b271b64865f05_f54a7b72746c062f_u128),
0u128);
}