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fix const align_offset implementation

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This commit is contained in:
Lukas Markeffsky 2022-11-15 15:55:37 +01:00
parent 8717455b9d
commit 9e5d497b67
2 changed files with 61 additions and 36 deletions
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9
compiler/rustc_const_eval/src/const_eval/machine.rs
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@ -278,9 +278,8 @@ impl<'mir, 'tcx: 'mir> CompileTimeEvalContext<'mir, 'tcx> {
return u64::MAX;
}
let byte_offset = align - addr_mod_align;
if align % stride == 0 {
let byte_offset = align - addr_mod_align;
if byte_offset % stride == 0 {
return byte_offset / stride;
} else {
@ -296,8 +295,11 @@ impl<'mir, 'tcx: 'mir> CompileTimeEvalContext<'mir, 'tcx> {
return u64::MAX;
}
// Instead of `(addr + offset * stride) % align == 0`, we solve
// `((addr + offset * stride) / gcd) % (align / gcd) == 0`.
let addr2 = addr / gcd;
let align2 = align / gcd;
let stride2 = (stride / gcd) % align2;
let stride2 = stride / gcd;
let mut stride_inv = 1u64;
let mut mod_gate = 2u64;
@ -308,6 +310,7 @@ impl<'mir, 'tcx: 'mir> CompileTimeEvalContext<'mir, 'tcx> {
(mod_gate, overflow) = mod_gate.overflowing_mul(mod_gate);
}
let byte_offset = align2 - addr2 % align2;
byte_offset.wrapping_mul(stride_inv) % align2
}