Fix mulx #531
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Fix mulx #531
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vbgl
reviewed
Jul 19, 2023
proofs/compiler/x86_extra.v
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| let '(hi,lo) := wumul v1 v2 in | ||
| ok hi. |
|
Dumb fuzzer is happy with the fix. The bug used to trigger with just one single input. I ran it for 10min or so and I don't see any crashes. Thanks! |
Co-authored-by: Vincent Laporte <vbgl@users.noreply.github.com>
Co-authored-by: Vincent Laporte <vbgl@users.noreply.github.com>
Co-authored-by: Vincent Laporte <vbgl@users.noreply.github.com>
Co-authored-by: Vincent Laporte <vbgl@users.noreply.github.com>
Co-authored-by: Vincent Laporte <vbgl@users.noreply.github.com>
Co-authored-by: Vincent Laporte <vbgl@users.noreply.github.com>
Co-authored-by: Vincent Laporte <vbgl@users.noreply.github.com>
Co-authored-by: Vincent Laporte <vbgl@users.noreply.github.com>
vbgl
reviewed
Jul 19, 2023
CHANGELOG.md
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| @@ -25,8 +25,16 @@ | |||
| - Notation for string literals; there is no implicit zero terminator; | |||
| ([PR #517](https://github.com/jasmin-lang/jasmin/pull/517)). | |||
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| - Add the instruction `MULX_hi`, | |||
| `hi = #MULX(x, y);` is equivalent to `hi, _ = #MULX(x, y);` | |||
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Suggested change
| `hi = #MULX(x, y);` is equivalent to `hi, _ = #MULX(x, y);` | |
| `hi = #MULX_hi(x, y);` is equivalent to `hi, _ = #MULX(x, y);` |
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| /* FAIL | ||
| export fn test_ (reg u64 x, reg u64 y) -> reg u64 { | ||
| reg u64 hi, lo, z1, z2; | ||
| x = x; | ||
| (lo,lo) = #MULX(x, y); | ||
| z1 = lo; | ||
| z1 = lo << 1; | ||
| z1 += lo; | ||
| return z1; | ||
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|
||
| } | ||
| */ |
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| /* success, but mulx still use 2 differents registers for destination */ | ||
| /* But the extraction fail */ | ||
| /* | ||
| export fn test_lo_hi_ (reg u64 x, reg u64 y) -> reg u64 { | ||
| reg u64 hi, lo, z1, z2; | ||
| x = x; | ||
| (lo,lo) = #MULX_lo_hi(x, y); | ||
| z1 = lo; | ||
| z1 = z1 << 1; | ||
| z1 += lo; | ||
| return z1; | ||
| } | ||
| */ |
vbgl
approved these changes
Jul 19, 2023
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This should fix the semantic of the MULX instruction.
It introduces the operator
(lo, hi) = MULX_lo_hi (x,y); (this corresponds to the mulx of x86)
the previous MULX operator is then compiled to
(hi, lo) = MULX (x,y);
---->
(lo, hi) = MULX_lo_hi (x,y);
It also introduces
hi = MULX_hi (x, y) which is compiled to
(hi,hi) = MULX_lo_hi(x,y)
This is the only way to generate a mulx instruction where the two destination are
equals.