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x86: fix semantics of VPERMD, VPMADDWD, & VPMADDUBSW #442

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May 15, 2023
Merged

x86: fix semantics of VPERMD, VPMADDWD, & VPMADDUBSW #442

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e6f0c67
x86: fix semantics of VPERMD
vbgl May 12, 2023
b26196b
x86: fix semantics of VPMADDWD
vbgl May 12, 2023
8a96f9e
x86: fix semantics of VPMADDUBSW
vbgl May 12, 2023
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3 changes: 3 additions & 0 deletions CHANGELOG.md
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Original file line number Diff line number Diff line change
Expand Up @@ -125,6 +125,9 @@
([PR #422](https://github.com/jasmin-lang/jasmin/pull/422);
fixes [#421](https://github.com/jasmin-lang/jasmin/issues/421)).

- Fix semantics of the `VPERMD`, `VPMADDWD`, and `VPMADDUBSW` instructions
([PR #442](https://github.com/jasmin-lang/jasmin/pull/442)).

## Other changes

- Explicit if-then-else in flag combinations is no longer supported
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16 changes: 8 additions & 8 deletions proofs/lang/word.v
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Expand Up @@ -1499,8 +1499,8 @@ Definition wpermd1 (v: seq u32) (idx: u32) :=
let off := wunsigned idx mod 8 in
(v`_(Z.to_nat off))%R.

Definition wpermd sz (w1 idx: word sz) : word sz :=
let v := split_vec U32 w1 in
Definition wpermd sz (idx w: word sz) : word sz :=
let v := split_vec U32 w in
let i := split_vec U32 idx in
make_vec sz (map (wpermd1 v) i).

Expand Down Expand Up @@ -1551,15 +1551,15 @@ Fixpoint add_pairs (m: seq Z) : seq Z :=
else [::].

Definition wpmaddubsw sz (v1 v2: word sz) : word sz :=
let w1 := map wunsigned (split_vec VE8 v1) in
let w2 := map wsigned (split_vec VE8 v2) in
let result := [seq wrepr_saturated_signed sz z | z <- add_pairs (map2 *%R w1 w2) ] in
let w1 := map wunsigned (split_vec U8 v1) in
let w2 := map wsigned (split_vec U8 v2) in
let result := [seq wrepr_saturated_signed U16 z | z <- add_pairs (map2 *%R w1 w2) ] in
make_vec sz result.

Definition wpmaddwd sz (v1 v2: word sz) : word sz :=
let w1 := map wsigned (split_vec VE16 v1) in
let w2 := map wsigned (split_vec VE16 v2) in
let result := [seq wrepr sz z | z <- add_pairs (map2 *%R w1 w2) ] in
let w1 := map wsigned (split_vec U16 v1) in
let w2 := map wsigned (split_vec U16 v2) in
let result := [seq wrepr U32 z | z <- add_pairs (map2 *%R w1 w2) ] in
make_vec sz result.

(* Test case from the documentation: VPMADDWD wraps when all inputs are min-signed *)
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