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ISLE: Re-implement ValueSlice (#3784)

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The current definition of `ValueSlice` is not usable, since any call to
a constructor returning a `ValueSlice` will extend the mutable borrow
on the context taken by the constructor call, with the result that it
cannot be passed to any other constructor ever.

Re-implement `ValueSlice` as a pair of a `ValueList` identifer plus an
offset into the list.  This type can simply be copied without requiring
a borrow on the context.
This commit is contained in:
Ulrich Weigand
2022-02-25 00:24:40 +01:00
committed by GitHub
parent 07d615d3f7
commit b064e60087
9 changed files with 157 additions and 110 deletions
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22
cranelift/codegen/src/prelude.isle
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@@ -251,15 +251,33 @@
(decl value_list_slice (ValueSlice) ValueList)
(extern extractor infallible value_list_slice value_list_slice)
;; Extractor to test whether a `ValueSlice` is empty.
(decl value_slice_empty () ValueSlice)
(extern extractor value_slice_empty value_slice_empty)
;; Extractor to split a `ValueSlice` into its first element plus a tail.
(decl value_slice_unwrap (Value ValueSlice) ValueSlice)
(extern extractor value_slice_unwrap value_slice_unwrap)
;; Return the length of a `ValueSlice`.
(decl value_slice_len (ValueSlice) usize)
(extern constructor value_slice_len value_slice_len)
;; Return any element of a `ValueSlice`.
(decl value_slice_get (ValueSlice usize) Value)
(extern constructor value_slice_get value_slice_get)
;; Extractor to get the first element from a value list, along with its tail as
;; a `ValueSlice`.
(decl unwrap_head_value_list_1 (Value ValueSlice) ValueList)
(extern extractor infallible unwrap_head_value_list_1 unwrap_head_value_list_1)
(extractor (unwrap_head_value_list_1 head tail)
(value_list_slice (value_slice_unwrap head tail)))
;; Extractor to get the first two elements from a value list, along with its
;; tail as a `ValueSlice`.
(decl unwrap_head_value_list_2 (Value Value ValueSlice) ValueList)
(extern extractor infallible unwrap_head_value_list_2 unwrap_head_value_list_2)
(extractor (unwrap_head_value_list_2 head1 head2 tail)
(value_list_slice (value_slice_unwrap head1 (value_slice_unwrap head2 tail))))
;; Turn a `Writable<Reg>` into a `Reg` via `Writable::to_reg`.
(decl writable_reg_to_reg (WritableReg) Reg)