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aarch64: Implement bmask/bextend in ISLE (#4358)

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* aarch64: Implement `bmask`/`bextend` in ISLE

* cranelift: Remove vector versions of `bextend`

* aarch64: Cleanup `bmask`/`bextend` documentation
This commit is contained in:
Afonso Bordado
2022-07-01 17:37:18 +01:00
committed by GitHub
parent 64759f04a4
commit 38ecd3744f
7 changed files with 63 additions and 60 deletions
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40
cranelift/codegen/src/isa/aarch64/lower.isle
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@@ -1124,6 +1124,46 @@
(rule (lower (bint x))
(and_imm $I32 x (u64_into_imm_logic $I32 1)))
;;;; Rules for `bmask`/`bextend` ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Bextend and Bmask both simply sign-extend. This works for:
;; - Bextend, because booleans are stored as 0 / -1, so we
;; sign-extend the -1 to a -1 in the wider width.
;; - Bmask, because the resulting integer mask value must be
;; all-ones (-1) if the argument is true.
;; Use a common helper to type cast bools to either bool or integer types.
(decl cast_bool (Type Type Value) InstOutput)
(rule (lower (has_type out_ty (bextend x @ (value_type in_ty))))
(cast_bool in_ty out_ty x))
(rule (lower (has_type out_ty (bmask x @ (value_type in_ty))))
(cast_bool in_ty out_ty x))
;; If the target has the same or a smaller size than the source, it's a no-op.
(rule (cast_bool $B8 $I8 x) x)
(rule (cast_bool $B16 (fits_in_16 _out) x) x)
(rule (cast_bool $B32 (fits_in_32 _out) x) x)
(rule (cast_bool $B64 (fits_in_64 _out) x) x)
;; Casting between 128 bits is a noop
(rule (cast_bool (ty_int_bool_128 _in) (ty_int_bool_128 _out) x)
x)
;; Converting from 128 bits to anything below we just ignore the top register
(rule (cast_bool (ty_int_bool_128 _in) (fits_in_64 _out) x)
(value_regs_get x 0))
;; Extend to 64 bits first, then this will be all 0s or all 1s and we can
;; duplicate to both halves of 128 bits
(rule (cast_bool in (ty_int_bool_128 _out) x)
(let ((tmp Reg (extend x $true (ty_bits in) 64)))
(value_regs tmp tmp)))
;; Values that fit in a single register are sign extended normally
(rule (cast_bool (fits_in_64 in) (fits_in_64 out) x)
(extend x $true (ty_bits in) (ty_bits out)))
;;;; Rules for `popcnt` ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; The implementation of `popcnt` for scalar types is done by moving the value