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ISLE rule cleanups (#5389)

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* cranelift-codegen: Use ISLE matching, not same_value

The `same_value` function just wrapped an equality test into an external
constructor, but we can do that with ISLE's equality constraints
instead.

* riscv64: Remove custom condition-code tests

The `lower_icmp` term exists solely to decide whether to sign-extend or
zero-extend the comparison operands, based on whether the condition code
requires a signed comparison. It additionally tested whether the
condition code was == or !=, but produced the same result as for other
unsigned comparisons.

We already have `signed_cond_code` in the ISLE prelude, which classifies
the total-ordering condition codes according to whether they're signed.
It also lumps == and != in the "unsigned" camp, as desired.

So this commit uses the existing method from the prelude instead of
riscv64-local definitions.

Because this version has no constraints on the left-hand side of the
rule in the unsigned case, ISLE generates Rust that always returns
`Some`. That shows that the current use of `unwrap` is justified, at the
only Rust-side call-site of `constructor_lower_icmp`, which is in
cranelift/codegen/src/isa/riscv64/lower/isle.rs.

* ISLE prelude: make offset32 infallible

This extractor always returns `Some`, so it doesn't need to be fallible.
This commit is contained in:
Jamey Sharp
2022-12-06 18:55:59 -08:00
committed by GitHub
parent 0eb22429d1
commit 29b23d41b6
7 changed files with 15 additions and 71 deletions
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24
cranelift/codegen/src/isa/riscv64/inst.isle
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@@ -1766,29 +1766,13 @@
(value_regs_get x 0))
(convert ValueRegs Reg convert_valueregs_reg)
;;; intcc is not equal nor ne.
;;; intcc is >= <= ...
;;; return alongside with if signed.
(decl intcc_is_gt_etc (IntCC bool) IntCC)
(extern extractor intcc_is_gt_etc intcc_is_gt_etc)
(decl intcc_is_eq_or_ne (IntCC) IntCC)
(extern extractor intcc_is_eq_or_ne intcc_is_eq_or_ne)
;;; lower icmp
(decl lower_icmp (IntCC ValueRegs ValueRegs Type) Reg)
;;; eq or ne.
(rule -1
(lower_icmp (intcc_is_eq_or_ne cc) x y ty)
(gen_icmp cc (ext_int_if_need $false x ty) (ext_int_if_need $false y ty) ty))
;;;; singed >= ...
(rule
(lower_icmp (intcc_is_gt_etc cc $true) x y ty)
(rule 1 (lower_icmp cc x y ty)
(if (signed_cond_code cc))
(gen_icmp cc (ext_int_if_need $true x ty) (ext_int_if_need $true y ty) ty))
;;;; unsigned >= ...
(rule
(lower_icmp (intcc_is_gt_etc cc $false) x y ty)
(gen_icmp cc (ext_int_if_need $false x ty ) (ext_int_if_need $false y ty) ty))
(rule (lower_icmp cc x y ty)
(gen_icmp cc (ext_int_if_need $false x ty) (ext_int_if_need $false y ty) ty))
(decl lower_icmp_over_flow (ValueRegs ValueRegs Type) Reg)