riscv64: Add support for the xnor instruction (#7279)

* riscv64: Refactor `bnot` lowering rules

Move them to `lower.isle` and clean them up a bit too.

* riscv64: Add support for xnor

cranelift/codegen/src/isa/riscv64/inst.isle

@@ -1558,6 +1558,12 @@
 (rule (rv_orn rs1 rs2)
   (alu_rrr (AluOPRRR.Orn) rs1 rs2))
 
+;; Helper for emitting the `xnor` ("Exclusive NOR") instruction.
+;; rd ← ~(rs1 ^ rs2)
+(decl rv_xnor (XReg XReg) XReg)
+(rule (rv_xnor rs1 rs2)
+  (alu_rrr (AluOPRRR.Xnor) rs1 rs2))
+
 ;; Helper for emitting the `clz` ("Count Leading Zero Bits") instruction.
 (decl rv_clz (XReg) XReg)
 (rule (rv_clz rs1)
@@ -2008,23 +2014,6 @@
 (rule (select_addi (fits_in_64 ty)) (AluOPRRI.Addi))
 
 
-(decl gen_bnot (Type ValueRegs) ValueRegs)
-(rule 2 (gen_bnot (ty_scalar_float ty) x)
-  (let ((val FReg (value_regs_get x 0))
-        (x_val XReg (move_f_to_x val ty))
-        (inverted XReg (rv_not x_val))
-        (res FReg (move_x_to_f inverted (float_int_of_same_size ty))))
-    (value_reg res)))
-
-(rule 1 (gen_bnot $I128 x)
-  (let ((lo XReg (rv_not (value_regs_get x 0)))
-        (hi XReg (rv_not (value_regs_get x 1))))
-    (value_regs lo hi)))
-
-(rule 0 (gen_bnot (ty_int_ref_scalar_64 _) x)
-  (rv_not (value_regs_get x 0)))
-
-
 (decl gen_andi (XReg u64) XReg)
 (rule 1 (gen_andi x (imm12_from_u64 y))
   (rv_andi x y))

cranelift/codegen/src/isa/riscv64/lower.isle

@@ -934,12 +934,25 @@
 (extern constructor binvi_imm binvi_imm)
 
 ;;;; Rules for `bnot` ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
-(rule 0 (lower (has_type (ty_scalar ty) (bnot x)))
-  (gen_bnot ty x))
 
-(rule 1 (lower (has_type (ty_vec_fits_in_register ty) (bnot x)))
+(rule 0 (lower (has_type (ty_int_ref_scalar_64 _) (bnot x)))
+  (rv_not x))
+
+(rule 1 (lower (has_type (ty_scalar_float ty) (bnot x)))
+  (move_x_to_f (rv_not (move_f_to_x x ty)) (float_int_of_same_size ty)))
+
+(rule 2 (lower (has_type $I128 (bnot x)))
+  (value_regs
+    (rv_not (value_regs_get x 0))
+    (rv_not (value_regs_get x 1))))
+
+(rule 3 (lower (has_type (ty_vec_fits_in_register ty) (bnot x)))
   (rv_vnot_v x (unmasked) ty))
 
+(rule 4 (lower (has_type (ty_int_ref_scalar_64 _) (bnot (bxor x y))))
+  (if-let $true (has_zbb))
+  (rv_xnor x y))
+
 ;;;; Rules for `bit_reverse` ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 (rule (lower (has_type (fits_in_64 (ty_int ty)) (bitrev x)))
   (lower_bit_reverse x ty))

cranelift/filetests/filetests/isa/riscv64/wasm/zbb.wat

@@ -20,8 +20,16 @@
     (i32.rotr (local.get 0) (i32.const 100)))
   (func (export "rori") (param i64) (result i64)
     (i64.rotr (local.get 0) (i64.const 40)))
-)
 
+  (func (export "xnor32_1") (param i32 i32) (result i32)
+    (i32.xor (i32.xor (local.get 0) (local.get 1)) (i32.const -1)))
+  (func (export "xnor32_2") (param i32 i32) (result i32)
+    (i32.xor (i32.const -1) (i32.xor (local.get 0) (local.get 1))))
+  (func (export "xnor64_1") (param i64 i64) (result i64)
+    (i64.xor (i64.xor (local.get 0) (local.get 1)) (i64.const -1)))
+  (func (export "xnor64_2") (param i64 i64) (result i64)
+    (i64.xor (i64.const -1) (i64.xor (local.get 0) (local.get 1))))
+)
 ;; function u0:0:
 ;; block0:
 ;;   j label1
@@ -77,3 +85,31 @@
 ;; block1:
 ;;   rori a0,a0,40
 ;;   ret
+;;
+;; function u0:8:
+;; block0:
+;;   j label1
+;; block1:
+;;   xnor a0,a0,a1
+;;   ret
+;;
+;; function u0:9:
+;; block0:
+;;   j label1
+;; block1:
+;;   xnor a0,a0,a1
+;;   ret
+;;
+;; function u0:10:
+;; block0:
+;;   j label1
+;; block1:
+;;   xnor a0,a0,a1
+;;   ret
+;;
+;; function u0:11:
+;; block0:
+;;   j label1
+;; block1:
+;;   xnor a0,a0,a1
+;;   ret