Cranelift: Implement 'iabs' for scalar types on x86_64 (#5527)

* Implement 'iabs' for scalar types on x86_64

* Small fix

cranelift/codegen/src/isa/x64/lower.isle

@@ -1129,6 +1129,20 @@
             (neg Xmm (x64_psubq (imm $I64X2 0) rx)))
         (x64_blendvpd neg rx neg)))
 
+;; `i64` and smaller.
+
+(rule -1 (lower (has_type (fits_in_64 ty) (iabs x)))
+      (let ((src Gpr x)
+            (neg ProducesFlags (x64_neg_paired ty src))
+            ;; Manually extract the result from the neg, then ignore
+            ;; it below, since we need to pass it into the cmove
+            ;; before we pass the cmove to with_flags_reg.
+            (neg_result Gpr (produces_flags_get_reg neg))
+            ;; When the neg instruction sets the sign flag, 
+            ;; takes the original (non-negative) value.
+            (cmove ConsumesFlags (cmove ty (CC.S) src neg_result)))
+        (with_flags_reg (produces_flags_ignore neg) cmove)))
+
 ;;;; Rules for `fabs` ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
 (rule (lower (has_type $F32 (fabs x)))

cranelift/codegen/src/prelude_lower.isle

@@ -362,6 +362,7 @@
 ;; Get the produced register out of a ProducesFlags.
 (decl produces_flags_get_reg (ProducesFlags) Reg)
 (rule (produces_flags_get_reg (ProducesFlags.ProducesFlagsReturnsReg _ reg)) reg)
+(rule (produces_flags_get_reg (ProducesFlags.ProducesFlagsReturnsResultWithConsumer _ reg)) reg)
 
 ;; Modify a ProducesFlags to use it only for its side-effect, ignoring
 ;; its result.