x64: Migrate trapif and trapff to ISLE (#4545)

https://github.com/bytecodealliance/wasmtime/pull/4545

cranelift/codegen/src/prelude.isle

@@ -147,6 +147,10 @@
 (decl valid_reg () Reg)
 (extern extractor valid_reg valid_reg)
 
+;; Mark this value as used, to ensure that it gets lowered.
+(decl mark_value_used (Value) Unit)
+(extern constructor mark_value_used mark_value_used)
+
 ;; Put the given value into a register.
 ;;
 ;; Asserts that the value fits into a single register, and doesn't require
@@ -563,6 +567,11 @@
 ;; Variant determines how result is given when combined with a
 ;; ConsumesFlags. See `with_flags` below for more.
 (type ProducesFlags (enum
+                     ;; For cases where the flags have been produced by another
+                     ;; instruction, and we have out-of-band reasons to know
+                     ;; that they won't be clobbered by the time we depend on
+                     ;; them.
+                     (AlreadyExistingFlags)
                      (ProducesFlagsSideEffect (inst MInst))
                      ;; Not directly combinable with a ConsumesFlags;
                      ;; used in s390x and unwrapped directly by `trapif`.
@@ -574,6 +583,7 @@
 ;; Variant determines how result is given when combined with a
 ;; ProducesFlags. See `with_flags` below for more.
 (type ConsumesFlags (enum
+                     (ConsumesFlagsSideEffect (inst MInst))
                      (ConsumesFlagsReturnsResultWithProducer (inst MInst) (result Reg))
                      (ConsumesFlagsReturnsReg (inst MInst) (result Reg))
                      (ConsumesFlagsTwiceReturnsValueRegs (inst1 MInst)
@@ -667,6 +677,30 @@
       (let ((v ValueRegs (with_flags p c)))
         (value_regs_get v 0)))
 
+;; Indicate that the current state of the flags register from the instruction
+;; that produces this Value is relied on.
+(decl flags_to_producesflags (Value) ProducesFlags)
+(rule (flags_to_producesflags val)
+      (let ((_ Unit (mark_value_used val)))
+        (ProducesFlags.AlreadyExistingFlags)))
+
+;; Combine a flags-producing instruction and a flags-consuming instruction that
+;; produces no results.
+;;
+;; This function handles the following case only:
+;; - ProducesFlagsSideEffect + ConsumesFlagsSideEffect
+(decl with_flags_side_effect (ProducesFlags ConsumesFlags) SideEffectNoResult)
+
+(rule (with_flags_side_effect
+        (ProducesFlags.AlreadyExistingFlags)
+        (ConsumesFlags.ConsumesFlagsSideEffect c))
+      (SideEffectNoResult.Inst c))
+
+(rule (with_flags_side_effect
+        (ProducesFlags.ProducesFlagsSideEffect p)
+        (ConsumesFlags.ConsumesFlagsSideEffect c))
+      (SideEffectNoResult.Inst2 p c))
+
 ;;;; Helpers for Working with TrapCode ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
 (decl trap_code_division_by_zero () TrapCode)