Move emit and emit_safepoint to prelude.isle

Even though the implementation of emit and emit_safepoint may
be platform-specific, the interface ought to be common so that
other code in prelude.isle may safely call these constructors.

This patch moves the definition of emit (from all platforms)
and emit_safepoint (s390x only) to prelude.isle.  This required
adding an emit_safepoint implementation to aarch64 and x64 as
well - the latter is still a stub as special move mitosis
handling will be required.

cranelift/codegen/src/isa/aarch64/inst.isle

@@ -1371,13 +1371,6 @@
 
 ;; Instruction creation helpers ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
-;; Emit an instruction.
-;;
-;; This is low-level and side-effectful; it should only be used as an
-;; implementation detail by helpers that preserve the SSA facade themselves.
-(decl emit (MInst) Unit)
-(extern constructor emit emit)
-
 ;; Helper for creating the zero register.
 (decl zero_reg () Reg)
 (extern constructor zero_reg zero_reg)

cranelift/codegen/src/isa/aarch64/lower/isle.rs

@@ -203,6 +203,10 @@ where
         self.emitted_insts.push((inst.clone(), false));
     }
 
+    fn emit_safepoint(&mut self, inst: &MInst) -> Unit {
+        self.emitted_insts.push((inst.clone(), true));
+    }
+
     fn cond_br_zero(&mut self, reg: Reg) -> CondBrKind {
         CondBrKind::Zero(reg)
     }

cranelift/codegen/src/isa/aarch64/lower/isle/generated_code.manifest

@@ -1,4 +1,4 @@
 src/clif.isle 9ea75a6f790b5c03
-src/prelude.isle 51d2aef2566c1c96
-src/isa/aarch64/inst.isle f946561093de4ff5
+src/prelude.isle 2bfcafbef6b29358
+src/isa/aarch64/inst.isle 944323ff7d6db098
 src/isa/aarch64/lower.isle 2d2e1e076a0c8a23

cranelift/codegen/src/isa/s390x/inst.isle

@@ -1290,15 +1290,6 @@
 
 ;; Instruction creation helpers ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
-;; Emit an instruction.
-;;
-;; This is low-level and side-effectful; it should only be used as an
-;; implementation detail by helpers that preserve the SSA facade themselves.
-(decl emit (MInst) Unit)
-(extern constructor emit emit)
-(decl emit_safepoint (MInst) Unit)
-(extern constructor emit_safepoint emit_safepoint)
-
 ;; Helper for emitting `MInst.AluRRR` instructions.
 (decl alu_rrr (Type ALUOp Reg Reg) Reg)
 (rule (alu_rrr ty op src1 src2)
@@ -2195,11 +2186,6 @@
 (rule (debugtrap_impl)
       (SideEffectNoResult.Inst (MInst.Debugtrap)))
 
-(decl safepoint (SideEffectNoResult) ValueRegs)
-(rule (safepoint (SideEffectNoResult.Inst inst))
-      (let ((_ Unit (emit_safepoint inst)))
-        (value_regs_invalid)))
-
 
 ;; Helpers for handling boolean conditions ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 

cranelift/codegen/src/isa/s390x/lower/isle/generated_code.manifest

@@ -1,4 +1,4 @@
 src/clif.isle 9ea75a6f790b5c03
-src/prelude.isle 51d2aef2566c1c96
-src/isa/s390x/inst.isle d7bfd05fb4d4a66d
+src/prelude.isle 2bfcafbef6b29358
+src/isa/s390x/inst.isle 1d525c87f7c77c26
 src/isa/s390x/lower.isle 57dcc39cbab2d1c6

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

@@ -613,13 +613,6 @@
 ;; maintain the invariant that each temporary register they allocate and define
 ;; only gets defined the once.
 
-;; Emit an instruction.
-;;
-;; This is low-level and side-effectful; it should only be used as an
-;; implementation detail by helpers that preserve the SSA facade themselves.
-(decl emit (MInst) Unit)
-(extern constructor emit emit)
-
 ;; Helper for emitting `MInst.AluRmiR` instructions.
 (decl alu_rmi_r (Type AluRmiROpcode Reg RegMemImm) Reg)
 (rule (alu_rmi_r ty opcode src1 src2)

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

@@ -231,6 +231,10 @@ where
         }
     }
 
+    fn emit_safepoint(&mut self, _inst: &MInst) -> Unit {
+        unimplemented!();
+    }
+
     #[inline]
     fn nonzero_u64_fits_in_u32(&mut self, x: u64) -> Option<u64> {
         if x != 0 && x < u64::from(u32::MAX) {

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

@@ -1,4 +1,4 @@
 src/clif.isle 9ea75a6f790b5c03
-src/prelude.isle 51d2aef2566c1c96
-src/isa/x64/inst.isle 61004acbb1289816
+src/prelude.isle 2bfcafbef6b29358
+src/isa/x64/inst.isle bbb6a3d201200cc8
 src/isa/x64/lower.isle 82db7f7d47ac7809

cranelift/codegen/src/prelude.isle

@@ -277,6 +277,19 @@
 (extractor (u64_from_iconst x)
            (def_inst (iconst (u64_from_imm64 x))))
 
+;; Instruction creation helpers ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+;; Emit an instruction.
+;;
+;; This is low-level and side-effectful; it should only be used as an
+;; implementation detail by helpers that preserve the SSA facade themselves.
+
+(decl emit (MInst) Unit)
+(extern constructor emit emit)
+
+(decl emit_safepoint (MInst) Unit)
+(extern constructor emit_safepoint emit_safepoint)
+
 ;;;; Helpers for Side-Effectful Instructions Without Results ;;;;;;;;;;;;;;;;;;;
 
 (type SideEffectNoResult (enum (Inst (inst MInst))))
@@ -288,6 +301,12 @@
       (let ((_ Unit (emit inst)))
         (value_regs_invalid)))
 
+;; Similarly, but emit the side-effectful instruction as a safepoint.
+(decl safepoint (SideEffectNoResult) ValueRegs)
+(rule (safepoint (SideEffectNoResult.Inst inst))
+      (let ((_ Unit (emit_safepoint inst)))
+        (value_regs_invalid)))
+
 ;;;; Helpers for Working with Flags ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
 ;; Newtype wrapper around `MInst` for instructions that are used for their