machinst: Steal the used/defs Sets when emitting a call in ABICall;

cranelift/codegen/src/isa/aarch64/abi.rs

@@ -72,6 +72,7 @@ use alloc::vec::Vec;
 
 use regalloc::{RealReg, Reg, RegClass, Set, SpillSlot, Writable};
 
+use core::mem;
 use log::{debug, trace};
 
 /// A location for an argument or return value.
@@ -1267,8 +1268,11 @@ impl ABICall for AArch64ABICall {
         }
     }
 
-    fn emit_call<C: LowerCtx<I = Self::I>>(&self, ctx: &mut C) {
-        let (uses, defs) = (self.uses.clone(), self.defs.clone());
+    fn emit_call<C: LowerCtx<I = Self::I>>(&mut self, ctx: &mut C) {
+        let (uses, defs) = (
+            mem::replace(&mut self.uses, Set::empty()),
+            mem::replace(&mut self.defs, Set::empty()),
+        );
         match &self.dest {
             &CallDest::ExtName(ref name, RelocDistance::Near) => ctx.emit(Inst::Call {
                 dest: name.clone(),

cranelift/codegen/src/isa/aarch64/lower_inst.rs

@@ -1263,7 +1263,7 @@ pub(crate) fn lower_insn_to_regs<C: LowerCtx<I = Inst>>(ctx: &mut C, insn: IRIns
 
         Opcode::Call | Opcode::CallIndirect => {
             let loc = ctx.srcloc(insn);
-            let (abi, inputs) = match op {
+            let (mut abi, inputs) = match op {
                 Opcode::Call => {
                     let (extname, dist) = ctx.call_target(insn).unwrap();
                     let extname = extname.clone();

cranelift/codegen/src/machinst/abi.rs

@@ -167,5 +167,5 @@ pub trait ABICall {
     /// registers are also logically defs, but should never be read; their
     /// values are "defined" (to the regalloc) but "undefined" in every other
     /// sense.)
-    fn emit_call<C: LowerCtx<I = Self::I>>(&self, ctx: &mut C);
+    fn emit_call<C: LowerCtx<I = Self::I>>(&mut self, ctx: &mut C);
 }