mach backend: use vectors instead of sets to remember set of uses/defs for calls;

This avoids the set uniqueness (hashing) test, reduces memory
churn when re-mapping virtual register onto real registers, and is
generally more memory-efficient.

Cargo.lock

@@ -1640,9 +1640,9 @@ dependencies = [
 
 [[package]]
 name = "regalloc"
-version = "0.0.24"
+version = "0.0.25"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5842bece8a4b1690ffa6d9d959081c1d5d851ee4337a36c0a121fafe8c16add2"
+checksum = "cca5b48c9db66c5ba084e4660b4c0cfe8b551a96074bc04b7c11de86ad0bf1f9"
 dependencies = [
  "log",
  "rustc-hash",

cranelift/codegen/Cargo.toml

@@ -25,7 +25,7 @@ smallvec = { version = "1.0.0" }
 thiserror = "1.0.4"
 byteorder = { version = "1.3.2", default-features = false }
 peepmatic-runtime = { path = "../peepmatic/crates/runtime", optional = true }
-regalloc = "0.0.24"
+regalloc = "0.0.25"
 # It is a goal of the cranelift-codegen crate to have minimal external dependencies.
 # Please don't add any unless they are essential to the task of creating binary
 # machine code. Integration tests that need external dependencies can be

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

@@ -655,21 +655,21 @@ fn is_caller_save(call_conv: isa::CallConv, r: RealReg) -> bool {
     }
 }
 
-fn get_caller_saves_set(call_conv: isa::CallConv) -> Set<Writable<Reg>> {
-    let mut set = Set::empty();
+fn get_caller_saves(call_conv: isa::CallConv) -> Vec<Writable<Reg>> {
+    let mut caller_saved = Vec::new();
     for i in 0..29 {
         let x = writable_xreg(i);
         if is_caller_save(call_conv, x.to_reg().to_real_reg()) {
-            set.insert(x);
+            caller_saved.push(x);
         }
     }
     for i in 0..32 {
         let v = writable_vreg(i);
         if is_caller_save(call_conv, v.to_reg().to_real_reg()) {
-            set.insert(v);
+            caller_saved.push(v);
         }
     }
-    set
+    caller_saved
 }
 
 impl ABIBody for AArch64ABIBody {
@@ -1111,28 +1111,28 @@ enum CallDest {
 /// AArch64 ABI object for a function call.
 pub struct AArch64ABICall {
     sig: ABISig,
-    uses: Set<Reg>,
-    defs: Set<Writable<Reg>>,
+    uses: Vec<Reg>,
+    defs: Vec<Writable<Reg>>,
     dest: CallDest,
     loc: ir::SourceLoc,
     opcode: ir::Opcode,
 }
 
-fn abisig_to_uses_and_defs(sig: &ABISig) -> (Set<Reg>, Set<Writable<Reg>>) {
+fn abisig_to_uses_and_defs(sig: &ABISig) -> (Vec<Reg>, Vec<Writable<Reg>>) {
     // Compute uses: all arg regs.
-    let mut uses = Set::empty();
+    let mut uses = Vec::new();
     for arg in &sig.args {
         match arg {
-            &ABIArg::Reg(reg, _) => uses.insert(reg.to_reg()),
+            &ABIArg::Reg(reg, _) => uses.push(reg.to_reg()),
             _ => {}
         }
     }
 
     // Compute defs: all retval regs, and all caller-save (clobbered) regs.
-    let mut defs = get_caller_saves_set(sig.call_conv);
+    let mut defs = get_caller_saves(sig.call_conv);
     for ret in &sig.rets {
         match ret {
-            &ABIArg::Reg(reg, _) => defs.insert(Writable::from_reg(reg.to_reg())),
+            &ABIArg::Reg(reg, _) => defs.push(Writable::from_reg(reg.to_reg())),
             _ => {}
         }
     }
@@ -1271,14 +1271,14 @@ impl ABICall for AArch64ABICall {
 
     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()),
+            mem::replace(&mut self.uses, Default::default()),
+            mem::replace(&mut self.defs, Default::default()),
         );
         match &self.dest {
             &CallDest::ExtName(ref name, RelocDistance::Near) => ctx.emit(Inst::Call {
                 dest: Box::new(name.clone()),
-                uses: Box::new(uses),
-                defs: Box::new(defs),
+                uses: uses.into_boxed_slice(),
+                defs: defs.into_boxed_slice(),
                 loc: self.loc,
                 opcode: self.opcode,
             }),
@@ -1291,16 +1291,16 @@ impl ABICall for AArch64ABICall {
                 });
                 ctx.emit(Inst::CallInd {
                     rn: spilltmp_reg(),
-                    uses: Box::new(uses),
-                    defs: Box::new(defs),
+                    uses: uses.into_boxed_slice(),
+                    defs: defs.into_boxed_slice(),
                     loc: self.loc,
                     opcode: self.opcode,
                 });
             }
             &CallDest::Reg(reg) => ctx.emit(Inst::CallInd {
                 rn: reg,
-                uses: Box::new(uses),
-                defs: Box::new(defs),
+                uses: uses.into_boxed_slice(),
+                defs: defs.into_boxed_slice(),
                 loc: self.loc,
                 opcode: self.opcode,
             }),

cranelift/codegen/src/isa/aarch64/inst/emit_tests.rs

@@ -2114,8 +2114,8 @@ fn test_aarch64_binemit() {
     insns.push((
         Inst::Call {
             dest: Box::new(ExternalName::testcase("test0")),
-            uses: Box::new(Set::empty()),
-            defs: Box::new(Set::empty()),
+            uses: Vec::new().into_boxed_slice(),
+            defs: Vec::new().into_boxed_slice(),
             loc: SourceLoc::default(),
             opcode: Opcode::Call,
         },
@@ -2126,8 +2126,8 @@ fn test_aarch64_binemit() {
     insns.push((
         Inst::CallInd {
             rn: xreg(10),
-            uses: Box::new(Set::empty()),
-            defs: Box::new(Set::empty()),
+            uses: Vec::new().into_boxed_slice(),
+            defs: Vec::new().into_boxed_slice(),
             loc: SourceLoc::default(),
             opcode: Opcode::CallIndirect,
         },

cranelift/codegen/src/isa/aarch64/inst/mod.rs

@@ -12,7 +12,7 @@ use crate::machinst::*;
 use crate::{settings, CodegenError, CodegenResult};
 
 use regalloc::{RealRegUniverse, Reg, RegClass, SpillSlot, VirtualReg, Writable};
-use regalloc::{RegUsageCollector, RegUsageMapper, Set};
+use regalloc::{RegUsageCollector, RegUsageMapper};
 
 use alloc::boxed::Box;
 use alloc::vec::Vec;
@@ -650,16 +650,16 @@ pub enum Inst {
     /// target.
     Call {
         dest: Box<ExternalName>,
-        uses: Box<Set<Reg>>,
-        defs: Box<Set<Writable<Reg>>>,
+        uses: Box<[Reg]>,
+        defs: Box<[Writable<Reg>]>,
         loc: SourceLoc,
         opcode: Opcode,
     },
     /// A machine indirect-call instruction.
     CallInd {
         rn: Reg,
-        uses: Box<Set<Reg>>,
-        defs: Box<Set<Writable<Reg>>>,
+        uses: Box<[Reg]>,
+        defs: Box<[Writable<Reg>]>,
         loc: SourceLoc,
         opcode: Opcode,
     },
@@ -1729,19 +1729,12 @@ fn aarch64_map_regs<RUM: RegUsageMapper>(inst: &mut Inst, mapper: &RUM) {
             ref mut defs,
             ..
         } => {
-            // TODO: add `map_mut()` to regalloc.rs's Set.
-            let new_uses = uses.map(|r| {
-                let mut r = *r;
-                map_use(mapper, &mut r);
-                r
-            });
-            let new_defs = defs.map(|r| {
-                let mut r = *r;
-                map_def(mapper, &mut r);
-                r
-            });
-            *uses = Box::new(new_uses);
-            *defs = Box::new(new_defs);
+            for r in uses.iter_mut() {
+                map_use(mapper, r);
+            }
+            for r in defs.iter_mut() {
+                map_def(mapper, r);
+            }
         }
         &mut Inst::Ret | &mut Inst::EpiloguePlaceholder => {}
         &mut Inst::CallInd {
@@ -1750,19 +1743,12 @@ fn aarch64_map_regs<RUM: RegUsageMapper>(inst: &mut Inst, mapper: &RUM) {
             ref mut rn,
             ..
         } => {
-            // TODO: add `map_mut()` to regalloc.rs's Set.
-            let new_uses = uses.map(|r| {
-                let mut r = *r;
-                map_use(mapper, &mut r);
-                r
-            });
-            let new_defs = defs.map(|r| {
-                let mut r = *r;
-                map_def(mapper, &mut r);
-                r
-            });
-            *uses = Box::new(new_uses);
-            *defs = Box::new(new_defs);
+            for r in uses.iter_mut() {
+                map_use(mapper, r);
+            }
+            for r in defs.iter_mut() {
+                map_def(mapper, r);
+            }
             map_use(mapper, rn);
         }
         &mut Inst::CondBr { ref mut kind, .. } | &mut Inst::OneWayCondBr { ref mut kind, .. } => {

cranelift/codegen/src/machinst/abi.rs

@@ -167,5 +167,8 @@ 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.)
+    ///
+    /// This function should only be called once, as it is allowed to re-use
+    /// parts of the ABICall object in emitting instructions.
     fn emit_call<C: LowerCtx<I = Self::I>>(&mut self, ctx: &mut C);
 }