Cranelift: pass iterators to ABIMachineSpec::compute_arg_locs (#5095)

Instead of slices. This gives us more flexibility to pass custom sequences
without needing to allocate a `Vec` to hold them and pass in as a slice.

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

@@ -87,13 +87,16 @@ impl ABIMachineSpec for AArch64MachineDeps {
         16
     }
 
-    fn compute_arg_locs(
+    fn compute_arg_locs<'a, I>(
         call_conv: isa::CallConv,
         _flags: &settings::Flags,
-        params: &[ir::AbiParam],
+        params: I,
         args_or_rets: ArgsOrRets,
         add_ret_area_ptr: bool,
-    ) -> CodegenResult<(ABIArgVec, i64, Option<usize>)> {
+    ) -> CodegenResult<(ABIArgVec, i64, Option<usize>)>
+    where
+        I: IntoIterator<Item = &'a ir::AbiParam>,
+    {
         let is_apple_cc = call_conv.extends_apple_aarch64();
 
         // See AArch64 ABI (https://github.com/ARM-software/abi-aa/blob/2021Q1/aapcs64/aapcs64.rst#64parameter-passing), sections 6.4.

cranelift/codegen/src/isa/riscv64/abi.rs

@@ -56,13 +56,16 @@ impl ABIMachineSpec for Riscv64MachineDeps {
         16
     }
 
-    fn compute_arg_locs(
+    fn compute_arg_locs<'a, I>(
         call_conv: isa::CallConv,
         _flags: &settings::Flags,
-        params: &[ir::AbiParam],
+        params: I,
         args_or_rets: ArgsOrRets,
         add_ret_area_ptr: bool,
-    ) -> CodegenResult<(ABIArgVec, i64, Option<usize>)> {
+    ) -> CodegenResult<(ABIArgVec, i64, Option<usize>)>
+    where
+        I: IntoIterator<Item = &'a ir::AbiParam>,
+    {
         // All registers that can be used as parameters or rets.
         // both start and end are included.
         let (x_start, x_end, f_start, f_end) = if args_or_rets == ArgsOrRets::Args {

cranelift/codegen/src/isa/s390x/abi.rs

@@ -221,13 +221,16 @@ impl ABIMachineSpec for S390xMachineDeps {
         8
     }
 
-    fn compute_arg_locs(
+    fn compute_arg_locs<'a, I>(
         call_conv: isa::CallConv,
         _flags: &settings::Flags,
-        params: &[ir::AbiParam],
+        params: I,
         args_or_rets: ArgsOrRets,
         add_ret_area_ptr: bool,
-    ) -> CodegenResult<(ABIArgVec, i64, Option<usize>)> {
+    ) -> CodegenResult<(ABIArgVec, i64, Option<usize>)>
+    where
+        I: IntoIterator<Item = &'a ir::AbiParam>,
+    {
         let mut next_gpr = 0;
         let mut next_fpr = 0;
         let mut next_vr = 0;
@@ -245,7 +248,7 @@ impl ABIMachineSpec for S390xMachineDeps {
             next_gpr += 1;
         }
 
-        for (i, mut param) in params.iter().copied().enumerate() {
+        for (i, mut param) in params.into_iter().copied().enumerate() {
             let intreg = in_int_reg(param.value_type);
             let fltreg = in_flt_reg(param.value_type);
             let vecreg = in_vec_reg(param.value_type);

cranelift/codegen/src/isa/x64/abi.rs

@@ -81,13 +81,16 @@ impl ABIMachineSpec for X64ABIMachineSpec {
         16
     }
 
-    fn compute_arg_locs(
+    fn compute_arg_locs<'a, I>(
         call_conv: isa::CallConv,
         flags: &settings::Flags,
-        params: &[ir::AbiParam],
+        params: I,
         args_or_rets: ArgsOrRets,
         add_ret_area_ptr: bool,
-    ) -> CodegenResult<(ABIArgVec, i64, Option<usize>)> {
+    ) -> CodegenResult<(ABIArgVec, i64, Option<usize>)>
+    where
+        I: IntoIterator<Item = &'a ir::AbiParam>,
+    {
         let is_fastcall = call_conv.extends_windows_fastcall();
 
         let mut next_gpr = 0;

cranelift/codegen/src/machinst/abi.rs

@@ -345,13 +345,15 @@ pub trait ABIMachineSpec {
     /// Returns the list of argument locations, the stack-space used (rounded up
     /// to as alignment requires), and if `add_ret_area_ptr` was passed, the
     /// index of the extra synthetic arg that was added.
-    fn compute_arg_locs(
+    fn compute_arg_locs<'a, I>(
         call_conv: isa::CallConv,
         flags: &settings::Flags,
-        params: &[ir::AbiParam],
+        params: I,
         args_or_rets: ArgsOrRets,
         add_ret_area_ptr: bool,
-    ) -> CodegenResult<(ABIArgVec, i64, Option<usize>)>;
+    ) -> CodegenResult<(ABIArgVec, i64, Option<usize>)>
+    where
+        I: IntoIterator<Item = &'a ir::AbiParam>;
 
     /// Returns the offset from FP to the argument area, i.e., jumping over the saved FP, return
     /// address, and maybe other standard elements depending on ABI (e.g. Wasm TLS reg).