Implement SystemV struct argument passing

cranelift/codegen/meta/src/cdsl/types.rs

@@ -407,6 +407,8 @@ impl fmt::Debug for VectorType {
 #[derive(Clone, Copy, PartialEq, Eq, Hash)]
 pub(crate) enum SpecialType {
     Flag(shared_types::Flag),
+    // FIXME remove once the old style backends are removed.
+    StructArgument,
 }
 
 impl SpecialType {
@@ -421,6 +423,9 @@ impl SpecialType {
                 "CPU flags representing the result of a floating point comparison. These
                 flags can be tested with a :type:`floatcc` condition code.",
             ),
+            SpecialType::StructArgument => {
+                String::from("After legalization sarg__ arguments will get this type.")
+            }
         }
     }
 
@@ -428,6 +433,7 @@ impl SpecialType {
     pub fn lane_bits(self) -> u64 {
         match self {
             SpecialType::Flag(_) => 0,
+            SpecialType::StructArgument => 0,
         }
     }
 
@@ -436,6 +442,7 @@ impl SpecialType {
         match self {
             SpecialType::Flag(shared_types::Flag::IFlags) => 1,
             SpecialType::Flag(shared_types::Flag::FFlags) => 2,
+            SpecialType::StructArgument => 3,
         }
     }
 }
@@ -445,6 +452,7 @@ impl fmt::Display for SpecialType {
         match *self {
             SpecialType::Flag(shared_types::Flag::IFlags) => write!(f, "iflags"),
             SpecialType::Flag(shared_types::Flag::FFlags) => write!(f, "fflags"),
+            SpecialType::StructArgument => write!(f, "sarg__"),
         }
     }
 }
@@ -456,6 +464,7 @@ impl fmt::Debug for SpecialType {
             "{}",
             match *self {
                 SpecialType::Flag(_) => format!("FlagsType({})", self),
+                SpecialType::StructArgument => format!("StructArgument"),
             }
         )
     }
@@ -469,12 +478,14 @@ impl From<shared_types::Flag> for SpecialType {
 
 pub(crate) struct SpecialTypeIterator {
     flag_iter: shared_types::FlagIterator,
+    done: bool,
 }
 
 impl SpecialTypeIterator {
     fn new() -> Self {
         Self {
             flag_iter: shared_types::FlagIterator::new(),
+            done: false,
         }
     }
 }
@@ -485,7 +496,12 @@ impl Iterator for SpecialTypeIterator {
         if let Some(f) = self.flag_iter.next() {
             Some(SpecialType::from(f))
         } else {
-            None
+            if !self.done {
+                self.done = true;
+                Some(SpecialType::StructArgument)
+            } else {
+                None
+            }
         }
     }
 }

cranelift/codegen/meta/src/isa/x86/encodings.rs

@@ -465,6 +465,7 @@ fn define_moves(e: &mut PerCpuModeEncodings, shared_defs: &SharedDefinitions, r:
     let sextend = shared.by_name("sextend");
     let set_pinned_reg = shared.by_name("set_pinned_reg");
     let uextend = shared.by_name("uextend");
+    let dummy_sarg__ = shared.by_name("dummy_sarg__");
 
     // Shorthands for recipes.
     let rec_copysp = r.template("copysp");
@@ -482,6 +483,7 @@ fn define_moves(e: &mut PerCpuModeEncodings, shared_defs: &SharedDefinitions, r:
     let rec_umr_reg_to_ssa = r.template("umr_reg_to_ssa");
     let rec_urm_noflags = r.template("urm_noflags");
     let rec_urm_noflags_abcd = r.template("urm_noflags_abcd");
+    let rec_dummy_sarg__ = r.recipe("dummy_sarg__");
 
     // The pinned reg is fixed to a certain value entirely user-controlled, so it generates nothing!
     e.enc64_rec(get_pinned_reg.bind(I64), rec_get_pinned_reg, 0);
@@ -747,6 +749,8 @@ fn define_moves(e: &mut PerCpuModeEncodings, shared_defs: &SharedDefinitions, r:
         copy_to_ssa.bind(F32),
         rec_furm_reg_to_ssa.opcodes(&MOVSS_LOAD),
     );
+
+    e.enc_32_64_rec(dummy_sarg__, rec_dummy_sarg__, 0);
 }
 
 #[inline(never)]

cranelift/codegen/meta/src/isa/x86/recipes.rs

@@ -1270,6 +1270,12 @@ pub(crate) fn define<'shared>(
         );
     }
 
+    recipes.add_recipe(
+        EncodingRecipeBuilder::new("dummy_sarg__", &formats.nullary, 0)
+            .operands_out(vec![Stack::new(gpr)])
+            .emit(""),
+    );
+
     // XX+rd id with Abs4 function relocation.
     recipes.add_template_recipe(
         EncodingRecipeBuilder::new("fnaddr4", &formats.func_addr, 4)

cranelift/codegen/meta/src/shared/instructions.rs

@@ -1863,6 +1863,31 @@ pub(crate) fn define(
         .can_load(true),
     );
 
+    let Sarg = &TypeVar::new(
+        "Sarg",
+        "Any scalar or vector type with as most 128 lanes",
+        TypeSetBuilder::new()
+            .specials(vec![crate::cdsl::types::SpecialType::StructArgument])
+            .build(),
+    );
+    let sarg__ = &Operand::new("sarg__", Sarg);
+
+    // FIXME remove once the old style codegen backends are removed.
+    ig.push(
+        Inst::new(
+            "dummy_sarg__",
+            r#"
+        This creates a sarg__
+
+        This instruction is internal and should not be created by
+        Cranelift users.
+        "#,
+            &formats.nullary,
+        )
+        .operands_in(vec![])
+        .operands_out(vec![sarg__]),
+    );
+
     let src = &Operand::new("src", &imm.regunit);
     let dst = &Operand::new("dst", &imm.regunit);