Rollup merge of rust-lang#141569 - workingjubilee:canonicalize-abi, r=bjorn3

Replace ad-hoc ABI "adjustments" with an `AbiMap` to `CanonAbi`

Our `conv_from_spec_abi`, `adjust_abi`, and `is_abi_supported` combine to give us a very confusing way of reasoning about what _actual_ calling convention we want to lower our code to and whether we want to compile the resulting code at all. Instead of leaving this code as a miniature adventure game in which someone tries to combine stateful mutations into a Rube Goldberg machine that will let them escape the maze and arrive at the promised land of codegen, we let `AbiMap` devour this complexity. Once you have an `AbiMap`, you can answer which `ExternAbi`s will lower to what `CanonAbi`s (and whether they will lower at all).

Removed:
- `conv_from_spec_abi` replaced by `AbiMap::canonize_abi`
- `adjust_abi` replaced by same
- `Conv::PreserveAll` as unused
- `Conv::Cold` as unused
- `enum Conv` replaced by `enum CanonAbi`

target-spec.json changes:
- If you have a target-spec.json then now your "entry-abi" key will be specified in terms of one of the `"{abi}"` strings Rust recognizes, e.g.
```json
    "entry-abi": "C",
    "entry-abi": "win64",
    "entry-abi": "aapcs",
```

Author: matthiaskrgr

compiler/rustc_abi/src/canon_abi.rs

@@ -0,0 +1,136 @@
+use std::fmt;
+
+#[cfg(feature = "nightly")]
+use rustc_macros::HashStable_Generic;
+
+use crate::ExternAbi;
+
+/// Calling convention to determine codegen
+///
+/// CanonAbi erases certain distinctions ExternAbi preserves, but remains target-dependent.
+/// There are still both target-specific variants and aliasing variants, though much fewer.
+/// The reason for this step is the frontend may wish to show an ExternAbi but implement that ABI
+/// using a different ABI than the string per se, or describe irrelevant differences, e.g.
+/// - extern "system"
+/// - extern "cdecl"
+/// - extern "C-unwind"
+/// In that sense, this erases mere syntactic distinctions to create a canonical *directive*,
+/// rather than picking the "actual" ABI.
+#[derive(Copy, Clone, Debug)]
+#[derive(PartialOrd, Ord, PartialEq, Eq, Hash)]
+#[cfg_attr(feature = "nightly", derive(HashStable_Generic))]
+pub enum CanonAbi {
+    // NOTE: the use of nested variants for some ABIs is for many targets they don't matter,
+    // and this pushes the complexity of their reasoning to target-specific code,
+    // allowing a `match` to easily exhaustively ignore these subcategories of variants.
+    // Otherwise it is very tempting to avoid matching exhaustively!
+    C,
+    Rust,
+    RustCold,
+
+    /// ABIs relevant to 32-bit Arm targets
+    Arm(ArmCall),
+    /// ABI relevant to GPUs: the entry point for a GPU kernel
+    GpuKernel,
+
+    /// ABIs relevant to bare-metal interrupt targets
+    // FIXME(workingjubilee): a particular reason for this nesting is we might not need these?
+    // interrupt ABIs should have the same properties:
+    // - uncallable by Rust calls, as LLVM rejects it in most cases
+    // - uses a preserve-all-registers *callee* convention
+    // - should always return `-> !` (effectively... it can't use normal `ret`)
+    // what differs between targets is
+    // - allowed arguments: x86 differs slightly, having 2-3 arguments which are handled magically
+    // - may need special prologues/epilogues for some interrupts, without affecting "call ABI"
+    Interrupt(InterruptKind),
+
+    /// ABIs relevant to Windows or x86 targets
+    X86(X86Call),
+}
+
+impl fmt::Display for CanonAbi {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        self.to_erased_extern_abi().as_str().fmt(f)
+    }
+}
+
+impl CanonAbi {
+    /// convert to the ExternAbi that *shares a string* with this CanonAbi
+    ///
+    /// A target-insensitive mapping of CanonAbi to ExternAbi, convenient for "forwarding" impls.
+    /// Importantly, the set of CanonAbi values is a logical *subset* of ExternAbi values,
+    /// so this is injective: if you take an ExternAbi to a CanonAbi and back, you have lost data.
+    const fn to_erased_extern_abi(self) -> ExternAbi {
+        match self {
+            CanonAbi::C => ExternAbi::C { unwind: false },
+            CanonAbi::Rust => ExternAbi::Rust,
+            CanonAbi::RustCold => ExternAbi::RustCold,
+            CanonAbi::Arm(arm_call) => match arm_call {
+                ArmCall::Aapcs => ExternAbi::Aapcs { unwind: false },
+                ArmCall::CCmseNonSecureCall => ExternAbi::CCmseNonSecureCall,
+                ArmCall::CCmseNonSecureEntry => ExternAbi::CCmseNonSecureEntry,
+            },
+            CanonAbi::GpuKernel => ExternAbi::GpuKernel,
+            CanonAbi::Interrupt(interrupt_kind) => match interrupt_kind {
+                InterruptKind::Avr => ExternAbi::AvrInterrupt,
+                InterruptKind::AvrNonBlocking => ExternAbi::AvrNonBlockingInterrupt,
+                InterruptKind::Msp430 => ExternAbi::Msp430Interrupt,
+                InterruptKind::RiscvMachine => ExternAbi::RiscvInterruptM,
+                InterruptKind::RiscvSupervisor => ExternAbi::RiscvInterruptS,
+                InterruptKind::X86 => ExternAbi::X86Interrupt,
+            },
+            CanonAbi::X86(x86_call) => match x86_call {
+                X86Call::Fastcall => ExternAbi::Fastcall { unwind: false },
+                X86Call::Stdcall => ExternAbi::Stdcall { unwind: false },
+                X86Call::SysV64 => ExternAbi::SysV64 { unwind: false },
+                X86Call::Thiscall => ExternAbi::Thiscall { unwind: false },
+                X86Call::Vectorcall => ExternAbi::Vectorcall { unwind: false },
+                X86Call::Win64 => ExternAbi::Win64 { unwind: false },
+            },
+        }
+    }
+}
+
+/// Callee codegen for interrupts
+///
+/// This is named differently from the "Call" enums because it is different:
+/// these "ABI" differences are not relevant to callers, since there is "no caller".
+/// These only affect callee codegen. making their categorization as distinct ABIs a bit peculiar.
+#[derive(Copy, Clone, Debug)]
+#[derive(PartialOrd, Ord, PartialEq, Eq, Hash)]
+#[cfg_attr(feature = "nightly", derive(HashStable_Generic))]
+pub enum InterruptKind {
+    Avr,
+    AvrNonBlocking,
+    Msp430,
+    RiscvMachine,
+    RiscvSupervisor,
+    X86,
+}
+
+/// ABIs defined for x86-{32,64}
+///
+/// One of SysV64 or Win64 may alias the C ABI, and arguably Win64 is cross-platform now?
+#[derive(Clone, Copy, Debug)]
+#[derive(PartialOrd, Ord, PartialEq, Eq, Hash)]
+#[cfg_attr(feature = "nightly", derive(HashStable_Generic))]
+pub enum X86Call {
+    /// "fastcall" has both GNU and Windows variants
+    Fastcall,
+    /// "stdcall" has both GNU and Windows variants
+    Stdcall,
+    SysV64,
+    Thiscall,
+    Vectorcall,
+    Win64,
+}
+
+/// ABIs defined for 32-bit Arm
+#[derive(Copy, Clone, Debug)]
+#[derive(PartialOrd, Ord, PartialEq, Eq, Hash)]
+#[cfg_attr(feature = "nightly", derive(HashStable_Generic))]
+pub enum ArmCall {
+    Aapcs,
+    CCmseNonSecureCall,
+    CCmseNonSecureEntry,
+}

compiler/rustc_abi/src/extern_abi.rs

@@ -7,6 +7,8 @@ use rustc_data_structures::stable_hasher::{HashStable, StableHasher, StableOrd};
 #[cfg(feature = "nightly")]
 use rustc_macros::{Decodable, Encodable};
 
+use crate::AbiFromStrErr;
+
 #[cfg(test)]
 mod tests;
 
@@ -99,11 +101,6 @@ macro_rules! abi_impls {
     }
 }
 
-#[derive(Debug)]
-pub enum AbiFromStrErr {
-    Unknown,
-}
-
 abi_impls! {
     ExternAbi = {
             C { unwind: false } =><= "C",

compiler/rustc_abi/src/lib.rs

@@ -55,13 +55,14 @@ use rustc_index::{Idx, IndexSlice, IndexVec};
 use rustc_macros::{Decodable_NoContext, Encodable_NoContext, HashStable_Generic};
 
 mod callconv;
+mod canon_abi;
+mod extern_abi;
 mod layout;
 #[cfg(test)]
 mod tests;
 
-mod extern_abi;
-
 pub use callconv::{Heterogeneous, HomogeneousAggregate, Reg, RegKind};
+pub use canon_abi::{ArmCall, CanonAbi, InterruptKind, X86Call};
 pub use extern_abi::{ExternAbi, all_names};
 #[cfg(feature = "nightly")]
 pub use layout::{FIRST_VARIANT, FieldIdx, Layout, TyAbiInterface, TyAndLayout, VariantIdx};
@@ -1895,3 +1896,11 @@ pub enum StructKind {
     /// A univariant, but with a prefix of an arbitrary size & alignment (e.g., enum tag).
     Prefixed(Size, Align),
 }
+
+#[derive(Clone, Debug)]
+pub enum AbiFromStrErr {
+    /// not a known ABI
+    Unknown,
+    /// no "-unwind" variant can be used here
+    NoExplicitUnwind,
+}

compiler/rustc_codegen_cranelift/src/abi/mod.rs

@@ -10,7 +10,7 @@ use std::mem;
 use cranelift_codegen::ir::{ArgumentPurpose, SigRef};
 use cranelift_codegen::isa::CallConv;
 use cranelift_module::ModuleError;
-use rustc_abi::ExternAbi;
+use rustc_abi::{CanonAbi, ExternAbi, X86Call};
 use rustc_codegen_ssa::base::is_call_from_compiler_builtins_to_upstream_monomorphization;
 use rustc_codegen_ssa::errors::CompilerBuiltinsCannotCall;
 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
@@ -19,7 +19,7 @@ use rustc_middle::ty::layout::FnAbiOf;
 use rustc_middle::ty::print::with_no_trimmed_paths;
 use rustc_session::Session;
 use rustc_span::source_map::Spanned;
-use rustc_target::callconv::{Conv, FnAbi, PassMode};
+use rustc_target::callconv::{FnAbi, PassMode};
 use smallvec::SmallVec;
 
 use self::pass_mode::*;
@@ -42,32 +42,27 @@ fn clif_sig_from_fn_abi<'tcx>(
     Signature { params, returns, call_conv }
 }
 
-pub(crate) fn conv_to_call_conv(sess: &Session, c: Conv, default_call_conv: CallConv) -> CallConv {
+pub(crate) fn conv_to_call_conv(
+    sess: &Session,
+    c: CanonAbi,
+    default_call_conv: CallConv,
+) -> CallConv {
     match c {
-        Conv::Rust | Conv::C => default_call_conv,
-        Conv::Cold | Conv::PreserveMost | Conv::PreserveAll => CallConv::Cold,
-        Conv::X86_64SysV => CallConv::SystemV,
-        Conv::X86_64Win64 => CallConv::WindowsFastcall,
-
-        // Should already get a back compat warning
-        Conv::X86Fastcall | Conv::X86Stdcall | Conv::X86ThisCall | Conv::X86VectorCall => {
-            default_call_conv
-        }
-
-        Conv::X86Intr | Conv::RiscvInterrupt { .. } => {
-            sess.dcx().fatal(format!("interrupt call conv {c:?} not yet implemented"))
+        CanonAbi::Rust | CanonAbi::C => default_call_conv,
+        CanonAbi::RustCold => CallConv::Cold,
+
+        CanonAbi::X86(x86_call) => match x86_call {
+            X86Call::SysV64 => CallConv::SystemV,
+            X86Call::Win64 => CallConv::WindowsFastcall,
+            // Should already get a back compat warning
+            _ => default_call_conv,
+        },
+
+        CanonAbi::Interrupt(_) | CanonAbi::Arm(_) => {
+            sess.dcx().fatal("call conv {c:?} is not yet implemented")
         }
-
-        Conv::ArmAapcs => sess.dcx().fatal("aapcs call conv not yet implemented"),
-        Conv::CCmseNonSecureCall => {
-            sess.dcx().fatal("C-cmse-nonsecure-call call conv is not yet implemented");
-        }
-        Conv::CCmseNonSecureEntry => {
-            sess.dcx().fatal("C-cmse-nonsecure-entry call conv is not yet implemented");
-        }
-
-        Conv::Msp430Intr | Conv::GpuKernel | Conv::AvrInterrupt | Conv::AvrNonBlockingInterrupt => {
-            unreachable!("tried to use {c:?} call conv which only exists on an unsupported target");
+        CanonAbi::GpuKernel => {
+            unreachable!("tried to use {c:?} call conv which only exists on an unsupported target")
         }
     }
 }
@@ -610,7 +605,7 @@ pub(crate) fn codegen_terminator_call<'tcx>(
         target: CallTarget,
         call_args: &mut Vec<Value>,
     ) {
-        if fn_abi.conv != Conv::C {
+        if fn_abi.conv != CanonAbi::C {
             fx.tcx.dcx().span_fatal(
                 source_info.span,
                 format!("Variadic call for non-C abi {:?}", fn_abi.conv),

compiler/rustc_codegen_gcc/src/abi.rs

@@ -1,7 +1,7 @@
 #[cfg(feature = "master")]
 use gccjit::FnAttribute;
 use gccjit::{ToLValue, ToRValue, Type};
-use rustc_abi::{Reg, RegKind};
+use rustc_abi::{ArmCall, CanonAbi, InterruptKind, Reg, RegKind, X86Call};
 use rustc_codegen_ssa::traits::{AbiBuilderMethods, BaseTypeCodegenMethods};
 use rustc_data_structures::fx::FxHashSet;
 use rustc_middle::bug;
@@ -10,8 +10,6 @@ use rustc_middle::ty::layout::LayoutOf;
 #[cfg(feature = "master")]
 use rustc_session::config;
 use rustc_target::callconv::{ArgAttributes, CastTarget, FnAbi, PassMode};
-#[cfg(feature = "master")]
-use rustc_target::callconv::{Conv, RiscvInterruptKind};
 
 use crate::builder::Builder;
 use crate::context::CodegenCx;
@@ -238,29 +236,16 @@ impl<'gcc, 'tcx> FnAbiGccExt<'gcc, 'tcx> for FnAbi<'tcx, Ty<'tcx>> {
 }
 
 #[cfg(feature = "master")]
-pub fn conv_to_fn_attribute<'gcc>(conv: Conv, arch: &str) -> Option<FnAttribute<'gcc>> {
+pub fn conv_to_fn_attribute<'gcc>(conv: CanonAbi, arch: &str) -> Option<FnAttribute<'gcc>> {
     let attribute = match conv {
-        Conv::C | Conv::Rust => return None,
-        Conv::CCmseNonSecureCall => {
-            if arch == "arm" {
-                FnAttribute::ArmCmseNonsecureCall
-            } else {
-                return None;
-            }
-        }
-        Conv::CCmseNonSecureEntry => {
-            if arch == "arm" {
-                FnAttribute::ArmCmseNonsecureEntry
-            } else {
-                return None;
-            }
-        }
-        Conv::Cold => FnAttribute::Cold,
-        // NOTE: the preserve attributes are not yet implemented in GCC:
-        // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110899
-        Conv::PreserveMost => return None,
-        Conv::PreserveAll => return None,
-        Conv::GpuKernel => {
+        CanonAbi::C | CanonAbi::Rust => return None,
+        CanonAbi::Arm(arm_call) => match arm_call {
+            ArmCall::CCmseNonSecureCall => FnAttribute::ArmCmseNonsecureCall,
+            ArmCall::CCmseNonSecureEntry => FnAttribute::ArmCmseNonsecureEntry,
+            ArmCall::Aapcs => FnAttribute::ArmPcs("aapcs"),
+        },
+        CanonAbi::RustCold => FnAttribute::Cold,
+        CanonAbi::GpuKernel => {
             if arch == "amdgpu" {
                 FnAttribute::GcnAmdGpuHsaKernel
             } else if arch == "nvptx64" {
@@ -270,26 +255,24 @@ pub fn conv_to_fn_attribute<'gcc>(conv: Conv, arch: &str) -> Option<FnAttribute<
             }
         }
         // TODO(antoyo): check if those AVR attributes are mapped correctly.
-        Conv::AvrInterrupt => FnAttribute::AvrSignal,
-        Conv::AvrNonBlockingInterrupt => FnAttribute::AvrInterrupt,
-        Conv::ArmAapcs => FnAttribute::ArmPcs("aapcs"),
-        Conv::Msp430Intr => FnAttribute::Msp430Interrupt,
-        Conv::RiscvInterrupt { kind } => {
-            let kind = match kind {
-                RiscvInterruptKind::Machine => "machine",
-                RiscvInterruptKind::Supervisor => "supervisor",
-            };
-            FnAttribute::RiscvInterrupt(kind)
-        }
-        Conv::X86Fastcall => FnAttribute::X86FastCall,
-        Conv::X86Intr => FnAttribute::X86Interrupt,
-        Conv::X86Stdcall => FnAttribute::X86Stdcall,
-        Conv::X86ThisCall => FnAttribute::X86ThisCall,
-        // NOTE: the vectorcall calling convention is not yet implemented in GCC:
-        // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89485
-        Conv::X86VectorCall => return None,
-        Conv::X86_64SysV => FnAttribute::X86SysvAbi,
-        Conv::X86_64Win64 => FnAttribute::X86MsAbi,
+        CanonAbi::Interrupt(interrupt_kind) => match interrupt_kind {
+            InterruptKind::Avr => FnAttribute::AvrSignal,
+            InterruptKind::AvrNonBlocking => FnAttribute::AvrInterrupt,
+            InterruptKind::Msp430 => FnAttribute::Msp430Interrupt,
+            InterruptKind::RiscvMachine => FnAttribute::RiscvInterrupt("machine"),
+            InterruptKind::RiscvSupervisor => FnAttribute::RiscvInterrupt("supervisor"),
+            InterruptKind::X86 => FnAttribute::X86Interrupt,
+        },
+        CanonAbi::X86(x86_call) => match x86_call {
+            X86Call::Fastcall => FnAttribute::X86FastCall,
+            X86Call::Stdcall => FnAttribute::X86Stdcall,
+            X86Call::Thiscall => FnAttribute::X86ThisCall,
+            // // NOTE: the vectorcall calling convention is not yet implemented in GCC:
+            // // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89485
+            X86Call::Vectorcall => return None,
+            X86Call::SysV64 => FnAttribute::X86SysvAbi,
+            X86Call::Win64 => FnAttribute::X86MsAbi,
+        },
     };
     Some(attribute)
 }

compiler/rustc_codegen_gcc/src/int.rs

@@ -3,11 +3,11 @@
 //! 128-bit integers on 32-bit platforms and thus require to be handled manually.
 
 use gccjit::{BinaryOp, ComparisonOp, FunctionType, Location, RValue, ToRValue, Type, UnaryOp};
-use rustc_abi::{Endian, ExternAbi};
+use rustc_abi::{CanonAbi, Endian, ExternAbi};
 use rustc_codegen_ssa::common::{IntPredicate, TypeKind};
 use rustc_codegen_ssa::traits::{BackendTypes, BaseTypeCodegenMethods, BuilderMethods, OverflowOp};
 use rustc_middle::ty::{self, Ty};
-use rustc_target::callconv::{ArgAbi, ArgAttributes, Conv, FnAbi, PassMode};
+use rustc_target::callconv::{ArgAbi, ArgAttributes, FnAbi, PassMode};
 
 use crate::builder::{Builder, ToGccComp};
 use crate::common::{SignType, TypeReflection};
@@ -397,7 +397,7 @@ impl<'a, 'gcc, 'tcx> Builder<'a, 'gcc, 'tcx> {
             ret: arg_abi,
             c_variadic: false,
             fixed_count: 3,
-            conv: Conv::C,
+            conv: CanonAbi::C,
             can_unwind: false,
         };
         fn_abi.adjust_for_foreign_abi(self.cx, ExternAbi::C { unwind: false });