Auto merge of #117919 - daxpedda:wasm-c-abi, r=wesleywiser

Introduce perma-unstable `wasm-c-abi` flag
Now that `wasm-bindgen` v0.2.88 supports the spec-compliant C ABI, the idea is to switch to that in a future version of Rust. In the meantime it would be good to let people test and play around with it.
This PR introduces a new perma-unstable `-Zwasm-c-abi` compiler flag, which switches to the new spec-compliant C ABI when targeting `wasm32-unknown-unknown`.
Alternatively, we could also stabilize this and then deprecate it when we switch. I will leave this to the Rust maintainers to decide.
This is a companion PR to #117918, but they could be merged independently.
MCP: rust-lang/compiler-team#703
Tracking issue: #122532

Author: bors

compiler/rustc_codegen_gcc/src/builder.rs

@@ -31,7 +31,7 @@ use rustc_span::Span;
 use rustc_target::abi::{
 self, call::FnAbi,Align,HasDataLayout,Size,TargetDataLayout,WrappingRange,
 };
-use rustc_target::spec::{HasTargetSpec,Target};
+use rustc_target::spec::{HasTargetSpec,HasWasmCAbiOpt,Target,WasmCAbi};
 
 usecrate::common::{type_is_pointer,SignType,TypeReflection};
 usecrate::context::CodegenCx;
@@ -2352,6 +2352,12 @@ impl<'tcx> HasTargetSpec for Builder<'_, '_, 'tcx> {
 }
 }
 
+impl<'tcx>HasWasmCAbiOptforBuilder<'_,'_,'tcx>{
+fnwasm_c_abi_opt(&self) -> WasmCAbi{
+self.cx.wasm_c_abi_opt()
+}
+}
+
 pubtraitToGccComp{
 fnto_gcc_comparison(&self) -> ComparisonOp;
 }

compiler/rustc_codegen_gcc/src/context.rs

@@ -20,7 +20,7 @@ use rustc_span::{source_map::respan, Span};
 use rustc_target::abi::{
  call::FnAbi,HasDataLayout,PointeeInfo,Size,TargetDataLayout,VariantIdx,
 };
-use rustc_target::spec::{HasTargetSpec,Target,TlsModel};
+use rustc_target::spec::{HasTargetSpec,HasWasmCAbiOpt,Target,TlsModel,WasmCAbi};
 
 usecrate::callee::get_fn;
 usecrate::common::SignType;
@@ -557,6 +557,12 @@ impl<'gcc, 'tcx> HasTargetSpec for CodegenCx<'gcc, 'tcx> {
 }
 }
 
+impl<'gcc,'tcx>HasWasmCAbiOptforCodegenCx<'gcc,'tcx>{
+fnwasm_c_abi_opt(&self) -> WasmCAbi{
+self.tcx.sess.opts.unstable_opts.wasm_c_abi
+}
+}
+
 impl<'gcc,'tcx>LayoutOfHelpers<'tcx>forCodegenCx<'gcc,'tcx>{
 typeLayoutOfResult = TyAndLayout<'tcx>;
 

compiler/rustc_interface/src/tests.rs

@@ -19,7 +19,9 @@ use rustc_span::edition::{Edition, DEFAULT_EDITION};
 use rustc_span::source_map::{RealFileLoader,SourceMapInputs};
 use rustc_span::symbol::sym;
 use rustc_span::{FileName,SourceFileHashAlgorithm};
-use rustc_target::spec::{CodeModel,LinkerFlavorCli,MergeFunctions,PanicStrategy,RelocModel};
+use rustc_target::spec::{
+CodeModel,LinkerFlavorCli,MergeFunctions,PanicStrategy,RelocModel,WasmCAbi,
+};
 use rustc_target::spec::{RelroLevel,SanitizerSet,SplitDebuginfo,StackProtector,TlsModel};
 use std::collections::{BTreeMap,BTreeSet};
 use std::num::NonZero;
@@ -851,6 +853,7 @@ fn test_unstable_options_tracking_hash() {
 tracked!(verify_llvm_ir,true);
 tracked!(virtual_function_elimination,true);
 tracked!(wasi_exec_model,Some(WasiExecModel::Reactor));
+tracked!(wasm_c_abi,WasmCAbi::Spec);
 // tidy-alphabetical-end
 
 macro_rules! tracked_no_crate_hash {

compiler/rustc_middle/src/ty/layout.rs

@@ -15,7 +15,9 @@ use rustc_span::symbol::{sym, Symbol};
 use rustc_span::{ErrorGuaranteed,Span,DUMMY_SP};
 use rustc_target::abi::call::FnAbi;
 use rustc_target::abi::*;
-use rustc_target::spec::{abi::AbiasSpecAbi,HasTargetSpec,PanicStrategy,Target};
+use rustc_target::spec::{
+ abi::AbiasSpecAbi,HasTargetSpec,HasWasmCAbiOpt,PanicStrategy,Target,WasmCAbi,
+};
 
 use std::borrow::Cow;
 use std::cmp;
@@ -483,6 +485,12 @@ impl<'tcx> HasTargetSpec for TyCtxt<'tcx> {
 }
 }
 
+impl<'tcx>HasWasmCAbiOptforTyCtxt<'tcx>{
+fnwasm_c_abi_opt(&self) -> WasmCAbi{
+self.sess.opts.unstable_opts.wasm_c_abi
+}
+}
+
 impl<'tcx>HasTyCtxt<'tcx>forTyCtxt<'tcx>{
 #[inline]
 fntcx(&self) -> TyCtxt<'tcx>{
@@ -528,6 +536,12 @@ impl<'tcx, T: HasTargetSpec> HasTargetSpec for LayoutCx<'tcx, T> {
 }
 }
 
+impl<'tcx,T:HasWasmCAbiOpt>HasWasmCAbiOptforLayoutCx<'tcx,T>{
+fnwasm_c_abi_opt(&self) -> WasmCAbi{
+self.tcx.wasm_c_abi_opt()
+}
+}
+
 impl<'tcx,T:HasTyCtxt<'tcx>>HasTyCtxt<'tcx>forLayoutCx<'tcx,T>{
 fntcx(&self) -> TyCtxt<'tcx>{
 self.tcx.tcx()

compiler/rustc_session/src/config.rs

@@ -2880,7 +2880,7 @@ pub(crate) mod dep_tracking {
 use rustc_feature::UnstableFeatures;
 use rustc_span::edition::Edition;
 use rustc_span::RealFileName;
-use rustc_target::spec::{CodeModel,MergeFunctions,PanicStrategy,RelocModel};
+use rustc_target::spec::{CodeModel,MergeFunctions,PanicStrategy,RelocModel,WasmCAbi};
 use rustc_target::spec::{
 RelroLevel,SanitizerSet,SplitDebuginfo,StackProtector,TargetTriple,TlsModel,
 };
@@ -2978,6 +2978,7 @@ pub(crate) mod dep_tracking {
 Polonius,
 InliningThreshold,
 FunctionReturn,
+WasmCAbi,
 );
 
 impl<T1,T2>DepTrackingHashfor(T1,T2)

compiler/rustc_session/src/options.rs

@@ -8,7 +8,9 @@ use rustc_data_structures::profiling::TimePassesFormat;
 use rustc_data_structures::stable_hasher::Hash64;
 use rustc_errors::ColorConfig;
 use rustc_errors::{LanguageIdentifier,TerminalUrl};
-use rustc_target::spec::{CodeModel,LinkerFlavorCli,MergeFunctions,PanicStrategy,SanitizerSet};
+use rustc_target::spec::{
+CodeModel,LinkerFlavorCli,MergeFunctions,PanicStrategy,SanitizerSet,WasmCAbi,
+};
 use rustc_target::spec::{
 RelocModel,RelroLevel,SplitDebuginfo,StackProtector,TargetTriple,TlsModel,
 };
@@ -441,6 +443,7 @@ mod desc {
 "either a boolean (`yes`, `no`, `on`, `off`, etc), or a non-negative number";
 pubconst parse_llvm_module_flag:&str = "<key>:<type>:<value>:<behavior>. Type must currently be `u32`. Behavior should be one of (`error`, `warning`, `require`, `override`, `append`, `appendunique`, `max`, `min`)";
 pubconst parse_function_return:&str = "`keep` or `thunk-extern`";
+pubconst parse_wasm_c_abi:&str = "`legacy` or `spec`";
 }
 
 mod parse {
@@ -1433,6 +1436,15 @@ mod parse {
 }
 true
 }
+
+pub(crate)fnparse_wasm_c_abi(slot:&mutWasmCAbi,v:Option<&str>) -> bool{
+match v {
+Some("spec") => *slot = WasmCAbi::Spec,
+Some("legacy") => *slot = WasmCAbi::Legacy,
+ _ => returnfalse,
+}
+true
+}
 }
 
 options!{
@@ -2061,6 +2073,8 @@ written to standard error output)"),
  Requires `-Clto[=[fat,yes]]`"),
  wasi_exec_model:Option<WasiExecModel> = (None, parse_wasi_exec_model,[TRACKED],
 "whether to build a wasi command or reactor"),
+ wasm_c_abi:WasmCAbi = (WasmCAbi::Legacy, parse_wasm_c_abi,[TRACKED],
+"use spec-compliant C ABI for `wasm32-unknown-unknown` (default: legacy)"),
  write_long_types_to_disk:bool = (true, parse_bool,[UNTRACKED],
 "whether long type names should be written to files instead of being printed in errors"),
 // tidy-alphabetical-end

compiler/rustc_target/src/abi/call/mod.rs

@@ -1,6 +1,6 @@
 usecrate::abi::{self,Abi,Align,FieldsShape,Size};
 usecrate::abi::{HasDataLayout,TyAbiInterface,TyAndLayout};
-usecrate::spec::{self,HasTargetSpec};
+usecrate::spec::{self,HasTargetSpec,HasWasmCAbiOpt};
 use rustc_span::Symbol;
 use std::fmt;
 use std::str::FromStr;
@@ -829,7 +829,7 @@ impl<'a, Ty> FnAbi<'a, Ty> {
 ) -> Result<(),AdjustForForeignAbiError>
 where
 Ty:TyAbiInterface<'a,C> + Copy,
-C:HasDataLayout + HasTargetSpec,
+C:HasDataLayout + HasTargetSpec + HasWasmCAbiOpt,
 {
 if abi == spec::abi::Abi::X86Interrupt{
 ifletSome(arg) = self.args.first_mut(){
@@ -886,7 +886,9 @@ impl<'a, Ty> FnAbi<'a, Ty> {
 "sparc" => sparc::compute_abi_info(cx,self),
 "sparc64" => sparc64::compute_abi_info(cx,self),
 "nvptx64" => {
-if cx.target_spec().adjust_abi(abi,self.c_variadic) == spec::abi::Abi::PtxKernel{
+if cx.target_spec().adjust_abi(cx, abi,self.c_variadic)
+ == spec::abi::Abi::PtxKernel
+{
  nvptx64::compute_ptx_kernel_abi_info(cx,self)
 }else{
  nvptx64::compute_abi_info(self)
@@ -895,7 +897,7 @@ impl<'a, Ty> FnAbi<'a, Ty> {
 "hexagon" => hexagon::compute_abi_info(self),
 "riscv32" | "riscv64" => riscv::compute_abi_info(cx,self),
 "wasm32" | "wasm64" => {
-if cx.target_spec().adjust_abi(abi,self.c_variadic) == spec::abi::Abi::Wasm{
+if cx.target_spec().adjust_abi(cx,abi,self.c_variadic) == spec::abi::Abi::Wasm{
  wasm::compute_wasm_abi_info(self)
 }else{
  wasm::compute_c_abi_info(cx,self)

compiler/rustc_target/src/spec/mod.rs

@@ -37,7 +37,7 @@
 usecrate::abi::call::Conv;
 usecrate::abi::{Endian,Integer,Size,TargetDataLayout,TargetDataLayoutErrors};
 usecrate::json::{Json,ToJson};
-usecrate::spec::abi::{lookup as lookup_abi,Abi};
+usecrate::spec::abi::Abi;
 usecrate::spec::crt_objects::CrtObjects;
 use rustc_fs_util::try_canonicalize;
 use rustc_serialize::{Decodable,Decoder,Encodable,Encoder};
@@ -1915,6 +1915,19 @@ impl HasTargetSpec for Target {
 }
 }
 
+/// Which C ABI to use for `wasm32-unknown-unknown`.
+#[derive(Debug,Copy,Clone,Hash,PartialEq,Eq)]
+pubenumWasmCAbi{
+/// Spec-compliant C ABI.
+Spec,
+/// Legacy ABI. Which is non-spec-compliant.
+Legacy,
+}
+
+pubtraitHasWasmCAbiOpt{
+fnwasm_c_abi_opt(&self) -> WasmCAbi;
+}
+
 typeStaticCow<T> = Cow<'static,T>;
 
 /// Optional aspects of a target specification.
@@ -2273,9 +2286,6 @@ pub struct TargetOptions {
 /// distributed with the target, the sanitizer should still appear in this list for the target.
 pubsupported_sanitizers:SanitizerSet,
 
-/// If present it's a default value to use for adjusting the C ABI.
-pubdefault_adjusted_cabi:Option<Abi>,
-
 /// Minimum number of bits in #[repr(C)] enum. Defaults to the size of c_int
 pubc_enum_min_bits:Option<u64>,
 
@@ -2507,7 +2517,6 @@ impl Default for TargetOptions {
 // `Off` is supported by default, but targets can remove this manually, e.g. Windows.
 supported_split_debuginfo:Cow::Borrowed(&[SplitDebuginfo::Off]),
 supported_sanitizers:SanitizerSet::empty(),
-default_adjusted_cabi:None,
 c_enum_min_bits:None,
 generate_arange_section:true,
 supports_stack_protector:true,
@@ -2538,9 +2547,21 @@ impl DerefMut for Target {
 
 implTarget{
 /// Given a function ABI, turn it into the correct ABI for this target.
-pubfnadjust_abi(&self,abi:Abi,c_variadic:bool) -> Abi{
+pubfnadjust_abi<C>(&self,cx:&C,abi:Abi,c_variadic:bool) -> Abi
+where
+C:HasWasmCAbiOpt,
+{
 match abi {
-Abi::C{ .. } => self.default_adjusted_cabi.unwrap_or(abi),
+Abi::C{ .. } => {
+ifself.arch == "wasm32"
+ && self.os == "unknown"
+ && cx.wasm_c_abi_opt() == WasmCAbi::Legacy
+{
+Abi::Wasm
+}else{
+ abi
+}
+}
 
 // On Windows, `extern "system"` behaves like msvc's `__stdcall`.
 // `__stdcall` only applies on x86 and on non-variadic functions:
@@ -3079,16 +3100,6 @@ impl Target {
 }
 }
 });
-($key_name:ident,Option<Abi>) => ({
-let name = (stringify!($key_name)).replace("_","-");
- obj.remove(&name).and_then(|o| o.as_str().and_then(|s| {
-match lookup_abi(s){
-Ok(abi) => base.$key_name = Some(abi),
- _ => returnSome(Err(format!("'{}' is not a valid value for abi", s))),
-}
-Some(Ok(()))
-})).unwrap_or(Ok(()))
-});
 ($key_name:ident,TargetFamilies) => ({
 ifletSome(value) = obj.remove("target-family"){
 ifletSome(v) = value.as_array(){
@@ -3238,7 +3249,6 @@ impl Target {
 key!(split_debuginfo,SplitDebuginfo)?;
 key!(supported_split_debuginfo, fallible_list)?;
 key!(supported_sanitizers,SanitizerSet)?;
-key!(default_adjusted_cabi,Option<Abi>)?;
 key!(generate_arange_section,bool);
 key!(supports_stack_protector,bool);
 key!(entry_name);
@@ -3502,10 +3512,6 @@ impl ToJson for Target {
 target_option_val!(entry_abi);
 target_option_val!(supports_xray);
 
-ifletSome(abi) = self.default_adjusted_cabi{
- d.insert("default-adjusted-cabi".into(),Abi::name(abi).to_json());
-}
-
 // Serializing `-Clink-self-contained` needs a dynamic key to support the
 // backwards-compatible variants.
  d.insert(self.link_self_contained.json_key().into(),self.link_self_contained.to_json());

compiler/rustc_target/src/spec/targets/wasm32_unknown_unknown.rs

@@ -10,23 +10,12 @@
 //! This target is more or less managed by the Rust and WebAssembly Working
 //! Group nowadays at <https://github.com/rustwasm>.
 
-usecrate::spec::abi::Abi;
 usecrate::spec::{base,Cc,LinkerFlavor,Target};
 
 pubfntarget() -> Target{
 letmut options = base::wasm::options();
  options.os = "unknown".into();
 
-// This is a default for backwards-compatibility with the original
-// definition of this target oh-so-long-ago. Once the "wasm" ABI is
-// stable and the wasm-bindgen project has switched to using it then there's
-// no need for this and it can be removed.
-//
-// Currently this is the reason that this target's ABI is mismatched with
-// clang's ABI. This means that, in the limit, you can't merge C and Rust
-// code on this target due to this ABI mismatch.
- options.default_adjusted_cabi = Some(Abi::Wasm);
-
  options.add_pre_link_args(
 LinkerFlavor::WasmLld(Cc::No),
 &[

compiler/rustc_ty_utils/src/abi.rs

@@ -322,7 +322,7 @@ fn fn_sig_for_fn_abi<'tcx>(
 #[inline]
 fnconv_from_spec_abi(tcx:TyCtxt<'_>,abi:SpecAbi,c_variadic:bool) -> Conv{
 use rustc_target::spec::abi::Abi::*;
-match tcx.sess.target.adjust_abi(abi, c_variadic){
+match tcx.sess.target.adjust_abi(&tcx,abi, c_variadic){
 RustIntrinsic | Rust | RustCall => Conv::Rust,
 
 // This is intentionally not using `Conv::Cold`, as that has to preserve