Auto merge of #90382 - alexcrichton:wasm64-libstd, r=joshtriplett

std: Get the standard library compiling for wasm64

This commit goes through and updates various `#[cfg]` as appropriate to
get the wasm64-unknown-unknown target behaving similarly to the
wasm32-unknown-unknown target. Most of this is just updating various
conditions for `target_arch = "wasm32"` to also account for `target_arch
= "wasm64"` where appropriate. This commit also lists `wasm64` as an
allow-listed architecture to not have the `restricted_std` feature
enabled, enabling experimentation with `-Z build-std` externally.

The main goal of this commit is to enable playing around with
`wasm64-unknown-unknown` externally via `-Z build-std` in a way that's
similar to the `wasm32-unknown-unknown` target. These targets are
effectively the same and only differ in their pointer size, but wasm64
is much newer and has much less ecosystem/library support so it'll still
take time to get wasm64 fully-fledged.

compiler/rustc_target/src/asm/mod.rs

@@ -189,6 +189,7 @@ pub enum InlineAsmArch {
     S390x,
     SpirV,
     Wasm32,
+    Wasm64,
     Bpf,
 }
 
@@ -212,6 +213,7 @@ impl FromStr for InlineAsmArch {
             "s390x" => Ok(Self::S390x),
             "spirv" => Ok(Self::SpirV),
             "wasm32" => Ok(Self::Wasm32),
+            "wasm64" => Ok(Self::Wasm64),
             "bpf" => Ok(Self::Bpf),
             _ => Err(()),
         }
@@ -318,7 +320,7 @@ impl InlineAsmReg {
             InlineAsmArch::SpirV => {
                 Self::SpirV(SpirVInlineAsmReg::parse(arch, has_feature, target, &name)?)
             }
-            InlineAsmArch::Wasm32 => {
+            InlineAsmArch::Wasm32 | InlineAsmArch::Wasm64 => {
                 Self::Wasm(WasmInlineAsmReg::parse(arch, has_feature, target, &name)?)
             }
             InlineAsmArch::Bpf => {
@@ -529,7 +531,9 @@ impl InlineAsmRegClass {
             }
             InlineAsmArch::S390x => Self::S390x(S390xInlineAsmRegClass::parse(arch, name)?),
             InlineAsmArch::SpirV => Self::SpirV(SpirVInlineAsmRegClass::parse(arch, name)?),
-            InlineAsmArch::Wasm32 => Self::Wasm(WasmInlineAsmRegClass::parse(arch, name)?),
+            InlineAsmArch::Wasm32 | InlineAsmArch::Wasm64 => {
+                Self::Wasm(WasmInlineAsmRegClass::parse(arch, name)?)
+            }
             InlineAsmArch::Bpf => Self::Bpf(BpfInlineAsmRegClass::parse(arch, name)?),
         })
     }
@@ -725,7 +729,7 @@ pub fn allocatable_registers(
             spirv::fill_reg_map(arch, has_feature, target, &mut map);
             map
         }
-        InlineAsmArch::Wasm32 => {
+        InlineAsmArch::Wasm32 | InlineAsmArch::Wasm64 => {
             let mut map = wasm::regclass_map();
             wasm::fill_reg_map(arch, has_feature, target, &mut map);
             map

compiler/rustc_target/src/spec/mod.rs

@@ -1357,6 +1357,9 @@ pub struct TargetOptions {
 
     /// Minimum number of bits in #[repr(C)] enum. Defaults to 32.
     pub c_enum_min_bits: u64,
+
+    /// Whether or not the DWARF `.debug_aranges` section should be generated.
+    pub generate_arange_section: bool,
 }
 
 impl Default for TargetOptions {
@@ -1462,6 +1465,7 @@ impl Default for TargetOptions {
             supported_sanitizers: SanitizerSet::empty(),
             default_adjusted_cabi: None,
             c_enum_min_bits: 32,
+            generate_arange_section: true,
         }
     }
 }
@@ -2047,6 +2051,7 @@ impl Target {
         key!(supported_sanitizers, SanitizerSet)?;
         key!(default_adjusted_cabi, Option<Abi>)?;
         key!(c_enum_min_bits, u64);
+        key!(generate_arange_section, bool);
 
         if base.is_builtin {
             // This can cause unfortunate ICEs later down the line.
@@ -2286,6 +2291,7 @@ impl ToJson for Target {
         target_option_val!(split_debuginfo);
         target_option_val!(supported_sanitizers);
         target_option_val!(c_enum_min_bits);
+        target_option_val!(generate_arange_section);
 
         if let Some(abi) = self.default_adjusted_cabi {
             d.insert("default-adjusted-cabi".to_string(), Abi::name(abi).to_json());

compiler/rustc_target/src/spec/wasm32_unknown_emscripten.rs

@@ -37,7 +37,7 @@ pub fn target() -> Target {
         is_like_emscripten: true,
         panic_strategy: PanicStrategy::Unwind,
         post_link_args,
-        families: vec!["unix".to_string()],
+        families: vec!["unix".to_string(), "wasm".to_string()],
         ..options
     };
     Target {

compiler/rustc_target/src/spec/wasm64_unknown_unknown.rs

@@ -23,11 +23,15 @@ pub fn target() -> Target {
     // For now this target just never has an entry symbol no matter the output
     // type, so unconditionally pass this.
     clang_args.push("-Wl,--no-entry".to_string());
-    options
-        .pre_link_args
-        .get_mut(&LinkerFlavor::Lld(LldFlavor::Wasm))
-        .unwrap()
-        .push("--no-entry".to_string());
+
+    let lld_args = options.pre_link_args.get_mut(&LinkerFlavor::Lld(LldFlavor::Wasm)).unwrap();
+    lld_args.push("--no-entry".to_string());
+    lld_args.push("-mwasm64".to_string());
+
+    // Any engine that implements wasm64 will surely implement the rest of these
+    // features since they were all merged into the official spec by the time
+    // wasm64 was designed.
+    options.features = "+bulk-memory,+mutable-globals,+sign-ext,+nontrapping-fptoint".to_string();
 
     Target {
         llvm_target: "wasm64-unknown-unknown".to_string(),

compiler/rustc_target/src/spec/wasm_base.rs

@@ -128,6 +128,12 @@ pub fn options() -> TargetOptions {
         // gdb scripts don't work on wasm blobs
         emit_debug_gdb_scripts: false,
 
+        // There's more discussion of this at
+        // https://bugs.llvm.org/show_bug.cgi?id=52442 but the general result is
+        // that this isn't useful for wasm and has tricky issues with
+        // representation, so this is disabled.
+        generate_arange_section: false,
+
         ..Default::default()
     }
 }