rustbuild: RISC-V is no longer an experimental LLVM target

This commit moves RISC-V from the experimental LLVM targets to the
regular LLVM targets. RISC-V was made non-experimental in
https://reviews.llvm.org/rL366399

I have also sorted the list of LLVM targets, and changed the code
around setting llvm_exp_targets (and its default) to match the code
setting llvm_targets (and its default), ensuring future changes to
the defaults, as LLVM targets become stable, affect as few places as
possible.

config.toml.example

@@ -57,14 +57,14 @@
 # support. You'll need to write a target specification at least, and most
 # likely, teach rustc about the C ABI of the target. Get in touch with the
 # Rust team and file an issue if you need assistance in porting!
-#targets = "X86;ARM;AArch64;Mips;PowerPC;SystemZ;MSP430;Sparc;NVPTX;Hexagon"
+#targets = "AArch64;ARM;Hexagon;MSP430;Mips;NVPTX;PowerPC;RISCV;Sparc;SystemZ;X86"
 
 # LLVM experimental targets to build support for. These targets are specified in
 # the same format as above, but since these targets are experimental, they are
 # not built by default and the experimental Rust compilation targets that depend
 # on them will not work unless the user opts in to building them. By default the
-# `WebAssembly` and `RISCV` targets are enabled when compiling LLVM from scratch.
-#experimental-targets = "WebAssembly;RISCV"
+# `WebAssembly` target is enabled when compiling LLVM from scratch.
+#experimental-targets = "WebAssembly"
 
 # Cap the number of parallel linker invocations when compiling LLVM.
 # This can be useful when building LLVM with debug info, which significantly

src/bootstrap/config.rs

@@ -75,7 +75,7 @@ pub struct Config {
     pub llvm_link_shared: bool,
     pub llvm_clang_cl: Option<String>,
     pub llvm_targets: Option<String>,
-    pub llvm_experimental_targets: String,
+    pub llvm_experimental_targets: Option<String>,
     pub llvm_link_jobs: Option<u32>,
     pub llvm_version_suffix: Option<String>,
     pub llvm_use_linker: Option<String>,
@@ -524,8 +524,7 @@ impl Config {
             set(&mut config.llvm_static_stdcpp, llvm.static_libstdcpp);
             set(&mut config.llvm_link_shared, llvm.link_shared);
             config.llvm_targets = llvm.targets.clone();
-            config.llvm_experimental_targets = llvm.experimental_targets.clone()
-                .unwrap_or_else(|| "WebAssembly;RISCV".to_string());
+            config.llvm_experimental_targets = llvm.experimental_targets.clone();
             config.llvm_link_jobs = llvm.link_jobs;
             config.llvm_version_suffix = llvm.version_suffix.clone();
             config.llvm_clang_cl = llvm.clang_cl.clone();

src/bootstrap/native.rs

@@ -125,14 +125,17 @@ impl Step for Llvm {
         } else {
             match builder.config.llvm_targets {
                 Some(ref s) => s,
-                None => "X86;ARM;AArch64;Mips;PowerPC;SystemZ;MSP430;Sparc;NVPTX;Hexagon",
+                None => "AArch64;ARM;Hexagon;MSP430;Mips;NVPTX;PowerPC;RISCV;Sparc;SystemZ;X86",
             }
         };
 
         let llvm_exp_targets = if self.emscripten {
             ""
         } else {
-            &builder.config.llvm_experimental_targets[..]
+            match builder.config.llvm_experimental_targets {
+                Some(ref s) => s,
+                None => "WebAssembly",
+            }
         };
 
         let assertions = if builder.config.llvm_assertions {"ON"} else {"OFF"};