rust-target-config: match riscv target names with what rust expects

Official rust risc-v targets are prefixed with riscv32gc- and riscv64gc-:
https://doc.rust-lang.org/nightly/rustc/platform-support.html

Particularly crossbeam-utils make important build time decisions
for atomics based on those names, and so we need to match ours
with official targets.

On the other hand, the actual definitions for those targets do not
use the 'gc' suffix in 'arch' and 'llvm-target' fields, and so we
need to follow that too, to avoid cryptic mismatch errors from rust-llvm:
https://github.com/rust-lang/rust/blob/master/compiler/rustc_target/src/spec/riscv32gc_unknown_linux_gnu.rs

(From OE-Core rev: 1cfb9c8a59d98ccc9b0510cd28fb933f72fb6b6c)

Signed-off-by: Alexander Kanavin <alex@linutronix.de>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes-recipe/rust-target-config.bbclass

@@ -231,19 +231,19 @@ TARGET_POINTER_WIDTH[powerpc64le] = "64"
 TARGET_C_INT_WIDTH[powerpc64le] = "64"
 MAX_ATOMIC_WIDTH[powerpc64le] = "64"
 
-## riscv32-unknown-linux-{gnu, musl}
-DATA_LAYOUT[riscv32] = "e-m:e-p:32:32-i64:64-n32-S128"
-TARGET_ENDIAN[riscv32] = "little"
-TARGET_POINTER_WIDTH[riscv32] = "32"
-TARGET_C_INT_WIDTH[riscv32] = "32"
-MAX_ATOMIC_WIDTH[riscv32] = "32"
-
-## riscv64-unknown-linux-{gnu, musl}
-DATA_LAYOUT[riscv64] = "e-m:e-p:64:64-i64:64-i128:128-n64-S128"
-TARGET_ENDIAN[riscv64] = "little"
-TARGET_POINTER_WIDTH[riscv64] = "64"
-TARGET_C_INT_WIDTH[riscv64] = "64"
-MAX_ATOMIC_WIDTH[riscv64] = "64"
+## riscv32gc-unknown-linux-{gnu, musl}
+DATA_LAYOUT[riscv32gc] = "e-m:e-p:32:32-i64:64-n32-S128"
+TARGET_ENDIAN[riscv32gc] = "little"
+TARGET_POINTER_WIDTH[riscv32gc] = "32"
+TARGET_C_INT_WIDTH[riscv32gc] = "32"
+MAX_ATOMIC_WIDTH[riscv32gc] = "32"
+
+## riscv64gc-unknown-linux-{gnu, musl}
+DATA_LAYOUT[riscv64gc] = "e-m:e-p:64:64-i64:64-i128:128-n64-S128"
+TARGET_ENDIAN[riscv64gc] = "little"
+TARGET_POINTER_WIDTH[riscv64gc] = "64"
+TARGET_C_INT_WIDTH[riscv64gc] = "64"
+MAX_ATOMIC_WIDTH[riscv64gc] = "64"
 
 # Convert a normal arch (HOST_ARCH, TARGET_ARCH, BUILD_ARCH, etc) to something
 # rust's internals won't choke on.
@@ -258,9 +258,21 @@ def arch_to_rust_target_arch(arch):
         return "arm"
     elif arch == "powerpc64le":
         return "powerpc64"
+    elif arch == "riscv32gc":
+        return "riscv32"
+    elif arch == "riscv64gc":
+        return "riscv64"
     else:
         return arch
 
+# Convert a rust target string to a llvm-compatible triplet
+def rust_sys_to_llvm_target(sys):
+    if sys.startswith('riscv32gc-'):
+        return sys.replace('riscv32gc-', 'riscv32-', 1)
+    if sys.startswith('riscv64gc-'):
+        return sys.replace('riscv64gc-', 'riscv64-', 1)
+    return sys
+
 # generates our target CPU value
 def llvm_cpu(d):
     cpu = d.getVar('PACKAGE_ARCH')
@@ -334,7 +346,7 @@ def rust_gen_target(d, thing, wd, arch):
 
     # build tspec
     tspec = {}
-    tspec['llvm-target'] = rustsys
+    tspec['llvm-target'] = rust_sys_to_llvm_target(rustsys)
     tspec['data-layout'] = d.getVarFlag('DATA_LAYOUT', arch_abi)
     if tspec['data-layout'] is None:
         bb.fatal("No rust target defined for %s" % arch_abi)

meta/lib/oe/rust.py

@@ -8,4 +8,6 @@
 def arch_to_rust_arch(arch):
     if arch == "ppc64le":
         return "powerpc64le"
+    if arch in ('riscv32', 'riscv64'):
+        return arch + 'gc'
     return arch