rust: generate an appropriate cpu for targets

This generates an appropriate CPU value for the targets. For ARM it
leaves the default of 'generic' since we build up all the different CPU
differences in the 'features' field but for x86/x86_64 we need to pass
an appropriate CPU value.

Signed-off-by: Doug Goldstein <cardoe@cardoe.com>

recipes-devtools/rust/rust.inc

@@ -166,6 +166,23 @@ def arch_to_rust_target_arch(arch):
     else:
         return arch
 
+# generates our target CPU value
+def llvm_cpu(d):
+    cpu = d.getVar('TUNE_PKGARCH', True)
+    target = d.getVar('TRANSLATED_TARGET_ARCH', True)
+
+    trans = {}
+    trans['corei7-64'] = "corei7"
+    trans['core2-32'] = "core2"
+    trans['x86-64'] = "x86-64"
+    trans['i686'] = "i686"
+    trans['i586'] = "i586"
+
+    try:
+        return trans[cpu]
+    except:
+        return trans.get(target, "generic")
+
 def post_link_args_for(d, thing, arch):
     post_link_args = (d.getVar('{}_POST_LINK_ARGS'.format(thing), True) or "").split()
     post_link_args.extend((d.getVarFlag('POST_LINK_ARGS', arch, True) or "").split())
@@ -181,11 +198,14 @@ def ldflags_for(d, thing, arch):
     a.extend(post_link_args_for(d, thing, arch))
     return a
 
+TARGET_LLVM_CPU="${@llvm_cpu(d)}"
 TARGET_LLVM_FEATURES = "${@llvm_features_from_tune(d)}"
+TARGET_LLVM_CPU_class-cross="${@llvm_cpu(d)}"
 TARGET_LLVM_FEATURES_class-cross  = "${@llvm_features_from_tune(d)}"
 
 # class-native implies TARGET=HOST, and TUNE_FEATURES only describes the real
 # (original) target.
+TARGET_LLVM_CPU="${@llvm_cpu(d)}"
 TARGET_LLVM_FEATURES_class-native = ""
 
 def rust_gen_target(d, thing, wd):
@@ -210,6 +230,7 @@ def rust_gen_target(d, thing, wd):
     tspec['env'] = "gnu"
     tspec['linker'] = "{}{}gcc".format(d.getVar('CCACHE', True), prefix)
     tspec['objcopy'] = "{}objcopy".format(prefix)
+    tspec['cpu'] = d.getVar('TARGET_LLVM_CPU', True)
     if features is not "":
         tspec['features'] = features
     tspec['dynamic-linking'] = True