Allow specifying key "llvm-abiname" in target specification

This addresses rust-lang#65024, as it allows RISC-V target specification
files to set "llvm-abiname": "lp64d". In general, it is useful
for the programmer to be able to set this codegen parameter,
which other languages usually expose under a compiler argument
like "-mabi=<XYZ>".

src/librustc_codegen_llvm/back/write.rs

@@ -161,6 +161,7 @@ pub fn target_machine_factory(sess: &Session, optlvl: config::OptLevel, find_fea
     let cpu = SmallCStr::new(llvm_util::target_cpu(sess));
     let features = features.join(",");
     let features = CString::new(features).unwrap();
+    let abi = SmallCStr::new(&sess.target.target.options.llvm_abiname);
     let is_pie_binary = !find_features && is_pie_binary(sess);
     let trap_unreachable = sess.target.target.options.trap_unreachable;
     let emit_stack_size_section = sess.opts.debugging_opts.emit_stack_sizes;
@@ -170,7 +171,7 @@ pub fn target_machine_factory(sess: &Session, optlvl: config::OptLevel, find_fea
     Arc::new(move || {
         let tm = unsafe {
             llvm::LLVMRustCreateTargetMachine(
-                triple.as_ptr(), cpu.as_ptr(), features.as_ptr(),
+                triple.as_ptr(), cpu.as_ptr(), features.as_ptr(), abi.as_ptr(),
                 code_model,
                 reloc_model,
                 opt_level,

src/librustc_codegen_llvm/llvm/ffi.rs

@@ -1684,6 +1684,7 @@ extern "C" {
     pub fn LLVMRustCreateTargetMachine(Triple: *const c_char,
                                        CPU: *const c_char,
                                        Features: *const c_char,
+                                       Abi: *const c_char,
                                        Model: CodeModel,
                                        Reloc: RelocMode,
                                        Level: CodeGenOptLevel,

src/librustc_target/spec/mod.rs

@@ -793,7 +793,10 @@ pub struct TargetOptions {
     pub merge_functions: MergeFunctions,
 
     /// Use platform dependent mcount function
-    pub target_mcount: String
+    pub target_mcount: String,
+
+    /// LLVM ABI name, corresponds to the '-mabi' parameter available in multilib C compilers
+    pub llvm_abiname: String,
 }
 
 impl Default for TargetOptions {
@@ -880,6 +883,7 @@ impl Default for TargetOptions {
             override_export_symbols: None,
             merge_functions: MergeFunctions::Aliases,
             target_mcount: "mcount".to_string(),
+            llvm_abiname: "".to_string(),
         }
     }
 }
@@ -1196,6 +1200,7 @@ impl Target {
         key!(override_export_symbols, opt_list);
         key!(merge_functions, MergeFunctions)?;
         key!(target_mcount);
+        key!(llvm_abiname);
 
         if let Some(array) = obj.find("abi-blacklist").and_then(Json::as_array) {
             for name in array.iter().filter_map(|abi| abi.as_string()) {
@@ -1414,6 +1419,7 @@ impl ToJson for Target {
         target_option_val!(override_export_symbols);
         target_option_val!(merge_functions);
         target_option_val!(target_mcount);
+        target_option_val!(llvm_abiname);
 
         if default.abi_blacklist != self.options.abi_blacklist {
             d.insert("abi-blacklist".to_string(), self.options.abi_blacklist.iter()

src/rustllvm/PassWrapper.cpp

@@ -343,7 +343,7 @@ extern "C" const char* LLVMRustGetHostCPUName(size_t *len) {
 
 extern "C" LLVMTargetMachineRef LLVMRustCreateTargetMachine(
     const char *TripleStr, const char *CPU, const char *Feature,
-    LLVMRustCodeModel RustCM, LLVMRustRelocMode RustReloc,
+    const char *ABIStr, LLVMRustCodeModel RustCM, LLVMRustRelocMode RustReloc,
     LLVMRustCodeGenOptLevel RustOptLevel, bool UseSoftFloat,
     bool PositionIndependentExecutable, bool FunctionSections,
     bool DataSections,
@@ -374,6 +374,7 @@ extern "C" LLVMTargetMachineRef LLVMRustCreateTargetMachine(
   Options.FunctionSections = FunctionSections;
   Options.MCOptions.AsmVerbose = AsmComments;
   Options.MCOptions.PreserveAsmComments = AsmComments;
+  Options.MCOptions.ABIName = ABIStr;
 
   if (TrapUnreachable) {
     // Tell LLVM to codegen `unreachable` into an explicit trap instruction.