[RISCV][Driver] Allow the use of CPUs with a different XLEN than the triple.

[kito-cheng]

Summary

Our downstream toolchain release got some issue is we set the default
triple by creating symbolic link of clang like riscv64-unknown-elf-clang,
and has lots of multi-lib config including rv32's config.

However when we trying to set arch by a 32 bit CPU like generic-rv32
but got error message below:
error: unsupported argument 'generic-rv32' to option '-mcpu='

generic-rv32 is listed in the output of -mcpu=help, that
might be confusing for user since help message say supported.

So let clang driver also consider -mcpu option during computing
the target triple to archvie that.

[craig.topper]

What is the interaction between this and the -m32 and -m64 options?

[craig.topper]

LGTM

[asb]

LGTM.

[zixuan-wu]

Thx. It has solved the issue D129824.

clang/lib/Driver/Driver.cpp

 //===--- Driver.cpp - Clang GCC Compatible Driver -------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #include "clang/Driver/Driver.h"
 #include "ToolChains/AIX.h"
 #include "ToolChains/AMDGPU.h"
 #include "ToolChains/AMDGPUOpenMP.h"
 #include "ToolChains/AVR.h"
 #include "ToolChains/Ananas.h"
+#include "ToolChains/Arch/RISCV.h"
 #include "ToolChains/BareMetal.h"
 #include "ToolChains/CSKYToolChain.h"
 #include "ToolChains/Clang.h"
 #include "ToolChains/CloudABI.h"
 #include "ToolChains/Contiki.h"
 #include "ToolChains/CrossWindows.h"
 #include "ToolChains/Cuda.h"
 #include "ToolChains/Darwin.h"
if ((A = Args.getLastArg(options::OPT_mabi_EQ))) {
           Target.setEnvironment(llvm::Triple::GNUABI64);
       }
     }
   }
 
   // If target is RISC-V adjust the target triple according to
   // provided architecture name
   if (Target.isRISCV()) {
-    if ((A = Args.getLastArg(options::OPT_march_EQ))) {
-      StringRef ArchName = A->getValue();
+    if (Args.hasArg(options::OPT_march_EQ) ||
+        Args.hasArg(options::OPT_mcpu_EQ)) {
+      StringRef ArchName = tools::riscv::getRISCVArch(Args, Target);
       if (ArchName.startswith_insensitive("rv32"))
         Target.setArch(llvm::Triple::riscv32);
       else if (ArchName.startswith_insensitive("rv64"))
         Target.setArch(llvm::Triple::riscv64);
     }
   }
 
   return Target;

clang/test/Driver/riscv-arch.c

 // RUN: -fsyntax-only 2>&1 | FileCheck -check-prefix=RV32-X-S-INVAL %s
 // RV32-X-S-INVAL: error: invalid arch name 'rv32isdef_xabc',
 // RV32-X-S-INVAL: unsupported standard supervisor-level extension 'sdef'
 
 // RUN: %clang --target=riscv32-unknown-elf -march=rv32i -### %s \
 // RUN: -fsyntax-only 2>&1 | FileCheck -check-prefix=RV32-TARGET %s
 // RUN: %clang --target=riscv64-unknown-elf -march=rv32i -### %s \
 // RUN: -fsyntax-only 2>&1 | FileCheck -check-prefix=RV32-TARGET %s
+// RUN: %clang --target=riscv32-unknown-elf -mcpu=generic-rv32 -### %s \
+// RUN: -fsyntax-only 2>&1 | FileCheck -check-prefix=RV32-TARGET %s
+// RUN: %clang --target=riscv64-unknown-elf -mcpu=generic-rv32 -### %s \
+// RUN: -fsyntax-only 2>&1 | FileCheck -check-prefix=RV32-TARGET %s
 // RV32-TARGET: "-triple" "riscv32-unknown-unknown-elf"
 
 // RUN: %clang --target=riscv32-unknown-elf -march=rv64i -### %s \
 // RUN: -fsyntax-only 2>&1 | FileCheck -check-prefix=RV64-TARGET %s
 // RUN: %clang --target=riscv64-unknown-elf -march=rv64i -### %s \
 // RUN: -fsyntax-only 2>&1 | FileCheck -check-prefix=RV64-TARGET %s
+// RUN: %clang --target=riscv32-unknown-elf -mcpu=generic-rv64 -### %s \
+// RUN: -fsyntax-only 2>&1 | FileCheck -check-prefix=RV64-TARGET %s
+// RUN: %clang --target=riscv64-unknown-elf -mcpu=generic-rv64 -### %s \
+// RUN: -fsyntax-only 2>&1 | FileCheck -check-prefix=RV64-TARGET %s
 // RV64-TARGET: "-triple" "riscv64-unknown-unknown-elf"
 
 // RUN: %clang --target=riscv32-unknown-elf -march=rv32ifzfh01p0 -### %s \
 // RUN: -fsyntax-only 2>&1 | FileCheck -check-prefix=RV32-ZFH %s
 // RUN: %clang --target=riscv32-unknown-elf -march=rv32ifzfh -### %s \
 // RUN: -fsyntax-only 2>&1 | FileCheck -check-prefix=RV32-ZFH %s
 // RV32-ZFH: "-target-feature" "+zfh"
 

clang/test/Driver/riscv-cpus.c

 
 // Check failed cases
 
 // RUN: %clang --target=riscv32 -### -c %s 2>&1 -mcpu=generic-rv321 | FileCheck -check-prefix=FAIL-MCPU-NAME %s
 // FAIL-MCPU-NAME: error: unsupported argument 'generic-rv321' to option '-mcpu='
 
 // RUN: %clang --target=riscv32 -### -c %s 2>&1 -mcpu=generic-rv32 -march=rv64i | FileCheck -check-prefix=MISMATCH-ARCH %s
 // MISMATCH-ARCH: cpu 'generic-rv32' does not support rv64
-
-// RUN: %clang --target=riscv32 -### -c %s 2>&1 -mcpu=generic-rv64 | FileCheck -check-prefix=MISMATCH-MCPU %s
-// MISMATCH-MCPU: error: cpu 'generic-rv64' does not support rv32