[Driver] Support -mcmodel= for LoongArch (#72514)

7e42545 rejects unsupported mcmodel options, but normal/medium/extreme
should be supported models for LoongArch according to [gcc
document](https://gcc.gnu.org/onlinedocs/gcc/LoongArch-Options.html).

The mappings among `gcc`, `clang driver`, `clang cc1` and `LLVM (i.e.
llc --code-model=)` are:

|     gcc      |  clang driver |  clang cc1   |    LLVM    |
| -------------  | ------------------ | ----------------- | -------------- |
| normal    |      normal     |   small        |    small    |
| medium  |     medium     |   medium    |    medium |
| extreme  |     extreme     |  large         |     large     |

Link: https://reviews.llvm.org/D150522

Author: SixWeining

clang/lib/Driver/ToolChains/Clang.cpp

@@ -5756,6 +5756,18 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
       if (CM == "large" && RelocationModel != llvm::Reloc::Static)
         D.Diag(diag::err_drv_argument_only_allowed_with)
             << A->getAsString(Args) << "-fno-pic";
+    } else if (Triple.isLoongArch()) {
+      if (CM == "extreme" &&
+          Args.hasFlagNoClaim(options::OPT_fplt, options::OPT_fno_plt, false))
+        D.Diag(diag::err_drv_argument_not_allowed_with)
+            << A->getAsString(Args) << "-fplt";
+      Ok = CM == "normal" || CM == "medium" || CM == "extreme";
+      // Convert to LLVM recognizable names.
+      if (Ok)
+        CM = llvm::StringSwitch<StringRef>(CM)
+                 .Case("normal", "small")
+                 .Case("extreme", "large")
+                 .Default(CM);
     } else if (Triple.isPPC64() || Triple.isOSAIX()) {
       Ok = CM == "small" || CM == "medium" || CM == "large";
     } else if (Triple.isRISCV()) {

clang/test/Driver/mcmodel.c

@@ -15,6 +15,14 @@
 // RUN: not %clang -### -c --target=aarch64 -mcmodel=medium %s 2>&1 | FileCheck --check-prefix=ERR-MEDIUM %s
 // RUN: not %clang -### -c --target=aarch64 -mcmodel=kernel %s 2>&1 | FileCheck --check-prefix=ERR-KERNEL %s
 // RUN: not %clang --target=aarch64_32-linux -### -S -mcmodel=small %s 2>&1 | FileCheck --check-prefix=ERR-AARCH64_32 %s
+// RUN: %clang --target=loongarch64 -### -S -mcmodel=normal %s 2>&1 | FileCheck --check-prefix=SMALL %s
+// RUN: %clang --target=loongarch64 -### -S -mcmodel=medium %s 2>&1 | FileCheck --check-prefix=MEDIUM %s
+// RUN: %clang --target=loongarch64 -### -S -mcmodel=extreme %s 2>&1 | FileCheck --check-prefix=LARGE %s
+// RUN: not %clang --target=loongarch64 -### -S -mcmodel=tiny %s 2>&1 | FileCheck --check-prefix=ERR-TINY %s
+// RUN: not %clang --target=loongarch64 -### -S -mcmodel=small %s 2>&1 | FileCheck --check-prefix=ERR-SMALL %s
+// RUN: not %clang --target=loongarch64 -### -S -mcmodel=kernel %s 2>&1 | FileCheck --check-prefix=ERR-KERNEL %s
+// RUN: not %clang --target=loongarch64 -### -S -mcmodel=large %s 2>&1 | FileCheck --check-prefix=ERR-LARGE %s
+// RUN: not %clang --target=loongarch64 -### -S -mcmodel=extreme -fplt %s 2>&1 | FileCheck --check-prefix=ERR-LOONGARCH64-PLT-EXTREME %s
 
 // TINY: "-mcmodel=tiny"
 // SMALL: "-mcmodel=small"
@@ -25,9 +33,14 @@
 
 // INVALID: error: unsupported argument 'lager' to option '-mcmodel=' for target '{{.*}}'
 
+// ERR-TINY:   error: unsupported argument 'tiny' to option '-mcmodel=' for target '{{.*}}'
+// ERR-SMALL:  error: unsupported argument 'small' to option '-mcmodel=' for target '{{.*}}'
 // ERR-MEDIUM: error: unsupported argument 'medium' to option '-mcmodel=' for target '{{.*}}'
 // ERR-KERNEL: error: unsupported argument 'kernel' to option '-mcmodel=' for target '{{.*}}'
 // ERR-LARGE:  error: unsupported argument 'large' to option '-mcmodel=' for target '{{.*}}'
 
 // AARCH64-PIC-LARGE: error: invalid argument '-mcmodel=large' only allowed with '-fno-pic'
 // ERR-AARCH64_32: error: unsupported argument 'small' to option '-mcmodel=' for target 'aarch64_32-unknown-linux'
+
+// ERR-LOONGARCH64-PLT-LARGE: error: invalid argument '-mcmodel=large' not allowed with '-fplt'
+// ERR-LOONGARCH64-PLT-EXTREME: error: invalid argument '-mcmodel=extreme' not allowed with '-fplt'