[mips] Prevent PIC to be set to level 2

[abeserminji]

Summary

MIPS does not use PIC level 2 for historical reasons, even with -fPIC/-mxgot/multigot options.
This patch makes Clang behave more like GCC.

[sdardis]

This patch looks mostly ok, but I think there are some small issues with it.

Can you separate the new warnings/error relating to -fno-pic / -mabicalls into another patch from the change which alters the behaviour of PIC / pic ?

The title of the patch is misleading, as you're adding warnings related to -fno-pic / -mabicalls and changing how pic is defined.

[abeserminji]

Resolved a comment.

[abeserminji]

Updated the patch. Now this patch only forces PIC to level 1.

[sdardis]

lib/Driver/ToolChains/CommonArgs.cpp

1017

Can you reformulate this comment to say that MIPS does not use PIC level 2? Also, please add a note stating that even with -mxgot / -fPIC / multigot , MIPS does not use PIC level 2 unlike other architecutres for historical reasons.

[sdardis]

You should also update the description of the patch.

[abeserminji]

Comments resolved.

[sdardis]

LGTM.

lib/Driver/ToolChains/CommonArgs.cpp

if (!EmbeddedPISupported)
           << LastRWPIArg->getSpelling() << Triple.str();
     RWPI = true;
   }
 
   // ROPI and RWPI are not compatible with PIC or PIE.
   if ((ROPI || RWPI) && (PIC || PIE))
     ToolChain.getDriver().Diag(diag::err_drv_ropi_rwpi_incompatible_with_pic);
 
-  // When targettng MIPS64 with N64, the default is PIC, unless -mno-abicalls is
-  // used.
-  if ((Triple.getArch() == llvm::Triple::mips64 ||
-       Triple.getArch() == llvm::Triple::mips64el) &&
-      Args.hasArg(options::OPT_mno_abicalls))
+  if (Triple.getArch() == llvm::Triple::mips ||
+       Triple.getArch() == llvm::Triple::mipsel ||
+       Triple.getArch() == llvm::Triple::mips64 ||
+       Triple.getArch() == llvm::Triple::mips64el) {
+    // When targettng MIPS with -mno-abicalls, it's always static.
+    if(Args.hasArg(options::OPT_mno_abicalls))
       return std::make_tuple(llvm::Reloc::Static, 0U, false);
+    // Unlike other architectures, MIPS, even with -fPIC/-mxgot/multigot,
+    // does not use PIC level 2 for historical reasons.
+    IsPICLevelTwo = false;
+  }
 
   if (PIC)
     return std::make_tuple(llvm::Reloc::PIC_, IsPICLevelTwo ? 2U : 1U, PIE);
 
   llvm::Reloc::Model RelocM = llvm::Reloc::Static;
   if (ROPI && RWPI)
     RelocM = llvm::Reloc::ROPI_RWPI;
   else if (ROPI)

test/Driver/pic.c

 // RUN: %clang -c %s -target arm-linux-androideabi24 -### 2>&1 \
 // RUN:   | FileCheck %s --check-prefix=CHECK-PIE2
 //
 // RUN: %clang -c %s -target mipsel-linux-android -### 2>&1 \
 // RUN:   | FileCheck %s --check-prefix=CHECK-PIC1
 // RUN: %clang -c %s -target mipsel-linux-android14 -### 2>&1 \
 // RUN:   | FileCheck %s --check-prefix=CHECK-PIC1
 // RUN: %clang -c %s -target mipsel-linux-android16 -### 2>&1 \
-// RUN:   | FileCheck %s --check-prefix=CHECK-PIE2
+// RUN:   | FileCheck %s --check-prefix=CHECK-PIE1
 // RUN: %clang -c %s -target mipsel-linux-android24 -### 2>&1 \
-// RUN:   | FileCheck %s --check-prefix=CHECK-PIE2
+// RUN:   | FileCheck %s --check-prefix=CHECK-PIE1
 //
 // 64-bit Android targets are always PIE.
 // RUN: %clang -c %s -target aarch64-linux-android -### 2>&1 \
 // RUN:   | FileCheck %s --check-prefix=CHECK-PIE2
 // RUN: %clang -c %s -target aarch64-linux-android24 -### 2>&1 \
 // RUN:   | FileCheck %s --check-prefix=CHECK-PIE2
 // RUN: %clang -c %s -target arm64-linux-android -### 2>&1 \
 // RUN:   | FileCheck %s --check-prefix=CHECK-PIE2