AMDGPU: Enable PIC by default for amdgcn

[msearles]

LGTM

[kzhuravl]

I thought we could override isPICDefault in AMDGPUToolChain instead of doing what is posted. But AMDGPUToolChain is only created for AMDHSA OS.

Do we want to enable PIC by default for all AMDGCNs? Or only for AMDHSA?

[kzhuravl]

Ping.

[t-tye]

For now seems reasonable to fix amdgpu as PIC. If/when other clients of amdgpu have tool chains defined then can switch to controling in the toolchain isPICDefault() function.

cfe/trunk/lib/Driver/ToolChains/CommonArgs.cpp

case llvm::Triple::sparcv9:
       IsPICLevelTwo = true; // "-fPIE"
       break;
 
     default:
       break;
     }
   }
 
+  // AMDGPU-specific defaults for PIC.
+  if (Triple.getArch() == llvm::Triple::amdgcn)
+    PIC = true;
+
   // The last argument relating to either PIC or PIE wins, and no
   // other argument is used. If the last argument is any flavor of the
   // '-fno-...' arguments, both PIC and PIE are disabled. Any PIE
   // option implicitly enables PIC at the same level.
   Arg *LastPICArg = Args.getLastArg(options::OPT_fPIC, options::OPT_fno_PIC,
                                     options::OPT_fpic, options::OPT_fno_pic,
                                     options::OPT_fPIE, options::OPT_fno_PIE,
                                     options::OPT_fpie, options::OPT_fno_pie);

cfe/trunk/test/Driver/amdgcn-toolchain-pic.cl

+// RUN: %clang -### -target amdgcn-- -mcpu=gfx803 %s 2>&1 | FileCheck %s
+// RUN: %clang -### -target amdgcn-amd- -mcpu=gfx803 %s 2>&1 | FileCheck %s
+// RUN: %clang -### -target amdgcn-amd-amdhsa -mcpu=gfx803 %s 2>&1 | FileCheck %s
+// RUN: %clang -### -target amdgcn-amd-amdpal -mcpu=gfx803 %s 2>&1 | FileCheck %s
+// RUN: %clang -### -target amdgcn-amd-mesa3d -mcpu=gfx803 %s 2>&1 | FileCheck %s
+
+// CHECK: clang{{.*}} "-mrelocation-model" "pic" "-pic-level" "1"