[PowerPC] Support ELFv1/ELFv2 ABI selection via -mabi= option

While Clang now supports both ELFv1 and ELFv2 ABIs, their use is currently
hard-coded via the target triple: powerpc64-linux is always ELFv1, while
powerpc64le-linux is always ELFv2.

These are of course the most common scenarios, but in principle it is
possible to support the ELFv2 ABI on big-endian or the ELFv1 ABI on
little-endian systems (and GCC does support that), and there are some
special use cases for that (e.g. certain Linux kernel versions could
only be built using ELFv1 on LE).

This patch implements the Clang side of supporting this, based on the
LLVM commit 214072.  The command line options -mabi=elfv1 or -mabi=elfv2
select the desired ABI if present.  (If not, Clang uses the same default
rules as now.)

Specifically, the patch implements the following changes based on the
presence of the -mabi= option:

In the driver:
- Pass the appropiate -target-abi flag to the back-end
- Select the correct dynamic loader version (/lib64/ld64.so.[12])

In the preprocessor:
- Define _CALL_ELF to the appropriate value (1 or 2)

In the compiler back-end:
- Select the correct ABI in TargetInfo.cpp
- Select the desired ABI for LLVM via feature (elfv1/elfv2)

llvm-svn: 214074

1 files changed, 6 insertions, 2 deletions

diff --git a/clang/lib/CodeGen/TargetInfo.cpp b/clang/lib/CodeGen/TargetInfo.cpp
index 1a1ac8bd925..ca99ba580a5 100644
--- a/clang/lib/CodeGen/TargetInfo.cpp
+++ b/clang/lib/CodeGen/TargetInfo.cpp
@@ -6799,16 +6799,20 @@ const TargetCodeGenInfo &CodeGenModule::getTargetCodeGenInfo() {
     return *(TheTargetCodeGenInfo = new PPC32TargetCodeGenInfo(Types));
   case llvm::Triple::ppc64:
     if (Triple.isOSBinFormatELF()) {
-      // FIXME: Should be switchable via command-line option.
       PPC64_SVR4_ABIInfo::ABIKind Kind = PPC64_SVR4_ABIInfo::ELFv1;
+      if (getTarget().getABI() == "elfv2")
+        Kind = PPC64_SVR4_ABIInfo::ELFv2;
+
       return *(TheTargetCodeGenInfo =
                new PPC64_SVR4_TargetCodeGenInfo(Types, Kind));
     } else
       return *(TheTargetCodeGenInfo = new PPC64TargetCodeGenInfo(Types));
   case llvm::Triple::ppc64le: {
     assert(Triple.isOSBinFormatELF() && "PPC64 LE non-ELF not supported!");
-    // FIXME: Should be switchable via command-line option.
     PPC64_SVR4_ABIInfo::ABIKind Kind = PPC64_SVR4_ABIInfo::ELFv2;
+    if (getTarget().getABI() == "elfv1")
+      Kind = PPC64_SVR4_ABIInfo::ELFv1;
+
     return *(TheTargetCodeGenInfo =
              new PPC64_SVR4_TargetCodeGenInfo(Types, Kind));
   }