[Driver] Default Generic_GCC ppc/ppc64/ppc64le to -fasynchronous-unwind-tables

[MaskRay]

Summary

GCC made the switch on 2018-04-10 ("rs6000: Enable -fasynchronous-unwind-tables by default").
In Clang, FreeBSD/NetBSD powerpc have already defaulted to -fasynchronous-unwind-tables.

This patch defaults Generic_GCC powerpc (which affects Linux) to use -fasynchronous-unwind-tables.

[MaskRay]

Ping:)

[MaskRay]

Gentle ping

[MaskRay]

Gentle ping..

[MaskRay]

Ping

[nemanjai]

LGTM.

clang/test/Driver/ppc-features.cpp

43

Curious - how come no check for PPC64BE?

[MaskRay]

Improve BE test

clang/docs/ReleaseNotes.rst

 - On ELF, ``-gz`` now defaults to ``-gz=zlib`` with the integrated assembler.
   It produces ``SHF_COMPRESSED`` style compression of debug information. GNU
   binutils 2.26 or newer, or lld is required to link produced object files. Use
   ``-gz=zlib-gnu`` to get the old behavior.
 - Now that `this` pointers are tagged with `nonnull` and `dereferenceable(N)`,
   `-fno-delete-null-pointer-checks` has gained the power to remove the
   `nonnull` attribute on `this` for configurations that need it to be nullable.
 - ``-gsplit-dwarf`` no longer implies ``-g2``.
+- ``-fasynchronous-unwind-tables`` is now the default on Linux AArch64/PowerPC.
+  This behavior matches newer GCC.
+  (`D91760 <https://reviews.llvm.org/D91760>`_)
+  (`D92054 <https://reviews.llvm.org/D92054>`_)
 
 Removed Compiler Flags
 -------------------------
 
 The following options no longer exist.
 
 - clang-cl's ``/Zd`` flag no longer exist. But ``-gline-tables-only`` still
   exists and does the same thing.

clang/lib/Driver/ToolChains/Gnu.cpp

void Generic_GCC::printVerboseInfo(raw_ostream &OS) const {
   GCCInstallation.print(OS);
   CudaInstallation.print(OS);
   RocmInstallation.print(OS);
 }
 
 bool Generic_GCC::IsUnwindTablesDefault(const ArgList &Args) const {
   switch (getArch()) {
   case llvm::Triple::aarch64:
+  case llvm::Triple::ppc:
+  case llvm::Triple::ppc64:
+  case llvm::Triple::ppc64le:
   case llvm::Triple::x86_64:
     return true;
   default:
     return false;
   }
 }
 
 bool Generic_GCC::isPICDefault() const {

clang/test/Driver/ppc-features.cpp

 /// Check default CC1 and linker options for ppc32.
 // RUN: %clang -### -target powerpc-unknown-linux-gnu %s 2>&1 | FileCheck --check-prefix=PPC32 %s
-// PPC32: "-mfloat-abi" "hard"
+// PPC32:      "-munwind-tables"
+// PPC32-SAME: "-mfloat-abi" "hard"
 
 // PPC32: "-m" "elf32ppclinux"
 
 // check -msoft-float option for ppc32
 // RUN: %clang -target powerpc-unknown-linux-gnu %s -msoft-float -### -o %t.o 2>&1 | FileCheck --check-prefix=CHECK-SOFTFLOAT %s
 // CHECK-SOFTFLOAT: "-target-feature" "-hard-float"
 
 // check -mfloat-abi=soft option for ppc32

 // CHECK-SECUREPLT: "-target-feature" "+secure-plt"
 
 // check -mfloat-abi=x option
 // RUN: %clang -target powerpc-unknown-linux-gnu %s -mfloat-abi=x -### -o %t.o 2>&1 | FileCheck --check-prefix=CHECK-ERRMSG %s
 // CHECK-ERRMSG: error: invalid float ABI '-mfloat-abi=x'
 
 
 /// Check default CC1 and linker options for ppc64.
-// RUN: %clang -### -target powerpc64le-unknown-linux-gnu %s 2>&1 | FileCheck --check-prefix=PPC64 %s
-// RUN: %clang -### -target powerpc64-unknown-linux-gnu %s 2>&1 | FileCheck -check-prefix=PPC64BE %s
-// PPC64: "-mfloat-abi" "hard"
+// RUN: %clang -### -target powerpc64le-unknown-linux-gnu %s 2>&1 | FileCheck --check-prefixes=PPC64,PPC64LE %s
+// RUN: %clang -### -target powerpc64-unknown-linux-gnu %s 2>&1 | FileCheck --check-prefixes=PPC64,PPC64BE %s
+// PPC64:      "-munwind-tables"
+// PPC64-SAME: "-mfloat-abi" "hard"
 
-// PPC64: "-m" "elf64lppc"
+// PPC64LE: "-m" "elf64lppc"
 // PPC64BE: "-m" "elf64ppc"
 
 // check -msoft-float option for ppc64
 // RUN: %clang -target powerpc64-unknown-linux-gnu %s -msoft-float -### -o %t.o 2>&1 | FileCheck --check-prefix=CHECK-SOFTFLOAT64 %s
 // CHECK-SOFTFLOAT64: "-target-feature" "-hard-float"
 
 // check -mfloat-abi=soft option for ppc64
 // RUN: %clang -target powerpc64-unknown-linux-gnu %s -mfloat-abi=soft -### -o %t.o 2>&1 | FileCheck --check-prefix=CHECK-FLOATABISOFT64 %s