[PPC] Enable -fomit-frame-pointer by default for PPC

[inouehrs]

Summary

This patch enables -fomit-frame-pointer option by default for PowerPC if -O1 or above optimization level is specified.
GCC already enables this option by default for -O1 or above in all of ppc32, ppc64 and ppc64le.
This option gives some performance improvements in many programs by reducing the overhead in method prologue and epilogue.

[hfinkel]

We should have regression tests for this. Maybe update test/Driver/frame-pointer-elim.c?

[inouehrs]

Thank you for the comment.
I added regression tests for PPC in test/Driver/frame-pointer.c as for other platforms.

[hfinkel]

LGTM

lib/Driver/Tools.cpp

static bool useFramePointerForTargetByDefault(const ArgList &Args,
 
   if (Triple.isOSLinux() || Triple.getOS() == llvm::Triple::CloudABI) {
     switch (Triple.getArch()) {
     // Don't use a frame pointer on linux if optimizing for certain targets.
     case llvm::Triple::mips64:
     case llvm::Triple::mips64el:
     case llvm::Triple::mips:
     case llvm::Triple::mipsel:
+    case llvm::Triple::ppc:
+    case llvm::Triple::ppc64:
+    case llvm::Triple::ppc64le:
     case llvm::Triple::systemz:
     case llvm::Triple::x86:
     case llvm::Triple::x86_64:
       return !areOptimizationsEnabled(Args);
     default:
       return true;
     }
   }

test/Driver/frame-pointer.c

 // RUN: %clang -target x86_64-pc-linux -### -S -Os %s -o %t.s 2>&1 | FileCheck -check-prefix=CHECKs-64 %s
 // RUN: %clang -target x86_64-pc-win32-macho -### -S -O3 %s -o %t.s 2>&1 | FileCheck -check-prefix=CHECK-MACHO-64 %s
 
 // Trust the above to get the optimizations right, and just test other targets
 // that want this by default.
 // RUN: %clang -target s390x-pc-linux -### -S -O0 %s -o %t.s 2>&1 | FileCheck -check-prefix=CHECK0-64 %s
 // RUN: %clang -target s390x-pc-linux -### -S -O1 %s -o %t.s 2>&1 | FileCheck -check-prefix=CHECK1-64 %s
 
+// RUN: %clang -target powerpc-unknown-linux-gnu -### -S -O0 %s -o %t.s 2>&1 | FileCheck -check-prefix=CHECK0-64 %s
+// RUN: %clang -target powerpc-unknown-linux-gnu -### -S -O1 %s -o %t.s 2>&1 | FileCheck -check-prefix=CHECK1-64 %s
+// RUN: %clang -target powerpc64-unknown-linux-gnu -### -S -O0 %s -o %t.s 2>&1 | FileCheck -check-prefix=CHECK0-64 %s
+// RUN: %clang -target powerpc64-unknown-linux-gnu -### -S -O1 %s -o %t.s 2>&1 | FileCheck -check-prefix=CHECK1-64 %s
+// RUN: %clang -target powerpc64le-unknown-linux-gnu -### -S -O0 %s -o %t.s 2>&1 | FileCheck -check-prefix=CHECK0-64 %s
+// RUN: %clang -target powerpc64le-unknown-linux-gnu -### -S -O1 %s -o %t.s 2>&1 | FileCheck -check-prefix=CHECK1-64 %s
+
 // RUN: %clang -target mips-linux-gnu -### -S -O0 %s -o %t.s 2>&1 | FileCheck -check-prefix=CHECK0-32 %s
 // RUN: %clang -target mips-linux-gnu -### -S -O1 %s -o %t.s 2>&1 | FileCheck -check-prefix=CHECK1-32 %s
 // RUN: %clang -target mipsel-linux-gnu -### -S -O0 %s -o %t.s 2>&1 | FileCheck -check-prefix=CHECK0-32 %s
 // RUN: %clang -target mipsel-linux-gnu -### -S -O1 %s -o %t.s 2>&1 | FileCheck -check-prefix=CHECK1-32 %s
 // RUN: %clang -target mips64-linux-gnu -### -S -O0 %s -o %t.s 2>&1 | FileCheck -check-prefix=CHECK0-32 %s
 // RUN: %clang -target mips64-linux-gnu -### -S -O1 %s -o %t.s 2>&1 | FileCheck -check-prefix=CHECK1-32 %s
 // RUN: %clang -target mips64el-linux-gnu -### -S -O0 %s -o %t.s 2>&1 | FileCheck -check-prefix=CHECK0-32 %s
 // RUN: %clang -target mips64el-linux-gnu -### -S -O1 %s -o %t.s 2>&1 | FileCheck -check-prefix=CHECK1-32 %s