[Driver] Don't use frame pointer on Fuchsia when optimizations are enabled

[phosek]

Summary

This matches the standard behavior on other platforms.

[mcgrathr]

lgtm but be sure that Fuchsia target users get clear release-notes warning about the change.

clang/lib/Driver/ToolChains/Clang.cpp

static bool useFramePointerForTargetByDefault(const ArgList &Args,
   case llvm::Triple::amdgcn:
   case llvm::Triple::r600:
   case llvm::Triple::csky:
     return !areOptimizationsEnabled(Args);
   default:
     break;
   }
 
-  if (Triple.isOSNetBSD()) {
+  if (Triple.isOSFuchsia() || Triple.isOSNetBSD()) {
     return !areOptimizationsEnabled(Args);
   }
 
   if (Triple.isOSLinux() || Triple.getOS() == llvm::Triple::CloudABI ||
       Triple.isOSHurd()) {
     switch (Triple.getArch()) {
     // Don't use a frame pointer on linux if optimizing for certain targets.
     case llvm::Triple::arm:

clang/test/Driver/fuchsia.c

 // CHECK: "-L[[SYSROOT]]{{/|\\\\}}lib"
 // CHECK-X86_64: "[[RESOURCE_DIR]]{{/|\\\\}}lib{{/|\\\\}}x86_64-unknown-fuchsia{{/|\\\\}}libclang_rt.builtins.a"
 // CHECK-AARCH64: "[[RESOURCE_DIR]]{{/|\\\\}}lib{{/|\\\\}}aarch64-unknown-fuchsia{{/|\\\\}}libclang_rt.builtins.a"
 // CHECK-RISCV64: "[[RESOURCE_DIR]]{{/|\\\\}}lib{{/|\\\\}}riscv64-unknown-fuchsia{{/|\\\\}}libclang_rt.builtins.a"
 // CHECK: "-lc"
 // CHECK-NOT: crtend.o
 // CHECK-NOT: crtn.o
 
+// RUN: %clang -### %s --target=x86_64-unknown-fuchsia 2>&1 \
+// RUN:     | FileCheck %s -check-prefix=CHECK-FP-ALL
+// RUN: %clang -### %s --target=aarch64-unknown-fuchsia 2>&1 \
+// RUN:     | FileCheck %s -check-prefix=CHECK-FP-NONLEAF
+// RUN: %clang -### %s --target=x86_64-unknown-fuchsia -O3 2>&1 \
+// RUN:     | FileCheck %s -check-prefix=CHECK-FP-NONE
+// RUN: %clang -### %s --target=aarch64-unknown-fuchsia -O3 2>&1 \
+// RUN:     | FileCheck %s -check-prefix=CHECK-FP-NONE
+// CHECK-FP-ALL: "-mframe-pointer=all"
+// CHECK-FP-NONLEAF: "-mframe-pointer=non-leaf"
+// CHECK-FP-NONE: "-mframe-pointer=none"
+
 // RUN: %clang -### %s --target=x86_64-unknown-fuchsia -rtlib=libgcc -fuse-ld=lld 2>&1 \
 // RUN:     | FileCheck %s -check-prefix=CHECK-RTLIB
 // CHECK-RTLIB: error: invalid runtime library name in argument '-rtlib=libgcc'
 
 // RUN: %clang -### %s --target=x86_64-unknown-fuchsia -static -fuse-ld=lld 2>&1 \
 // RUN:     | FileCheck %s -check-prefix=CHECK-STATIC
 // CHECK-STATIC: "-Bstatic"
 // CHECK-STATIC: "-Bdynamic"