[clang] [MSVC] Enable unwind tables for ARM

[mstorsjo]

Summary

The backend now can generate working unwind information for this
target.

[MaskRay]

This needs a test. There is existing testing gap as this change does not break any clang/test/Driver test.

@@ -449,13 +449,15 @@ bool MSVCToolChain::IsUnwindTablesDefault(const ArgList &Args) const {
   // All non-x86_32 Windows targets require unwind tables. However, LLVM
   // doesn't know how to generate them for all targets, so only enable
   // the ones that are actually implemented.
-  return getArch() == llvm::Triple::x86_64 ||
-         getArch() == llvm::Triple::aarch64;
+  //return getArch() == llvm::Triple::x86_64 ||
+  //       getArch() == llvm::Triple::aarch64;
+  return false;
 }

I think you may add windows-gnu RUN lines somewhere (perhaps mingw.cpp) to test both PIC and -funwind-tables= options, then remove windows-gnu RUN lines from pic.c.
(We should strive to use fewer RUN lines to achieve the same coverage.)

[mstorsjo]

Added testing, including testing for the existing architectures.

There was a good match for testing for this in windows-exceptions.cpp - unfortunately it ends up with 2 more RUN lines, but it fits in so well there so I'd rather not try to place it somewhere else right now.

[MaskRay]

LGTM.

[MaskRay]

(I still think it helps to drop some RUN lines from pic.c but that change can be separate.)

clang/lib/Driver/ToolChains/MSVC.cpp

 bool MSVCToolChain::IsUnwindTablesDefault(const ArgList &Args) const {
   // Don't emit unwind tables by default for MachO targets.
   if (getTriple().isOSBinFormatMachO())
     return false;
 
   // All non-x86_32 Windows targets require unwind tables. However, LLVM
   // doesn't know how to generate them for all targets, so only enable
   // the ones that are actually implemented.
-  return getArch() == llvm::Triple::x86_64 ||
-         getArch() == llvm::Triple::aarch64;
+  return getArch() == llvm::Triple::x86_64 || getArch() == llvm::Triple::arm ||
+         getArch() == llvm::Triple::thumb || getArch() == llvm::Triple::aarch64;
 }
 
 bool MSVCToolChain::isPICDefault() const {
   return getArch() == llvm::Triple::x86_64 ||
          getArch() == llvm::Triple::aarch64;
 }
 
 bool MSVCToolChain::isPIEDefault(const llvm::opt::ArgList &Args) const {

clang/test/Driver/windows-exceptions.cpp

-// RUN: %clang -target i686-windows-msvc -c %s -### 2>&1 | FileCheck -check-prefix=MSVC %s
-// RUN: %clang -target x86_64-windows-msvc -c %s -### 2>&1 | FileCheck -check-prefix=MSVC %s
+// RUN: %clang -target i686-windows-msvc -c %s -### 2>&1 | FileCheck -check-prefix=MSVC -check-prefix=MSVC-NOSEH %s
+// RUN: %clang -target x86_64-windows-msvc -c %s -### 2>&1 | FileCheck -check-prefix=MSVC -check-prefix=MSVC-SEH %s
+// RUN: %clang -target armv7-windows-msvc -c %s -### 2>&1 | FileCheck -check-prefix=MSVC -check-prefix=MSVC-SEH %s
+// RUN: %clang -target aarch64-windows-msvc -c %s -### 2>&1 | FileCheck -check-prefix=MSVC -check-prefix=MSVC-SEH %s
 // RUN: %clang -target i686-windows-gnu -c %s -### 2>&1 | FileCheck -check-prefix=MINGW-DWARF %s
 // RUN: %clang -target x86_64-windows-gnu -c %s -### 2>&1 | FileCheck -check-prefix=MINGW-SEH %s
 // RUN: %clang -target aarch64-windows-gnu -fdwarf-exceptions -c %s -### 2>&1 | FileCheck -check-prefix=MINGW-DWARF %s
 // RUN: %clang -target aarch64-windows-gnu -c %s -### 2>&1 | FileCheck -check-prefix=MINGW-SEH %s
 
 MSVC-NOT: -exception-model=dwarf
 MSVC-NOT: -exception-model=seh
+MSVC-NOSEH-NOT: -funwind-tables=2
+MSVC-SEH: -funwind-tables=2
 MINGW-DWARF: -exception-model=dwarf
 MINGW-SEH: -funwind-tables=2
 MINGW-SEH: -exception-model=seh