clang-cl: Remove -O0 option

[thakis]

Summary

cl.exe doesn't understand it; there's /Od instead. See also the review
thread for r229575.

Update lots of compiler-rt tests to use -Od instead of -O0.
Ran rg -l 'clang_cl.*O0' compiler-rt/test/ | xargs sed -i -c 's/-O0/-Od/'

[thakis]

I did check that we now warn, like you had requested:

$ out/gn/bin/clang-cl test.cc /O0 /c
clang: warning: argument unused during compilation: '/O0' [-Wunused-command-line-argument]

Adding a test for that felt weird though, so I didn't.

[rnk]

Does clang-cl -O0 without a / still work, though? It's used:

$ git grep O0 ../compiler-rt/test/asan/TestCases/Windows/
../compiler-rt/test/asan/TestCases/Windows/aligned_mallocs.cc:// RUN: %clang_cl_asan -O0 %s -Fe%t
../compiler-rt/test/asan/TestCases/Windows/allocators_sanity.cc:// RUN: %clang_cl_asan -O0 %s -Fe%t
../compiler-rt/test/asan/TestCases/Windows/beginthreadex.cc:// RUN: %clang_cl_asan -O0 %s -Fe%t
../compiler-rt/test/asan/TestCases/Windows/bitfield.cc:// RUN: %clang_cl_asan -O0 %s -Fe%t
../compiler-rt/test/asan/TestCases/Windows/bitfield_uaf.cc:// RUN: %clang_cl_asan -O0 %s -Fe%t
../compiler-rt/test/asan/TestCases/Windows/calloc_left_oob.cc:// RUN: %clang_cl_asan -O0 %s -Fe%t
../compiler-rt/test/asan/TestCases/Windows/calloc_right_oob.cc:// RUN: %clang_cl_asan -O0 %s -Fe%t
...

[thakis]

In D64506#1579251, @rnk wrote:

Does clang-cl -O0 without a / still work, though? It's used:

$ git grep O0 ../compiler-rt/test/asan/TestCases/Windows/
../compiler-rt/test/asan/TestCases/Windows/aligned_mallocs.cc:// RUN: %clang_cl_asan -O0 %s -Fe%t
../compiler-rt/test/asan/TestCases/Windows/allocators_sanity.cc:// RUN: %clang_cl_asan -O0 %s -Fe%t
../compiler-rt/test/asan/TestCases/Windows/beginthreadex.cc:// RUN: %clang_cl_asan -O0 %s -Fe%t
../compiler-rt/test/asan/TestCases/Windows/bitfield.cc:// RUN: %clang_cl_asan -O0 %s -Fe%t
../compiler-rt/test/asan/TestCases/Windows/bitfield_uaf.cc:// RUN: %clang_cl_asan -O0 %s -Fe%t
../compiler-rt/test/asan/TestCases/Windows/calloc_left_oob.cc:// RUN: %clang_cl_asan -O0 %s -Fe%t
../compiler-rt/test/asan/TestCases/Windows/calloc_right_oob.cc:// RUN: %clang_cl_asan -O0 %s -Fe%t
...

Oh thanks, I only ran clang tests, not compiler-rt tests.

It no longer works, O isn't a CoreOption:

$ out/gn/bin/clang-cl test.cc -O0 /c
clang: warning: argument unused during compilation: '-O0' [-Wunused-command-line-argument]

But these tests should just use /Od, right?

[thakis]

update tests

(not yet executed, don't have a win machine today)

[rnk]

lgtm

clang/include/clang/Driver/CLCompatOptions.td

 def _SLASH_J : CLFlag<"J">, HelpText<"Make char type unsigned">,
   Alias<funsigned_char>;
 
 // The _SLASH_O option handles all the /O flags, but we also provide separate
 // aliased options to provide separate help messages.
 def _SLASH_O : CLJoined<"O">,
   HelpText<"Set multiple /O flags at once; e.g. '/O2y-' for '/O2 /Oy-'">,
   MetaVarName<"<flags>">;
-// FIXME: Not sure why we have -O0 here; MSVC doesn't support that.
-def : CLFlag<"O0">, Alias<O0>, HelpText<"Disable optimization">;
 def : CLFlag<"O1">, Alias<_SLASH_O>, AliasArgs<["1"]>,
   HelpText<"Optimize for size  (same as /Og     /Os /Oy /Ob2 /GF /Gy)">;
 def : CLFlag<"O2">, Alias<_SLASH_O>, AliasArgs<["2"]>,
   HelpText<"Optimize for speed (same as /Og /Oi /Ot /Oy /Ob2 /GF /Gy)">;
 def : CLFlag<"Ob0">, Alias<_SLASH_O>, AliasArgs<["b0"]>,
   HelpText<"Disable function inlining">;
 def : CLFlag<"Ob1">, Alias<_SLASH_O>, AliasArgs<["b1"]>,
   HelpText<"Only inline functions which are (explicitly or implicitly) marked inline">;