Flang driver compiler options request

[jeffhammond]

The Flang and Clang drivers are separate but many Clang flags make sense for Flang, because they are not language specific. Here is a list of flags that Flang should support.

As these are documented on https://clang.llvm.org/docs/ClangCommandLineReference.html, I will only list the option, not what it does.

currently known to be blocking, e.g. in Spack and CMake use cases

• -w, --no-warnings
• -mtune
• -Qunused-arguments

not known to be blockers but things I use regularly

• -Wl and -Xlinker
• -framework (MacOS-specific AFAIK)
• -time
• -static-openmp

code generation flags that have known utility

• -mno-gather
• -mno-scatter
• -mrecip

[llvmbot]

@llvm/issue-subscribers-flang-driver

Author: Jeff Hammond (jeffhammond)

The Flang and Clang drivers are separate but many Clang flags make sense for Flang, because they are not language specific. Here is a list of flags that Flang should support.

As these are documented on https://clang.llvm.org/docs/ClangCommandLineReference.html, I will only list the option, not what it does.

currently known to be blocking, e.g. in Spack and CMake use cases

• -w, --no-warnings
• -mtune, -march, -mcpu
• -Qunused-arguments

not known to be blockers but things I use regularly

• -Wl and -Xlinker
• -framework (MacOS-specific AFAIK)
• -time
• -static-openmp

generally useful in LLVM projects

• -mllvm
• -mmlir

code generation flags that have known utility

• -mno-gather
• -mno-scatter
• -mrecip

[banach-space]

Thanks for creating this meta-ticket, that's much appreciated! While I won't have the bandwidth to implement this, I amavailable to review relevant PRs.

[AlexisPerry]

I'm working on mtune already, so I'll be sure to let you know here when I have the patch up for it.

[AlexisPerry]

Initial patch for -w support: #90420

[h-vetinari]

I wasn't aware of this issue when I opened #92459 for --visibility=, which is IMO quite important.

Other things I needed to patch out of default meson behaviour to get somewhere (i.e., flang 18 does not support these yet):

• options related to dependency file generation, in particular -MD, -MQ, -MF
• -fdiagnostics-color=always

[AlexisPerry]

PR for basic mtune support: #95043

[AlexisPerry]

PR #98517 for basic mtune support has been merged (the previous on having been reverted).

[h-vetinari]

More missing flags in flang 19: -fno-aligned-allocation, -nostdlib