109 Commits

Author SHA1 Message Date
Alex Brachet
df5beebc98 [Driver] Add --vfsoverlay flag
This flag implies `-ivfsoverlay`, and additionally passes the same
argument to the linker if it supports it. At present the only linker
which does is lld-link, so this functionality has only been added to
the MSVC toolchain. Additionally this option has been made a
CoreOption so that clang-cl can use it without `-Xclang`

Differential Revision: https://reviews.llvm.org/D141808
2023-02-13 17:25:45 +00:00
Archibald Elliott
d768bf994f [NFC][TargetParser] Replace uses of llvm/Support/Host.h
The forwarding header is left in place because of its use in
`polly/lib/External/isl/interface/extract_interface.cc`, but I have
added a GCC warning about the fact it is deprecated, because it is used
in `isl` from where it is included by Polly.
2023-02-10 09:59:46 +00:00
Fangrui Song
2c5d49cffc [Driver] llvm::Optional => std::optional
and change a few referenced Basic and llvm/lib/WindowsDriver API
2022-12-03 20:17:05 +00:00
Tim Northover
4388b56d52 Refactor unwind table driver interface to expose default level. NFC. 2022-09-20 10:47:18 +01:00
Kazu Hirata
981cbfb592 [clang] Don't include StringSwitch.h (NFC)
These files don't seem to use StringSwitch.
2022-09-18 22:21:32 -07:00
Petr Hosek
6741f0f912 Revert "[Driver] Support libc++ in MSVC"
This reverts commit a4230319f7af786f4d947f39a870f339b32a6fe7.

This is causing build failures in the 2-stage build.
2022-08-18 08:22:43 +00:00
Petr Hosek
a4230319f7 [Driver] Support libc++ in MSVC
This implements support for using libc++ headers in MSVC toolchain.
We only support libc++ headers that are part of the toolchain, and
not headers installed elsewhere on the system.

Differential Revision: https://reviews.llvm.org/D101479
2022-08-18 04:04:40 +00:00
Diana Picus
26041e1700 Update link job for flang on windows
When linking a Fortran program, we need to add the runtime libraries to
the command line. This is exactly what we do for Linux/Darwin, but the
MSVC interface is slightly different (e.g. -libpath instead of -L).

We also remove oldnames and libcmt, since they're not needed at the
moment and they bring in more dependencies.

We also pass `/subsystem:console` to the linker so it can figure out the
right entry point. This is only needed for MSVC's `link.exe`. For LLD it
is redundant but doesn't hurt.

Differential Revision: https://reviews.llvm.org/D126291

Co-authored-by: Markus Mützel <markus.muetzel@gmx.de>
2022-06-20 07:25:10 +00:00
Kazu Hirata
06decd0b41 [clang] Use value_or instead of getValueOr (NFC) 2022-06-18 23:21:34 -07:00
Martin Storsjö
e8402d5de8 [clang] [MSVC] Enable unwind tables for ARM
The backend now can generate working unwind information for this
target.

Improve the existing windows-exceptions.cpp testcase to check for
the state of unwind tables on all MSVC architectures.

Differential Revision: https://reviews.llvm.org/D126862
2022-06-03 09:32:00 +03:00
Yaxun (Sam) Liu
062317f72e [HIP] Add HIP runtime library arguments for linker
Add -L -l options for linker.

Reviewed by: Artem Belevich

Differential Revision: https://reviews.llvm.org/D124545
2022-04-28 11:12:23 -04:00
Akira Hatanaka
3b578ae908 [Driver] Call hasFlag instead of hasArg
`_HAS_STATIC_RTTI` should be set to 0 only by `-fno-rtti` according to the
summary of https://reviews.llvm.org/D103771.

rdar://92039243

Differential Revision: https://reviews.llvm.org/D124312
2022-04-22 20:14:50 -07:00
Peter Kasting
c5fb05f663 Reland: Make lld-link work in a non-MSVC shell, add /winsysroot:
This relands 73e585e44d (and 0574b5fc657451), with a fix for
the failing test (by using Optional<StringRef>s instead of
making StringRef::empty() mean absence of value).

Differential Revision: https://reviews.llvm.org/D118070
2022-02-16 09:22:39 -05:00
Douglas Yung
437d4e01fe Revert "try to fix windows build after 73e585e44d" and
Revert "Reland "[lld/coff] Make lld-link work in a non-MSVC shell, add /winsysroot:""

This reverts commit 0574b5fc657451c9d13d3f6d8fe14ea15c23a681 and 73e585e44d68cf77e2e3274e98c9615156a7d909.

This change is causing the test Driver/cl-options.c to fail on Windows buildbots.
https://lab.llvm.org/staging/#/builders/204/builds/1343
2022-02-11 23:47:53 -08:00
Nico Weber
73e585e44d Reland "[lld/coff] Make lld-link work in a non-MSVC shell, add /winsysroot:"
This relands commit b3b2538df100ec, except that the new files in Support
are instead in a new library WindowsDriver.
2022-02-11 17:07:33 -05:00
Adrian Prantl
baac665adf Revert "[lld/coff] Make lld-link work in a non-MSVC shell, add /winsysroot:"
This reverts commit b3b2538df100ec7f6587b0ee70819a3c8ee2c27e,
it introduced a cycklic module depenency that broke the -DLLVM_ENABLE_MODULES=1 build.
2022-02-11 13:07:23 -08:00
Peter Kasting
b3b2538df1 [lld/coff] Make lld-link work in a non-MSVC shell, add /winsysroot:
Makes lld-link work in a non-MSVC shell by autodetecting MSVC toolchain. Also
adds support for /winsysroot and a few other switches.

All this is done by refactoring to share code with clang-cl's existing support
for the same.

Differential Revision: https://reviews.llvm.org/D118070
2022-02-11 13:55:18 -05:00
Muhammad Omair Javaid
cd817231ec [clang-cl] Bump default -fms-compatibility-version to 19.14
clang-cl MSVC required version is 19.20 now. Update the default
-fms-compatibility-version to 19.14.

Differential Revision: https://reviews.llvm.org/D114639
2022-02-09 13:54:25 +05:00
Alexandre Ganea
83d59e05b2 Re-land [LLD] Remove global state in lldCommon
Move all variables at file-scope or function-static-scope into a hosting structure (lld::CommonLinkerContext) that lives at lldMain()-scope. Drivers will inherit from this structure and add their own global state, in the same way as for the existing COFFLinkerContext.

See discussion in https://lists.llvm.org/pipermail/llvm-dev/2021-June/151184.html

The previous land f860fe362282ed69b9d4503a20e5d20b9a041189 caused issues in https://lab.llvm.org/buildbot/#/builders/123/builds/8383, fixed by 22ee510dac9440a74b2e5b3fe3ff13ccdbf55af3.

Differential Revision: https://reviews.llvm.org/D108850
2022-01-20 14:53:26 -05:00
Alexandre Ganea
5af2433e17 [clang-cl] Support the /HOTPATCH flag
This patch adds support for the MSVC /HOTPATCH flag: https://docs.microsoft.com/sv-se/cpp/build/reference/hotpatch-create-hotpatchable-image?view=msvc-170&viewFallbackFrom=vs-2019

The flag is translated to a new -fms-hotpatch flag, which in turn adds a 'patchable-function' attribute for each function in the TU. This is then picked up by the PatchableFunction pass which would generate a TargetOpcode::PATCHABLE_OP of minsize = 2 (which means the target instruction must resolve to at least two bytes). TargetOpcode::PATCHABLE_OP is only implemented for x86/x64. When targetting ARM/ARM64, /HOTPATCH isn't required (instructions are always 2/4 bytes and suitable for hotpatching).

Additionally, when using /Z7, we generate a 'hot patchable' flag in the CodeView debug stream, in the S_COMPILE3 record. This flag is then picked up by LLD (or link.exe) and is used in conjunction with the linker /FUNCTIONPADMIN flag to generate extra space before each function, to accommodate for live patching long jumps. Please see: d703b92296/lld/COFF/Writer.cpp (L1298)

The outcome is that we can finally use Live++ or Recode along with clang-cl.

NOTE: It seems that MSVC cl.exe always enables /HOTPATCH on x64 by default, although if we did the same I thought we might generate sub-optimal code (if this flag was active by default). Additionally, MSVC always generates a .debug$S section and a S_COMPILE3 record, which Clang doesn't do without /Z7. Therefore, the following MSVC command-line "cl /c file.cpp" would have to be written with Clang such as "clang-cl /c file.cpp /HOTPATCH /Z7" in order to obtain the same result.

Depends on D43002, D80833 and D81301 for the full feature.

Differential Revision: https://reviews.llvm.org/D116511
2022-01-20 12:57:19 -05:00
Kagami Sascha Rosylight
9c195bae31 [clang] Add include path for cppwinrt on Windows SDK 10.0.17134+
This fixes https://github.com/llvm/llvm-project/issues/53112 by adding
cppwinrt to the include path when the SDK version is higher than
10.0.17134.0.

Differential revision: https://reviews.llvm.org/D117407
2022-01-18 09:14:23 +01:00
James Farrell
219672b8dd Revert "Revert "Use VersionTuple for parsing versions in Triple, fixing issues that caused the original change to be reverted. This makes it possible to distinguish between "16" and "16.0" after parsing, which previously was not possible.""
This reverts commit 63a6348cad6caccf285c1661bc60d8ba5a40c972.

Differential Revision: https://reviews.llvm.org/D115254
2021-12-07 23:15:21 +00:00
James Farrell
63a6348cad Revert "Use VersionTuple for parsing versions in Triple, fixing issues that caused the original change to be reverted. This makes it possible to distinguish between "16" and "16.0" after parsing, which previously was not possible."
This reverts commit 50324670342d9391f62671685f4d6b4880a4ea9a.
2021-12-06 17:35:26 +00:00
James Farrell
5032467034 Use VersionTuple for parsing versions in Triple, fixing issues that caused the original change to be reverted. This makes it possible to distinguish between "16" and "16.0" after parsing, which previously was not possible.
This reverts commit 40d5eeac6cd89a2360c3ba997cbaa816abca828c.

Differential Revision: https://reviews.llvm.org/D114885
2021-12-06 14:57:47 +00:00
Nikita Popov
40d5eeac6c Revert "Use VersionTuple for parsing versions in Triple. This makes it possible to distinguish between "16" and "16.0" after parsing, which previously was not possible."
This reverts commit 1e8286467036d8ef1a972de723f805a4981b2692.

llvm/test/Transforms/LoopStrengthReduce/X86/2009-11-10-LSRCrash.ll fails
with assertion failure:

llc: /home/nikic/llvm-project/llvm/include/llvm/ADT/Optional.h:196: T& llvm::optional_detail::OptionalStorage<T, true>::getValue() & [with T = unsigned int]: Assertion `hasVal' failed.
...
 #8 0x00005633843af5cb llvm::MCStreamer::emitVersionForTarget(llvm::Triple const&, llvm::VersionTuple const&)
 #9 0x0000563383b47f14 llvm::AsmPrinter::doInitialization(llvm::Module&)
2021-11-30 18:36:32 +01:00
James Farrell
1e82864670 Use VersionTuple for parsing versions in Triple. This makes it possible to distinguish between "16" and "16.0" after parsing, which previously was not possible.
See also https://github.com/android/ndk/issues/1455.

Differential Revision: https://reviews.llvm.org/D114163
2021-11-30 15:44:23 +00:00
Yaxun (Sam) Liu
0309e50f33 [Driver] Fix ToolChain::getSanitizerArgs
The driver uses class SanitizerArgs to store parsed sanitizer arguments. It keeps a cached
SanitizerArgs object in ToolChain and uses it for different jobs. This does not work if
the sanitizer options are different for different jobs, which could happen when an
offloading toolchain translates the options for different jobs.

To fix this, SanitizerArgs should be created by using the actual arguments passed
to jobs instead of the original arguments passed to the driver, since the toolchain
may change the original arguments. And the sanitizer arguments should be diagnose
once.

This patch also fixes HIP toolchain for handling -fgpu-sanitize: a warning is emitted
for GPU's not supporting sanitizer and skipped. This is for backward compatibility
with existing -fsanitize options. -fgpu-sanitize is also turned on by default.

Reviewed by: Artem Belevich, Evgenii Stepanov

Differential Revision: https://reviews.llvm.org/D111443
2021-11-11 17:17:08 -05:00
Martin Storsjö
b541845ea0 [clang] [Windows] Mark PIC as implicitly enabled for aarch64, just like for x86_64
This doesn't practically affect the code generation.

Differential Revision: https://reviews.llvm.org/D111707
2021-10-13 22:55:00 +03:00
Nico Weber
951f362e25 [clang-cl] Add a /diasdkdir flag and make /winsysroot imply it
D109708 added "DIA SDK" to our win sysroot for hermetic builds
that use LLVM_ENABLE_DIA_SDK. But the build system still has to
manually pass flags pointing to it.

Since we have a /winsysroot flag, make it look at DIA SDK in
the sysroot.

With this, the following is enough to compile the DIA2Dump example:

out\gn\bin\clang-cl ^
  "sysroot\DIA SDK\Samples\DIA2Dump\DIA2Dump.cpp" ^
  "sysroot\DIA SDK\Samples\DIA2Dump\PrintSymbol.cpp" ^
  "sysroot\DIA SDK\Samples\DIA2Dump\regs.cpp" ^
  /diasdkdir "sysroot\DIA SDK" ^
  ole32.lib oleaut32.lib diaguids.lib

Differential Revision: https://reviews.llvm.org/D109828
2021-09-16 07:42:32 -04:00
Martin Storsjö
e5c7c171e5 [clang] Rename StringRef _lower() method calls to _insensitive()
This is mostly a mechanical change, but a testcase that contains
parts of the StringRef class (clang/test/Analysis/llvm-conventions.cpp)
isn't touched.
2021-06-25 00:22:01 +03:00
Hans Wennborg
5958dc75ce Try to fix clang/test/Driver/cl-include.c failure
Somewhat speculative. Example failures:
https://lab.llvm.org/buildbot/#/builders/5/builds/8857/steps/9/logs/stdio
https://lab.llvm.org/buildbot/#/builders/123/builds/4621/steps/8/logs/stdio
2021-06-21 17:19:00 +02:00
Hans Wennborg
3063a54722 [clang-cl] Implement /external:I, /external:env, and EXTERNAL_INCLUDE support (PR36003)
This patch does three things:

- Map the /external:I flag to -isystem

- Add support for the /external:env:<var> flag which reads system
  include paths from the <var> environment variable

- Pick up system include dirs EXTERNAL_INCLUDE in addition to the old
  INCLUDE environment variable.

Differential revision: https://reviews.llvm.org/D104387
2021-06-21 15:36:14 +02:00
Markus Böck
c9889c44ec [clang-cl] Don't expand /permissive- to /ZC:strictStrings yet
Follow up on rGc70b0e808da8

/Zc:strictStrings is an alias to an option part of the -W group. When the driver tries to render the option back to a string for the cc1 invocation, it sadly gets rendered with the original spelling instead of the alias, causing issues reported here: https://reviews.llvm.org/D103773#inline-989447

I am thinking it's the best to revert this part of the patch until I figured out how to correctly add the arg and until /Zc:strictStrings- exists/is needed.
2021-06-19 13:28:32 +02:00
Petr Hosek
22f194909a Revert "[Driver] Support libc++ in MSVC"
This reverts commit 9625d61eb66c12388875e081b63ebed7e42c6bbb since
libc++ currently has issues with disabled exceptions which breaks
the runtimes build.
2021-06-11 00:45:56 -07:00
Markus Böck
c70b0e808d [clang-cl] Add /permissive and /permissive-
This patch adds the command line options /permissive and /permissive- to clang-cl. These flags are used in MSVC to enable various /Zc language conformance options at once. In particular, /permissive is used to enable the various non standard behaviour of MSVC, while /permissive- is the opposite.

When either of two command lines are specified they are simply expanded to the various underlying /Zc options. In particular when /permissive is passed it currently expands to:

/Zc:twoPhase- (disable two phase lookup)
-fno-operator-names (disable C++ operator keywords)
/permissive- expands to the opposites of these flags + /Zc:strictStrings (/Zc:strictStrings- does not currently exist). In the future, if any more MSVC workarounds are ever added they can easily be added to the expansion. One is also able to override settings done by permissive. Specifying /permissive- /Zc:twoPhase- will apply the settings from permissive minus, but disables two phase lookup.

Motivation for this patch was mainly parity with MSVC as well as compatibility with Windows SDK headers. The /permissive page from MSVC documents various workarounds that have to be done for the Windows SDK headers [1], when MSVC is used with /permissive-. In these, Microsoft often recommends simply compiling with /permissive for the specified source files. Since some of these also apply to clang-cl (which acts like /permissive- by default mostly), and some are currently implemented as "hacks" within clang that I'd like to remove, adding /permissive and /permissive- to be in full parity with MSVC and Microsofts documentation made sense to me.

[1] https://docs.microsoft.com/en-us/cpp/build/reference/permissive-standards-conformance?view=msvc-160#windows-header-issues

Differential Revision: https://reviews.llvm.org/D103773
2021-06-10 17:06:19 +02:00
Markus Böck
936d6756cc [clang][msvc] Define _HAS_STATIC_RTTI to 0, when compiling with -fno-rtti
When using the -fno-rtti option of the GCC style clang++, using typeid results in an error. The MSVC STL however kindly provides a define flag called _HAS_STATIC_RTTI, which either enables or disables uses of typeid throughout the STL. By default, if undefined, it is set to 1, enabling the use of typeid.

With this patch, _HAS_STATIC_RTTI is set to 0 when -fno-rtti is specified. This way various headers of the MSVC STL like functional can be consumed without compilation failures.

Differential Revision: https://reviews.llvm.org/D103771
2021-06-10 17:02:44 +02:00
Petr Hosek
9625d61eb6 [Driver] Support libc++ in MSVC
This implements support for using libc++ headers and library in the MSVC
toolchain.  We only support libc++ that is a part of the toolchain, and
not headers installed elsewhere on the system.

Differential Revision: https://reviews.llvm.org/D101479
2021-06-07 23:36:10 -07:00
Zequan Wu
59b8afe502 [clang-cl] Bump default -fms-compatibility-version to 19.14
MSVC required version is 19.14 now (https://reviews.llvm.org/D92515). Update the
default -fms-compatibility-version to 19.14.

Differential Revision: https://reviews.llvm.org/D103293
2021-05-27 20:40:37 -07:00
Petr Hosek
5ff79f001f Revert "[Driver] Support libc++ in MSVC"
This reverts commit b604301be3559fb85a11779db79fc9bda4b62bce since
it caused compilation failure in sanitizer_unwind_win.cpp when using
the runtimes build.
2021-05-22 15:49:46 -07:00
Petr Hosek
b604301be3 [Driver] Support libc++ in MSVC
This implements support for using libc++ headers and library in the MSVC
toolchain.  We only support libc++ that is a part of the toolchain, and
not headers installed elsewhere on the system.

Differential Revision: https://reviews.llvm.org/D101479
2021-05-22 13:32:23 -07:00
Artur Gainullin
192c6023e1 [Driver] Make the findVCToolChainViaEnvironment case-insensitive
PATH usage on Windows is case-insensitive. There could be situations
when toolchain path can't be obtained from PATH because of
case-sensitivity of the findVCToolChainViaEnvironment.

Reviewed By: rnk

Differential Revision: https://reviews.llvm.org/D100361
2021-04-13 13:36:37 -07:00
Maxim Kuvyrkov
2049fe5890 [WoA][MSVC] Use default linker setting in MSVC-compatible driver [take 2]
At the moment "link.exe" is hard-coded as default linker in MSVC.cpp,
so there's no way to use LLD as default linker for MSVC driver.

This patch adds checking of CLANG_DEFAULT_LINKER to MSVC.cpp and
updates unit-tests that expect link.exe linker to explicitly select it
via -fuse-ld=link, so that buildbots and other builds that set
-DCLANG_DEFAULT_LINKER=foobar don't fail these tests.

This is a squash of
- https://reviews.llvm.org/D98493 (MSVC.cpp change) and
- https://reviews.llvm.org/D98862 (unit-tests change)

Reviewed By: maxim-kuvyrkov

Differential Revision: https://reviews.llvm.org/D98935
2021-03-19 13:38:03 +00:00
Petr Hosek
ce97d8e6c7 Revert "[WoA][MSVC] Use default linker setting in MSVC-compatible driver"
This reverts commit ace56d41aca8cac7cead9c2c97278aa50fc945b1 which
broke builders that set CLANG_DEFAULT_LINKER.
2021-03-18 23:42:31 -07:00
Maxim Kuvyrkov
ace56d41ac [WoA][MSVC] Use default linker setting in MSVC-compatible driver
At the moment "link.exe" is hard-coded as default linker in MSVC.cpp,
so there's no way to use LLD as default linker for MSVC driver.

This patch adds checking of CLANG_DEFAULT_LINKER to MSVC.cpp.

Reviewed By: asl

Differential Revision: https://reviews.llvm.org/D98493
2021-03-18 07:42:55 +00:00
Wang, Pengfei
e7e67c930a Add Windows ehcont section support (/guard:ehcont).
Add option /guard:ehcont

Reviewed By: rnk

Differential Revision: https://reviews.llvm.org/D96709
2021-03-04 11:47:29 +08:00
Arthur Eubanks
6d52c48192 Rewrite MSVC toolchain discovery with VFS
This fixes an issue where the toolchain discovery doesn't respect the
VFS's current working directory, specifically clangd not respecting a
relative /winsysroot.

Reviewed By: rnk

Differential Revision: https://reviews.llvm.org/D97437
2021-02-25 12:50:08 -08:00
Hans Wennborg
6625680a58 [clang-cl] Remove the /fallback option
As discussed in
https://lists.llvm.org/pipermail/cfe-dev/2021-January/067524.html

It doesn't appear to be used, isn't really maintained, and adds some
complexity to the code. Let's remove it.

Differential revision: https://reviews.llvm.org/D95876
2021-02-04 10:33:16 +01:00
Nico Weber
82847436e9 clang-cl: Invent a /winsysroot concept
On non-Windows platforms, --sysroot can be used to make the compiler use
a single, hermetic directory for all header and library files.

This is useful, but difficult to do on Windows. After D95472 it's
possible to achieve this with two flags:

    out/gn/bin/clang-cl win.c -fuse-ld=lld \
        /vctoolsdir path/to/VC/Tools/MSVC/14.26.28801 \
        /winsdkdir path/to/win_sdk

But that's still cumbersome: It requires two flags instead of one, and
it requires writing down the (changing) VC/Tools/MSVC version.

This adds a new `/winsysroot <dir>` flag that's effectively an alias to
these two flags. With this, building against a hermetic Windows
toolchain only needs:

    out/gn/bin/clang-cl win.c -fuse-ld=lld /winsysroot path

`/winsysroot <dir>` is the same as adding

    /vctoolsdir <dir>/VC/Tools/MSVC/<vctoolsver>
    /winsdkdir <dir>/Windows Kits/<winsdkmajorversion>

`<vctoolsver>` is taken from `/vctoolsversion` if passed, or else it's
the name of the directory in `<dir>/VC/Tools/MSVC` that's the highest
numeric tuple.

`<winsdkmajorversion>` is the major version in /winsdkversion if passed,
else it's the name of the directory in `<dir>/Windows Kits` that's the
highest number.

So `/winsysroot <path>` requires this subfolder structure:

  path/
    VC/
      Tools/
        MSVC/
          14.26.28801  (or another number)
            include/
            ...
    Windows Kits/
      10/
        Include/
          10.0.19041.0/ (or another number)
            um/
            ...
        Lib/
          10.0.19041.0/ (or another number)
            um/
              x64/
              ...
            ...

Differential Revision: https://reviews.llvm.org/D95534
2021-01-29 09:47:00 -05:00
Nico Weber
412ac0e536 clang-cl: Prefer /vctoolsdir, /winsdkdir over LIB for link invocations
/vctoolsdir and /winsdkdir take precedence over the INCLUDE env var,
so they should also take precedence over LIB. It's not quite as neat
since LIB is still read by the linker and the linker just prefers
the -libpath: paths the driver now passes, but as long as all libraries
are present at /vctoolsdir and /winsdkdir, there's no harm in the linker
also looking at LIB later.

This fixes cl-options.c after a5d85cbe on Windows when LIB is set.
Another way to fix the test would be to prefix the clang-cl
line with `env --unset=LIB`, but I think it's better to fix the
flag to work as expected instead of making the test work around
the surprising behavior that LIB being set causes clang-cl to
not pass -libpath: flags to the linker when /vctoolsdir and
/winsdkdir are used.
2021-01-27 08:57:48 -05:00
Nico Weber
a5d85cbec5 clang-cl: Add /winsdkdir and /winsdkversion flags
These do for the Windows SDK path what D85998 did for
%VCToolsInstallDir% with /vctoolsdir: Offer a way to set them with an
explicit commandline switch.

With this (and /vctoolsdir), it's possible to compile and link
against hermetic vctools and winsdk directories with:

    out/gn/bin/clang-cl win.c -fuse-ld=lld \
        /vctoolsdir path/to/VC/Tools/MSVC/14.26.28801 \
        /winsdkdir path/to/win_sdk

compared to a long list of -imsvc and /link /libpath: flags.

While here:
- Change the case of the "Include" folder inside the windows sdk
  from "include" to "Include" to match on-disk case. Since the
  Windows file system is case-insensitive this isn't a behavior
  change, it's just a bit cleaner.
- Add libpath tests to the /vctoolsdir
- Add a FIXME about reading env vars for win sdk and ucrt sdk
  if these flags aren't present, to match the VCToolsInstallDir
  logic

We should also cache all these computed paths in the driver instead
of computing them every time they're queried, but that's for a future
patch.

It'd also be nice to invent a /winsysroot: flag that sets both
/vctoolsdir: and /winsdkdir: to some well-known subdirectory.
That's for a future patch as well.

Differential Revision: https://reviews.llvm.org/D95472
2021-01-27 06:37:51 -05:00