[PATCH] D111952: [clang] [MinGW] Guess the right ix86 arch name spelling as sysroot

[Martin Storsjö via Phabricator via cfe-commits]

mstorsjo created this revision.
mstorsjo added reviewers: phosek, MaskRay.
Herald added subscribers: pengfei, kristof.beyls.
mstorsjo requested review of this revision.
Herald added a project: clang.

For x86, most contempory mingw toolchains use i686 as 32 bit
x86 arch target.

As long as the target triple is set to the right form, this works
fine, either as the compiler's default target, or via e.g.
a triple prefix like i686-w64-mingw32-clang.

However, if the unprefixed toolchain targets x86_64, but the user
tries to switch it to target 32 bit by adding the -m32 option, the
computeTargetTriple function in Clang, together with
Triple::get32BitArchVariant, sets the arch to i386. This causes
the right sysroot to not be found.

When targeting an arch where there are potential spelling ambiguities
with respect to the sysroots (i386 and arm), check if the driver can
find a sysroot with the arch name - if not, try a couple other
candidates.

Other design ideas considered: It would fit in better with the design
to do this kind of arch name fixups in computeTargetTriple (it
already has a couple other OS/arch specific cases), but the
heuristics for detecting the potential right choice ties in quite
closely with how the toolchain looks for the implicit sysroot to use,
so I'd prefer to keep that logic in the toolchain::MinGW class/file.

This is done as a wrapper function before invoking the toolchain::MinGW()
constructor, because the MinGW() constructor can't run code of its own
until the superclass ToolChain() constructor returns. The fixups need to
be done before the ToolChain() constructor, because it uses the Triple
for per-target runtime directories.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D111952

Files:
  clang/lib/Driver/Driver.cpp
  clang/lib/Driver/ToolChains/MinGW.cpp
  clang/lib/Driver/ToolChains/MinGW.h
  clang/test/Driver/mingw-sysroot.cpp

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