clang-cl: Implement initial limited support for precompiled headers.

In the gcc precompiled header model, one explicitly runs clang with `-x
c++-header` on a .h file to produce a gch file, and then includes the header
with `-include foo.h` and if a .gch file exists for that header it gets used.
This is documented at
http://clang.llvm.org/docs/UsersManual.html#precompiled-headers

cl.exe's model is fairly different, and controlled by the two flags /Yc and
/Yu. A pch file is generated as a side effect of a regular compilation when
/Ycheader.h is passed. While the compilation is running, the compiler keeps
track of #include lines in the main translation unit and writes everything up
to an `#include "header.h"` line into a pch file. Conversely, /Yuheader.h tells
the compiler to skip all code in the main TU up to and including `#include
"header.h"` and instead load header.pch. (It's also possible to use /Yc and /Yu
without an argument, in that case a `#pragma hrdstop` takes the role of
controlling the point where pch ends and real code begins.)

This patch implements limited support for this in that it requires the pch
header to be passed as a /FI force include flag – with this restriction,
it can be implemented almost completely in the driver with fairly small amounts
of code. For /Yu, this is trivial, and for /Yc a separate pch action is added
that runs before the actual compilation. After r261774, the first failing
command makes a compilation stop – this means if the pch fails to build the
main compilation won't run, which is what we want. However, in /fallback builds
we need to run the main compilation even if the pch build fails so that the
main compilation's fallback can run. To achieve this, add a ForceSuccessCommand
that pretends that the pch build always succeeded in /fallback builds (the main
compilation will then fail to open the pch and run the fallback cl.exe
invocation).

If /Yc /Yu are used in a setup that clang-cl doesn't implement yet, clang-cl
will now emit a "not implemented yet; flag ignored" warning that can be
disabled using -Wno-clang-cl-pch.

Since clang-cl doesn't yet serialize some important things (most notably
`pragma comment(lib, ...)`, this feature is disabled by default and only
enabled by an internal driver flag. Once it's more stable, this internal flag
will disappear.

(The default stdafx.h setup passes stdafx.h as explicit argument to /Yc but not
as /FI – instead every single TU has to `#include <stdafx.h>` as first thing it
does. Implementing support for this should be possible with the approach in
this patch with minimal frontend changes by passing a --stop-at / --start-at
flag from the driver to the frontend. This is left for a follow-up. I don't
think we ever want to support `#pragma hdrstop`, and supporting it with this
approach isn't easy: This approach relies on the driver knowing the pch
filename in advance, and `#pragma hdrstop(out.pch)` can set the output
filename, so the driver can't know about it in advance.)

clang-cl now also honors /Fp and puts pch files in the same spot that cl.exe
would put them, but the pch file format is of course incompatible. This has
ramifications on /fallback, so /Yc /Yu aren't passed through to cl.exe in
/fallback builds.

http://reviews.llvm.org/D17695


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@262420 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 309 insertions, 0 deletions

diff --git a/test/Driver/cl-pch.cpp b/test/Driver/cl-pch.cpp
new file mode 100644
index 0000000000..f415794064
--- /dev/null
+++ b/test/Driver/cl-pch.cpp
@@ -0,0 +1,309 @@
+// Note: %s and %S must be preceded by --, otherwise it may be interpreted as a
+// command-line option, e.g. on Mac where %s is commonly under /Users.
+
+// /Yc
+// RUN: %clang_cl -internal-enable-pch -Werror /Ycpchfile.h /FIpchfile.h /c -### -- %s 2>&1 \
+// RUN:   | FileCheck -check-prefix=CHECK-YC %s
+// 1. Build .pch file.
+// CHECK-YC: cc1
+// CHECK-YC: -emit-pch
+// CHECK-YC: -o
+// CHECK-YC: pchfile.pch
+// CHECK-YC: -x
+// CHECK-YC: "c++"
+// 2. Use .pch file.
+// CHECK-YC: cc1
+// CHECK-YC: -emit-obj
+// CHECK-YC: -include-pch
+// CHECK-YC: pchfile.pch
+
+// /Yc /Fo
+// /Fo overrides the .obj output filename, but not the .pch filename
+// RUN: %clang_cl -internal-enable-pch -Werror /Fomyobj.obj /Ycpchfile.h /FIpchfile.h /c -### -- %s 2>&1 \
+// RUN:   | FileCheck -check-prefix=CHECK-YCO %s
+// 1. Build .pch file.
+// CHECK-YCO: cc1
+// CHECK-YCO: -emit-pch
+// CHECK-YCO: -o
+// CHECK-YCO: pchfile.pch
+// 2. Use .pch file.
+// CHECK-YCO: cc1
+// CHECK-YCO: -emit-obj
+// CHECK-YCO: -include-pch
+// CHECK-YCO: pchfile.pch
+// CHECK-YCO: -o
+// CHECK-YCO: myobj.obj
+
+// /Yc /Y-
+// /Y- disables pch generation
+// RUN: %clang_cl -internal-enable-pch -Werror /Y- /Ycpchfile.h /FIpchfile.h /c -### -- %s 2>&1 \
+// RUN:   | FileCheck -check-prefix=CHECK-YC-Y_ %s
+// CHECK-YC-Y_-NOT: -emit-pch
+// CHECK-YC-Y_-NOT: -include-pch
+
+// /Yu
+// RUN: %clang_cl -internal-enable-pch -Werror /Yupchfile.h /FIpchfile.h /c -### -- %s 2>&1 \
+// RUN:   | FileCheck -check-prefix=CHECK-YU %s
+// Use .pch file, but don't build it.
+// CHECK-YU-NOT: -emit-pch
+// CHECK-YU: cc1
+// CHECK-YU: -emit-obj
+// CHECK-YU: -include-pch
+// CHECK-YU: pchfile.pch
+
+// /Yu /Y-
+// RUN: %clang_cl -internal-enable-pch -Werror /Y- /Yupchfile.h /FIpchfile.h /c -### -- %s 2>&1 \
+// RUN:   | FileCheck -check-prefix=CHECK-YU-Y_ %s
+// CHECK-YU-Y_-NOT: -emit-pch
+// CHECK-YU-Y_-NOT: -include-pch
+
+// /Yc /Yu -- /Yc overrides /Yc if they both refer to the same file
+// RUN: %clang_cl -internal-enable-pch -Werror /Ycpchfile.h /Yupchfile.h /FIpchfile.h /c -### -- %s 2>&1 \
+// RUN:   | FileCheck -check-prefix=CHECK-YC-YU %s
+// 1. Build .pch file.
+// CHECK-YC-YU: cc1
+// CHECK-YC-YU: -emit-pch
+// CHECK-YC-YU: -o
+// CHECK-YC-YU: pchfile.pch
+// 2. Use .pch file.
+// CHECK-YC-YU: cc1
+// CHECK-YC-YU: -emit-obj
+// CHECK-YC-YU: -include-pch
+// CHECK-YC-YU: pchfile.pch
+
+// If /Yc /Yu refer to different files, semantics are pretty wonky.  Since this
+// doesn't seem like something that's important in practice, just punt for now.
+// RUN: %clang_cl -internal-enable-pch -Werror /Ycfoo1.h /Yufoo2.h /FIfoo1.h /FIfoo2.h /c -### -- %s 2>&1 \
+// RUN:   | FileCheck -check-prefix=CHECK-YC-YU-MISMATCH %s
+// CHECK-YC-YU-MISMATCH: error: support for '/Yc' and '/Yu' with different filenames not implemented yet; flags ignored
+
+// Similarly, punt on /Yc with more than one input file.
+// RUN: %clang_cl -internal-enable-pch -Werror /Ycfoo1.h /FIfoo1.h /c -### -- %s %s 2>&1 \
+// RUN:   | FileCheck -check-prefix=CHECK-YC-MULTIINPUT %s
+// CHECK-YC-MULTIINPUT: error: support for '/Yc' with more than one source file not implemented yet; flag ignored
+
+// /Yc /Yu /Y-
+// RUN: %clang_cl -internal-enable-pch -Werror /Ycpchfile.h /Yupchfile.h /FIpchfile.h /Y- /c -### -- %s 2>&1 \
+// RUN:   | FileCheck -check-prefix=CHECK-YC-YU-Y_ %s
+// CHECK-YC-YU-Y_-NOT: -emit-pch
+// CHECK-YC-YU-Y_-NOT: -include-pch
+
+// Test computation of pch filename in various cases.
+
+// /Yu /Fpout.pch => out.pch is filename
+// RUN: %clang_cl -internal-enable-pch -Werror /Yupchfile.h /FIpchfile.h /Fpout.pch /c -### -- %s 2>&1 \
+// RUN:   | FileCheck -check-prefix=CHECK-YUFP1 %s
+// Use .pch file, but don't build it.
+// CHECK-YUFP1: -include-pch
+// CHECK-YUFP1: out.pch
+
+// /Yu /Fpout => out.pch is filename (.pch gets added if no extension present)
+// RUN: %clang_cl -internal-enable-pch -Werror /Yupchfile.h /FIpchfile.h /Fpout.pch /c -### -- %s 2>&1 \
+// RUN:   | FileCheck -check-prefix=CHECK-YUFP2 %s
+// Use .pch file, but don't build it.
+// CHECK-YUFP2: -include-pch
+// CHECK-YUFP2: out.pch
+
+// /Yu /Fpout.bmp => out.bmp is filename (.pch not added when extension present)
+// RUN: %clang_cl -internal-enable-pch -Werror /Yupchfile.h /FIpchfile.h /Fpout.bmp /c -### -- %s 2>&1 \
+// RUN:   | FileCheck -check-prefix=CHECK-YUFP3 %s
+// Use .pch file, but don't build it.
+// CHECK-YUFP3: -include-pch
+// CHECK-YUFP3: out.bmp
+
+// /Yusub/dir.h => sub/dir.pch
+// RUN: %clang_cl -internal-enable-pch -Werror /Yusub/pchfile.h /FIsub/pchfile.h /c -### -- %s 2>&1 \
+// RUN:   | FileCheck -check-prefix=CHECK-YUFP4 %s
+// Use .pch file, but don't build it.
+// CHECK-YUFP4: -include-pch
+// CHECK-YUFP4: sub/pchfile.pch
+
+// /Yudir.h /Isub => dir.pch
+// RUN: %clang_cl -internal-enable-pch -Werror /Yupchfile.h /FIpchfile.h /Isub /c -### -- %s 2>&1 \
+// RUN:   | FileCheck -check-prefix=CHECK-YUFP5 %s
+// Use .pch file, but don't build it.
+// CHECK-YUFP5: -include-pch
+// CHECK-YUFP5: pchfile.pch
+
+// FIXME: /Fpdir: use dir/VCx0.pch when dir is directory, where x is major MSVS
+// version in use.
+
+// Spot-check one use of /Fp with /Yc too, else trust the /Yu test cases above
+// also all assume to /Yc.
+// RUN: %clang_cl -internal-enable-pch -Werror /Ycpchfile.h /FIpchfile.h /Fpsub/file.pch /c -### -- %s 2>&1 \
+// RUN:   | FileCheck -check-prefix=CHECK-YCFP %s
+// 1. Build .pch file.
+// CHECK-YCFP: cc1
+// CHECK-YCFP: -emit-pch
+// CHECK-YCFP: -o
+// CHECK-YCFP: sub/file.pch
+// 2. Use .pch file.
+// CHECK-YCFP: cc1
+// CHECK-YCFP: -emit-obj
+// CHECK-YCFP: -include-pch
+// CHECK-YCFP: sub/file.pch
+
+// /Ycfoo2.h /FIfoo1.h /FIfoo2.h /FIfoo3.h
+// => foo1 and foo2 go into pch, foo3 into main compilation
+// /Yc
+// RUN: %clang_cl -internal-enable-pch -Werror /Ycfoo2.h /FIfoo1.h /FIfoo2.h /FIfoo3.h /c -### -- %s 2>&1 \
+// RUN:   | FileCheck -check-prefix=CHECK-YCFIFIFI %s
+// 1. Build .pch file: Includes foo1.h (but NOT foo3.h) and compiles foo2.h
+// CHECK-YCFIFIFI: cc1
+// CHECK-YCFIFIFI: -emit-pch
+// CHECK-YCFIFIFI: -include
+// CHECK-YCFIFIFI: foo1.h
+// CHECK-YCFIFIFI-NOT: foo2.h
+// CHECK-YCFIFIFI-NOT: foo3.h
+// CHECK-YCFIFIFI: -o
+// CHECK-YCFIFIFI: foo2.pch
+// CHECK-YCFIFIFI: -x
+// CHECK-YCFIFIFI: "c++"
+// CHECK-YCFIFIFI: foo2.h
+// 2. Use .pch file: Inlucdes foo2.pch and foo3.h
+// CHECK-YCFIFIFI: cc1
+// CHECK-YCFIFIFI: -emit-obj
+// CHECK-YCFIFIFI-NOT: foo1.h
+// CHECK-YCFIFIFI-NOT: foo2.h
+// CHECK-YCFIFIFI: -include-pch
+// CHECK-YCFIFIFI: foo2.pch
+// CHECK-YCFIFIFI: -include
+// CHECK-YCFIFIFI: foo3.h
+
+// /Yucfoo2.h /FIfoo1.h /FIfoo2.h /FIfoo3.h
+// => foo1 foo2 filtered out, foo3 into main compilation
+// RUN: %clang_cl -internal-enable-pch -Werror /Yufoo2.h /FIfoo1.h /FIfoo2.h /FIfoo3.h /c -### -- %s 2>&1 \
+// RUN:   | FileCheck -check-prefix=CHECK-YUFIFIFI %s
+// Use .pch file, but don't build it.
+// CHECK-YUFIFIFI-NOT: -emit-pch
+// CHECK-YUFIFIFI: cc1
+// CHECK-YUFIFIFI: -emit-obj
+// CHECK-YUFIFIFI-NOT: foo1.h
+// CHECK-YUFIFIFI-NOT: foo2.h
+// CHECK-YUFIFIFI: -include-pch
+// CHECK-YUFIFIFI: foo2.pch
+// CHECK-YUFIFIFI: -include
+// CHECK-YUFIFIFI: foo3.h
+
+// FIXME: Implement support for /Ycfoo.h / /Yufoo.h without /FIfoo.h
+// RUN: %clang_cl -internal-enable-pch -Werror /Ycfoo.h /c -### -- %s 2>&1 \
+// RUN:   | FileCheck -check-prefix=CHECK-YC-NOFI %s
+// CHECK-YC-NOFI: error: support for '/Yc' without a corresponding /FI flag not implemented yet; flag ignored
+// RUN: %clang_cl -internal-enable-pch -Werror /Yufoo.h /c -### -- %s 2>&1 \
+// RUN:   | FileCheck -check-prefix=CHECK-YU-NOFI %s
+// CHECK-YU-NOFI: error: support for '/Yu' without a corresponding /FI flag not implemented yet; flag ignored
+
+// /Yc and /FI relative to /I paths...
+// The rules are:
+// Yu/Yc and FI parameter must match exactly, else it's not found
+// Must match literally exactly: /FI./foo.h /Ycfoo.h does _not_ work.
+// However, the path can be relative to /I paths.
+// FIXME: Update the error messages below once /FI is no longer required, but
+// these test cases all should stay failures as they fail with cl.exe.
+
+// Check that ./ isn't canonicalized away.
+// RUN: %clang_cl -internal-enable-pch -Werror /Ycpchfile.h /FI./pchfile.h /c -### -- %s 2>&1 \
+// RUN:   | FileCheck -check-prefix=CHECK-YC-I1 %s
+// CHECK-YC-I1: support for '/Yc' without a corresponding /FI flag not implemented yet; flag ignored
+
+// Check that ./ isn't canonicalized away.
+// RUN: %clang_cl -internal-enable-pch -Werror /Yc./pchfile.h /FIpchfile.h /c -### -- %s 2>&1 \
+// RUN:   | FileCheck -check-prefix=CHECK-YC-I2 %s
+// CHECK-YC-I2: support for '/Yc' without a corresponding /FI flag not implemented yet; flag ignored
+
+// With an actual /I argument.
+// RUN: %clang_cl -internal-enable-pch -Werror /Ifoo /Ycpchfile.h /FIpchfile.h /c -### -- %s 2>&1 \
+// RUN:   | FileCheck -check-prefix=CHECK-YC-I3 %s
+// 1. This writes pchfile.pch into the root dir, even if this will pick up
+//    foo/pchfile.h
+// CHECK-YC-I3: cc1
+// CHECK-YC-I3: -emit-pch
+// CHECK-YC-I3: -o
+// CHECK-YC-I3: pchfile.pch
+// 2. Use .pch file.
+// CHECK-YC-I3: cc1
+// CHECK-YC-I3: -emit-obj
+// CHECK-YC-I3: -include-pch
+// CHECK-YC-I3: pchfile.pch
+
+// Check that ./ isn't canonicalized away for /Yu either.
+// RUN: %clang_cl -internal-enable-pch -Werror /Yupchfile.h /FI./pchfile.h /c -### -- %s 2>&1 \
+// RUN:   | FileCheck -check-prefix=CHECK-YU-I1 %s
+// CHECK-YU-I1: support for '/Yu' without a corresponding /FI flag not implemented yet; flag ignored
+
+// But /FIfoo/bar.h /Ycfoo\bar.h does work, as does /FIfOo.h /Ycfoo.H
+// FIXME: This part isn't implemented yet. The following two tests should not
+// show an error but do regular /Yu handling.
+// RUN: %clang_cl -internal-enable-pch -Werror /YupchFILE.h /FI./pchfile.h /c -### -- %s 2>&1 \
+// RUN:   | FileCheck -check-prefix=CHECK-YU-CASE %s
+// CHECK-YU-CASE: support for '/Yu' without a corresponding /FI flag not implemented yet; flag ignored
+// RUN: %clang_cl -internal-enable-pch -Werror /Yu./pchfile.h /FI.\pchfile.h /c -### -- %s 2>&1 \
+// RUN:   | FileCheck -check-prefix=CHECK-YU-SLASH %s
+// CHECK-YU-SLASH: support for '/Yu' without a corresponding /FI flag not implemented yet; flag ignored
+
+// cl.exe warns on multiple /Yc, /Yu, /Fp arguments, but clang-cl silently just
+// uses the last one.  This is true for e.g. /Fo too, so not warning on this
+// is self-consistent with clang-cl's flag handling.
+
+// Interaction with /fallback
+
+// /Yc /fallback => /Yc not passed on (but /FI is)
+// RUN: %clang_cl -internal-enable-pch -Werror /Ycpchfile.h /FIpchfile.h /Fpfoo.pch /fallback /c -### -- %s 2>&1 \
+// RUN:   | FileCheck -check-prefix=CHECK-YC-FALLBACK %s
+// Note that in /fallback builds, if creation of the pch fails the main compile
+// does still run so that /fallback can have an effect (this part is not tested)
+// CHECK-YC-FALLBACK: cc1
+// CHECK-YC-FALLBACK: -emit-obj
+// CHECK-YC-FALLBACK: -include-pch
+// CHECK-YC-FALLBACK: foo.pch
+// CHECK-YC-FALLBACK: ||
+// CHECK-YC-FALLBACK: cl.exe
+// CHECK-YC-FALLBACK-NOT: -include-pch
+// CHECK-YC-FALLBACK-NOT: /Ycpchfile.h
+// CHECK-YC-FALLBACK: /FIpchfile.h
+// CHECK-YC-FALLBACK-NOT: /Fpfoo.pch
+
+// /Yu /fallback => /Yu not passed on (but /FI is)
+// RUN: %clang_cl -internal-enable-pch -Werror /Yupchfile.h /FIpchfile.h /Fpfoo.pch /fallback /c -### -- %s 2>&1 \
+// RUN:   | FileCheck -check-prefix=CHECK-YU-FALLBACK %s
+// CHECK-YU-FALLBACK-NOT: -emit-pch
+// CHECK-YU-FALLBACK: cc1
+// CHECK-YU-FALLBACK: -emit-obj
+// CHECK-YU-FALLBACK: -include-pch
+// CHECK-YU-FALLBACK: foo.pch
+// CHECK-YU-FALLBACK: ||
+// CHECK-YU-FALLBACK: cl.exe
+// CHECK-YU-FALLBACK-NOT: -include-pch
+// CHECK-YU-FALLBACK-NOT: /Yupchfile.h
+// CHECK-YU-FALLBACK: /FIpchfile.h
+// CHECK-YU-FALLBACK-NOT: /Fpfoo.pch
+
+// /FI without /Yu => pch file not used, even if it exists (different from
+// -include, which picks up .gch files if they exist).
+// RUN: touch %t.pch
+// RUN: %clang_cl -internal-enable-pch -Werror /FI%t.pch /Fp%t.pch /c -### -- %s 2>&1 \
+// RUN:   | FileCheck -check-prefix=CHECK-FI %s
+// CHECK-FI-NOT: -include-pch
+// CHECK-FI: -include
+
+// Test interaction of /Yc with language mode flags.
+
+// If /TC changes the input language to C, a c pch file should be produced.
+// RUN: %clang_cl /TC -internal-enable-pch -Werror /Ycpchfile.h /FIpchfile.h /c -### -- %s 2>&1 \
+// RUN:   | FileCheck -check-prefix=CHECK-YCTC %s
+// CHECK-YCTC: cc1
+// CHECK-YCTC: -emit-pch
+// CHECK-YCTC: -o
+// CHECK-YCTC: pchfile.pch
+// CHECK-YCTC: -x
+// CHECK-YCTP: "c"
+
+// Also check lower-case /Tc variant.
+// RUN: %clang_cl -internal-enable-pch -Werror /Ycpchfile.h /FIpchfile.h /c -### /Tc%s 2>&1 \
+// RUN:   | FileCheck -check-prefix=CHECK-YCTc %s
+// CHECK-YCTc: cc1
+// CHECK-YCTc: -emit-pch
+// CHECK-YCTc: -o
+// CHECK-YCTc: pchfile.pch
+// CHECK-YCTc: -x
+// CHECK-YCTc: "c"