Add pragma to perform module import and use it in -E output.

Many of our supported configurations support modules but do not have any
first-class syntax to perform a module import. This leaves us with a problem:
there is no way to represent the expansion of a #include that imports a module
in the -E output for such languages. (We don't want to just leave it as a
#include because that requires the consumer of the preprocessed source to have
the same file system layout and include paths as the creator.)

This patch adds a new pragma:

  #pragma clang module import MODULE.NAME.HERE

that imports a module, and changes -E and -frewrite-includes to use it when
rewriting a #include that maps to a module import. We don't make any attempt
to use a native language syntax import if one exists, to get more consistent
output. (If in the future, @import and #include have different semantics in
some way, the pragma will track the #include semantics.)

llvm-svn: 301725

1 files changed, 2 insertions, 2 deletions

diff --git a/clang/test/Modules/crash-vfs-path-symlink-component.m b/clang/test/Modules/crash-vfs-path-symlink-component.m
index 5be492514a0..4723a77c7e9 100644
--- a/clang/test/Modules/crash-vfs-path-symlink-component.m
+++ b/clang/test/Modules/crash-vfs-path-symlink-component.m
@@ -28,7 +28,7 @@
 // CHECK-NEXT: note: diagnostic msg: {{.*}}.m
 // CHECK-NEXT: note: diagnostic msg: {{.*}}.cache
 
-// CHECKSRC: @import cstd.stdio;
+// CHECKSRC: #pragma clang module import cstd.stdio
 
 // CHECKSH: # Crash reproducer
 // CHECKSH-NEXT: # Driver args: "-fsyntax-only"
@@ -65,4 +65,4 @@
 // RUN:     -fmodules-cache-path=%t/m/ 2>&1 \
 // RUN:     | FileCheck %s --check-prefix=CHECKOVERLAY
 
-// CHECKOVERLAY: @import cstd.stdio; /* clang -E: implicit import for "/{{[^ ].*}}/i/usr/x/../stdio.h" */
+// CHECKOVERLAY: #pragma clang module import cstd.stdio /* clang -E: implicit import