clang-cl: Remove -isystem, add -imsvc.

r260990 exposed -isystem in clang-cl. -isystem adds a directory to the front of
the system include search path. The idea was to use this to point to a hermetic
msvc install, but as it turns out this doesn't work: -isystem then adds the
hermetic headers in front of clang's builtin headers, and clang's headers that
are supposed to wrap msvc headers (say, stdarg.h) aren't picked up at all
anymore.

So revert that, and instead expose -imsvc which works as if the passed
directory was part of %INCLUDE%: The header is treated as a system header, but
it is searched after clang's lib/Header headers.

Fixes half of PRPR26751.

llvm-svn: 266108

2 files changed, 6 insertions, 5 deletions

diff --git a/clang/test/Driver/cl-options.c b/clang/test/Driver/cl-options.c
index c9e857332d7..4f82c5ade17 100644
--- a/clang/test/Driver/cl-options.c
+++ b/clang/test/Driver/cl-options.c
@@ -82,6 +82,12 @@
 // RUN: %clang_cl /I myincludedir -### -- %s 2>&1 | FileCheck -check-prefix=SLASH_I %s
 // SLASH_I: "-I" "myincludedir"
 
+// RUN: %clang_cl /imsvcmyincludedir -### -- %s 2>&1 | FileCheck -check-prefix=SLASH_imsvc %s
+// RUN: %clang_cl /imsvc myincludedir -### -- %s 2>&1 | FileCheck -check-prefix=SLASH_imsvc %s
+// Clang's resource header directory should be first:
+// SLASH_imsvc: "-internal-isystem" "{{[^"]*}}lib{{.}}clang{{[^"]*}}include"
+// SLASH_imsvc: "-internal-isystem" "myincludedir"
+
 // RUN: %clang_cl /J -### -- %s 2>&1 | FileCheck -check-prefix=J %s
 // J: -fno-signed-char
 
@@ -452,7 +458,6 @@
 // RUN:     -fno-ms-compatibility \
 // RUN:     -fms-extensions \
 // RUN:     -fno-ms-extensions \
-// RUN:     -isystem=some/path \
 // RUN:     -mllvm -disable-llvm-optzns \
 // RUN:     -Wunused-variable \
 // RUN:     -fmacro-backtrace-limit=0 \
diff --git a/clang/test/Driver/cl-pch-search.cpp b/clang/test/Driver/cl-pch-search.cpp
index fd503f1f801..118cf19efbd 100644
--- a/clang/test/Driver/cl-pch-search.cpp
+++ b/clang/test/Driver/cl-pch-search.cpp
@@ -4,7 +4,3 @@
 // REQUIRES: x86-registered-target
 // Check that pchfile.h next to to pchfile.cc is found correctly.
 // RUN: %clang_cl -Werror /Ycpchfile.h /FIpchfile.h /c /Fo%t.obj /Fp%t.pch -- %S/Inputs/pchfile.cpp 
-
-// Check that i_group flags other than -include aren't skipped (e.g. -isystem).
-#include "header0.h"
-// RUN: %clang_cl -Werror -isystem%S/Inputs /Yupchfile.h /FIpchfile.h /c /Fo%t.obj /Fp%t.pch -- %s