14 files changed, 172 insertions, 10 deletions
diff --git a/llvm/CMakeLists.txt b/llvm/CMakeLists.txt
index 64898ab..cbf4db6 100644
--- a/llvm/CMakeLists.txt
+++ b/llvm/CMakeLists.txt
@@ -539,6 +539,8 @@ set(FFI_INCLUDE_DIR "" CACHE PATH "Additional directory, where CMake should sear
 set(LLVM_TARGET_ARCH "host"
   CACHE STRING "Set target to use for LLVM JIT or use \"host\" for automatic detection.")
 
+option(LLVM_ENABLE_TERMINFO "Use terminfo database if available." ON)
+
 set(LLVM_ENABLE_LIBXML2 "ON" CACHE STRING "Use libxml2 if available. Can be ON, OFF, or FORCE_ON")
 
 option(LLVM_ENABLE_LIBEDIT "Use libedit if available." ON)
diff --git a/llvm/cmake/config-ix.cmake b/llvm/cmake/config-ix.cmake
index 0aae13e..7d2a4933 100644
--- a/llvm/cmake/config-ix.cmake
+++ b/llvm/cmake/config-ix.cmake
@@ -240,11 +240,21 @@ if(NOT LLVM_USE_SANITIZER MATCHES "Memory.*")
     else()
       set(HAVE_LIBEDIT 0)
     endif()
+    if(LLVM_ENABLE_TERMINFO)
+      if(LLVM_ENABLE_TERMINFO STREQUAL FORCE_ON)
+        find_package(Terminfo REQUIRED)
+      else()
+        find_package(Terminfo)
+      endif()
+      set(LLVM_ENABLE_TERMINFO "${Terminfo_FOUND}")
+    endif()
   else()
     set(HAVE_LIBEDIT 0)
+    set(LLVM_ENABLE_TERMINFO 0)
   endif()
 else()
   set(HAVE_LIBEDIT 0)
+  set(LLVM_ENABLE_TERMINFO 0)
 endif()
 
 if(LLVM_HAS_LOGF128)
diff --git a/llvm/cmake/modules/FindTerminfo.cmake b/llvm/cmake/modules/FindTerminfo.cmake
new file mode 100644
index 0000000..163af66
--- /dev/null
+++ b/llvm/cmake/modules/FindTerminfo.cmake
@@ -0,0 +1,55 @@
+# Attempts to discover terminfo library with a linkable setupterm function.
+#
+# Example usage:
+#
+# find_package(Terminfo)
+#
+# If successful, the following variables will be defined:
+# Terminfo_FOUND
+# Terminfo_LIBRARIES
+#
+# Additionally, the following import target will be defined:
+# Terminfo::terminfo
+
+find_library(Terminfo_LIBRARIES NAMES terminfo tinfo curses ncurses ncursesw)
+
+if(Terminfo_LIBRARIES)
+  include(CMakePushCheckState)
+  cmake_push_check_state()
+  list(APPEND CMAKE_REQUIRED_LIBRARIES ${Terminfo_LIBRARIES})
+  set(Terminfo_LINKABLE_SRC [=[
+    #ifdef __cplusplus
+    extern "C" {
+    #endif
+    int setupterm(char *term, int filedes, int *errret);
+    #ifdef __cplusplus
+    }
+    #endif
+    int main(void) { return setupterm(0, 0, 0); }
+    ]=])
+  if(DEFINED CMAKE_C_COMPILER)
+    include(CheckCSourceCompiles)
+    check_c_source_compiles("${Terminfo_LINKABLE_SRC}" Terminfo_LINKABLE)
+  else()
+    include(CheckCXXSourceCompiles)
+    check_cxx_source_compiles("${Terminfo_LINKABLE_SRC}" Terminfo_LINKABLE)
+  endif()
+  cmake_pop_check_state()
+endif()
+
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(Terminfo
+                                  FOUND_VAR
+                                    Terminfo_FOUND
+                                  REQUIRED_VARS
+                                    Terminfo_LIBRARIES
+                                    Terminfo_LINKABLE)
+mark_as_advanced(Terminfo_LIBRARIES
+                 Terminfo_LINKABLE)
+
+if(Terminfo_FOUND)
+  if(NOT TARGET Terminfo::terminfo)
+    add_library(Terminfo::terminfo UNKNOWN IMPORTED)
+    set_target_properties(Terminfo::terminfo PROPERTIES IMPORTED_LOCATION "${Terminfo_LIBRARIES}")
+  endif()
+endif()
diff --git a/llvm/cmake/modules/LLVMConfig.cmake.in b/llvm/cmake/modules/LLVMConfig.cmake.in
index 7e1501a..397bd581 100644
--- a/llvm/cmake/modules/LLVMConfig.cmake.in
+++ b/llvm/cmake/modules/LLVMConfig.cmake.in
@@ -60,6 +60,11 @@ if(LLVM_ENABLE_LIBEDIT)
   find_package(LibEdit)
 endif()
 
+set(LLVM_ENABLE_TERMINFO @LLVM_ENABLE_TERMINFO@)
+if(LLVM_ENABLE_TERMINFO)
+  find_package(Terminfo)
+endif()
+
 set(LLVM_ENABLE_THREADS @LLVM_ENABLE_THREADS@)
 
 set(LLVM_ENABLE_UNWIND_TABLES @LLVM_ENABLE_UNWIND_TABLES@)
diff --git a/llvm/docs/ReleaseNotes.rst b/llvm/docs/ReleaseNotes.rst
index c7c2c282..1e1ccb4 100644
--- a/llvm/docs/ReleaseNotes.rst
+++ b/llvm/docs/ReleaseNotes.rst
@@ -63,10 +63,6 @@ Changes to LLVM infrastructure
 Changes to building LLVM
 ------------------------
 
-- The ``LLVM_ENABLE_TERMINFO`` flag has been removed. LLVM no longer depends on
-  terminfo and now always uses the ``TERM`` environment variable for color
-  support autodetection.
-
 Changes to TableGen
 -------------------
 
diff --git a/llvm/include/llvm/Config/config.h.cmake b/llvm/include/llvm/Config/config.h.cmake
index ff30741..977c182 100644
--- a/llvm/include/llvm/Config/config.h.cmake
+++ b/llvm/include/llvm/Config/config.h.cmake
@@ -209,6 +209,9 @@
 /* Define to 1 if you have the <sys/types.h> header file. */
 #cmakedefine HAVE_SYS_TYPES_H ${HAVE_SYS_TYPES_H}
 
+/* Define if the setupterm() function is supported this platform. */
+#cmakedefine LLVM_ENABLE_TERMINFO ${LLVM_ENABLE_TERMINFO}
+
 /* Define to 1 if you have the <termios.h> header file. */
 #cmakedefine HAVE_TERMIOS_H ${HAVE_TERMIOS_H}
 
diff --git a/llvm/lib/Support/CMakeLists.txt b/llvm/lib/Support/CMakeLists.txt
index be4badc..03e8889 100644
--- a/llvm/lib/Support/CMakeLists.txt
+++ b/llvm/lib/Support/CMakeLists.txt
@@ -56,6 +56,9 @@ elseif( CMAKE_HOST_UNIX )
     STRING(REGEX REPLACE "^lib" "" Backtrace_LIBFILE ${Backtrace_LIBFILE})
     set(system_libs ${system_libs} ${Backtrace_LIBFILE})
   endif()
+  if( LLVM_ENABLE_TERMINFO )
+    set(imported_libs ${imported_libs} Terminfo::terminfo)
+  endif()
   set(system_libs ${system_libs} ${LLVM_ATOMIC_LIB})
   set(system_libs ${system_libs} ${LLVM_PTHREAD_LIB})
   if( UNIX AND NOT (BEOS OR HAIKU) )
@@ -322,6 +325,14 @@ if(LLVM_ENABLE_ZSTD)
   set(llvm_system_libs ${llvm_system_libs} "${zstd_library}")
 endif()
 
+if(LLVM_ENABLE_TERMINFO)
+  if(NOT terminfo_library)
+    get_property(terminfo_library TARGET Terminfo::terminfo PROPERTY LOCATION)
+  endif()
+  get_library_name(${terminfo_library} terminfo_library)
+  set(llvm_system_libs ${llvm_system_libs} "${terminfo_library}")
+endif()
+
 set_property(TARGET LLVMSupport PROPERTY LLVM_SYSTEM_LIBS "${llvm_system_libs}")
 
 
diff --git a/llvm/lib/Support/Unix/Process.inc b/llvm/lib/Support/Unix/Process.inc
index 84b10ff..ae90924 100644
--- a/llvm/lib/Support/Unix/Process.inc
+++ b/llvm/lib/Support/Unix/Process.inc
@@ -341,9 +341,17 @@ unsigned Process::StandardErrColumns() {
   return getColumns();
 }
 
-static bool terminalHasColors() {
-  // Check if the current terminal is one of terminals that are known to support
-  // ANSI color escape codes.
+#ifdef LLVM_ENABLE_TERMINFO
+// We manually declare these extern functions because finding the correct
+// headers from various terminfo, curses, or other sources is harder than
+// writing their specs down.
+extern "C" int setupterm(char *term, int filedes, int *errret);
+extern "C" struct term *set_curterm(struct term *termp);
+extern "C" int del_curterm(struct term *termp);
+extern "C" int tigetnum(char *capname);
+#endif
+
+bool checkTerminalEnvironmentForColors() {
   if (const char *TermStr = std::getenv("TERM")) {
     return StringSwitch<bool>(TermStr)
         .Case("ansi", true)
@@ -360,10 +368,54 @@ static bool terminalHasColors() {
   return false;
 }
 
+static bool terminalHasColors(int fd) {
+#ifdef LLVM_ENABLE_TERMINFO
+  // First, acquire a global lock because these C routines are thread hostile.
+  static std::mutex TermColorMutex;
+  std::lock_guard<std::mutex> G(TermColorMutex);
+
+  struct term *previous_term = set_curterm(nullptr);
+  int errret = 0;
+  if (setupterm(nullptr, fd, &errret) != 0)
+    // Regardless of why, if we can't get terminfo, we shouldn't try to print
+    // colors.
+    return false;
+
+  // Test whether the terminal as set up supports color output. How to do this
+  // isn't entirely obvious. We can use the curses routine 'has_colors' but it
+  // would be nice to avoid a dependency on curses proper when we can make do
+  // with a minimal terminfo parsing library. Also, we don't really care whether
+  // the terminal supports the curses-specific color changing routines, merely
+  // if it will interpret ANSI color escape codes in a reasonable way. Thus, the
+  // strategy here is just to query the baseline colors capability and if it
+  // supports colors at all to assume it will translate the escape codes into
+  // whatever range of colors it does support. We can add more detailed tests
+  // here if users report them as necessary.
+  //
+  // The 'tigetnum' routine returns -2 or -1 on errors, and might return 0 if
+  // the terminfo says that no colors are supported.
+  int colors_ti = tigetnum(const_cast<char *>("colors"));
+  bool HasColors =
+      colors_ti >= 0 ? colors_ti : checkTerminalEnvironmentForColors();
+
+  // Now extract the structure allocated by setupterm and free its memory
+  // through a really silly dance.
+  struct term *termp = set_curterm(previous_term);
+  (void)del_curterm(termp); // Drop any errors here.
+
+  // Return true if we found a color capabilities for the current terminal.
+  return HasColors;
+#else
+  // When the terminfo database is not available, check if the current terminal
+  // is one of terminals that are known to support ANSI color escape codes.
+  return checkTerminalEnvironmentForColors();
+#endif
+}
+
 bool Process::FileDescriptorHasColors(int fd) {
   // A file descriptor has colors if it is displayed and the terminal has
   // colors.
-  return FileDescriptorIsDisplayed(fd) && terminalHasColors();
+  return FileDescriptorIsDisplayed(fd) && terminalHasColors(fd);
 }
 
 bool Process::StandardOutHasColors() {
diff --git a/llvm/utils/gn/README.rst b/llvm/utils/gn/README.rst
index 52d03be..9ca5450 100644
--- a/llvm/utils/gn/README.rst
+++ b/llvm/utils/gn/README.rst
@@ -131,7 +131,7 @@ configure is used for three classes of feature checks:
 
 For the last two points, it would be nice if LLVM didn't have a single
 ``config.h`` header, but one header per toggle. That way, when e.g.
-``llvm_enable_zlib`` is toggled, only the 3 files caring about that setting
+``llvm_enable_terminfo`` is toggled, only the 3 files caring about that setting
 would need to be rebuilt, instead of everything including ``config.h``.
 
 GN doesn't believe in users setting arbitrary cflags from an environment
diff --git a/llvm/utils/gn/build/libs/terminfo/BUILD.gn b/llvm/utils/gn/build/libs/terminfo/BUILD.gn
new file mode 100644
index 0000000..10003d6
--- /dev/null
+++ b/llvm/utils/gn/build/libs/terminfo/BUILD.gn
@@ -0,0 +1,12 @@
+import("//llvm/utils/gn/build/libs/terminfo/enable.gni")
+
+config("terminfo_config") {
+  visibility = [ ":terminfo" ]
+  libs = [ "ncurses" ]
+}
+
+group("terminfo") {
+  if (llvm_enable_terminfo) {
+    public_configs = [ ":terminfo_config" ]
+  }
+}
diff --git a/llvm/utils/gn/build/libs/terminfo/enable.gni b/llvm/utils/gn/build/libs/terminfo/enable.gni
new file mode 100644
index 0000000..79ea2b6
--- /dev/null
+++ b/llvm/utils/gn/build/libs/terminfo/enable.gni
@@ -0,0 +1,4 @@
+declare_args() {
+  # Whether to link against terminfo.
+  llvm_enable_terminfo = false
+}
diff --git a/llvm/utils/gn/secondary/llvm/include/llvm/Config/BUILD.gn b/llvm/utils/gn/secondary/llvm/include/llvm/Config/BUILD.gn
index d8266fe..2da26d1 100644
--- a/llvm/utils/gn/secondary/llvm/include/llvm/Config/BUILD.gn
+++ b/llvm/utils/gn/secondary/llvm/include/llvm/Config/BUILD.gn
@@ -10,6 +10,7 @@ import("//llvm/utils/gn/build/buildflags.gni")
 import("//llvm/utils/gn/build/libs/curl/enable.gni")
 import("//llvm/utils/gn/build/libs/edit/enable.gni")
 import("//llvm/utils/gn/build/libs/pthread/enable.gni")
+import("//llvm/utils/gn/build/libs/terminfo/enable.gni")
 import("//llvm/utils/gn/build/libs/xar/enable.gni")
 import("//llvm/utils/gn/build/libs/xml/enable.gni")
 import("//llvm/utils/gn/build/libs/zlib/enable.gni")
@@ -293,6 +294,12 @@ write_cmake_config("config") {
     values += [ "HAVE_LIBEDIT=" ]
   }
 
+  if (llvm_enable_terminfo) {
+    values += [ "LLVM_ENABLE_TERMINFO=1" ]
+  } else {
+    values += [ "LLVM_ENABLE_TERMINFO=" ]
+  }
+
   if (llvm_enable_libxml2) {
     values += [ "LLVM_ENABLE_LIBXML2=1" ]
   } else {
diff --git a/llvm/utils/gn/secondary/llvm/lib/Support/BUILD.gn b/llvm/utils/gn/secondary/llvm/lib/Support/BUILD.gn
index 7728455..941d448 100644
--- a/llvm/utils/gn/secondary/llvm/lib/Support/BUILD.gn
+++ b/llvm/utils/gn/secondary/llvm/lib/Support/BUILD.gn
@@ -6,6 +6,7 @@ static_library("Support") {
     "//llvm/include/llvm/Support:write_vcsrevision",
     "//llvm/lib/Demangle",
     "//llvm/utils/gn/build/libs/pthread",
+    "//llvm/utils/gn/build/libs/terminfo",
     "//llvm/utils/gn/build/libs/zlib",
   ]
 
diff --git a/llvm/utils/gn/secondary/llvm/tools/llvm-config/BUILD.gn b/llvm/utils/gn/secondary/llvm/tools/llvm-config/BUILD.gn
index 711e4e3..bf50cd0f 100644
--- a/llvm/utils/gn/secondary/llvm/tools/llvm-config/BUILD.gn
+++ b/llvm/utils/gn/secondary/llvm/tools/llvm-config/BUILD.gn
@@ -1,6 +1,7 @@
 import("//llvm/lib/Target/targets_string.gni")
 import("//llvm/utils/gn/build/buildflags.gni")
 import("//llvm/utils/gn/build/libs/pthread/enable.gni")
+import("//llvm/utils/gn/build/libs/terminfo/enable.gni")
 import("//llvm/utils/gn/build/libs/xml/enable.gni")
 import("//llvm/utils/gn/build/libs/zlib/enable.gni")
 import("//llvm/utils/gn/build/write_cmake_config.gni")
@@ -35,7 +36,7 @@ write_cmake_config("BuildVariables.inc") {
     lib = ""
   }
 
-  # Windows doesn't use any of libxml2, zlib by default.
+  # Windows doesn't use any of libxml2, terminfo, zlib by default.
   # Make GN not warn about these variables being unused.
   not_needed([
                "l",
@@ -62,6 +63,9 @@ write_cmake_config("BuildVariables.inc") {
   if (llvm_enable_libxml2) {
     system_libs += " ${l}xml2${lib}"
   }
+  if (llvm_enable_terminfo) {
+    system_libs += " ${l}ncurses${lib}"
+  }
   if (llvm_enable_zlib) {
     system_libs += " ${l}z${lib}"
   }