Revert abb00753 "build: reduce CMake handling for zlib" (PR44780)

and follow-ups:
a2ca1c2d "build: disable zlib by default on Windows"
2181bf40 "[CMake] Link against ZLIB::ZLIB"
1079c68a "Attempt to fix ZLIB CMake logic on Windows"

This changed the output of llvm-config --system-libs, and more
importantly it broke stand-alone builds. Instead of piling on more fix
attempts, let's revert this to reduce the risk of more breakages.

(cherry picked from commit 916be8fd6a0a0feea4cefcbeb0c22c65848d7a2e)

1 files changed, 18 insertions, 15 deletions

diff --git a/llvm/cmake/config-ix.cmake b/llvm/cmake/config-ix.cmake
index fc66dbfcbe7..f758366bc79 100644
--- a/llvm/cmake/config-ix.cmake
+++ b/llvm/cmake/config-ix.cmake
@@ -56,6 +56,7 @@ check_include_file(sys/types.h HAVE_SYS_TYPES_H)
 check_include_file(termios.h HAVE_TERMIOS_H)
 check_include_file(unistd.h HAVE_UNISTD_H)
 check_include_file(valgrind/valgrind.h HAVE_VALGRIND_VALGRIND_H)
+check_include_file(zlib.h HAVE_ZLIB_H)
 check_include_file(fenv.h HAVE_FENV_H)
 check_symbol_exists(FE_ALL_EXCEPT "fenv.h" HAVE_DECL_FE_ALL_EXCEPT)
 check_symbol_exists(FE_INEXACT "fenv.h" HAVE_DECL_FE_INEXACT)
@@ -117,6 +118,19 @@ endif()
 # Don't look for these libraries if we're using MSan, since uninstrumented third
 # party code may call MSan interceptors like strlen, leading to false positives.
 if(NOT LLVM_USE_SANITIZER MATCHES "Memory.*")
+  set(HAVE_LIBZ 0)
+  if(LLVM_ENABLE_ZLIB)
+    foreach(library z zlib_static zlib)
+      string(TOUPPER ${library} library_suffix)
+      check_library_exists(${library} compress2 "" HAVE_LIBZ_${library_suffix})
+      if(HAVE_LIBZ_${library_suffix})
+        set(HAVE_LIBZ 1)
+        set(ZLIB_LIBRARIES "${library}")
+        break()
+      endif()
+    endforeach()
+  endif()
+
   # Don't look for these libraries on Windows.
   if (NOT PURE_WINDOWS)
     # Skip libedit if using ASan as it contains memory leaks.
@@ -501,21 +515,10 @@ else( LLVM_ENABLE_THREADS )
   message(STATUS "Threads disabled.")
 endif()
 
-if(LLVM_ENABLE_ZLIB)
-  if(LLVM_ENABLE_ZLIB STREQUAL FORCE_ON)
-    find_package(ZLIB REQUIRED)
-  else()
-    find_package(ZLIB)
-  endif()
-
-  if(ZLIB_FOUND)
-    set(LLVM_ENABLE_ZLIB "YES" CACHE STRING
-      "Use zlib for compression/decompression if available. Can be ON, OFF, or FORCE_ON"
-      FORCE)
-  else()
-    set(LLVM_ENABLE_ZLIB "NO" CACHE STRING
-      "Use zlib for compression/decompression if available. Can be ON, OFF, or FORCE_ON"
-      FORCE)
+if (LLVM_ENABLE_ZLIB )
+  # Check if zlib is available in the system.
+  if ( NOT HAVE_ZLIB_H OR NOT HAVE_LIBZ )
+    set(LLVM_ENABLE_ZLIB 0)
   endif()
 endif()