build: reduce CMake handling for zlib

Rather than handling zlib handling manually, use `find_package` from CMake
to find zlib properly. Use this to normalize the `LLVM_ENABLE_ZLIB`,
`HAVE_ZLIB`, `HAVE_ZLIB_H`. Furthermore, require zlib if `LLVM_ENABLE_ZLIB` is
set to `YES`, which requires the distributor to explicitly select whether
zlib is enabled or not. This simplifies the CMake handling and usage in
the rest of the tooling.

3 files changed, 4 insertions, 7 deletions

diff --git a/llvm/lib/Support/CMakeLists.txt b/llvm/lib/Support/CMakeLists.txt
index ddc4d2324a0..2fa641ff5da 100644
--- a/llvm/lib/Support/CMakeLists.txt
+++ b/llvm/lib/Support/CMakeLists.txt
@@ -1,7 +1,4 @@
-set(system_libs)
-if ( LLVM_ENABLE_ZLIB AND HAVE_LIBZ )
-  set(system_libs ${system_libs} ${ZLIB_LIBRARIES})
-endif()
+set(system_libs ${ZLIB_LIBRARY})
 if( MSVC OR MINGW )
   # libuuid required for FOLDERID_Profile usage in lib/Support/Windows/Path.inc.
   # advapi32 required for CryptAcquireContextW in lib/Support/Windows/Path.inc.
diff --git a/llvm/lib/Support/CRC.cpp b/llvm/lib/Support/CRC.cpp
index 7c008d3b599..a3dba1a3aa1 100644
--- a/llvm/lib/Support/CRC.cpp
+++ b/llvm/lib/Support/CRC.cpp
@@ -25,7 +25,7 @@
 
 using namespace llvm;
 
-#if LLVM_ENABLE_ZLIB == 0 || !HAVE_ZLIB_H
+#if !LLVM_ENABLE_ZLIB
 
 static const uint32_t CRCTable[256] = {
     0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, 0x706af48f,
diff --git a/llvm/lib/Support/Compression.cpp b/llvm/lib/Support/Compression.cpp
index 97d5ffaadf8..4165a2740cd 100644
--- a/llvm/lib/Support/Compression.cpp
+++ b/llvm/lib/Support/Compression.cpp
@@ -17,13 +17,13 @@
 #include "llvm/Support/Compiler.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Support/ErrorHandling.h"
-#if LLVM_ENABLE_ZLIB == 1 && HAVE_ZLIB_H
+#if LLVM_ENABLE_ZLIB
 #include <zlib.h>
 #endif
 
 using namespace llvm;
 
-#if LLVM_ENABLE_ZLIB == 1 && HAVE_LIBZ
+#if LLVM_ENABLE_ZLIB
 static Error createError(StringRef Err) {
   return make_error<StringError>(Err, inconvertibleErrorCode());
 }