[CMake] Simplify CMake handling for zlib

[phosek]

Summary

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.

This is a reland of rGabb0075 with all followup changes and fixes that should address
issues that were reported in PR44780.

[phosek]

Ping?

[smeenai]

lld/test/lit.site.cfg.py.in

17

This seems like an unintended/unrelated change.

llvm/cmake/config-ix.cmake

523–524

How come you're moving this out of the MSan check block? Isn't that a behavior change?

llvm/lib/Support/CMakeLists.txt

209

Even if there's no prefix, wouldn't you still wanna strip the suffix?

[JDevlieghere]

I'm in favor of this change. I'm not too happy with how this works in CMake, I've expressed similar concerns when the FORCE_ON approach was suggested in D71306.

I really like what we ended up with in LLDB. The TL;DR is that we have 3 values: ON, OFF and Auto. The later will resolve to either ON or OFF depending on whether the dependency was found. The "clever" part is that we use shadowing to avoid having another CMake variable without overwriting the cache.

Here's what it looks like in LLDB: https://github.com/llvm/llvm-project/blob/3df40007e6317955176dff0fa9e0b029dc4a11d1/lldb/cmake/modules/LLDBConfig.cmake#L26

Maybe we can consider something similar here? I'd be more than happy to hoist the corresponding CMake into llvm.

(edit: added myself as a reviewer so this shows up in my review queue)

llvm/cmake/config-ix.cmake

531

If I understand correctly, after running the configuration phase with LLVM_ENABLE_ZLIB to FORCE_ON, the cached value will be overwritten by ON?

[phosek]

In D79219#2029520, @JDevlieghere wrote:

I'm in favor of this change. I'm not too happy with how this works in CMake, I've expressed similar concerns when the FORCE_ON approach was suggested in D71306.

I really like what we ended up with in LLDB. The TL;DR is that we have 3 values: ON, OFF and Auto. The later will resolve to either ON or OFF depending on whether the dependency was found. The "clever" part is that we use shadowing to avoid having another CMake variable without overwriting the cache.

Here's what it looks like in LLDB: https://github.com/llvm/llvm-project/blob/3df40007e6317955176dff0fa9e0b029dc4a11d1/lldb/cmake/modules/LLDBConfig.cmake#L26

Maybe we can consider something similar here? I'd be more than happy to hoist the corresponding CMake into llvm.

(edit: added myself as a reviewer so this shows up in my review queue)

I'm fine either way, to me ON/OFF/AUTO and FORCE_ON/ON/OFF is just a different way to spell the same thing, my only concern would be breaking existing users who might be already relying on FORCE_ON.

llvm/cmake/config-ix.cmake

523–524

This was done in the original change, I'm not quite sure what's the motivation, @compnerd do you know?

531

Correct, we used FORCE_ON above when invoking find_package setting REQUIRED which makes the check fail if the library is missing. Recording this information is important for LLVM consumers because it'll be stored in LLVMConfig.cmake and AFAIU we don't want to propagate FORCE_ON there.

[JDevlieghere]

llvm/cmake/config-ix.cmake

531

I get that. My worry is that if for whatever reason the library disappears (system upgrade, package removal, ...) this will silently disable ZLIB support because now LLVM_ENABLE_ZLIB just equals on. This might sound far fetched, but happens all the time with "internal installs". This is why I prefer the ON/OFF/Auto approach because it doesn't update the cache variable, but would set the internal variable to either ON or OFF.

[labath]

llvm/cmake/config-ix.cmake

531

I agree with Jonas, though I don't think the actual values (FORCE_ON/ON vs. ON/Auto) really matter here. The important part is not overwriting the cache variables specified by the user, as that can create various problems with reconfigurations (like the zlib becoming unavailable example).

[smeenai]

Requesting changes to remove from my review queue while the above comments are being addressed.

[phosek]

llvm/cmake/config-ix.cmake

531

I've updated the change to shadow the variable as suggested by Jonas.

[JDevlieghere]

Thanks Petr, LGTM

[smeenai]

Oops, missed that I'd become a blocking reviewer for this (cos of requesting changes before).

[phosek]

I had to revert this change because it broke bots that don't have zlib installed. What I haven't realized is that the shadowed variable will only be accessible from the same file. I could move the logic from llvm/lib/Support/CMakeLists.txt into llvm/cmake/config-ix.cmake, but that doesn't handle all the other files that need to access that variable, such as all the */test/CMakeLists.txt files. So I don't know if shadowing is the way to go here. Maybe we should set a different internal cached variable (HAVE_LIBZ?) and use that to check if zlib is available. What do you think?

[labath]

I wouldn't mind separate (internal) cache variable, though I am somewhat surprised by this problem. A (non-cache) variable set in one of the parent scopes should still take precedence over a cache variable with the same name. And since config-ix.cmake is included from the top CMakeLists.txt, the value it defines should be available everywhere. Was this a problem for the regular build, or only for some of the more exotic build setups that don't start with llvm/CMakeLists.txt ?

[phosek]

In D79219#2152747, @labath wrote:

I wouldn't mind separate (internal) cache variable, though I am somewhat surprised by this problem. A (non-cache) variable set in one of the parent scopes should still take precedence over a cache variable with the same name. And since config-ix.cmake is included from the top CMakeLists.txt, the value it defines should be available everywhere. Was this a problem for the regular build, or only for some of the more exotic build setups that don't start with llvm/CMakeLists.txt ?

Never mind, it's working as expected. The problem is that we disable zlib detection on Windows which I missed before. I'm not sure why that's the case, I tested this on Windows and it seems to be working fine, but for now I've kept the existing behavior, we can consider enabling zlib on Windows in a follow up change.

[vsk]

@phosek I suspect this is causing a cmake error on the lldb standalone bot, would you mind taking a look?

http://lab.llvm.org:8080/green/view/LLDB/job/lldb-cmake-standalone/1858/

CMake Error at /Users/buildslave/jenkins/workspace/lldb-cmake-standalone/clang-build/lib/cmake/llvm/AddLLVM.cmake:823 (add_executable):
  Target "lit-cpuid" links to target "ZLIB::ZLIB" but the target was not
  found.  Perhaps a find_package() call is missing for an IMPORTED target, or
  an ALIAS target is missing?
Call Stack (most recent call first):
  cmake/modules/AddLLDB.cmake:165 (add_llvm_executable)
  utils/lit-cpuid/CMakeLists.txt:1 (add_lldb_executable)

[mehdi_amini]

mlir/examples/standalone/CMakeLists.txt

35 ↗

(On Diff #280331)

I am a bit unsure that it is desirable that it is desirable to need this change?
This requires every single user of LLVM to do this. Is there a way this can be done in the call to find_package(LLVM) instead?

[mehdi_amini]

mlir/examples/standalone/CMakeLists.txt

35 ↗

(On Diff #280331)

(Doc for the usual way to integrate LLVM: https://llvm.org/docs/CMake.html#embedding-llvm-in-your-project )

[stephenneuendorffer]

mlir/examples/standalone/CMakeLists.txt

35 ↗

(On Diff #280331)

I tend to agree with Mehdi. I think stuff like this which is *required* to use LLVM should get pushed into what LLVM exports. (Actually there is a bunch of other configuration stuff which also needs to get pushed into the export, otherwise configuration defaults are all wrong and things like that.)

[phosek]

mlir/examples/standalone/CMakeLists.txt

35 ↗

(On Diff #280331)

Implemented in D84691.

[hans]

In D79219#2153585, @phosek wrote:

In D79219#2152747, @labath wrote:

I wouldn't mind separate (internal) cache variable, though I am somewhat surprised by this problem. A (non-cache) variable set in one of the parent scopes should still take precedence over a cache variable with the same name. And since config-ix.cmake is included from the top CMakeLists.txt, the value it defines should be available everywhere. Was this a problem for the regular build, or only for some of the more exotic build setups that don't start with llvm/CMakeLists.txt ?

Never mind, it's working as expected. The problem is that we disable zlib detection on Windows which I missed before. I'm not sure why that's the case, I tested this on Windows and it seems to be working fine, but for now I've kept the existing behavior, we can consider enabling zlib on Windows in a follow up change.

:-( We rely on zlib on Windows, and we pass -DLLVM_ENABLE_ZLIB=FORCE_ON to ensure that the build breaks if it can't be used for some reason.

It seems your change both disabled use of zlib on Windows, and also removed the check which made that an error when using FORCE_ON, which means we didn't catch this until further down the line.

[hans]

Reverted in 3ab01550b632dad46f9595d74855749557ffd25c

[phosek]

Sorry about the breakage, that was an unintentional change. I have updated the patch and restored the original behavior on Windows.

[hans]

llvm/cmake/config-ix.cmake

178

Could this check be put back? E.g. for now it seems building with -DLLVM_USE_SANITIZERS=Memory and -DLLVM_ENABLE_ZLIB=FORCE_ON will silently not use zlib.

[lxfind]

@phosek, Under this change, now when I build LLVM (with a basic config cmake -G Ninja --LLVM_ENABLE_PROJECTS=clang ../llvm), in file build_dir/lib/cmake/llvm/LLVMExports.cmake, I see this:

set_target_properties(LLVMSupport PROPERTIES
  INTERFACE_LINK_LIBRARIES "curses;m;ZLIB::ZLIB;LLVMDemangle"

This seems broken to me. Can you take a look?

[phosek]

In D79219#2201109, @lxfind wrote:

@phosek, Under this change, now when I build LLVM (with a basic config cmake -G Ninja --LLVM_ENABLE_PROJECTS=clang ../llvm), in file build_dir/lib/cmake/llvm/LLVMExports.cmake, I see this:

set_target_properties(LLVMSupport PROPERTIES
  INTERFACE_LINK_LIBRARIES "curses;m;ZLIB::ZLIB;LLVMDemangle"

This seems broken to me. Can you take a look?

This is correct. That target is provided by find_package(ZLIB). In LLVMConfig.cmake, we invoke find_package(ZLIB) when zlib support is enabled. If you're using LLVMExports.cmake, you'll need to invoke find_package(ZLIB) yourself.

[kuhnel]

This patch broke the Windows compilation on buildbot and pre-merge testing. So I'll revert it to get pre-merge testing back online. Otherwise this will cause false-positives for pre-merge testing.

The error message:

FAILED: bin/llvm-profdata.exe 
cmd.exe /C "cd . && "C:\Program Files\CMake\bin\cmake.exe" -E vs_link_exe --intdir=tools\llvm-profdata\CMakeFiles\llvm-profdata.dir --rc="C:\Program Files (x86)\Windows Kits\10\bin\10.0.18362.0\x64\rc.exe" --mt="C:\Program Files (x86)\Windows Kits\10\bin\10.0.18362.0\x64\mt.exe" --manifests  -- C:\BuildTools\VC\Tools\MSVC\14.26.28801\bin\Hostx64\x64\link.exe /nologo tools\llvm-profdata\CMakeFiles\llvm-profdata.dir\llvm-profdata.cpp.obj tools\llvm-profdata\CMakeFiles\llvm-profdata.dir\__\__\resources\windows_version_resource.rc.res  /out:bin\llvm-profdata.exe /implib:lib\llvm-profdata.lib /pdb:bin\llvm-profdata.pdb /version:0.0  /machine:x64 /STACK:10000000 /INCREMENTAL:NO /subsystem:console  lib\LLVMCore.lib lib\LLVMProfileData.lib lib\LLVMSupport.lib lib\LLVMCore.lib lib\LLVMBinaryFormat.lib lib\LLVMRemarks.lib lib\LLVMBitstreamReader.lib lib\LLVMSupport.lib psapi.lib shell32.lib ole32.lib uuid.lib advapi32.lib C:\GnuWin\lib\zlib.lib delayimp.lib -delayload:shell32.dll -delayload:ole32.dll lib\LLVMDemangle.lib kernel32.lib user32.lib gdi32.lib winspool.lib shell32.lib ole32.lib oleaut32.lib uuid.lib comdlg32.lib advapi32.lib && cd ."
LINK: command "C:\BuildTools\VC\Tools\MSVC\14.26.28801\bin\Hostx64\x64\link.exe /nologo tools\llvm-profdata\CMakeFiles\llvm-profdata.dir\llvm-profdata.cpp.obj tools\llvm-profdata\CMakeFiles\llvm-profdata.dir\__\__\resources\windows_version_resource.rc.res /out:bin\llvm-profdata.exe /implib:lib\llvm-profdata.lib /pdb:bin\llvm-profdata.pdb /version:0.0 /machine:x64 /STACK:10000000 /INCREMENTAL:NO /subsystem:console lib\LLVMCore.lib lib\LLVMProfileData.lib lib\LLVMSupport.lib lib\LLVMCore.lib lib\LLVMBinaryFormat.lib lib\LLVMRemarks.lib lib\LLVMBitstreamReader.lib lib\LLVMSupport.lib psapi.lib shell32.lib ole32.lib uuid.lib advapi32.lib C:\GnuWin\lib\zlib.lib delayimp.lib -delayload:shell32.dll -delayload:ole32.dll lib\LLVMDemangle.lib kernel32.lib user32.lib gdi32.lib winspool.lib shell32.lib ole32.lib oleaut32.lib uuid.lib comdlg32.lib advapi32.lib /MANIFEST /MANIFESTFILE:bin\llvm-profdata.exe.manifest" failed (exit code 1120) with the following output:
LLVMSupport.lib(Compression.cpp.obj) : error LNK2019: unresolved external symbol compress2 referenced in function "class llvm::Error __cdecl llvm::zlib::compress(class llvm::StringRef,class llvm::SmallVectorImpl<char> &,int)" (?compress@zlib@llvm@@YA?AVError@2@VStringRef@2@AEAV?$SmallVectorImpl@D@2@H@Z)
LLVMSupport.lib(Compression.cpp.obj) : error LNK2019: unresolved external symbol compressBound referenced in function "class llvm::Error __cdecl llvm::zlib::compress(class llvm::StringRef,class llvm::SmallVectorImpl<char> &,int)" (?compress@zlib@llvm@@YA?AVError@2@VStringRef@2@AEAV?$SmallVectorImpl@D@2@H@Z)
LLVMSupport.lib(Compression.cpp.obj) : error LNK2019: unresolved external symbol uncompress referenced in function "class llvm::Error __cdecl llvm::zlib::uncompress(class llvm::StringRef,class llvm::SmallVectorImpl<char> &,unsigned __int64)" (?uncompress@zlib@llvm@@YA?AVError@2@VStringRef@2@AEAV?$SmallVectorImpl@D@2@_K@Z)
  Hint on symbols that are defined and could potentially match:
    "class llvm::Error __cdecl llvm::zlib::uncompress(class llvm::StringRef,class llvm::SmallVectorImpl<char> &,unsigned __int64)" (?uncompress@zlib@llvm@@YA?AVError@2@VStringRef@2@AEAV?$SmallVectorImpl@D@2@_K@Z)
    "class llvm::Error __cdecl llvm::zlib::uncompress(class llvm::StringRef,char *,unsigned __int64 &)" (?uncompress@zlib@llvm@@YA?AVError@2@VStringRef@2@PEADAEA_K@Z)
LLVMSupport.lib(Compression.cpp.obj) : error LNK2019: unresolved external symbol crc32 referenced in function "unsigned int __cdecl llvm::zlib::crc32(class llvm::StringRef)" (?crc32@zlib@llvm@@YAIVStringRef@2@@Z)
  Hint on symbols that are defined and could potentially match:
    "unsigned int __cdecl llvm::zlib::crc32(class llvm::StringRef)" (?crc32@zlib@llvm@@YAIVStringRef@2@@Z)
C:\GnuWin\lib\zlib.lib : warning LNK4272: library machine type 'x86' conflicts with target machine type 'x64'
bin\llvm-profdata.exe : fatal error LNK1120: 4 unresolved externals

[phosek]

How can I test this change on pre-merge bots? I haven't seen any builds posted on this change before.

[phosek]

In D79219#2201994, @kuhnel wrote:

This patch broke the Windows compilation on buildbot and pre-merge testing. So I'll revert it to get pre-merge testing back online. Otherwise this will cause false-positives for pre-merge testing.

The error message:

FAILED: bin/llvm-profdata.exe 
cmd.exe /C "cd . && "C:\Program Files\CMake\bin\cmake.exe" -E vs_link_exe --intdir=tools\llvm-profdata\CMakeFiles\llvm-profdata.dir --rc="C:\Program Files (x86)\Windows Kits\10\bin\10.0.18362.0\x64\rc.exe" --mt="C:\Program Files (x86)\Windows Kits\10\bin\10.0.18362.0\x64\mt.exe" --manifests  -- C:\BuildTools\VC\Tools\MSVC\14.26.28801\bin\Hostx64\x64\link.exe /nologo tools\llvm-profdata\CMakeFiles\llvm-profdata.dir\llvm-profdata.cpp.obj tools\llvm-profdata\CMakeFiles\llvm-profdata.dir\__\__\resources\windows_version_resource.rc.res  /out:bin\llvm-profdata.exe /implib:lib\llvm-profdata.lib /pdb:bin\llvm-profdata.pdb /version:0.0  /machine:x64 /STACK:10000000 /INCREMENTAL:NO /subsystem:console  lib\LLVMCore.lib lib\LLVMProfileData.lib lib\LLVMSupport.lib lib\LLVMCore.lib lib\LLVMBinaryFormat.lib lib\LLVMRemarks.lib lib\LLVMBitstreamReader.lib lib\LLVMSupport.lib psapi.lib shell32.lib ole32.lib uuid.lib advapi32.lib C:\GnuWin\lib\zlib.lib delayimp.lib -delayload:shell32.dll -delayload:ole32.dll lib\LLVMDemangle.lib kernel32.lib user32.lib gdi32.lib winspool.lib shell32.lib ole32.lib oleaut32.lib uuid.lib comdlg32.lib advapi32.lib && cd ."
LINK: command "C:\BuildTools\VC\Tools\MSVC\14.26.28801\bin\Hostx64\x64\link.exe /nologo tools\llvm-profdata\CMakeFiles\llvm-profdata.dir\llvm-profdata.cpp.obj tools\llvm-profdata\CMakeFiles\llvm-profdata.dir\__\__\resources\windows_version_resource.rc.res /out:bin\llvm-profdata.exe /implib:lib\llvm-profdata.lib /pdb:bin\llvm-profdata.pdb /version:0.0 /machine:x64 /STACK:10000000 /INCREMENTAL:NO /subsystem:console lib\LLVMCore.lib lib\LLVMProfileData.lib lib\LLVMSupport.lib lib\LLVMCore.lib lib\LLVMBinaryFormat.lib lib\LLVMRemarks.lib lib\LLVMBitstreamReader.lib lib\LLVMSupport.lib psapi.lib shell32.lib ole32.lib uuid.lib advapi32.lib C:\GnuWin\lib\zlib.lib delayimp.lib -delayload:shell32.dll -delayload:ole32.dll lib\LLVMDemangle.lib kernel32.lib user32.lib gdi32.lib winspool.lib shell32.lib ole32.lib oleaut32.lib uuid.lib comdlg32.lib advapi32.lib /MANIFEST /MANIFESTFILE:bin\llvm-profdata.exe.manifest" failed (exit code 1120) with the following output:
LLVMSupport.lib(Compression.cpp.obj) : error LNK2019: unresolved external symbol compress2 referenced in function "class llvm::Error __cdecl llvm::zlib::compress(class llvm::StringRef,class llvm::SmallVectorImpl<char> &,int)" (?compress@zlib@llvm@@YA?AVError@2@VStringRef@2@AEAV?$SmallVectorImpl@D@2@H@Z)
LLVMSupport.lib(Compression.cpp.obj) : error LNK2019: unresolved external symbol compressBound referenced in function "class llvm::Error __cdecl llvm::zlib::compress(class llvm::StringRef,class llvm::SmallVectorImpl<char> &,int)" (?compress@zlib@llvm@@YA?AVError@2@VStringRef@2@AEAV?$SmallVectorImpl@D@2@H@Z)
LLVMSupport.lib(Compression.cpp.obj) : error LNK2019: unresolved external symbol uncompress referenced in function "class llvm::Error __cdecl llvm::zlib::uncompress(class llvm::StringRef,class llvm::SmallVectorImpl<char> &,unsigned __int64)" (?uncompress@zlib@llvm@@YA?AVError@2@VStringRef@2@AEAV?$SmallVectorImpl@D@2@_K@Z)
  Hint on symbols that are defined and could potentially match:
    "class llvm::Error __cdecl llvm::zlib::uncompress(class llvm::StringRef,class llvm::SmallVectorImpl<char> &,unsigned __int64)" (?uncompress@zlib@llvm@@YA?AVError@2@VStringRef@2@AEAV?$SmallVectorImpl@D@2@_K@Z)
    "class llvm::Error __cdecl llvm::zlib::uncompress(class llvm::StringRef,char *,unsigned __int64 &)" (?uncompress@zlib@llvm@@YA?AVError@2@VStringRef@2@PEADAEA_K@Z)
LLVMSupport.lib(Compression.cpp.obj) : error LNK2019: unresolved external symbol crc32 referenced in function "unsigned int __cdecl llvm::zlib::crc32(class llvm::StringRef)" (?crc32@zlib@llvm@@YAIVStringRef@2@@Z)
  Hint on symbols that are defined and could potentially match:
    "unsigned int __cdecl llvm::zlib::crc32(class llvm::StringRef)" (?crc32@zlib@llvm@@YAIVStringRef@2@@Z)
C:\GnuWin\lib\zlib.lib : warning LNK4272: library machine type 'x86' conflicts with target machine type 'x64'
bin\llvm-profdata.exe : fatal error LNK1120: 4 unresolved externals

Looking at the error, it seems like you have a 32-bit version of zlib installed and in your search path on a 64-bit version of Windows. I'm not quite sure how to handle that in CMake.

[kuhnel]

In D79219#2202048, @phosek wrote:

How can I test this change on pre-merge bots? I haven't seen any builds posted on this change before.

You can just look at the mlir-windows buildbot, this also showed the failing build: http://lab.llvm.org:8011/builders/mlir-windows?numbuilds=200
However it's lagging behind quite a bit.

Pre-merge testing is using a different infrastructure and is not sending notifications on failing master build. We're still trying to figure out how to deal with a broken master branch properly without building every revision...
Right now it's building master every 4 hours using the same setup used for pre-merge testing: https://buildkite.com/llvm-project/llvm-master-build/builds

[kuhnel]

Looking at the error, it seems like you have a 32-bit version of zlib installed and in your search path on a 64-bit version of Windows. I'm not quite sure how to handle that in CMake.

For mlir-windows buildbot:
I have no clue on what is installed there.

For pre-merge testing:
I guess zlib is part of GNUWin32 package being installed. This is the recommended setup for Visual Studio. The pre-merge builds are running in a docker container on Windows, so you can check what software is being installed.

[lxfind]

In D79219#2201415, @phosek wrote:

In D79219#2201109, @lxfind wrote:

@phosek, Under this change, now when I build LLVM (with a basic config cmake -G Ninja --LLVM_ENABLE_PROJECTS=clang ../llvm), in file build_dir/lib/cmake/llvm/LLVMExports.cmake, I see this:

set_target_properties(LLVMSupport PROPERTIES
  INTERFACE_LINK_LIBRARIES "curses;m;ZLIB::ZLIB;LLVMDemangle"

This seems broken to me. Can you take a look?

This is correct. That target is provided by find_package(ZLIB). In LLVMConfig.cmake, we invoke find_package(ZLIB) when zlib support is enabled. If you're using LLVMExports.cmake, you'll need to invoke find_package(ZLIB) yourself.

@phosek, Thanks for the reply. I am not too familiar with this. Could you please elaborate more on why setting it to ZLIB::ZLIB here is more modern? And how one is expected to deal with ZLIB::ZLIB that shows up in LLVMExports.cmake` (in the modern way)? Should one string pattern matching for ZLIB::ZLIB and invoke find_package(ZLIB) again? (previously one could simply concatenate -l with the library name in there.

[phosek]

I have finally managed to reproduce the issue on my Windows machine, the latest version of the patch should address the issue. The previous logic would fail to find zlib altogether on Windows, which is why this issue haven't manifested before. find_package locates the zlib correctly, but we need to ensure that the library that was found can be used.

[phosek]

@kuhnel do you want to take a look or is it okay if I just submit the change?

[phosek]

In D79219#2203887, @lxfind wrote:

In D79219#2201415, @phosek wrote:

This is correct. That target is provided by find_package(ZLIB). In LLVMConfig.cmake, we invoke find_package(ZLIB) when zlib support is enabled. If you're using LLVMExports.cmake, you'll need to invoke find_package(ZLIB) yourself.

@phosek, Thanks for the reply. I am not too familiar with this. Could you please elaborate more on why setting it to ZLIB::ZLIB here is more modern? And how one is expected to deal with ZLIB::ZLIB that shows up in LLVMExports.cmake` (in the modern way)? Should one string pattern matching for ZLIB::ZLIB and invoke find_package(ZLIB) again? (previously one could simply concatenate -l with the library name in there.

@lxfind ZLIB::ZLIB is the name of the imported target that's defined by CMake when you invoke find_dependency(ZLIB). Ideally, you'd just use LLVMConfig.cmake which invokes that for you if needed. https://pabloariasal.github.io/2018/02/19/its-time-to-do-cmake-right/ has some more details.

ZLIB::ZLIB includes the correct include and library directory, so you no longer have to manually append -I or -l, all you need is to include ZLIB::ZLIB in the list of your dependencies, which is one advantage. Another advantage is that ZLIB::ZLIB can expand to different things, for example some users may want to statically link zlib in which case they would configure their build accordingly and ZLIB::ZLIB would expand into /path/to/libz.a (this is for example what we do in our toolchain build), others may be fine using the default system library in which case ZLIB::ZLIB would typically expand to just z.

[kuhnel]

@phosek sorry for the late reply, the builds on master are still green, so your changes are working on Windows as well.

Thank you for the extra work!

[haampie]

Great, one benefit of this is that zlib can now be detected in non-system libs. Maybe we should handle ncurses / TERMINFO in a similar manner? It currently has similar logic as finding zlib had

[haampie]

llvm/lib/Support/CMakeLists.txt

217

This will not work on macOS since cmake will find stub libraries by default (/path/to/libz.tbd), see https://github.com/Kitware/CMake/blob/master/Modules/Platform/Darwin.cmake#L71 for the search order.

Instead you most likely want to use CMAKE_FIND_LIBRARY_PREFIXES and CMAKE_FIND_LIBRARY_SUFFIXES

[mati865]

@phosek in MSYS2 (targeting x86_64-w64-windows-gnu) Zlib works properly for LLVM 10 but with master I'm now seeing:

-- Constructing LLVMBuild project information
-- DEBUG zlib_library=D:/msys64/mingw64/lib/libz.dll.a
CMake Error at lib/Support/CMakeLists.txt:9 (string):
  string sub-command REGEX, mode REPLACE: regex "^(lib|)" matched an empty
  string.
Call Stack (most recent call first):
  lib/Support/CMakeLists.txt:226 (get_system_libname)

-- DEBUG zlib_library=D:/msys64/mingw64/lib/libz.dll.a was printed by my change to help debugging it.
FYI zlib_library is set here: https://github.com/llvm/llvm-project/blob/8e06bf6b3a2e8d25e56cd52dca0cf3ff1b37b5d1/llvm/lib/Support/CMakeLists.txt#L218

[phosek]

In D79219#2231927, @mati865 wrote:

@phosek in MSYS2 (targeting x86_64-w64-windows-gnu) Zlib works properly for LLVM 10 but with master I'm now seeing:

-- Constructing LLVMBuild project information
-- DEBUG zlib_library=D:/msys64/mingw64/lib/libz.dll.a
CMake Error at lib/Support/CMakeLists.txt:9 (string):
  string sub-command REGEX, mode REPLACE: regex "^(lib|)" matched an empty
  string.
Call Stack (most recent call first):
  lib/Support/CMakeLists.txt:226 (get_system_libname)

-- DEBUG zlib_library=D:/msys64/mingw64/lib/libz.dll.a was printed by my change to help debugging it.
FYI zlib_library is set here: https://github.com/llvm/llvm-project/blob/8e06bf6b3a2e8d25e56cd52dca0cf3ff1b37b5d1/llvm/lib/Support/CMakeLists.txt#L218

Looks like that's an issue introduced by D86134 or D86245. Can you print the value of ${CMAKE_FIND_LIBRARY_PREFIXES} and ${CMAKE_FIND_LIBRARY_SUFFIXES} in your build?

[mati865]

@phosek

Looks like that's an issue introduced by D86134 or D86245.

Indeed, I apologize for bothering you. Should I move the discussion to one of patches created by @haampie?

Continuing the discussion with if( CMAKE_FIND_LIBRARY_PREFIXES ) and if( CMAKE_FIND_LIBRARY_SUFFIXES ) from https://reviews.llvm.org/D86245 changed to false llvm-config --system-libs prints -llibz.dll.a so we need those replaces to bring back correct -lz value.

Can you print the value of ${CMAKE_FIND_LIBRARY_PREFIXES} and ${CMAKE_FIND_LIBRARY_SUFFIXES} in your build?

-- CMAKE_FIND_LIBRARY_PREFIXES=lib;
-- CMAKE_FIND_LIBRARY_SUFFIXES=.dll.a;.a;.lib

Which matches https://gitlab.kitware.com/cmake/cmake/-/blob/269d1a86249ea037a2884133daffc8c44a38d926/Modules/Platform/Windows-GNU.cmake

clang/test/CMakeLists.txt

 # Test runner infrastructure for Clang. This configures the Clang test trees
 # for use by Lit, and delegates to LLVM's lit test handlers.
 
 if (CMAKE_CFG_INTDIR STREQUAL ".")
   set(LLVM_BUILD_MODE ".")
 else ()
   set(LLVM_BUILD_MODE "%(build_mode)s")
 endif ()
 
 string(REPLACE ${CMAKE_CFG_INTDIR} ${LLVM_BUILD_MODE} CLANG_TOOLS_DIR ${LLVM_RUNTIME_OUTPUT_INTDIR})
 
-if(CLANG_BUILT_STANDALONE)
-  # Set HAVE_LIBZ according to recorded LLVM_ENABLE_ZLIB value. This
-  # value is forced to 0 if zlib was not found, so it is fine to use it
-  # instead of HAVE_LIBZ (not recorded).
-  if(LLVM_ENABLE_ZLIB)
-    set(HAVE_LIBZ 1)
-  endif()
-endif()
-
 llvm_canonicalize_cmake_booleans(
   CLANG_BUILD_EXAMPLES
   CLANG_ENABLE_ARCMT
   CLANG_ENABLE_STATIC_ANALYZER
   CLANG_SPAWN_CC1
   ENABLE_BACKTRACES
   ENABLE_EXPERIMENTAL_NEW_PASS_MANAGER
-  HAVE_LIBZ
+  LLVM_ENABLE_ZLIB
   LLVM_ENABLE_PER_TARGET_RUNTIME_DIR
   LLVM_ENABLE_PLUGINS
   LLVM_ENABLE_THREADS)
 
 configure_lit_site_cfg(
   ${CMAKE_CURRENT_SOURCE_DIR}/lit.site.cfg.py.in
   ${CMAKE_CURRENT_BINARY_DIR}/lit.site.cfg.py
   MAIN_CONFIG

clang/test/lit.site.cfg.py.in

 config.lit_tools_dir = path(r"@LLVM_LIT_TOOLS_DIR@")
 config.clang_obj_root = path(r"@CLANG_BINARY_DIR@")
 config.clang_src_dir = path(r"@CLANG_SOURCE_DIR@")
 config.clang_tools_dir = path(r"@CLANG_TOOLS_DIR@")
 config.host_triple = "@LLVM_HOST_TRIPLE@"
 config.target_triple = "@TARGET_TRIPLE@"
 config.host_cxx = "@CMAKE_CXX_COMPILER@"
 config.llvm_use_sanitizer = "@LLVM_USE_SANITIZER@"
-config.have_zlib = @HAVE_LIBZ@
+config.have_zlib = @LLVM_ENABLE_ZLIB@
 config.clang_arcmt = @CLANG_ENABLE_ARCMT@
 config.clang_default_cxx_stdlib = "@CLANG_DEFAULT_CXX_STDLIB@"
 config.clang_staticanalyzer = @CLANG_ENABLE_STATIC_ANALYZER@
 config.clang_staticanalyzer_z3 = "@LLVM_WITH_Z3@"
 config.clang_examples = @CLANG_BUILD_EXAMPLES@
 config.enable_shared = @ENABLE_SHARED@
 config.enable_backtrace = @ENABLE_BACKTRACES@
 config.enable_experimental_new_pass_manager = @ENABLE_EXPERIMENTAL_NEW_PASS_MANAGER@

compiler-rt/test/lit.common.configured.in

 elif config.android:
   if config.target_arch == "i386":
     set_default("target_suffix", "-i686-android")
   else:
     set_default("target_suffix", "-%s-android" % config.target_arch)
 else:
   set_default("target_suffix", "-%s" % config.target_arch)
 
-set_default("have_zlib", "@HAVE_LIBZ@")
+set_default("have_zlib", "@LLVM_ENABLE_ZLIB@")
 set_default("libcxx_used", "@LLVM_LIBCXX_USED@")
 
 # LLVM tools dir can be passed in lit parameters, so try to
 # apply substitution.
 try:
   config.llvm_tools_dir = config.llvm_tools_dir % lit_config.params
   config.clang = config.clang % lit_config.params
   config.compiler_rt_libdir = config.compiler_rt_libdir % lit_config.params

lld/test/CMakeLists.txt

 set(LLVM_SOURCE_DIR "${LLVM_MAIN_SRC_DIR}")
 set(LLVM_BINARY_DIR "${LLVM_BINARY_DIR}")
 set(LLVM_BUILD_MODE "%(build_mode)s")
 set(LLVM_TOOLS_DIR "${LLVM_TOOLS_BINARY_DIR}/%(build_config)s")
 set(LLVM_LIBS_DIR "${LLVM_BINARY_DIR}/lib${LLVM_LIBDIR_SUFFIX}/%(build_config)s")
 
-if(LLD_BUILT_STANDALONE)
-  # Set HAVE_LIBZ according to recorded LLVM_ENABLE_ZLIB value. This
-  # value is forced to 0 if zlib was not found, so it is fine to use it
-  # instead of HAVE_LIBZ (not recorded).
-  if(LLVM_ENABLE_ZLIB)
-    set(HAVE_LIBZ 1)
-  endif()
-endif()
-
 llvm_canonicalize_cmake_booleans(
-  HAVE_LIBZ
+  LLVM_ENABLE_ZLIB
   LLVM_LIBXML2_ENABLED
   )
 
 configure_lit_site_cfg(
   ${CMAKE_CURRENT_SOURCE_DIR}/lit.site.cfg.py.in
   ${CMAKE_CURRENT_BINARY_DIR}/lit.site.cfg.py
   MAIN_CONFIG
   ${CMAKE_CURRENT_SOURCE_DIR}/lit.cfg.py

lld/test/lit.site.cfg.py.in

 @LIT_SITE_CFG_IN_HEADER@
 
 import lit.util
 
 config.have_dia_sdk = lit.util.pythonize_bool("@LLVM_ENABLE_DIA_SDK@")
 config.llvm_src_root = "@LLVM_SOURCE_DIR@"
 config.llvm_obj_root = "@LLVM_BINARY_DIR@"
 config.llvm_tools_dir = "@LLVM_TOOLS_DIR@"
 config.llvm_libs_dir = "@LLVM_LIBS_DIR@"
 config.llvm_libxml2_enabled = @LLVM_LIBXML2_ENABLED@
 config.lit_tools_dir = "@LLVM_LIT_TOOLS_DIR@"
 config.lld_obj_root = "@LLD_BINARY_DIR@"
 config.lld_libs_dir = "@LLVM_LIBRARY_OUTPUT_INTDIR@"
 config.lld_tools_dir = "@LLVM_RUNTIME_OUTPUT_INTDIR@"
 config.target_triple = "@TARGET_TRIPLE@"
 config.python_executable = "@Python3_EXECUTABLE@"
-config.have_zlib = @HAVE_LIBZ@
+config.have_zlib = @LLVM_ENABLE_ZLIB@
 config.sizeof_void_p = @CMAKE_SIZEOF_VOID_P@
 
 # Support substitution of the tools and libs dirs with user parameters. This is
 # used when we can't determine the tool dir at configuration time.
 try:
     config.llvm_tools_dir = config.llvm_tools_dir % lit_config.params
     config.llvm_libs_dir = config.llvm_libs_dir % lit_config.params
 except KeyError as e:
     key, = e.args
     lit_config.fatal("unable to find %r parameter, use '--param=%s=VALUE'" % (key,key))
 
 import lit.llvm
 lit.llvm.initialize(lit_config, config)
 
 # Let the main config do the real work.
 lit_config.load_config(config, "@LLD_SOURCE_DIR@/test/lit.cfg.py")

lldb/cmake/modules/LLDBStandalone.cmake

 else()
   set(LLVM_SHLIB_OUTPUT_INTDIR ${LLVM_LIBRARY_OUTPUT_INTDIR})
 endif()
 
 # We append the directory in which LLVMConfig.cmake lives. We expect LLVM's
 # CMake modules to be in that directory as well.
 list(APPEND CMAKE_MODULE_PATH "${LLVM_DIR}")
 
-if(LLVM_ENABLE_ZLIB)
-  find_package(ZLIB)
-endif()
-
 include(AddLLVM)
 include(TableGen)
 include(HandleLLVMOptions)
 include(CheckAtomic)
 include(LLVMDistributionSupport)
 
 set(PACKAGE_VERSION "${LLVM_PACKAGE_VERSION}")
 set(LLVM_INCLUDE_TESTS ON CACHE INTERNAL "")

lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunication.cpp

 #else
 #define DEBUGSERVER_BASENAME "lldb-server"
 #endif
 
 #if defined(HAVE_LIBCOMPRESSION)
 #include <compression.h>
 #endif
 
-#if defined(HAVE_LIBZ)
+#if LLVM_ENABLE_ZLIB
 #include <zlib.h>
 #endif
 
 using namespace lldb;
 using namespace lldb_private;
 using namespace lldb_private::process_gdb_remote;
 
 // GDBRemoteCommunication constructor
if (decompressed_bufsize != ULONG_MAX && decompressed_buffer != nullptr) {
       decompressed_bytes = compression_decode_buffer(
           decompressed_buffer, decompressed_bufsize,
           (uint8_t *)unescaped_content.data(), unescaped_content.size(),
           m_decompression_scratch, compression_type);
     }
   }
 #endif
 
-#if defined(HAVE_LIBZ)
+#if LLVM_ENABLE_ZLIB
   if (decompressed_bytes == 0 && decompressed_bufsize != ULONG_MAX &&
       decompressed_buffer != nullptr &&
       m_compression_type == CompressionType::ZlibDeflate) {
     z_stream stream;
     memset(&stream, 0, sizeof(z_stream));
     stream.next_in = (Bytef *)unescaped_content.data();
     stream.avail_in = (uInt)unescaped_content.size();
     stream.total_in = 0;

lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationClient.cpp

for (auto compression : supported_compressions) {
         avail_type = CompressionType::ZlibDeflate;
         avail_name = compression;
         break;
       }
     }
   }
 #endif
 
-#if defined(HAVE_LIBZ)
+#if LLVM_ENABLE_ZLIB
   if (avail_type == CompressionType::None) {
     for (auto compression : supported_compressions) {
       if (compression == "zlib-deflate") {
         avail_type = CompressionType::ZlibDeflate;
         avail_name = compression;
         break;
       }
     }

llvm/cmake/config-ix.cmake

 if( WIN32 AND NOT CYGWIN )
   # We consider Cygwin as another Unix
   set(PURE_WINDOWS 1)
 endif()
 
 include(CheckIncludeFile)
 include(CheckLibraryExists)
 include(CheckSymbolExists)
 include(CheckFunctionExists)
 include(CheckStructHasMember)
 include(CheckCCompilerFlag)
+include(CMakePushCheckState)
 
 include(CheckCompilerVersion)
 include(HandleLLVMStdlib)
 
 if( UNIX AND NOT (APPLE OR BEOS OR HAIKU) )
   # Used by check_symbol_exists:
   list(APPEND CMAKE_REQUIRED_LIBRARIES "m")
 endif()

 check_include_file(sys/param.h HAVE_SYS_PARAM_H)
 check_include_file(sys/resource.h HAVE_SYS_RESOURCE_H)
 check_include_file(sys/stat.h HAVE_SYS_STAT_H)
 check_include_file(sys/time.h HAVE_SYS_TIME_H)
 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)
 
 check_include_file(mach/mach.h HAVE_MACH_MACH_H)
 check_include_file(histedit.h HAVE_HISTEDIT_H)
 check_include_file(CrashReporterClient.h HAVE_CRASHREPORTERCLIENT_H)
 if(APPLE)
if(HAVE_LIBPTHREAD)
   # have it reported as '-l<lib>' instead of '-pthread'.
   # TODO: switch to -pthread once the rest of the build system can deal with it.
   set(CMAKE_THREAD_PREFER_PTHREAD TRUE)
   set(THREADS_HAVE_PTHREAD_ARG Off)
   find_package(Threads REQUIRED)
   set(LLVM_PTHREAD_LIB ${CMAKE_THREAD_LIBS_INIT})
 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()
+  if(LLVM_ENABLE_ZLIB STREQUAL FORCE_ON)
+    find_package(ZLIB REQUIRED)
+  elseif(NOT LLVM_USE_SANITIZER MATCHES "Memory.*")
+    find_package(ZLIB)
+  endif()
+  if(ZLIB_FOUND)
+    # Check if zlib we found is usable; for example, we may have found a 32-bit
+    # library on a 64-bit system which would result in a link-time failure.
+    cmake_push_check_state()
+    set(CMAKE_REQUIRED_INCLUDES ${ZLIB_INCLUDE_DIRS})
+    set(CMAKE_REQUIRED_LIBRARIES ${ZLIB_LIBRARY})
+    check_symbol_exists(compress2 zlib.h HAVE_ZLIB)
+    cmake_pop_check_state()
+    if(LLVM_ENABLE_ZLIB STREQUAL FORCE_ON AND NOT HAVE_ZLIB)
+      message(FATAL_ERROR "Failed to configure zlib")
+  endif()
+  set(LLVM_ENABLE_ZLIB "${HAVE_ZLIB}")
 
+# 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.*")
   # Don't look for these libraries on Windows.
   if (NOT PURE_WINDOWS)
     # Skip libedit if using ASan as it contains memory leaks.
     if (LLVM_ENABLE_LIBEDIT AND HAVE_HISTEDIT_H AND NOT LLVM_USE_SANITIZER MATCHES ".*Address.*")
       check_library_exists(edit el_init "" HAVE_LIBEDIT)
     else()
       set(HAVE_LIBEDIT 0)
     endif()
if (NOT PURE_WINDOWS)
     endif()
   endif()
 endif()
 
 if (LLVM_ENABLE_LIBXML2 STREQUAL "FORCE_ON" AND NOT LLVM_LIBXML2_ENABLED)
   message(FATAL_ERROR "Failed to congifure libxml2")
 endif()
 
-if (LLVM_ENABLE_ZLIB STREQUAL "FORCE_ON" AND NOT HAVE_LIBZ)
-  message(FATAL_ERROR "Failed to configure zlib")
-endif()
-
 check_library_exists(xar xar_open "" HAVE_LIBXAR)
 if(HAVE_LIBXAR)
   set(XAR_LIB xar)
 endif()
 
 # function checks
 check_symbol_exists(arc4random "stdlib.h" HAVE_DECL_ARC4RANDOM)
 find_package(Backtrace)
if( LLVM_ENABLE_THREADS )
   endif()
 endif()
 
 if( LLVM_ENABLE_THREADS )
   message(STATUS "Threads enabled.")
 else( LLVM_ENABLE_THREADS )
   message(STATUS "Threads disabled.")
 endif()
 
-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()
-
 if (LLVM_ENABLE_DOXYGEN)
   message(STATUS "Doxygen enabled.")
   find_package(Doxygen REQUIRED)
 
   if (DOXYGEN_FOUND)
     # If we find doxygen and we want to enable doxygen by default create a
     # global aggregate doxygen target for generating llvm and any/all
     # subprojects doxygen documentation.
     if (LLVM_BUILD_DOCS)
       add_custom_target(doxygen ALL)
     endif()
 
     option(LLVM_DOXYGEN_EXTERNAL_SEARCH "Enable doxygen external search." OFF)
     if (LLVM_DOXYGEN_EXTERNAL_SEARCH)
       set(LLVM_DOXYGEN_SEARCHENGINE_URL "" CACHE STRING "URL to use for external search.")
       set(LLVM_DOXYGEN_SEARCH_MAPPINGS "" CACHE STRING "Doxygen Search Mappings")

llvm/cmake/modules/LLVMConfig.cmake.in

 
 set(LLVM_ENABLE_TERMINFO @LLVM_ENABLE_TERMINFO@)
 
 set(LLVM_ENABLE_THREADS @LLVM_ENABLE_THREADS@)
 
 set(LLVM_ENABLE_UNWIND_TABLES @LLVM_ENABLE_UNWIND_TABLES@)
 
 set(LLVM_ENABLE_ZLIB @LLVM_ENABLE_ZLIB@)
+if(LLVM_ENABLE_ZLIB)
+  find_package(ZLIB)
+endif()
 
 set(LLVM_LIBXML2_ENABLED @LLVM_LIBXML2_ENABLED@)
 
 set(LLVM_WITH_Z3 @LLVM_WITH_Z3@)
 
 set(LLVM_ENABLE_DIA_SDK @LLVM_ENABLE_DIA_SDK@)
 
 set(LLVM_NATIVE_ARCH @LLVM_NATIVE_ARCH@)

llvm/include/llvm/Config/config.h.cmake

 #cmakedefine HAVE_LIBPTHREAD ${HAVE_LIBPTHREAD}
 
 /* Define to 1 if you have the `pthread_getname_np' function. */
 #cmakedefine HAVE_PTHREAD_GETNAME_NP ${HAVE_PTHREAD_GETNAME_NP}
 
 /* Define to 1 if you have the `pthread_setname_np' function. */
 #cmakedefine HAVE_PTHREAD_SETNAME_NP ${HAVE_PTHREAD_SETNAME_NP}
 
-/* Define to 1 if you have the `z' library (-lz). */
-#cmakedefine HAVE_LIBZ ${HAVE_LIBZ}
-
 /* Define to 1 if you have the <link.h> header file. */
 #cmakedefine HAVE_LINK_H ${HAVE_LINK_H}
 
 /* Define to 1 if you have the `lseek64' function. */
 #cmakedefine HAVE_LSEEK64 ${HAVE_LSEEK64}
 
 /* Define to 1 if you have the <mach/mach.h> header file. */
 #cmakedefine HAVE_MACH_MACH_H ${HAVE_MACH_MACH_H}

 #cmakedefine HAVE_TERMIOS_H ${HAVE_TERMIOS_H}
 
 /* Define to 1 if you have the <unistd.h> header file. */
 #cmakedefine HAVE_UNISTD_H ${HAVE_UNISTD_H}
 
 /* Define to 1 if you have the <valgrind/valgrind.h> header file. */
 #cmakedefine HAVE_VALGRIND_VALGRIND_H ${HAVE_VALGRIND_VALGRIND_H}
 
-/* Define to 1 if you have the <zlib.h> header file. */
-#cmakedefine HAVE_ZLIB_H ${HAVE_ZLIB_H}
-
 /* Have host's _alloca */
 #cmakedefine HAVE__ALLOCA ${HAVE__ALLOCA}
 
 /* Define to 1 if you have the `_chsize_s' function. */
 #cmakedefine HAVE__CHSIZE_S ${HAVE__CHSIZE_S}
 
 /* Define to 1 if you have the `_Unwind_Backtrace' function. */
 #cmakedefine HAVE__UNWIND_BACKTRACE ${HAVE__UNWIND_BACKTRACE}

llvm/lib/Support/CMakeLists.txt

-set(system_libs)
-if ( LLVM_ENABLE_ZLIB AND HAVE_LIBZ )
-  set(system_libs ${system_libs} ${ZLIB_LIBRARIES})
+if(LLVM_ENABLE_ZLIB)
+  set(imported_libs ZLIB::ZLIB)
 endif()
+
 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.
   set(system_libs ${system_libs} psapi shell32 ole32 uuid advapi32)
 elseif( CMAKE_HOST_UNIX )
   if( HAVE_LIBRT )
     set(system_libs ${system_libs} rt)
   endif()
# System
   Watchdog.cpp
 
   ADDITIONAL_HEADER_DIRS
   Unix
   Windows
   ${LLVM_MAIN_INCLUDE_DIR}/llvm/ADT
   ${LLVM_MAIN_INCLUDE_DIR}/llvm/Support
   ${Backtrace_INCLUDE_DIRS}
-  LINK_LIBS ${system_libs} ${delayload_flags} ${Z3_LINK_FILES}
+  LINK_LIBS ${system_libs} ${imported_libs} ${delayload_flags} ${Z3_LINK_FILES}
   )
 
-set_property(TARGET LLVMSupport PROPERTY LLVM_SYSTEM_LIBS "${system_libs}")
+set(llvm_system_libs ${system_libs})
+
+if(LLVM_ENABLE_ZLIB)
+  # CMAKE_BUILD_TYPE is only meaningful to single-configuration generators.
+  if(CMAKE_BUILD_TYPE)
+    string(TOUPPER ${CMAKE_BUILD_TYPE} build_type)
+    get_property(zlib_library TARGET ZLIB::ZLIB PROPERTY LOCATION_${build_type})
+  endif()
+  if(NOT zlib_library)
+    get_property(zlib_library TARGET ZLIB::ZLIB PROPERTY LOCATION)
+  endif()
+  get_filename_component(zlib_library ${zlib_library} NAME)
+  if(CMAKE_STATIC_LIBRARY_PREFIX AND CMAKE_STATIC_LIBRARY_SUFFIX AND
+      zlib_library MATCHES "^${CMAKE_STATIC_LIBRARY_PREFIX}.*${CMAKE_STATIC_LIBRARY_SUFFIX}$")
+    STRING(REGEX REPLACE "^${CMAKE_STATIC_LIBRARY_PREFIX}" "" zlib_library ${zlib_library})
+    STRING(REGEX REPLACE "${CMAKE_STATIC_LIBRARY_SUFFIX}$" "" zlib_library ${zlib_library})
+  endif()
+  if(CMAKE_SHARED_LIBRARY_PREFIX AND CMAKE_SHARED_LIBRARY_SUFFIX AND
+      zlib_library MATCHES "^${CMAKE_SHARED_LIBRARY_PREFIX}.*${CMAKE_SHARED_LIBRARY_SUFFIX}$")
+    STRING(REGEX REPLACE "^${CMAKE_SHARED_LIBRARY_PREFIX}" "" zlib_library ${zlib_library})
+    STRING(REGEX REPLACE "${CMAKE_SHARED_LIBRARY_SUFFIX}$" "" zlib_library ${zlib_library})
+  endif()
+  set(llvm_system_libs ${llvm_system_libs} "${zlib_library}")
+endif()
+
+set_property(TARGET LLVMSupport PROPERTY LLVM_SYSTEM_LIBS "${llvm_system_libs}")
 
 if(LLVM_WITH_Z3)
   target_include_directories(LLVMSupport SYSTEM
     PRIVATE
     ${Z3_INCLUDE_DIR}
     )
 endif()

llvm/lib/Support/CRC.cpp

 
 #include "llvm/Support/CRC.h"
 
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/Config/config.h"
 
 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,
     0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988,
     0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91, 0x1db71064, 0x6ab020f2,
     0xf3b97148, 0x84be41de, 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7,
     0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
     0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172,

llvm/lib/Support/Compression.cpp

 
 #include "llvm/Support/Compression.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Config/config.h"
 #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());
 }
 
 static StringRef convertZlibCodeToString(int Code) {
   switch (Code) {
   case Z_MEM_ERROR:
     return "zlib error: Z_MEM_ERROR";

llvm/test/CMakeLists.txt

 llvm_canonicalize_cmake_booleans(
   BUILD_SHARED_LIBS
   HAVE_LIBXAR
-  HAVE_LIBZ
   HAVE_OCAMLOPT
   HAVE_OCAML_OUNIT
   LLVM_ENABLE_DIA_SDK
   LLVM_ENABLE_FFI
   LLVM_ENABLE_THREADS
+  LLVM_ENABLE_ZLIB
   LLVM_INCLUDE_GO_TESTS
   LLVM_LIBXML2_ENABLED
   LLVM_LINK_LLVM_DYLIB
   LLVM_TOOL_LTO_BUILD
   LLVM_USE_INTEL_JITEVENTS
   LLVM_BUILD_EXAMPLES
   LLVM_ENABLE_PLUGINS
   LLVM_BYE_LINK_INTO_TOOLS

llvm/test/lit.site.cfg.py.in

 config.llvm_bindings = "@LLVM_BINDINGS@".split(' ')
 config.host_os = "@HOST_OS@"
 config.host_cc = "@HOST_CC@"
 config.host_cxx = "@HOST_CXX@"
 # Note: ldflags can contain double-quoted paths, so must use single quotes here.
 config.host_ldflags = '@HOST_LDFLAGS@'
 config.llvm_use_intel_jitevents = @LLVM_USE_INTEL_JITEVENTS@
 config.llvm_use_sanitizer = "@LLVM_USE_SANITIZER@"
-config.have_zlib = @HAVE_LIBZ@
+config.have_zlib = @LLVM_ENABLE_ZLIB@
 config.have_libxar = @HAVE_LIBXAR@
 config.have_dia_sdk = @LLVM_ENABLE_DIA_SDK@
 config.enable_ffi = @LLVM_ENABLE_FFI@
 config.build_examples = @LLVM_BUILD_EXAMPLES@
 config.enable_threads = @LLVM_ENABLE_THREADS@
 config.build_shared_libs = @BUILD_SHARED_LIBS@
 config.link_llvm_dylib = @LLVM_LINK_LLVM_DYLIB@
 config.llvm_libxml2_enabled = @LLVM_LIBXML2_ENABLED@

llvm/unittests/Support/CompressionTest.cpp

 #include "llvm/Config/config.h"
 #include "llvm/Support/Error.h"
 #include "gtest/gtest.h"
 
 using namespace llvm;
 
 namespace {
 
-#if LLVM_ENABLE_ZLIB == 1 && HAVE_LIBZ
+#if LLVM_ENABLE_ZLIB
 
 void TestZlibCompression(StringRef Input, int Level) {
   SmallString<32> Compressed;
   SmallString<32> Uncompressed;
 
   Error E = zlib::compress(Input, Compressed, Level);
   EXPECT_FALSE(E);
   consumeError(std::move(E));

llvm/utils/gn/secondary/clang/test/BUILD.gn

write_lit_config("lit_site_cfg") {
 
   if (clang_enable_static_analyzer) {
     extra_values += [ "CLANG_ENABLE_STATIC_ANALYZER=1" ]
   } else {
     extra_values += [ "CLANG_ENABLE_STATIC_ANALYZER=0" ]
   }
 
   if (llvm_enable_zlib) {
-    extra_values += [ "HAVE_LIBZ=1" ]
+    extra_values += [ "LLVM_ENABLE_ZLIB=1" ]
   } else {
-    extra_values += [ "HAVE_LIBZ=0" ]  # Must be 0.
+    extra_values += [ "LLVM_ENABLE_ZLIB=0" ]  # Must be 0.
   }
 
   if (host_cpu == "x64") {
     extra_values += [ "HOST_ARCH=x86_64" ]
   } else if (host_cpu == "arm64") {
     extra_values += [ "HOST_ARCH=arm64" ]
   } else if (host_cpu == "ppc64") {
     extra_values += [ "HOST_ARCH=powerpc64le" ]

llvm/utils/gn/secondary/compiler-rt/test/BUILD.gn

write_cmake_config("lit_common_configured") {
 
   if (current_os == "android") {
     values += [ "ANDROID_PYBOOL=True" ]
   } else {
     values += [ "ANDROID_PYBOOL=False" ]
   }
 
   if (llvm_enable_zlib) {
-    values += [ "HAVE_LIBZ=1" ]
+    values += [ "LLVM_ENABLE_ZLIB=1" ]
   } else {
-    values += [ "HAVE_LIBZ=0" ]
+    values += [ "LLVM_ENABLE_ZLIB=0" ]
   }
 }

llvm/utils/gn/secondary/lld/test/BUILD.gn

write_lit_cfg("lit_site_cfg") {
 
   if (llvm_enable_libxml2) {
     extra_values += [ "LLVM_LIBXML2_ENABLED=1" ]
   } else {
     extra_values += [ "LLVM_LIBXML2_ENABLED=0" ]  # Must be 0.
   }
 
   if (llvm_enable_zlib) {
-    extra_values += [ "HAVE_LIBZ=1" ]
+    extra_values += [ "LLVM_ENABLE_ZLIB=1" ]
   } else {
-    extra_values += [ "HAVE_LIBZ=0" ]  # Must be 0.
+    extra_values += [ "LLVM_ENABLE_ZLIB=0" ]  # Must be 0.
   }
 
   if (current_cpu == "x64" || current_cpu == "arm64" ||
       current_cpu == "ppc64") {
     extra_values += [ "CMAKE_SIZEOF_VOID_P=8" ]
   } else {
     extra_values += [ "CMAKE_SIZEOF_VOID_P=4" ]
   }

llvm/utils/gn/secondary/llvm/include/llvm/Config/BUILD.gn

write_cmake_config("config") {
   }
 
   if (llvm_enable_dia_sdk) {
     values += [ "LLVM_ENABLE_DIA_SDK=1" ]
   } else {
     values += [ "LLVM_ENABLE_DIA_SDK=" ]
   }
 
-  # FIXME: Once https://reviews.llvm.org/D79219 is in, remove the two
-  # redundant HAVE_ variables.
   if (llvm_enable_zlib) {
-    values += [
-      "HAVE_LIBZ=1",
-      "HAVE_ZLIB_H=1",
-      "LLVM_ENABLE_ZLIB=1",
-    ]
+    values += [ "LLVM_ENABLE_ZLIB=1" ]
   } else {
-    values += [
-      "HAVE_LIBZ=",
-      "HAVE_ZLIB_H=",
-      "LLVM_ENABLE_ZLIB=",
-    ]
+    values += [ "LLVM_ENABLE_ZLIB=" ]
   }
 
   if (llvm_enable_libxml2) {
     values += [ "LLVM_LIBXML2_ENABLED=1" ]
   } else {
     values += [ "LLVM_LIBXML2_ENABLED=" ]
   }
 }

llvm/utils/gn/secondary/llvm/test/BUILD.gn

write_lit_config("lit_site_cfg") {
 
   if (llvm_enable_threads) {
     extra_values += [ "LLVM_ENABLE_THREADS=1" ]
   } else {
     extra_values += [ "LLVM_ENABLE_THREADS=0" ]  # Must be 0.
   }
 
   if (llvm_enable_zlib) {
-    extra_values += [ "HAVE_LIBZ=1" ]
+    extra_values += [ "LLVM_ENABLE_ZLIB=1" ]
   } else {
-    extra_values += [ "HAVE_LIBZ=0" ]  # Must be 0.
+    extra_values += [ "LLVM_ENABLE_ZLIB=0" ]  # Must be 0.
   }
 }
 
 write_lit_config("lit_unit_site_cfg") {
   input = "//llvm/test/Unit/lit.site.cfg.py.in"
   output = llvm_lit_unit_site_cfg_file
   extra_values = [ "LLVM_BUILD_MODE=." ]
 }