[Support] [Windows] Conditionally compile the SetThreadInformation calls

[mstorsjo]

The declarations for this API are missing in older mingw-w64 headers (versions before v12). This API is also hidden if building with MS WinSDK if targeting versions before Windows 10.

Check whether THREAD_POWER_THROTTLING_CURRENT_VERSION is defined before using this API; this constant is a #define in both WinSDK and mingw-w64.

[llvmbot]

@llvm/pr-subscribers-llvm-support

Author: Martin Storsjö (mstorsjo)

Changes

The declarations for this API are missing in older mingw-w64 headers (versions before v12). This API is also hidden if building with MS WinSDK if targeting versions before Windows 10.

Check whether THREAD_POWER_THROTTLING_CURRENT_VERSION is defined before using this API; this constant is a #define in both WinSDK and mingw-w64.

---

Full diff: https://github.com/llvm/llvm-project/pull/151388.diff

1 Files Affected:

• (modified) llvm/lib/Support/Windows/Threading.inc (+2)

diff --git a/llvm/lib/Support/Windows/Threading.inc b/llvm/lib/Support/Windows/Threading.inc
index 8dd7c88fad34a..b11f216adeba4 100644
--- a/llvm/lib/Support/Windows/Threading.inc
+++ b/llvm/lib/Support/Windows/Threading.inc
@@ -136,6 +136,7 @@ HMODULE loadSystemModuleSecure(LPCWSTR lpModuleName) {
 } // namespace llvm::sys::windows
 
 SetThreadPriorityResult llvm::set_thread_priority(ThreadPriority Priority) {
+#ifdef THREAD_POWER_THROTTLING_CURRENT_VERSION
   HMODULE kernelM = llvm::sys::windows::loadSystemModuleSecure(L"kernel32.dll");
   if (kernelM) {
     // SetThreadInformation is only available on Windows 8 and later. Since we
@@ -166,6 +167,7 @@ SetThreadPriorityResult llvm::set_thread_priority(ThreadPriority Priority) {
                                : 0);
     }
   }
+#endif
 
   // https://docs.microsoft.com/en-us/windows/desktop/api/processthreadsapi/nf-processthreadsapi-setthreadpriority
   // Begin background processing mode. The system lowers the resource scheduling

[llvmbot]

@llvm/pr-subscribers-platform-windows

Author: Martin Storsjö (mstorsjo)

Changes

The declarations for this API are missing in older mingw-w64 headers (versions before v12). This API is also hidden if building with MS WinSDK if targeting versions before Windows 10.

Check whether THREAD_POWER_THROTTLING_CURRENT_VERSION is defined before using this API; this constant is a #define in both WinSDK and mingw-w64.

---

Full diff: https://github.com/llvm/llvm-project/pull/151388.diff

1 Files Affected:

• (modified) llvm/lib/Support/Windows/Threading.inc (+2)

diff --git a/llvm/lib/Support/Windows/Threading.inc b/llvm/lib/Support/Windows/Threading.inc
index 8dd7c88fad34a..b11f216adeba4 100644
--- a/llvm/lib/Support/Windows/Threading.inc
+++ b/llvm/lib/Support/Windows/Threading.inc
@@ -136,6 +136,7 @@ HMODULE loadSystemModuleSecure(LPCWSTR lpModuleName) {
 } // namespace llvm::sys::windows
 
 SetThreadPriorityResult llvm::set_thread_priority(ThreadPriority Priority) {
+#ifdef THREAD_POWER_THROTTLING_CURRENT_VERSION
   HMODULE kernelM = llvm::sys::windows::loadSystemModuleSecure(L"kernel32.dll");
   if (kernelM) {
     // SetThreadInformation is only available on Windows 8 and later. Since we
@@ -166,6 +167,7 @@ SetThreadPriorityResult llvm::set_thread_priority(ThreadPriority Priority) {
                                : 0);
     }
   }
+#endif
 
   // https://docs.microsoft.com/en-us/windows/desktop/api/processthreadsapi/nf-processthreadsapi-setthreadpriority
   // Begin background processing mode. The system lowers the resource scheduling

[Sharjeel-Khan]

Thanks, I just tested it locally and this fixed the issue.

[mstorsjo]

CC @timblechmann - will merge this one soon.

[timblechmann]

This API is also hidden if building with MS WinSDK if targeting versions before Windows 10.

makes me wonder if we want to declare/define these defines/struct if not provided by the windows headers? it would allow the use of EcoQoS no matter how llvm is built

[mstorsjo]

This API is also hidden if building with MS WinSDK if targeting versions before Windows 10.

makes me wonder if we want to declare/define these defines/struct if not provided by the windows headers? it would allow the use of EcoQoS no matter how llvm is built

Yes, certainly. Although in practice, I would think most people building with WinSDK end up using the default target version. I think many of those intentionally targeting older versions may be using mingw, where these declarations aren't hidden based on version anyway. (Although that can of course change in the future.) The degradation for those building in that configuration should be quite graceful (behaving like it did before).

Although if you feel strongly about it, I guess you can propose such a patch as well, but it requires a bit more testing, so I'd at least like to land this first, to unbreak @Sharjeel-Khan's builds.

[Sharjeel-Khan]

Yea, our buildbots have been stagnant for 2 days due to the failure. I would also push to land a fix asap to unbreak our builds.