[Mesa-dev] [PATCH] radeon-llvm: Start multithreaded before using llvm.

[Mathias Fröhlich]

This is required to make some of llvm's api calls
thread save. In particular the PassRegistry, which is
implicitly accessed while compiling shader programs.
The PassRegistry uses a mutex that is only active if
the llvm_is_multithreaded() returns true.
Calling llvm_start_multithreading() makes this happen
and by calling this function we try to make sure that
we can savely compile shaders in paralell.
Since there is also a call llvm_stop_multithreading()
in the llvm api, we cannot guarantee that this does
not get switched off while we are relying on this being
set, but for the easier use cases this fixes a race with
the radeon llvm compiler we have as of today.

Signed-off-by: Mathias Froehlich <Mathias.Froehlich at web.de>
---
 src/gallium/drivers/radeon/radeon_llvm_emit.cpp | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/src/gallium/drivers/radeon/radeon_llvm_emit.cpp 
b/src/gallium/drivers/radeon/radeon_llvm_emit.cpp
index 89130b3..eef55a8 100644
--- a/src/gallium/drivers/radeon/radeon_llvm_emit.cpp
+++ b/src/gallium/drivers/radeon/radeon_llvm_emit.cpp
@@ -35,6 +35,7 @@
 #include <llvm/Support/SourceMgr.h>
 #include <llvm/Support/TargetRegistry.h>
 #include <llvm/Support/TargetSelect.h>
+#include <llvm/Support/Threading.h>
 #include <llvm/Target/TargetData.h>
 #include <llvm/Target/TargetMachine.h>
 
@@ -57,6 +58,20 @@ void LLVMInitializeAMDGPUTargetInfo(void);
 }
 #endif
 
+namespace {
+
+class LLVMEnsureMultithreaded {
+public:
+   LLVMEnsureMultithreaded()
+   {
+      llvm_start_multithreaded();
+   }
+};
+
+static LLVMEnsureMultithreaded lLVMEnsureMultithreaded;
+
+}
+
 /**
  * Compile an LLVM module to machine code.
  *
-- 
1.7.11.4