[LPM] Reinstate r271652 to replace the CALL_ONCE_... macro in the legacy

pass manager with the new llvm::call_once facility.

This reverts commit r271657 and re-applies r271652 with a fix to
actually work with arguments. In the original version, we just ended up
directly calling std::call_once via ADL because of the std::once_flag
argument. The llvm::call_once never worked with arguments. Now,
llvm::call_once is a variadic template that perfectly forwards
everything. As a part of this it had to move to the header and we use
a generic functor rather than an explict function pointer. It would be
nice to use std::invoke here but we don't have it yet. That means
pointer to members won't work here, but that seems a tolerable
compromise.

I've also tested this by forcing the fallback path, so hopefully it
sticks this time.

Original commit message:
----
[LPM] Replace the CALL_ONCE_... macro in the legacy pass manager with
the new llvm::call_once facility.

This facility matches the standard APIs and when the platform supports
it actually directly uses the standard provided functionality. This is
both more efficient on some platforms and much more TSan friendly.

The only remaining user of the cas_flag and home-rolled atomics is the
fallback implementation of call_once. I have a patch that removes them
entirely, but it needs a Windows patch to land first.

This alone substantially cleans up the macros for the legacy pass
manager, and should subsume some of the work Mehdi was doing to clear
the path for TSan testing of ThinLTO, a really important step to have
reliable upstream testing of ThinLTO in all forms.

llvm-svn: 271781

3 files changed, 51 insertions, 27 deletions

diff --git a/llvm/include/llvm/CodeGen/Passes.h b/llvm/include/llvm/CodeGen/Passes.h
index 1e01d66a2ce..6c85c250cbb 100644
--- a/llvm/include/llvm/CodeGen/Passes.h
+++ b/llvm/include/llvm/CodeGen/Passes.h
@@ -377,8 +377,10 @@ namespace llvm {
   Registry.registerPass(*PI, true);                                            \
   return PI;                                                                   \
   }                                                                            \
+  LLVM_DEFINE_ONCE_FLAG(Initialize##passName##PassFlag);                       \
   void llvm::initialize##passName##Pass(PassRegistry &Registry) {              \
-    CALL_ONCE_INITIALIZATION(initialize##passName##PassOnce)                   \
+    llvm::call_once(Initialize##passName##PassFlag,                            \
+                    initialize##passName##PassOnce, std::ref(Registry));       \
   }
 
 /// This initializer registers TargetMachine constructor, so the pass being
diff --git a/llvm/include/llvm/PassSupport.h b/llvm/include/llvm/PassSupport.h
index f205c001f53..ba6d84f04ba 100644
--- a/llvm/include/llvm/PassSupport.h
+++ b/llvm/include/llvm/PassSupport.h
@@ -26,31 +26,13 @@
 #include "llvm/PassInfo.h"
 #include "llvm/PassRegistry.h"
 #include "llvm/Support/Atomic.h"
+#include "llvm/Support/Threading.h"
+#include <functional>
 
 namespace llvm {
 
 class TargetMachine;
 
-#define CALL_ONCE_INITIALIZATION(function)                                     \
-  static volatile sys::cas_flag initialized = 0;                               \
-  sys::cas_flag old_val = sys::CompareAndSwap(&initialized, 1, 0);             \
-  if (old_val == 0) {                                                          \
-    function(Registry);                                                        \
-    sys::MemoryFence();                                                        \
-    TsanIgnoreWritesBegin();                                                   \
-    TsanHappensBefore(&initialized);                                           \
-    initialized = 2;                                                           \
-    TsanIgnoreWritesEnd();                                                     \
-  } else {                                                                     \
-    sys::cas_flag tmp = initialized;                                           \
-    sys::MemoryFence();                                                        \
-    while (tmp != 2) {                                                         \
-      tmp = initialized;                                                       \
-      sys::MemoryFence();                                                      \
-    }                                                                          \
-  }                                                                            \
-  TsanHappensAfter(&initialized);
-
 #define INITIALIZE_PASS(passName, arg, name, cfg, analysis)                    \
   static void *initialize##passName##PassOnce(PassRegistry &Registry) {        \
     PassInfo *PI = new PassInfo(                                               \
@@ -59,8 +41,10 @@ class TargetMachine;
     Registry.registerPass(*PI, true);                                          \
     return PI;                                                                 \
   }                                                                            \
+  LLVM_DEFINE_ONCE_FLAG(Initialize##passName##PassFlag);                       \
   void llvm::initialize##passName##Pass(PassRegistry &Registry) {              \
-    CALL_ONCE_INITIALIZATION(initialize##passName##PassOnce)                   \
+    llvm::call_once(Initialize##passName##PassFlag,                            \
+                    initialize##passName##PassOnce, std::ref(Registry));       \
   }
 
 #define INITIALIZE_PASS_BEGIN(passName, arg, name, cfg, analysis)              \
@@ -77,8 +61,10 @@ class TargetMachine;
   Registry.registerPass(*PI, true);                                            \
   return PI;                                                                   \
   }                                                                            \
+  LLVM_DEFINE_ONCE_FLAG(Initialize##passName##PassFlag);                       \
   void llvm::initialize##passName##Pass(PassRegistry &Registry) {              \
-    CALL_ONCE_INITIALIZATION(initialize##passName##PassOnce)                   \
+    llvm::call_once(Initialize##passName##PassFlag,                            \
+                    initialize##passName##PassOnce, std::ref(Registry));       \
   }
 
 #define INITIALIZE_PASS_WITH_OPTIONS(PassName, Arg, Name, Cfg, Analysis)       \
@@ -166,8 +152,11 @@ struct RegisterAnalysisGroup : public RegisterAGBase {
     Registry.registerAnalysisGroup(&agName::ID, 0, *AI, false, true);          \
     return AI;                                                                 \
   }                                                                            \
+  LLVM_DEFINE_ONCE_FLAG(Initialize##agName##AnalysisGroupFlag);                \
   void llvm::initialize##agName##AnalysisGroup(PassRegistry &Registry) {       \
-    CALL_ONCE_INITIALIZATION(initialize##agName##AnalysisGroupOnce)            \
+    llvm::call_once(Initialize##agName##AnalysisGroupFlag,                     \
+                    initialize##agName##AnalysisGroupOnce,                     \
+                    std::ref(Registry));                                       \
   }
 
 #define INITIALIZE_AG_PASS(passName, agName, arg, name, cfg, analysis, def)    \
@@ -184,8 +173,10 @@ struct RegisterAnalysisGroup : public RegisterAGBase {
                                    true);                                      \
     return AI;                                                                 \
   }                                                                            \
+  LLVM_DEFINE_ONCE_FLAG(Initialize##passName##PassFlag);                       \
   void llvm::initialize##passName##Pass(PassRegistry &Registry) {              \
-    CALL_ONCE_INITIALIZATION(initialize##passName##PassOnce)                   \
+    llvm::call_once(Initialize##passName##PassFlag,                            \
+                    initialize##passName##PassOnce, std::ref(Registry));       \
   }
 
 #define INITIALIZE_AG_PASS_BEGIN(passName, agName, arg, n, cfg, analysis, def) \
@@ -203,8 +194,10 @@ struct RegisterAnalysisGroup : public RegisterAGBase {
   Registry.registerAnalysisGroup(&agName::ID, &passName::ID, *AI, def, true);  \
   return AI;                                                                   \
   }                                                                            \
+  LLVM_DEFINE_ONCE_FLAG(Initialize##passName##PassFlag);                       \
   void llvm::initialize##passName##Pass(PassRegistry &Registry) {              \
-    CALL_ONCE_INITIALIZATION(initialize##passName##PassOnce)                   \
+    llvm::call_once(Initialize##passName##PassFlag,                            \
+                    initialize##passName##PassOnce, std::ref(Registry));       \
   }
 
 //===---------------------------------------------------------------------------
diff --git a/llvm/include/llvm/Support/Threading.h b/llvm/include/llvm/Support/Threading.h
index b51d1f97fa9..9804dd8aff6 100644
--- a/llvm/include/llvm/Support/Threading.h
+++ b/llvm/include/llvm/Support/Threading.h
@@ -16,7 +16,9 @@
 #define LLVM_SUPPORT_THREADING_H
 
 #include "llvm/Config/llvm-config.h" // for LLVM_ON_UNIX
+#include "llvm/Support/Compiler.h"
 #include <ciso646> // So we can check the C++ standard lib macros.
+#include <functional>
 
 // We use std::call_once on all Unix platforms except for NetBSD with
 // libstdc++. That platform has a bug they are working to fix, and they'll
@@ -84,7 +86,34 @@ namespace llvm {
   ///
   /// \param flag Flag used for tracking whether or not this has run.
   /// \param UserFn Function to call once.
-  void call_once(once_flag &flag, void (*UserFn)(void));
+  template <typename Function, typename... Args>
+  void call_once(once_flag &flag, Function &&F, Args &&... ArgList) {
+#if LLVM_THREADING_USE_STD_CALL_ONCE
+    std::call_once(flag, std::forward<Function>(F),
+                   std::forward<Args>(ArgList)...);
+#else
+    // For other platforms we use a generic (if brittle) version based on our
+    // atomics.
+    sys::cas_flag old_val = sys::CompareAndSwap(&flag, Wait, Uninitialized);
+    if (old_val == Uninitialized) {
+      std::forward<Function>(F)(std::forward<Args>(ArgList)...);
+      sys::MemoryFence();
+      TsanIgnoreWritesBegin();
+      TsanHappensBefore(&flag);
+      flag = Done;
+      TsanIgnoreWritesEnd();
+    } else {
+      // Wait until any thread doing the call has finished.
+      sys::cas_flag tmp = flag;
+      sys::MemoryFence();
+      while (tmp != Done) {
+        tmp = flag;
+        sys::MemoryFence();
+      }
+    }
+    TsanHappensAfter(&flag);
+#endif
+  }
 }
 
 #endif