Check that there is only one use of a given global addr function

Author: zoecarver

lib/SILOptimizer/IPO/GlobalOpt.cpp

@@ -122,7 +122,8 @@ class SILGlobalOpt {
 
 protected:
   /// Checks if a given global variable is assigned only once.
-  bool isAssignedOnlyOnceInInitializer(SILGlobalVariable *SILG);
+  bool isAssignedOnlyOnceInInitializer(SILGlobalVariable *SILG,
+                                       SILFunction *globalAddrF);
 
   /// Reset all the maps of global variables.
   void reset();
@@ -640,13 +641,21 @@ static SILFunction *genGetterFromInit(SILOptFunctionBuilder &FunctionBuilder,
   return GetterF;
 }
 
-bool SILGlobalOpt::isAssignedOnlyOnceInInitializer(SILGlobalVariable *SILG) {
+bool SILGlobalOpt::isAssignedOnlyOnceInInitializer(SILGlobalVariable *SILG,
+                                                   SILFunction *globalAddrF) {
   if (SILG->isLet())
     return true;
 
   // If we should skip this, it is probably because there are multiple stores.
   // Return false if there are multiple stores or no stores.
-  if (GlobalVarSkipProcessing.count(SILG) || !GlobalVarStore.count(SILG))
+  if (GlobalVarSkipProcessing.count(SILG) || !GlobalVarStore.count(SILG) ||
+      // Check if there is more than one use the global addr function. If there
+      // is only one use, it must be the use that we are trying to optimize, so
+      // that is OK. If there is more than one use, one of the other uses may
+      // have a store attached to it which means there may be more than one
+      // assignment, so return false.
+      (GlobalInitCallMap.count(globalAddrF) &&
+       GlobalInitCallMap[globalAddrF].size() != 1))
     return false;
 
   // Otherwise, return true if this can't be used externally (false, otherwise).
@@ -697,7 +706,7 @@ replaceLoadsByKnownValue(BuiltinInst *CallToOnce, SILFunction *AddrF,
   LLVM_DEBUG(llvm::dbgs() << "GlobalOpt: replacing loads with known value for "
                           << SILG->getName() << '\n');
 
-  assert(isAssignedOnlyOnceInInitializer(SILG) &&
+  assert(isAssignedOnlyOnceInInitializer(SILG, AddrF) &&
          "The value of the initializer should be known at compile-time");
   assert(SILG->getDecl() &&
          "Decl corresponding to the global variable should be known");
@@ -810,7 +819,7 @@ void SILGlobalOpt::optimizeInitializer(SILFunction *AddrF,
                           << SILG->getName() << '\n');
 
   // Remove "once" call from the addressor.
-  if (!isAssignedOnlyOnceInInitializer(SILG) || !SILG->getDecl()) {
+  if (!isAssignedOnlyOnceInInitializer(SILG, AddrF) || !SILG->getDecl()) {
     LLVM_DEBUG(llvm::dbgs() << "GlobalOpt: building static initializer for "
                             << SILG->getName() << '\n');