CSE: remove redundant global initializer calls

Author: eeckstein

lib/SILOptimizer/Transforms/CSE.cpp

@@ -965,6 +965,11 @@ bool CSE::canHandle(SILInstruction *Inst) {
 
     if (isLazyPropertyGetter(AI))
       return true;
+      
+    if (SILFunction *callee = AI->getReferencedFunctionOrNull()) {
+      if (callee->isGlobalInit())
+        return true;
+    }
 
     return false;
   }

test/SILOptimizer/cse.sil

@@ -1267,3 +1267,31 @@ bb0(%0 : $Proto & Ping):
   return %12 : $Ping
 }
 
+sil [global_init] @$s4test10testGlobalSivau : $@convention(thin) () -> Builtin.RawPointer
+
+// CHECK-LABEL: sil @cse_global_init
+// CHECK:   [[P:%[0-9]+]] = apply 
+// CHECK:   [[A:%[0-9]+]] = pointer_to_address [[P]] 
+// CHECK:   begin_access [modify] [dynamic] [no_nested_conflict] [[A]]
+// CHECK:   begin_access [read] [dynamic] [no_nested_conflict] [[A]]
+// CHECK: // end sil function 'cse_global_init'
+sil @cse_global_init : $@convention(thin) () -> Int64 {
+bb0:
+  %2 = function_ref @$s4test10testGlobalSivau : $@convention(thin) () -> Builtin.RawPointer
+  %3 = apply %2() : $@convention(thin) () -> Builtin.RawPointer
+  %4 = pointer_to_address %3 : $Builtin.RawPointer to [strict] $*Int64
+  %5 = integer_literal $Builtin.Int64, 42
+  %6 = struct $Int64 (%5 : $Builtin.Int64)
+  %7 = begin_access [modify] [dynamic] [no_nested_conflict] %4 : $*Int64
+  store %6 to %7 : $*Int64
+  end_access %7 : $*Int64
+  %10 = function_ref @$s4test10testGlobalSivau : $@convention(thin) () -> Builtin.RawPointer
+  %11 = apply %10() : $@convention(thin) () -> Builtin.RawPointer
+  %12 = pointer_to_address %11 : $Builtin.RawPointer to [strict] $*Int64
+  %33 = begin_access [read] [dynamic] [no_nested_conflict] %12 : $*Int64
+  %35 = load %33 : $*Int64
+  end_access %33 : $*Int64
+  return %35 : $Int64
+}
+
+

test/SILOptimizer/global_init_opt.swift

@@ -0,0 +1,18 @@
+// RUN: %target-swift-frontend -parse-as-library -O -module-name=test %s -emit-sil | %FileCheck %s
+
+var gg: Int = {
+  print("gg init")
+  return 27
+}()
+
+// CHECK-LABEL: sil @$s4test3cseSiyF
+// CHECK:   builtin "once"
+// CHECK-NOT:   builtin "once"
+// CHECK:   [[G:%[0-9]+]] = load
+// CHECK-NOT:   builtin "once"
+// CHECK:   builtin "sadd_{{.*}}"([[G]] : $Builtin.Int{{[0-9]+}}, [[G]] : $Builtin.Int{{[0-9]+}}, %{{[0-9]+}} : $Builtin.Int1)
+// CHECK-NOT:   builtin "once"
+// CHECK: } // end sil function '$s4test3cseSiyF'
+public func cse() -> Int {
+  return gg + gg
+}