Don't move objc_autorelease calls past autorelease pool boundaries when

optimizing autorelease calls on phi nodes with null operands.
This fixes rdar://11207070.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@154642 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/Scalar/ObjCARC.cpp

@@ -1963,6 +1963,7 @@ namespace {
   /// use here.
   enum DependenceKind {
     NeedsPositiveRetainCount,
+    AutoreleasePoolBoundary,
     CanChangeRetainCount,
     RetainAutoreleaseDep,       ///< Blocks objc_retainAutorelease.
     RetainAutoreleaseRVDep,     ///< Blocks objc_retainAutoreleaseReturnValue.
@@ -1992,6 +1993,19 @@ Depends(DependenceKind Flavor, Instruction *Inst, const Value *Arg,
     }
   }
 
+  case AutoreleasePoolBoundary: {
+    InstructionClass Class = GetInstructionClass(Inst);
+    switch (Class) {
+    case IC_AutoreleasepoolPop:
+    case IC_AutoreleasepoolPush:
+      // These mark the end and begin of an autorelease pool scope.
+      return true;
+    default:
+      // Nothing else does this.
+      return false;
+    }
+  }
+
   case CanChangeRetainCount: {
     InstructionClass Class = GetInstructionClass(Inst);
     switch (Class) {
@@ -2009,6 +2023,7 @@ Depends(DependenceKind Flavor, Instruction *Inst, const Value *Arg,
   case RetainAutoreleaseDep:
     switch (GetBasicInstructionClass(Inst)) {
     case IC_AutoreleasepoolPop:
+    case IC_AutoreleasepoolPush:
       // Don't merge an objc_autorelease with an objc_retain inside a different
       // autoreleasepool scope.
       return true;
@@ -2376,9 +2391,34 @@ void ObjCARCOpt::OptimizeIndividualCalls(Function &F) {
 
         // Check that there is nothing that cares about the reference
         // count between the call and the phi.
-        FindDependencies(NeedsPositiveRetainCount, Arg,
+        switch (Class) {
-                         Inst->getParent(), Inst,
+        case IC_Retain:
-                         DependingInstructions, Visited, PA);
+        case IC_RetainBlock:
+          // These can always be moved up.
+          break;
+        case IC_Release:
+          // These can't be moved across things that care about the retain count.
+          FindDependencies(NeedsPositiveRetainCount, Arg,
+                           Inst->getParent(), Inst,
+                           DependingInstructions, Visited, PA);
+          break;
+        case IC_Autorelease:
+          // These can't be moved across autorelease pool scope boundaries.
+          FindDependencies(AutoreleasePoolBoundary, Arg,
+                           Inst->getParent(), Inst,
+                           DependingInstructions, Visited, PA);
+          break;
+        case IC_RetainRV:
+        case IC_AutoreleaseRV:
+          // Don't move these; the RV optimization depends on the autoreleaseRV
+          // being tail called, and the retainRV being immediately after a call
+          // (which might still happen if we get lucky with codegen layout, but
+          // it's not worth taking the chance).
+          continue;
+        default:
+          llvm_unreachable("Invalid dependence flavor");
+        }
+
         if (DependingInstructions.size() == 1 &&
             *DependingInstructions.begin() == PN) {
           Changed = true;

test/Transforms/ObjCARC/basic.ll

@@ -3,10 +3,12 @@
 target datalayout = "e-p:64:64:64"
 
 declare i8* @objc_retain(i8*)
+declare i8* @objc_retainAutoreleasedReturnValue(i8*)
 declare void @objc_release(i8*)
 declare i8* @objc_autorelease(i8*)
+declare i8* @objc_autoreleaseReturnValue(i8*)
 declare void @objc_autoreleasePoolPop(i8*)
-declare void @objc_autoreleasePoolPush()
+declare i8* @objc_autoreleasePoolPush()
 declare i8* @objc_retainBlock(i8*)
 
 declare i8* @objc_retainedObject(i8*)
@@ -526,7 +528,7 @@ entry:
 define void @test13d(i8* %x, i64 %n) {
 entry:
   call i8* @objc_retain(i8* %x) nounwind
-  call void @objc_autoreleasePoolPush()
+  call i8* @objc_autoreleasePoolPush()
   call i8* @objc_retain(i8* %x) nounwind
   call void @use_pointer(i8* %x)
   call void @use_pointer(i8* %x)
@@ -1400,7 +1402,7 @@ entry:
 ; CHECK-NEXT: call i8* @objc_autorelease(i8* %p)
 ; CHECK-NEXT: call void @use_pointer(i8* %p)
 ; CHECK-NEXT: call void @use_pointer(i8* %p)
-; CHECK-NEXT: call void @objc_autoreleasePoolPush()
+; CHECK-NEXT: call i8* @objc_autoreleasePoolPush()
 ; CHECK-NEXT: ret void
 ; CHECK-NEXT: }
 define void @test43b(i8* %p) {
@@ -1410,7 +1412,7 @@ entry:
   call i8* @objc_retain(i8* %p)
   call void @use_pointer(i8* %p)
   call void @use_pointer(i8* %p)
-  call void @objc_autoreleasePoolPush()
+  call i8* @objc_autoreleasePoolPush()
   call void @objc_release(i8* %p)
   ret void
 }
@@ -1797,6 +1799,78 @@ exit:
   ret void
 }
 
+; Move an autorelease past a phi with a null.
+
+; CHECK: define i8* @test65(
+; CHECK: if.then:
+; CHECK:   call i8* @objc_autorelease(
+; CHECK: return:
+; CHECK-NOT: @objc_autorelease
+; CHECK: }
+define i8* @test65(i1 %x) {
+entry:
+  br i1 %x, label %return, label %if.then
+
+if.then:                                          ; preds = %entry
+  %c = call i8* @returner()
+  %s = call i8* @objc_retainAutoreleasedReturnValue(i8* %c) nounwind
+  br label %return
+
+return:                                           ; preds = %if.then, %entry
+  %retval = phi i8* [ %s, %if.then ], [ null, %entry ]
+  %q = call i8* @objc_autorelease(i8* %retval) nounwind
+  ret i8* %retval
+}
+
+; Don't move an autorelease past an autorelease pool boundary.
+
+; CHECK: define i8* @test65b(
+; CHECK: if.then:
+; CHECK-NOT: @objc_autorelease
+; CHECK: return:
+; CHECK:   call i8* @objc_autorelease(
+; CHECK: }
+define i8* @test65b(i1 %x) {
+entry:
+  %t = call i8* @objc_autoreleasePoolPush()
+  br i1 %x, label %return, label %if.then
+
+if.then:                                          ; preds = %entry
+  %c = call i8* @returner()
+  %s = call i8* @objc_retainAutoreleasedReturnValue(i8* %c) nounwind
+  br label %return
+
+return:                                           ; preds = %if.then, %entry
+  %retval = phi i8* [ %s, %if.then ], [ null, %entry ]
+  call void @objc_autoreleasePoolPop(i8* %t)
+  %q = call i8* @objc_autorelease(i8* %retval) nounwind
+  ret i8* %retval
+}
+
+; Don't move an autoreleaseReuturnValue, which would break
+; the RV optimization.
+
+; CHECK: define i8* @test65c(
+; CHECK: if.then:
+; CHECK-NOT: @objc_autorelease
+; CHECK: return:
+; CHECK:   call i8* @objc_autoreleaseReturnValue(
+; CHECK: }
+define i8* @test65c(i1 %x) {
+entry:
+  br i1 %x, label %return, label %if.then
+
+if.then:                                          ; preds = %entry
+  %c = call i8* @returner()
+  %s = call i8* @objc_retainAutoreleasedReturnValue(i8* %c) nounwind
+  br label %return
+
+return:                                           ; preds = %if.then, %entry
+  %retval = phi i8* [ %s, %if.then ], [ null, %entry ]
+  %q = call i8* @objc_autoreleaseReturnValue(i8* %retval) nounwind
+  ret i8* %retval
+}
+
 declare void @bar(i32 ()*)
 
 ; A few real-world testcases.