Merge pull request #27664 from eeckstein/inout-aliasing

SILOptimizer: always assume that inout arguments are not aliasing

Author: eeckstein

include/swift/SIL/SILArgumentConvention.h

@@ -17,18 +17,6 @@
 
 namespace swift {
 
-enum class InoutAliasingAssumption {
-  /// Assume that an inout indirect parameter may alias other objects.
-  /// This is the safe assumption an optimization should make if it may break
-  /// memory safety in case the inout aliasing rule is violation.
-  Aliasing,
-
-  /// Assume that an inout indirect parameter cannot alias other objects.
-  /// Optimizations should only use this if they can guarantee that they will
-  /// not break memory safety even if the inout aliasing rule is violated.
-  NotAliasing
-};
-
 /// Conventions for apply operands and function-entry arguments in SIL.
 ///
 /// This is simply a union of ParameterConvention and ResultConvention
@@ -142,19 +130,14 @@ struct SILArgumentConvention {
   }
 
   /// Returns true if \p Value is a not-aliasing indirect parameter.
-  /// The \p isInoutAliasing specifies what to assume about the inout
-  /// convention.
-  /// See InoutAliasingAssumption.
-  bool isNotAliasedIndirectParameter(InoutAliasingAssumption isInoutAliasing) {
+  bool isNotAliasedIndirectParameter() {
     switch (Value) {
     case SILArgumentConvention::Indirect_In:
     case SILArgumentConvention::Indirect_In_Constant:
     case SILArgumentConvention::Indirect_Out:
     case SILArgumentConvention::Indirect_In_Guaranteed:
-      return true;
-
     case SILArgumentConvention::Indirect_Inout:
-      return isInoutAliasing == InoutAliasingAssumption::NotAliasing;
+      return true;
 
     case SILArgumentConvention::Indirect_InoutAliasable:
     case SILArgumentConvention::Direct_Unowned:

include/swift/SILOptimizer/Analysis/ValueTracking.h

@@ -26,16 +26,14 @@ namespace swift {
 /// any other pointer in the function.
 /// The \p assumeInoutIsNotAliasing specifies in no-aliasing is assumed for
 /// the @inout convention. See swift::isNotAliasedIndirectParameter().
-bool isNotAliasingArgument(SILValue V, InoutAliasingAssumption isInoutAliasing =
-                                         InoutAliasingAssumption::Aliasing);
+bool isNotAliasingArgument(SILValue V);
 
 /// Returns true if \p V is local inside its function. This means its underlying
 /// object either is a non-aliasing function argument or a locally allocated
 /// object.
 /// The \p assumeInoutIsNotAliasing specifies in no-aliasing is assumed for
 /// the @inout convention. See swift::isNotAliasedIndirectParameter().
-bool pointsToLocalObject(SILValue V, InoutAliasingAssumption isInoutAliasing =
-                                         InoutAliasingAssumption::Aliasing);
+bool pointsToLocalObject(SILValue V);
 
 enum class IsZeroKind {
   Zero,

lib/SILOptimizer/Analysis/ValueTracking.cpp

@@ -23,14 +23,13 @@
 using namespace swift;
 using namespace swift::PatternMatch;
 
-bool swift::isNotAliasingArgument(SILValue V,
-                                  InoutAliasingAssumption isInoutAliasing) {
+bool swift::isNotAliasingArgument(SILValue V) {
   auto *Arg = dyn_cast<SILFunctionArgument>(V);
   if (!Arg)
     return false;
 
   SILArgumentConvention Conv = Arg->getArgumentConvention();
-  return Conv.isNotAliasedIndirectParameter(isInoutAliasing);
+  return Conv.isNotAliasedIndirectParameter();
 }
 
 /// Check if the parameter \V is based on a local object, e.g. it is an
@@ -81,10 +80,9 @@ static bool isLocalObject(SILValue Obj) {
   return true;
 }
 
-bool swift::pointsToLocalObject(SILValue V,
-                                InoutAliasingAssumption isInoutAliasing) {
+bool swift::pointsToLocalObject(SILValue V) {
   V = getUnderlyingObject(V);
-  return isLocalObject(V) || isNotAliasingArgument(V, isInoutAliasing);
+  return isLocalObject(V) || isNotAliasingArgument(V);
 }
 
 /// Check if the value \p Value is known to be zero, non-zero or unknown.

test/SILOptimizer/basic-aa.sil

@@ -114,7 +114,7 @@ bb1(%1 : $*Builtin.NativeObject, %2 : $*Builtin.NativeObject):
 // CHECK: PAIR #1.
 // CHECK-NEXT: %0 = argument of bb0
 // CHECK-NEXT: %1 = argument of bb0
-// CHECK-NEXT: MayAlias
+// CHECK-NEXT: NoAlias
 sil @inout_args_may_alias: $@convention(thin) (@inout Builtin.NativeObject, @inout Builtin.NativeObject) -> () {
 bb0(%0 : $*Builtin.NativeObject, %1 : $*Builtin.NativeObject):
   %2 = tuple()

test/SILOptimizer/dead_store_elim.sil

@@ -469,6 +469,24 @@ bb3:
   return %9999 : $()
 }
 
+sil @unknown : $@convention(thin) () -> ()
+
+// CHECK-LABEL: sil @inout_is_not_aliasing : $@convention(thin) (@inout Builtin.Int32) -> () {
+// CHECK: bb0
+// CHECK-NEXT: integer_literal
+// CHECK-NEXT: function_ref
+// CHECK: return
+sil @inout_is_not_aliasing : $@convention(thin) (@inout Builtin.Int32) -> () {
+bb0(%0 : $*Builtin.Int32):
+  %1 = integer_literal $Builtin.Int32, 0
+  store %1 to %0 : $*Builtin.Int32
+  %f = function_ref @unknown : $@convention(thin) () -> ()
+  %3 = apply %f() : $@convention(thin) () -> ()
+  store %1 to %0 : $*Builtin.Int32
+  %9999 = tuple()
+  return %9999 : $()
+}
+
 // We should be able to remove the store in bb0, but we currently
 // can't due to deficiency in alias analysis.
 //

test/SILOptimizer/redundant_load_elim.sil

@@ -588,8 +588,9 @@ bb5:
 // CHECK: store
 // CHECK-NOT: = load
 // CHECK: bb2:
-// CHECK: bb3:
-// CHECK: = load
+// CHECK: bb3([[A:%[0-9]+]] : $Builtin.Int32):
+// CHECK-NOT: = load
+// CHECK: apply %{{[0-9]+}}([[A]])
 sil @load_to_load_conflicting_branches_diamond : $@convention(thin) (@inout Builtin.Int32) -> () {
 // %0                                             // users: %1, %4, %9, %11, %16, %21
 bb0(%0 : $*Builtin.Int32):