AliasAnalysis: better handling of init_enum_data_addr and init_existential_addr.

Look "through" those instructions when trying to find the underlying objects.

Author: eeckstein

lib/SILOptimizer/Analysis/AliasAnalysis.cpp

@@ -569,6 +569,15 @@ AliasResult AliasAnalysis::alias(SILValue V1, SILValue V2,
   return Result;
 }
 
+/// Get the underlying object, looking through init_enum_data_addr and
+/// init_existential_addr.
+static SILValue stripInitEnumAndExistentialAddr(SILValue v) {
+  while (isa<InitEnumDataAddrInst>(v) || isa<InitExistentialAddrInst>(v)) {
+    v = getUnderlyingObject(cast<SingleValueInstruction>(v)->getOperand(0));
+  }
+  return v;
+}
+
 /// The main AA entry point. Performs various analyses on V1, V2 in an attempt
 /// to disambiguate the two values.
 AliasResult AliasAnalysis::aliasInner(SILValue V1, SILValue V2,
@@ -614,9 +623,12 @@ AliasResult AliasAnalysis::aliasInner(SILValue V1, SILValue V2,
   LLVM_DEBUG(llvm::dbgs() << "        Underlying V1:" << *O1);
   LLVM_DEBUG(llvm::dbgs() << "        Underlying V2:" << *O2);
 
-  // If O1 and O2 do not equal, see if we can prove that they cannot be the
-  // same object. If we can, return No Alias.
-  if (O1 != O2 && aliasUnequalObjects(O1, O2))
+  // If the underlying objects are not equal, see if we can prove that they
+  // cannot be the same object. If we can, return No Alias.
+  // For this we even look through init_enum_data_addr and init_existential_addr.
+  SILValue StrippedO1 = stripInitEnumAndExistentialAddr(O1);
+  SILValue StrippedO2 = stripInitEnumAndExistentialAddr(O2);
+  if (StrippedO1 != StrippedO2 && aliasUnequalObjects(StrippedO1, StrippedO2))
     return AliasResult::NoAlias;
 
   // Ok, either O1, O2 are the same or we could not prove anything based off of

test/SILOptimizer/basic-aa.sil

@@ -579,3 +579,97 @@ bb0:
   %2 = tuple()
   return %2 : $()
 }
+
+struct TwoInts {
+  var a: Int
+  var b: Int
+}
+
+struct StructWithOptional {
+  var i: Optional<TwoInts>
+}
+
+// CHECK-LABEL: @init_enum_data_addr
+// CHECK:      PAIR #3.
+// CHECK-NEXT: %0 = argument of bb0 : $*StructWithOptional
+// CHECK-NEXT:   %3 = init_enum_data_addr %2 : $*Optional<TwoInts>, #Optional.some!enumelt
+// CHECK-NEXT: NoAlias
+// CHECK:      PAIR #4.
+// CHECK-NEXT: %0 = argument of bb0 : $*StructWithOptional
+// CHECK-NEXT:   %4 = struct_element_addr %3 : $*TwoInts, #TwoInts.a
+// CHECK-NEXT: NoAlias
+// CHECK:      PAIR #5.
+// CHECK-NEXT: %0 = argument of bb0 : $*StructWithOptional
+// CHECK-NEXT:   %5 = struct_element_addr %3 : $*TwoInts, #TwoInts.b
+// CHECK-NEXT: NoAlias
+// CHECK:      PAIR #14.
+// CHECK-NEXT:   %2 = struct_element_addr %1 : $*StructWithOptional, #StructWithOptional.i
+// CHECK-NEXT:   %3 = init_enum_data_addr %2 : $*Optional<TwoInts>, #Optional.some!enumelt
+// CHECK-NEXT: MayAlias
+// CHECK:      PAIR #15.
+// CHECK-NEXT:   %2 = struct_element_addr %1 : $*StructWithOptional, #StructWithOptional.i
+// CHECK-NEXT:   %4 = struct_element_addr %3 : $*TwoInts, #TwoInts.a
+// CHECK-NEXT: MayAlias
+// CHECK:      PAIR #16.
+// CHECK-NEXT:   %2 = struct_element_addr %1 : $*StructWithOptional, #StructWithOptional.i
+// CHECK-NEXT:   %5 = struct_element_addr %3 : $*TwoInts, #TwoInts.b
+// CHECK-NEXT: MayAlias
+// CHECK:      PAIR #19.
+// CHECK-NEXT:   %3 = init_enum_data_addr %2 : $*Optional<TwoInts>, #Optional.some!enumelt
+// CHECK-NEXT:   %4 = struct_element_addr %3 : $*TwoInts, #TwoInts.a
+// CHECK-NEXT: PartialAlias
+// CHECK:      PAIR #20.
+// CHECK-NEXT:   %3 = init_enum_data_addr %2 : $*Optional<TwoInts>, #Optional.some!enumelt
+// CHECK-NEXT:   %5 = struct_element_addr %3 : $*TwoInts, #TwoInts.b
+// CHECK-NEXT: PartialAlias
+// CHECK:      PAIR #23.
+// CHECK-NEXT:   %4 = struct_element_addr %3 : $*TwoInts, #TwoInts.a
+// CHECK-NEXT:   %5 = struct_element_addr %3 : $*TwoInts, #TwoInts.b
+// CHECK-NEXT: NoAlias
+sil @init_enum_data_addr : $@convention(thin) (@in_guaranteed StructWithOptional) -> () {
+bb0(%0 : $*StructWithOptional):
+  %1 = alloc_stack $StructWithOptional
+  %2 = struct_element_addr %1 : $*StructWithOptional, #StructWithOptional.i
+  %3 = init_enum_data_addr %2 : $*Optional<TwoInts>, #Optional.some!enumelt
+  %4 = struct_element_addr %3 : $*TwoInts, #TwoInts.a
+  %5 = struct_element_addr %3 : $*TwoInts, #TwoInts.b
+  dealloc_stack %1 : $*StructWithOptional
+  %6 = tuple ()
+  return %6 : $()
+}
+
+protocol P {}
+
+struct S : P {
+  var i: Int
+}
+
+// CHECK-LABEL: @init_existential_addr
+// CHECK:      PAIR #3.
+// CHECK-NEXT:   %0 = argument of bb0 : $P
+// CHECK-NEXT:   %3 = init_existential_addr %2 : $*P, $S
+// CHECK-NEXT: NoAlias
+// CHECK:      PAIR #12.
+// CHECK-NEXT:   %2 = alloc_stack $P
+// CHECK-NEXT:   %3 = init_existential_addr %2 : $*P, $S
+// CHECK-NEXT: MayAlias
+// CHECK:      PAIR #13.
+// CHECK-NEXT:   %2 = alloc_stack $P
+// CHECK-NEXT:   %4 = struct_element_addr %3 : $*S, #S.i
+// CHECK-NEXT: MayAlias
+// CHECK:      PAIR #16.
+// CHECK-NEXT:   %3 = init_existential_addr %2 : $*P, $S
+// CHECK-NEXT:   %4 = struct_element_addr %3 : $*S, #S.i
+// CHECK-NEXT: PartialAlias
+sil @init_existential_addr : $@convention(thin) (P) -> () {
+bb0(%0 : $P):
+  %1 = alloc_stack $S
+  %2 = alloc_stack $P
+  %3 = init_existential_addr %2 : $*P, $S
+  %4 = struct_element_addr %3 : $*S, #S.i
+  dealloc_stack %2 : $*P
+  dealloc_stack %1 : $*S
+  %6 = tuple ()
+  return %6 : $()
+}
+