[mlir] better handling of function result attributes

Specifically, handle the siutation where some alias classes are
associateded with pointer operands that cannot be written into. In such
a case, even if the results of the function may alias the operands, the
alias classes of the operands are known not to point to anything that
the function could have written.

Additionally, don't include results marked as `noalias` into the common
alias class of function results.

enzyme/Enzyme/MLIR/Analysis/AliasAnalysis.h

@@ -335,12 +335,6 @@ class AliasClassLattice : public dataflow::AbstractSparseLattice {
  const AliasClassSet &getAliasClassesObject() const { return aliasClasses; }
 
 private:
- struct UndefinedState {};
-
- AliasClassLattice(Value value, AliasClassSet &&classes)
- : dataflow::AbstractSparseLattice(value),
- aliasClasses(std::move(classes)) {}
-
  AliasClassSet aliasClasses;
 };
 

enzyme/test/MLIR/AliasAnalysis/func_attributes.mlir

@@ -224,11 +224,7 @@ func.func private @callee() -> (!llvm.ptr {llvm.noalias}) attributes {
 }
 
 // CHECK: points-to-pointer sets
-<<<<<<< HEAD
 // CHECK-NEXT: distinct[{{.+}}]<"func-return0"> points to {<unknown>}
-=======
-// CHECK-NEXT: distinct[{{.+}}]<"func-return"> points to {<unknown>}
->>>>>>> e5d11b44 ([mlir] add a proper "undefined" state to pointer analyses)
 func.func @func_return_noalias() -> !llvm.ptr {
  %0 = call @callee() {tag = "func-return"} : () -> !llvm.ptr
  return %0 : !llvm.ptr
@@ -239,11 +235,7 @@ func.func @func_return_noalias() -> !llvm.ptr {
 // CHECK: tag "func-return" Unknown AC
 // CHECK: "func-return" and "func-return": MayAlias
 // CHECK: points-to-pointer sets
-<<<<<<< HEAD
 // CHECK-NEXT: distinct[{{.*}}]<"func-return0"> points to {<unknown>}
-=======
-// CHECK-NEXT: distinct[{{.*}}]<"func-return"> points to {<unknown>}
->>>>>>> e5d11b44 ([mlir] add a proper "undefined" state to pointer analyses)
 func.func private @callee() -> (!llvm.ptr {llvm.noalias}, !llvm.ptr) attributes {
  memory = #llvm.memory_effects<other = read,
  argMem = readwrite,
@@ -265,13 +257,8 @@ func.func private @callee() -> (!llvm.ptr {llvm.noalias}) attributes {
 
 // CHECK: "func-1-return" and "func-2-return": NoAlias
 // CHECK: points-to-pointer sets
-<<<<<<< HEAD
 // CHECK-DAG: distinct[{{.+}}]<"func-1-return0"> points to {<unknown>}
 // CHECK-DAG: distinct[{{.+}}]<"func-2-return0"> points to {<unknown>}
-=======
-// CHECK-DAG: distinct[{{.+}}]<"func-return-1"> points to {<unknown>}
-// CHECK-DAG: distinct[{{.+}}]<"func-return-2"> points to {<unknown>}
->>>>>>> e5d11b44 ([mlir] add a proper "undefined" state to pointer analyses)
 func.func @caller() -> !llvm.ptr {
  %0 = call @callee() {tag = "func-1-return"} : () -> !llvm.ptr
  %1 = call @callee() {tag = "func-2-return"} : () -> !llvm.ptr