[flang] Add FIR AliasAnalysis alias() wrapper to allow external getSource() method (#115073)

Adding a wrapper around alias(mlir::Value lhs, mlir::Value rhs) to allow
user to provide Source objects.

Author: SusanTan

flang/include/flang/Optimizer/Analysis/AliasAnalysis.h

@@ -60,18 +60,18 @@ struct AliasAnalysis {
   //  module top
   //    real, pointer :: a(:)
   //  end module
-  //  
+  //
   //  subroutine test()
   //    use top
   //    a(1) = 1
   //  end subroutine
   //  -------------------------------------------------
-  // 
+  //
   //  flang -fc1 -emit-fir test.f90 -o test.fir
   //
   //  ------------------- test.fir --------------------
-  //  fir.global @_QMtopEa : !fir.box<!fir.ptr<!fir.array<?xf32>>> 
-  //  
+  //  fir.global @_QMtopEa : !fir.box<!fir.ptr<!fir.array<?xf32>>>
+  //
   //  func.func @_QPtest() {
   //    %c1 = arith.constant 1 : index
   //    %cst = arith.constant 1.000000e+00 : f32
@@ -100,12 +100,12 @@ struct AliasAnalysis {
   // Additionally, because it is relied on in HLFIR lowering, we allow querying
   // on a box SSA value, which is interpreted as querying on its data.
   //
-  // So in the above example, !fir.ref<f32> and !fir.box<!fir.ptr<!fir.array<?xf32>>> is data, 
+  // So in the above example, !fir.ref<f32> and !fir.box<!fir.ptr<!fir.array<?xf32>>> is data,
   // while !fir.ref<!fir.box<!fir.ptr<!fir.array<?xf32>>>> is not data.
 
   // This also applies to function arguments. In the example below, %arg0
   // is data, %arg1 is not data but a load of %arg1 is.
-  // 
+  //
   // func.func @_QFPtest2(%arg0: !fir.ref<f32>, %arg1: !fir.ref<!fir.box<!fir.ptr<f32>>> )  {
   //    %0 = fir.load %arg1 : !fir.ref<!fir.box<!fir.ptr<f32>>>
   //    ... }
@@ -183,6 +183,10 @@ struct AliasAnalysis {
   friend llvm::raw_ostream &operator<<(llvm::raw_ostream &os,
                                        const AliasAnalysis::Source &op);
 
+  /// Given the values and their sources, return their aliasing behavior.
+  mlir::AliasResult alias(Source lhsSrc, Source rhsSrc, mlir::Value lhs,
+                          mlir::Value rhs);
+
   /// Given two values, return their aliasing behavior.
   mlir::AliasResult alias(mlir::Value lhs, mlir::Value rhs);
 
@@ -193,7 +197,8 @@ struct AliasAnalysis {
   /// If getInstantiationPoint is true, the search for the source
   /// will stop at [hl]fir.declare if it represents a dummy
   /// argument declaration (i.e. it has the dummy_scope operand).
-  Source getSource(mlir::Value, bool getInstantiationPoint = false);
+  fir::AliasAnalysis::Source getSource(mlir::Value,
+                                       bool getInstantiationPoint = false);
 
 private:
   /// Return true, if `ty` is a reference type to an object of derived type

flang/lib/Optimizer/Analysis/AliasAnalysis.cpp

@@ -130,11 +130,19 @@ bool AliasAnalysis::Source::mayBeActualArgWithPtr(
 }
 
 AliasResult AliasAnalysis::alias(mlir::Value lhs, mlir::Value rhs) {
+  // A wrapper around alias(Source lhsSrc, Source rhsSrc, mlir::Value lhs,
+  // mlir::Value rhs) This allows a user to provide Source that may be obtained
+  // through other dialects
+  auto lhsSrc = getSource(lhs);
+  auto rhsSrc = getSource(rhs);
+  return alias(lhsSrc, rhsSrc, lhs, rhs);
+}
+
+AliasResult AliasAnalysis::alias(Source lhsSrc, Source rhsSrc, mlir::Value lhs,
+                                 mlir::Value rhs) {
   // TODO: alias() has to be aware of the function scopes.
   // After MLIR inlining, the current implementation may
   // not recognize non-aliasing entities.
-  auto lhsSrc = getSource(lhs);
-  auto rhsSrc = getSource(rhs);
   bool approximateSource = lhsSrc.approximateSource || rhsSrc.approximateSource;
   LLVM_DEBUG(llvm::dbgs() << "\nAliasAnalysis::alias\n";
              llvm::dbgs() << "  lhs: " << lhs << "\n";