[flang-commits] [flang] [flang] AliasAnalysis: distinguish addr of arg vs. addr in arg (PR #87723)

[Renaud Kauffmann via flang-commits]

================
@@ -399,19 +404,30 @@ AliasAnalysis::Source AliasAnalysis::getSource(mlir::Value v) {
   if (!defOp && type == SourceKind::Unknown)
     // Check if the memory source is coming through a dummy argument.
     if (isDummyArgument(v)) {
-      type = SourceKind::Argument;
       ty = v.getType();
       if (fir::valueHasFirAttribute(v, fir::getTargetAttrName()))
         attributes.set(Attribute::Target);
-
       if (Source::isPointerReference(ty))
         attributes.set(Attribute::Pointer);
+      if (followBoxAddr && fir::isa_ref_type(ty))
----------------
Renaud-K wrote:

I was due for an example of box, passed by value:
```
subroutine test(p)
  real [,TARGET] :: p(:)
end subroutine test
```
```
func.func @_QPtest(%arg0: !fir.box<!fir.array<?xf32>> {fir.bindc_name = "p", fir.target})
```
I am not the expert here (that would be @jeanPerier ), but the rationale was to communicate in FIR that the callee does not modify the box and that therefore, to the caller, the box is a shallow constant. They do end up being passed by reference in codegen but show as values in FIR. 

https://github.com/llvm/llvm-project/pull/87723