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Fix address space computation in expand_debug_expr

For the AVR target, assertions in convert_debug_memory_address cause a
couple of ICEs (see PR 52472). Jakub suggested returning a NULL rtx,
which works, but on debugging further, I found that expand_debug_expr
appears to incorrectly compute the address space for ADDR_EXPR and

For ADDR_EXPR, TREE_TYPE(exp) is a POINTER_TYPE (always?), but in 
the generic address space, even if the object whose address is taken 
is in a different address space. expand_debug_expr takes 
TYPE_ADDR_SPACE(TREE_TYPE(exp)) and therefore computes the address 
space as generic. convert_debug_memory_address then asserts that the 
mode is a valid pointer mode in the address space and fails.

Similarly, for MEM_REFs, TREE_TYPE(exp) is the type of the
dereferenced value, and therefore checking if it is a POINTER_TYPE
doesn't help for a single pointer dereference. The address space
gets computed as generic even if the pointer points to a different
address space. The address mode for the generic address space is
passed to convert_debug_memory_address, and the assertion that that mode
must match the mode of the rtx then fails.

The below patch attempts to fix this by picking the right TREE_TYPE to
pass to TYPE_ADDR_SPACE for MEM_REF (use type of arg 0) and 
ADDR_EXPR (check for pointer type and look at nested addr space). 

Does this look reasonable or did I get it all wrong?


diff --git gcc/cfgexpand.c gcc/cfgexpand.c
index 8b0e466..ca78953 100644
--- gcc/cfgexpand.c
+++ gcc/cfgexpand.c
@@ -3941,8 +3941,8 @@ expand_debug_expr (tree exp)
 	  op0 = plus_constant (inner_mode, op0, INTVAL (op1));
-      if (POINTER_TYPE_P (TREE_TYPE (exp)))
+      if (POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND (exp, 0))))
@@ -4467,7 +4467,11 @@ expand_debug_expr (tree exp)
 	  return NULL;
-      as = TYPE_ADDR_SPACE (TREE_TYPE (exp));
+      if (POINTER_TYPE_P (TREE_TYPE (exp)))
+        as = TYPE_ADDR_SPACE (TREE_TYPE (TREE_TYPE (exp)));
+      else
+        as = TYPE_ADDR_SPACE (TREE_TYPE (exp));
       op0 = convert_debug_memory_address (mode, XEXP (op0, 0), as);
       return op0;

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