static void record_set PROTO((rtx, rtx));
static rtx find_base_term PROTO((rtx));
static int base_alias_check PROTO((rtx, rtx));
+static int mode_alias_check PROTO((rtx, rtx, int (*)(rtx)));
/* Set up all info needed to perform alias analysis on memory references. */
align memory references, as is done on the Alpha.
Nice to notice that varying addresses cannot conflict with fp if no
- local variables had their addresses taken, but that's too hard now. */
+ local variables had their addresses taken, but that's too hard now.
+
+ TODO: (symbol_ref foo) can not alias (plus REG N) if N is a positive
+ integer because REG would have to point outside of the object, which
+ is not allowed in C or C++. */
static int
generate aligned addresses from unaligned addresses, for instance, the
alpha storeqi_unaligned pattern. */
+
+/* This subroutine implements the type and struct/varying part of the
+ alias check.
+
+ Return 0 if the memory references can never alias.
+ Return 1 if the values of the addresses should be checked. */
+
+static int
+mode_alias_check (x, y, varies)
+ register rtx x, y;
+ int (*varies) PROTO ((rtx));
+{
+ enum machine_mode x_mode = GET_MODE (x), y_mode = GET_MODE (y);
+ rtx x_addr = XEXP (x, 0), y_addr = XEXP (y, 0);
+ int x_varies, y_varies, x_struct, y_struct;
+
+ /* If either address is an AND then neither the mode check nor the
+ struct/varying check is valid. */
+ if (GET_CODE (x_addr) == AND || GET_CODE (y_addr) == AND)
+ return 1;
+
+ x_struct = MEM_IN_STRUCT_P (x);
+ y_struct = MEM_IN_STRUCT_P (y);
+
+ /* QImode and BLKmode references can alias anything. */
+ if (x_mode == QImode || x_mode == BLKmode
+ || y_mode == QImode || y_mode == BLKmode)
+ return 1;
+
+ /* Otherwise, different modes can only alias if they are structure
+ references. gcc bitfield operations can access an entire word,
+ but that word may also contain integers accessed directly.
+
+ ??? It appears that bitfield accesses can not be larger than
+ word_mode?
+ ??? Can complex modes alias their components? */
+ if (x_mode != y_mode && ! (x_struct && y_struct))
+ return 0;
+
+ /* Modes are the same or may alias. */
+
+ /* No alias if one reference is a struct at a varying address and the
+ other is a scalar at a fixed address.
+
+ If either reference is a varying scalar or a fixed struct nothing
+ is known about aliasing. */
+ x_varies = varies (x_addr);
+ if (x_struct != x_varies)
+ return 1;
+ y_varies = varies (y_addr);
+ if (y_struct != y_varies)
+ return 1;
+
+ /* Both are varying structs or fixed scalars. Check that they are not
+ the same type. */
+ return (x_struct == y_struct);
+}
+
/* Read dependence: X is read after read in MEM takes place. There can
only be a dependence here if both reads are volatile. */
if (! base_alias_check (XEXP (x, 0), XEXP (mem, 0)))
return 0;
+ if (! mode_alias_check (x, mem, varies))
+ return 0;
+
x_addr = canon_rtx (XEXP (x, 0));
mem_addr = canon_rtx (XEXP (mem, 0));
if (mem_mode == VOIDmode)
mem_mode = GET_MODE (mem);
- if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr,
- SIZE_FOR_MODE (x), x_addr, 0))
- return 0;
-
- /* If both references are struct references, or both are not, nothing
- is known about aliasing.
-
- If either reference is QImode or BLKmode, ANSI C permits aliasing.
-
- If both addresses are constant, or both are not, nothing is known
- about aliasing. */
- if (MEM_IN_STRUCT_P (x) == MEM_IN_STRUCT_P (mem)
- || mem_mode == QImode || mem_mode == BLKmode
- || GET_MODE (x) == QImode || GET_MODE (x) == BLKmode
- || GET_CODE (x_addr) == AND || GET_CODE (mem_addr) == AND
- || varies (x_addr) == varies (mem_addr))
- return 1;
-
- /* One memory reference is to a constant address, one is not.
- One is to a structure, the other is not.
-
- If either memory reference is a variable structure the other is a
- fixed scalar and there is no aliasing. */
- if ((MEM_IN_STRUCT_P (mem) && varies (mem_addr))
- || (MEM_IN_STRUCT_P (x) && varies (x_addr)))
- return 0;
-
- return 1;
+ return memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr,
+ SIZE_FOR_MODE (x), x_addr, 0);
}
/* Anti dependence: X is written after read in MEM takes place. */
x_addr = XEXP (x, 0);
mem_addr = XEXP (mem, 0);
- return (memrefs_conflict_p (SIZE_FOR_MODE (mem), mem_addr,
- SIZE_FOR_MODE (x), x_addr, 0)
- && ! (MEM_IN_STRUCT_P (mem) && rtx_addr_varies_p (mem)
- && GET_MODE (mem) != QImode
- && GET_CODE (mem_addr) != AND
- && ! MEM_IN_STRUCT_P (x) && ! rtx_addr_varies_p (x))
- && ! (MEM_IN_STRUCT_P (x) && rtx_addr_varies_p (x)
- && GET_MODE (x) != QImode
- && GET_CODE (x_addr) != AND
- && ! MEM_IN_STRUCT_P (mem) && ! rtx_addr_varies_p (mem)));
+ if (! mode_alias_check (x, mem, rtx_varies_p))
+ return 0;
+
+ return memrefs_conflict_p (SIZE_FOR_MODE (mem), mem_addr,
+ SIZE_FOR_MODE (x), x_addr, 0);
}
/* Output dependence: X is written after store in MEM takes place. */
x = canon_rtx (x);
mem = canon_rtx (mem);
- return (memrefs_conflict_p (SIZE_FOR_MODE (mem), XEXP (mem, 0),
- SIZE_FOR_MODE (x), XEXP (x, 0), 0)
- && ! (MEM_IN_STRUCT_P (mem) && rtx_addr_varies_p (mem)
- && GET_MODE (mem) != QImode
- && GET_CODE (XEXP (mem, 0)) != AND
- && ! MEM_IN_STRUCT_P (x) && ! rtx_addr_varies_p (x))
- && ! (MEM_IN_STRUCT_P (x) && rtx_addr_varies_p (x)
- && GET_MODE (x) != QImode
- && GET_CODE (XEXP (x, 0)) != AND
- && ! MEM_IN_STRUCT_P (mem) && ! rtx_addr_varies_p (mem)));
+ if (! mode_alias_check (x, mem, rtx_varies_p))
+ return 0;
+
+ return memrefs_conflict_p (SIZE_FOR_MODE (mem), XEXP (mem, 0),
+ SIZE_FOR_MODE (x), XEXP (x, 0), 0);
}
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