return 0;
}
-/* Return 0 if the use of X as an address in a MEM can cause a trap. */
+/* Return nonzero if the use of X as an address in a MEM can cause a trap.
+ MODE is the mode of the MEM (not that of X) and UNALIGNED_MEMS controls
+ whether nonzero is returned for unaligned memory accesses on strict
+ alignment machines. */
-int
-rtx_addr_can_trap_p (rtx x)
+static int
+rtx_addr_can_trap_p_1 (rtx x, enum machine_mode mode, bool unaligned_mems)
{
enum rtx_code code = GET_CODE (x);
return 1;
case CONST:
- return rtx_addr_can_trap_p (XEXP (x, 0));
+ return rtx_addr_can_trap_p_1 (XEXP (x, 0), mode, unaligned_mems);
case PLUS:
- /* An address is assumed not to trap if it is an address that can't
- trap plus a constant integer or it is the pic register plus a
- constant. */
- return ! ((! rtx_addr_can_trap_p (XEXP (x, 0))
- && GET_CODE (XEXP (x, 1)) == CONST_INT)
- || (XEXP (x, 0) == pic_offset_table_rtx
- && CONSTANT_P (XEXP (x, 1))));
+ /* An address is assumed not to trap if:
+ - it is an address that can't trap plus a constant integer,
+ with the proper remainder modulo the mode size if we are
+ considering unaligned memory references. */
+ if (!rtx_addr_can_trap_p_1 (XEXP (x, 0), mode, unaligned_mems)
+ && GET_CODE (XEXP (x, 1)) == CONST_INT)
+ {
+ HOST_WIDE_INT offset;
+
+ if (!STRICT_ALIGNMENT
+ || !unaligned_mems
+ || GET_MODE_SIZE (mode) == 0)
+ return 0;
+
+ offset = INTVAL (XEXP (x, 1));
+
+#ifdef SPARC_STACK_BOUNDARY_HACK
+ /* ??? The SPARC port may claim a STACK_BOUNDARY higher than
+ the real alignment of %sp. However, when it does this, the
+ alignment of %sp+STACK_POINTER_OFFSET is STACK_BOUNDARY. */
+ if (SPARC_STACK_BOUNDARY_HACK
+ && (XEXP (x, 0) == stack_pointer_rtx
+ || XEXP (x, 0) == hard_frame_pointer_rtx))
+ offset -= STACK_POINTER_OFFSET;
+#endif
+
+ return offset % GET_MODE_SIZE (mode) != 0;
+ }
+
+ /* - or it is the pic register plus a constant. */
+ if (XEXP (x, 0) == pic_offset_table_rtx && CONSTANT_P (XEXP (x, 1)))
+ return 0;
+
+ return 1;
case LO_SUM:
case PRE_MODIFY:
- return rtx_addr_can_trap_p (XEXP (x, 1));
+ return rtx_addr_can_trap_p_1 (XEXP (x, 1), mode, unaligned_mems);
case PRE_DEC:
case PRE_INC:
case POST_DEC:
case POST_INC:
case POST_MODIFY:
- return rtx_addr_can_trap_p (XEXP (x, 0));
+ return rtx_addr_can_trap_p_1 (XEXP (x, 0), mode, unaligned_mems);
default:
break;
return 1;
}
+/* Return nonzero if the use of X as an address in a MEM can cause a trap. */
+
+int
+rtx_addr_can_trap_p (rtx x)
+{
+ return rtx_addr_can_trap_p_1 (x, VOIDmode, false);
+}
+
/* Return true if X is an address that is known to not be zero. */
bool
return 0;
}
\f
-/* Return nonzero if evaluating rtx X might cause a trap. */
+/* Return nonzero if evaluating rtx X might cause a trap. UNALIGNED_MEMS
+ controls whether nonzero is returned for unaligned memory accesses on
+ strict alignment machines. */
-int
-may_trap_p (rtx x)
+static int
+may_trap_p_1 (rtx x, bool unaligned_mems)
{
int i;
enum rtx_code code;
/* Memory ref can trap unless it's a static var or a stack slot. */
case MEM:
- if (MEM_NOTRAP_P (x))
+ if (MEM_NOTRAP_P (x)
+ && (!STRICT_ALIGNMENT || !unaligned_mems))
return 0;
- return rtx_addr_can_trap_p (XEXP (x, 0));
+ return
+ rtx_addr_can_trap_p_1 (XEXP (x, 0), GET_MODE (x), unaligned_mems);
/* Division by a non-constant might trap. */
case DIV:
{
if (fmt[i] == 'e')
{
- if (may_trap_p (XEXP (x, i)))
+ if (may_trap_p_1 (XEXP (x, i), unaligned_mems))
return 1;
}
else if (fmt[i] == 'E')
{
int j;
for (j = 0; j < XVECLEN (x, i); j++)
- if (may_trap_p (XVECEXP (x, i, j)))
+ if (may_trap_p_1 (XVECEXP (x, i, j), unaligned_mems))
return 1;
}
}
return 0;
}
+
+/* Return nonzero if evaluating rtx X might cause a trap. */
+
+int
+may_trap_p (rtx x)
+{
+ return may_trap_p_1 (x, false);
+}
+
+/* Same as above, but additionally return non-zero if evaluating rtx X might
+ cause a fault. We define a fault for the purpose of this function as a
+ erroneous execution condition that cannot be encountered during the normal
+ execution of a valid program; the typical example is an unaligned memory
+ access on a strict alignment machine. The compiler guarantees that it
+ doesn't generate code that will fault from a valid program, but this
+ guarantee doesn't mean anything for individual instructions. Consider
+ the following example:
+
+ struct S { int d; union { char *cp; int *ip; }; };
+
+ int foo(struct S *s)
+ {
+ if (s->d == 1)
+ return *s->ip;
+ else
+ return *s->cp;
+ }
+
+ on a strict alignment machine. In a valid program, foo will never be
+ invoked on a structure for which d is equal to 1 and the underlying
+ unique field of the union not aligned on a 4-byte boundary, but the
+ expression *s->ip might cause a fault if considered individually.
+
+ At the RTL level, potentially problematic expressions will almost always
+ verify may_trap_p; for example, the above dereference can be emitted as
+ (mem:SI (reg:P)) and this expression is may_trap_p for a generic register.
+ However, suppose that foo is inlined in a caller that causes s->cp to
+ point to a local character variable and guarantees that s->d is not set
+ to 1; foo may have been effectively translated into pseudo-RTL as:
+
+ if ((reg:SI) == 1)
+ (set (reg:SI) (mem:SI (%fp - 7)))
+ else
+ (set (reg:QI) (mem:QI (%fp - 7)))
+
+ Now (mem:SI (%fp - 7)) is considered as not may_trap_p since it is a
+ memory reference to a stack slot, but it will certainly cause a fault
+ on a strict alignment machine. */
+
+int
+may_trap_or_fault_p (rtx x)
+{
+ return may_trap_p_1 (x, true);
+}
\f
/* Return nonzero if X contains a comparison that is not either EQ or NE,
i.e., an inequality. */
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