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Re: [PATCH] Fix PR rtl-optimization/23585 (delay slots)
> I think I would prefer to see may_trap_p turned into a static
> may_trap_p_1, with a parameter to replace the file static
> unaligned_memrefs_trap_p. Other than that, and the aforementioned
> SPARC_STACK_BOUNDARY_HACK comments, the patch looks OK to me.
Revised version attached. Only exercised on the testcase for now; I'll do a
complete testing cycle if/when I install it.
> Please wait a day to see if there any other comments, though.
Sure, I'll wait a few days.
2005-10-16 ?Eric Botcazou ?<ebotcazou@libertysurf.fr>
????????PR rtl-optimization/23585
????????* rtlanal.c (rtx_addr_can_trap_p_1): New predicate extracted from...
????????(rtx_addr_can_trap_p): ... here. Invoke rtx_addr_can_trap_p_1.
(may_trap_p_1): New predicate extracted from...
(may_trap_p): ... here. Invoke (may_trap_p_1.
????????(may_trap_or_fault_p): New predicate.
????????* rtl.h (may_trap_or_fault_p): Declare it.
????????* reorg.c (steal_delay_list_from_target): Use may_trap_or_fault_p
????????instead of may_trap_p.
????????(steal_delay_list_from_fallthrough): Likewise.
????????(fill_simple_delay_slots): Likewise.
????????(fill_slots_from_thread): Likewise.
* function.c (pad_to_arg_alignment): Rework comment about
SPARC_STACK_BOUNDARY_HACK.
* config/sparc/sparc.h: Likewise.
--
Eric Botcazou
Index: function.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/function.c,v
retrieving revision 1.604.8.1
diff -u -p -r1.604.8.1 function.c
--- function.c 10 Mar 2005 15:11:04 -0000 1.604.8.1
+++ function.c 17 Oct 2005 09:16:16 -0000
@@ -3518,10 +3518,9 @@ pad_to_arg_alignment (struct args_size *
HOST_WIDE_INT sp_offset = STACK_POINTER_OFFSET;
#ifdef SPARC_STACK_BOUNDARY_HACK
- /* The sparc port has a bug. It sometimes claims a STACK_BOUNDARY
- higher than the real alignment of %sp. However, when it does this,
- the alignment of %sp+STACK_POINTER_OFFSET will be STACK_BOUNDARY.
- This is a temporary hack while the sparc port is fixed. */
+ /* ??? 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)
sp_offset = 0;
#endif
Index: reorg.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/reorg.c,v
retrieving revision 1.104.8.1
diff -u -p -r1.104.8.1 reorg.c
--- reorg.c 3 Sep 2005 19:09:51 -0000 1.104.8.1
+++ reorg.c 17 Oct 2005 09:16:17 -0000
@@ -1334,7 +1334,7 @@ steal_delay_list_from_target (rtx insn,
if (! must_annul
&& ((condition == const_true_rtx
|| (! insn_sets_resource_p (trial, other_needed, 0)
- && ! may_trap_p (PATTERN (trial)))))
+ && ! may_trap_or_fault_p (PATTERN (trial)))))
? eligible_for_delay (insn, total_slots_filled, trial, flags)
: (must_annul || (delay_list == NULL && new_delay_list == NULL))
&& (must_annul = 1,
@@ -1428,7 +1428,7 @@ steal_delay_list_from_fallthrough (rtx i
if (! must_annul
&& ((condition == const_true_rtx
|| (! insn_sets_resource_p (trial, other_needed, 0)
- && ! may_trap_p (PATTERN (trial)))))
+ && ! may_trap_or_fault_p (PATTERN (trial)))))
? eligible_for_delay (insn, *pslots_filled, trial, flags)
: (must_annul || delay_list == NULL) && (must_annul = 1,
check_annul_list_true_false (1, delay_list)
@@ -2320,7 +2320,7 @@ fill_simple_delay_slots (int non_jumps_p
#ifdef HAVE_cc0
&& ! (reg_mentioned_p (cc0_rtx, pat) && ! sets_cc0_p (pat))
#endif
- && ! (maybe_never && may_trap_p (pat))
+ && ! (maybe_never && may_trap_or_fault_p (pat))
&& (trial = try_split (pat, trial, 0))
&& eligible_for_delay (insn, slots_filled, trial, flags)
&& ! can_throw_internal(trial))
@@ -2373,7 +2373,7 @@ fill_simple_delay_slots (int non_jumps_p
#ifdef HAVE_cc0
&& ! reg_mentioned_p (cc0_rtx, PATTERN (next_trial))
#endif
- && ! (maybe_never && may_trap_p (PATTERN (next_trial)))
+ && ! (maybe_never && may_trap_or_fault_p (PATTERN (next_trial)))
&& (next_trial = try_split (PATTERN (next_trial), next_trial, 0))
&& eligible_for_delay (insn, slots_filled, next_trial, flags)
&& ! can_throw_internal (trial))
@@ -2653,7 +2653,7 @@ fill_slots_from_thread (rtx insn, rtx co
if (!must_annul
&& (condition == const_true_rtx
|| (! insn_sets_resource_p (trial, &opposite_needed, 1)
- && ! may_trap_p (pat))))
+ && ! may_trap_or_fault_p (pat))))
{
old_trial = trial;
trial = try_split (pat, trial, 0);
Index: rtlanal.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/rtlanal.c,v
retrieving revision 1.211.8.2
diff -u -p -r1.211.8.2 rtlanal.c
--- rtlanal.c 16 Aug 2005 08:45:59 -0000 1.211.8.2
+++ rtlanal.c 17 Oct 2005 09:16:18 -0000
@@ -223,10 +223,13 @@ rtx_varies_p (rtx x, int for_alias)
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);
@@ -252,27 +255,52 @@ rtx_addr_can_trap_p (rtx 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)
+ 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;
@@ -282,6 +310,14 @@ rtx_addr_can_trap_p (rtx x)
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
@@ -2067,10 +2103,12 @@ side_effects_p (rtx x)
return 0;
}
-/* 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;
@@ -2104,9 +2142,11 @@ may_trap_p (rtx x)
/* 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:
@@ -2183,19 +2223,73 @@ may_trap_p (rtx x)
{
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);
+}
/* Return nonzero if X contains a comparison that is not either EQ or NE,
i.e., an inequality. */
Index: rtl.h
===================================================================
RCS file: /cvs/gcc/gcc/gcc/rtl.h,v
retrieving revision 1.536.4.1
diff -u -p -r1.536.4.1 rtl.h
--- rtl.h 6 Sep 2005 19:44:28 -0000 1.536.4.1
+++ rtl.h 17 Oct 2005 09:16:19 -0000
@@ -1609,6 +1609,7 @@ extern int side_effects_p (rtx);
extern int volatile_refs_p (rtx);
extern int volatile_insn_p (rtx);
extern int may_trap_p (rtx);
+extern int may_trap_or_fault_p (rtx);
extern int inequality_comparisons_p (rtx);
extern rtx replace_rtx (rtx, rtx, rtx);
extern rtx replace_regs (rtx, rtx *, unsigned int, int);
Index: config/sparc/sparc.h
===================================================================
RCS file: /cvs/gcc/gcc/gcc/config/sparc/sparc.h,v
retrieving revision 1.273.8.3
diff -u -p -r1.273.8.3 sparc.h
--- config/sparc/sparc.h 15 Apr 2005 19:25:04 -0000 1.273.8.3
+++ config/sparc/sparc.h 17 Oct 2005 09:16:20 -0000
@@ -816,11 +816,9 @@ if (TARGET_ARCH64 \
/* Boundary (in *bits*) on which stack pointer should be aligned. */
/* FIXME, this is wrong when TARGET_ARCH64 and TARGET_STACK_BIAS, because
- then sp+2047 is 128-bit aligned so sp is really only byte-aligned. */
+ then %sp+2047 is 128-bit aligned so %sp is really only byte-aligned. */
#define STACK_BOUNDARY (TARGET_ARCH64 ? 128 : 64)
-/* Temporary hack until the FIXME above is fixed. This macro is used
- only in pad_to_arg_alignment in function.c; see the comment there
- for details about what it does. */
+/* Temporary hack until the FIXME above is fixed. */
#define SPARC_STACK_BOUNDARY_HACK (TARGET_ARCH64 && TARGET_STACK_BIAS)
/* ALIGN FRAMES on double word boundaries */