There are a number of problems in the interaction between secondary
memory and subregs. If we reload the inner of a subreg, we forget about
this when deciding whether to use secondary memory, and just use
REGNO_REG_CLASS on the (now reloaded) inner.
Also, we don't really know what to do if we get a subreg of something
that's not a register, such as a symbol_ref. This is another part of the
patch below, using a variant of find_valid_class that works in this case.
The original testcase we had was the artificial test included in the
patch, which involves reinterpreting a pointer to a string constant as a
floating point value. Since then, we've also found a larger Altivec
testcase which crashes the compiler without this patch.
Bootstrapped and tested on i686-linux. It's also been in several of our
internal trees, going back to even 4.4-based ones IIRC, and has had
testing for several architectures. Ok for the i386 part? I intend to
check the reload bits in soon if there are no objections.
Bernd
* reload.c (find_valid_class_1): New static function.
(push_reload): Use it when reloading a SYMBOL_REG as the inner
of a subreg. Keep better track of needed classes for the
secondary memory case.
* config/i386/i386.h (LIMIT_RELOAD_CLASS): Limit INT_SSE_REGS to
GENERAL_REGS.
* reload1.c (replaced_subreg): New static function.
(gen_reload): Use it when deciding whether to use secondary
memory.
Index: gcc/reload.c
===================================================================
--- gcc/reload.c (revision 189284)
+++ gcc/reload.c (working copy)
@@ -707,6 +707,55 @@ find_valid_class (enum machine_mode oute
return best_class;
}
+
+/* We are trying to reload a subreg of something that is not a register.
+ Find the largest class which has at least one register valid in
+ mode MODE. OUTER is the mode of the subreg, DEST_CLASS the class in
+ which we would eventually like to obtain the object. */
+
+static enum reg_class
+find_valid_class_1 (enum machine_mode outer ATTRIBUTE_UNUSED,
+ enum machine_mode mode ATTRIBUTE_UNUSED,
+ enum reg_class dest_class ATTRIBUTE_UNUSED)
+{
+ int best_cost = -1;
+ int rclass;
+ int regno;
+ enum reg_class best_class = NO_REGS;
+ unsigned int best_size = 0;
+ int cost;
+
+ for (rclass = 1; rclass < N_REG_CLASSES; rclass++)
+ {
+ int bad = 0;
+ for (regno = 0; regno < FIRST_PSEUDO_REGISTER && !bad; regno++)
+ if (TEST_HARD_REG_BIT (reg_class_contents[rclass], regno)
+ && !HARD_REGNO_MODE_OK (regno, mode))
+ bad = 1;
+
+ if (bad)
+ continue;
+
+ cost = register_move_cost (outer, (enum reg_class) rclass, dest_class);
+
+ if ((reg_class_size[rclass] > best_size
+ && (best_cost < 0 || best_cost >= cost))
+ || best_cost > cost)
+ {
+ best_class = (enum reg_class) rclass;
+ best_size = reg_class_size[rclass];
+ best_cost = register_move_cost (outer, (enum reg_class) rclass,
+ dest_class);
+ }
+ }
+
+ gcc_assert (best_size != 0);
+
+#ifdef LIMIT_RELOAD_CLASS
+ best_class = LIMIT_RELOAD_CLASS (mode, best_class);
+#endif
+ return best_class;
+}
/* Return the number of a previously made reload that can be combined with
a new one, or n_reloads if none of the existing reloads can be used.
@@ -925,6 +974,8 @@ push_reload (rtx in, rtx out, rtx *inloc
int secondary_in_reload = -1, secondary_out_reload = -1;
enum insn_code secondary_in_icode = CODE_FOR_nothing;
enum insn_code secondary_out_icode = CODE_FOR_nothing;
+ enum reg_class subreg_in_class ATTRIBUTE_UNUSED;
+ subreg_in_class = NO_REGS;
/* INMODE and/or OUTMODE could be VOIDmode if no mode
has been specified for the operand. In that case,
@@ -1091,16 +1142,18 @@ push_reload (rtx in, rtx out, rtx *inloc
if (in != 0 && reload_inner_reg_of_subreg (in, inmode, false))
{
- enum reg_class in_class = rclass;
-
if (REG_P (SUBREG_REG (in)))
- in_class
+ subreg_in_class
= find_valid_class (inmode, GET_MODE (SUBREG_REG (in)),
subreg_regno_offset (REGNO (SUBREG_REG (in)),
GET_MODE (SUBREG_REG (in)),
SUBREG_BYTE (in),
GET_MODE (in)),
REGNO (SUBREG_REG (in)));
+ else if (GET_CODE (SUBREG_REG (in)) == SYMBOL_REF)
+ subreg_in_class = find_valid_class_1 (inmode,
+ GET_MODE (SUBREG_REG (in)),
+ rclass);
/* This relies on the fact that emit_reload_insns outputs the
instructions for input reloads of type RELOAD_OTHER in the same
@@ -1108,7 +1161,7 @@ push_reload (rtx in, rtx out, rtx *inloc
RELOAD_OTHER, we are guaranteed that this inner reload will be
output before the outer reload. */
push_reload (SUBREG_REG (in), NULL_RTX, &SUBREG_REG (in), (rtx *) 0,
- in_class, VOIDmode, VOIDmode, 0, 0, opnum, type);
+ subreg_in_class, VOIDmode, VOIDmode, 0, 0, opnum, type);
dont_remove_subreg = 1;
}
@@ -1327,13 +1380,15 @@ push_reload (rtx in, rtx out, rtx *inloc
So add an additional reload. */
#ifdef SECONDARY_MEMORY_NEEDED
- /* If a memory location is needed for the copy, make one. */
- if (in != 0
+ if (subreg_in_class == NO_REGS
+ && in != 0
&& (REG_P (in)
|| (GET_CODE (in) == SUBREG && REG_P (SUBREG_REG (in))))
- && reg_or_subregno (in) < FIRST_PSEUDO_REGISTER
- && SECONDARY_MEMORY_NEEDED (REGNO_REG_CLASS (reg_or_subregno (in)),
- rclass, inmode))
+ && reg_or_subregno (in) < FIRST_PSEUDO_REGISTER)
+ subreg_in_class = REGNO_REG_CLASS (reg_or_subregno (in));
+ /* If a memory location is needed for the copy, make one. */
+ if (subreg_in_class != NO_REGS
+ && SECONDARY_MEMORY_NEEDED (subreg_in_class, rclass, inmode))
get_secondary_mem (in, inmode, opnum, type);
#endif
Index: gcc/testsuite/gcc.c-torture/compile/20120727-1.c
===================================================================
--- gcc/testsuite/gcc.c-torture/compile/20120727-1.c (revision 0)
+++ gcc/testsuite/gcc.c-torture/compile/20120727-1.c (revision 0)
@@ -0,0 +1,11 @@
+union {
+ char *p;
+ float f;
+} u;
+
+void
+f (void)
+{
+ u.p = "";
+ u.f += 1.1;
+}
Index: gcc/config/i386/i386.h
===================================================================
--- gcc/config/i386/i386.h (revision 189284)
+++ gcc/config/i386/i386.h (working copy)
@@ -1376,7 +1376,8 @@ enum reg_class
((MODE) == QImode && !TARGET_64BIT \
&& ((CLASS) == ALL_REGS || (CLASS) == GENERAL_REGS \
|| (CLASS) == LEGACY_REGS || (CLASS) == INDEX_REGS) \
- ? Q_REGS : (CLASS))
+ ? Q_REGS \
+ : (CLASS) == INT_SSE_REGS ? GENERAL_REGS : (CLASS))
/* If we are copying between general and FP registers, we need a memory
location. The same is true for SSE and MMX registers. */
Index: gcc/reload1.c
===================================================================
--- gcc/reload1.c (revision 189284)
+++ gcc/reload1.c (working copy)
@@ -8468,6 +8468,18 @@ emit_insn_if_valid_for_reload (rtx insn)
return NULL;
}
+/* If X is not a subreg, return it unmodified. If it is a subreg,
+ look up whether we made a replacement for the SUBREG_REG. Return
+ either the replacement or the SUBREG_REG. */
+
+static rtx
+replaced_subreg (rtx x)
+{
+ if (GET_CODE (x) == SUBREG)
+ return find_replacement (&SUBREG_REG (x));
+ return x;
+}
+
/* Emit code to perform a reload from IN (which may be a reload register) to
OUT (which may also be a reload register). IN or OUT is from operand
OPNUM with reload type TYPE.
@@ -8478,7 +8490,7 @@ static rtx
gen_reload (rtx out, rtx in, int opnum, enum reload_type type)
{
rtx last = get_last_insn ();
- rtx tem;
+ rtx tem, tem1, tem2;
/* If IN is a paradoxical SUBREG, remove it and try to put the
opposite SUBREG on OUT. Likewise for a paradoxical SUBREG on OUT. */
@@ -8615,14 +8627,12 @@ gen_reload (rtx out, rtx in, int opnum,
#ifdef SECONDARY_MEMORY_NEEDED
/* If we need a memory location to do the move, do it that way. */
- else if ((REG_P (in)
- || (GET_CODE (in) == SUBREG && REG_P (SUBREG_REG (in))))
- && reg_or_subregno (in) < FIRST_PSEUDO_REGISTER
- && (REG_P (out)
- || (GET_CODE (out) == SUBREG && REG_P (SUBREG_REG (out))))
- && reg_or_subregno (out) < FIRST_PSEUDO_REGISTER
- && SECONDARY_MEMORY_NEEDED (REGNO_REG_CLASS (reg_or_subregno (in)),
- REGNO_REG_CLASS (reg_or_subregno (out)),
+ else if ((tem1 = replaced_subreg (in), tem2 = replaced_subreg (out),
+ (REG_P (tem1) && REG_P (tem2)))
+ && REGNO (tem1) < FIRST_PSEUDO_REGISTER
+ && REGNO (tem2) < FIRST_PSEUDO_REGISTER
+ && SECONDARY_MEMORY_NEEDED (REGNO_REG_CLASS (REGNO (tem1)),
+ REGNO_REG_CLASS (REGNO (tem2)),
GET_MODE (out)))
{
/* Get the memory to use and rewrite both registers to its mode. */
