[PATCH], PR target/85358, Fix __ibm128 being converter to __float128 on PowerPC ISA 3.0 (power9)
Michael Meissner
meissner@linux.vnet.ibm.com
Mon Apr 16 17:41:00 GMT 2018
As I was working on PR target/85075 (to flesh some bugs with IEEE 128-bit
support on the PowerPC, particularly with switching the default of long
double), I noticed that for explicit IBM extended double, the compiler was
converting the __ibm128 type to an IEEE 128-bit type, because those types had
hardware support in ISA 3.0 (power9).
Unfortunately, IBM extended double (a pair of doubles meant to give you more
mantissa precision but not more expoenent range), is not completely
representable in IEEE 128-bit floating point. There are likely some exposed
corner cases involved, and the bottom bits might not be the same.
While I would prefer IBM extended double to disappear entirely, I do think we
need to deal with it for a few versions still to come.
I tried to come up with machine dependent ways to prevent the automatic
widening from occuring, but I couldn't get anything to work reliably. This
patch adds a new target hook that says whether the automatic widening between
two modes should be allowed. The default hook says to allow all of the default
widenings to occur, while the PowerPC override says IBM extended double does
not widen to IEEE 128-bit and vice versa.
Given we are in stage4 right now, it is not the time to add new hooks, but here
is the patch. If it doesn't go into GCC 8, is it acceptable for being put
early into GCC 9 with a backport before 8.2 comes out?
I have tested this patch using bootstrap builds on a power8 little system, a
power7 big endian system (both 32-bit and 64-bit), and an x86_64 bit system
with no regressions.
[gcc]
2018-04-13 Michael Meissner <meissner@linux.vnet.ibm.com>
PR target/85358
* target.def (default_widening_p): New target hook to say whether
default widening between modes should be done.
* targhooks.h (hook_bool_mode_mode_bool_true): New declaration.
* targhooks.c (hook_bool_mode_mode_bool_true): New default target
hook.
* optabs.c (expand_binop): Before doing default widening, check
whether the backend allows the widening.
(expand_twoval_unop): Likewise.
(expand_twoval_binop): Likewise.
(widen_leading): Likewise.
(widen_bswap): Likewise.
(expand_unop): Likewise.
* cse.c (cse_insn): Likewise.
* combine.c (simplify_comparison): Likewise.
* var-tracking.c (prepare_call_arguments): Likewise.
* config/rs6000/rs6000.c (TARGET_DEFAULT_WIDENING_P): Define
target hook to prevent IBM extended double and IEEE 128-bit
floating point from being converted to each by default.
(rs6000_default_widening_p): Likewise.
* doc/tm.texi (TARGET_DEFAULT_WIDENING_P): Document the new
default widening hook.
* doc/tm.texi.in (TARGET_DEFAULT_WIDENING_P): Likewise.
[gcc/testsuite]
2018-04-13 Michael Meissner <meissner@linux.vnet.ibm.com>
PR target/85358
* gcc.target/powerpc/pr85358.c: New test to make sure __ibm128
does not widen to __float128 on ISA 3.0 systems.
--
Michael Meissner, IBM
IBM, M/S 2506R, 550 King Street, Littleton, MA 01460-6245, USA
email: meissner@linux.vnet.ibm.com, phone: +1 (978) 899-4797
-------------- next part --------------
Index: gcc/target.def
===================================================================
--- gcc/target.def (revision 259376)
+++ gcc/target.def (working copy)
@@ -3486,6 +3486,13 @@ If this hook allows @code{val} to have a
hook_bool_mode_uhwi_false)
DEFHOOK
+(default_widening_p,
+ "Return true if GCC can automatically widen from @var{from_mode} to\n\
+@var{to_mode}. Conversions are unsigned if @var{unsigned_p} is true.",
+ bool, (machine_mode, machine_mode, bool),
+ hook_bool_mode_mode_bool_true)
+
+DEFHOOK
(libgcc_floating_mode_supported_p,
"Define this to return nonzero if libgcc provides support for the \n\
floating-point mode @var{mode}, which is known to pass \n\
Index: gcc/targhooks.c
===================================================================
--- gcc/targhooks.c (revision 259376)
+++ gcc/targhooks.c (working copy)
@@ -2336,4 +2336,12 @@ default_select_early_remat_modes (sbitma
{
}
+bool
+hook_bool_mode_mode_bool_true (machine_mode from_mode ATTRIBUTE_UNUSED,
+ machine_mode to_mode ATTRIBUTE_UNUSED,
+ bool unsigned_p ATTRIBUTE_UNUSED)
+{
+ return true;
+}
+
#include "gt-targhooks.h"
Index: gcc/targhooks.h
===================================================================
--- gcc/targhooks.h (revision 259376)
+++ gcc/targhooks.h (working copy)
@@ -288,5 +288,6 @@ extern enum flt_eval_method
default_excess_precision (enum excess_precision_type ATTRIBUTE_UNUSED);
extern bool default_stack_clash_protection_final_dynamic_probe (rtx);
extern void default_select_early_remat_modes (sbitmap);
+extern bool hook_bool_mode_mode_bool_true (machine_mode, machine_mode, bool);
#endif /* GCC_TARGHOOKS_H */
Index: gcc/optabs.c
===================================================================
--- gcc/optabs.c (revision 259376)
+++ gcc/optabs.c (working copy)
@@ -1284,14 +1284,15 @@ expand_binop (machine_mode mode, optab b
FOR_EACH_WIDER_MODE (wider_mode, mode)
{
machine_mode next_mode;
- if (optab_handler (binoptab, wider_mode) != CODE_FOR_nothing
- || (binoptab == smul_optab
- && GET_MODE_WIDER_MODE (wider_mode).exists (&next_mode)
- && (find_widening_optab_handler ((unsignedp
- ? umul_widen_optab
- : smul_widen_optab),
- next_mode, mode)
- != CODE_FOR_nothing)))
+ if ((optab_handler (binoptab, wider_mode) != CODE_FOR_nothing
+ || (binoptab == smul_optab
+ && GET_MODE_WIDER_MODE (wider_mode).exists (&next_mode)
+ && (find_widening_optab_handler ((unsignedp
+ ? umul_widen_optab
+ : smul_widen_optab),
+ next_mode, mode)
+ != CODE_FOR_nothing)))
+ && targetm.default_widening_p (mode, wider_mode, unsignedp))
{
rtx xop0 = op0, xop1 = op1;
int no_extend = 0;
@@ -1834,9 +1835,10 @@ expand_binop (machine_mode mode, optab b
gcc_assert (!convert_optab_p (binoptab));
FOR_EACH_WIDER_MODE (wider_mode, mode)
{
- if (optab_handler (binoptab, wider_mode)
- || (methods == OPTAB_LIB
- && optab_libfunc (binoptab, wider_mode)))
+ if ((optab_handler (binoptab, wider_mode)
+ || (methods == OPTAB_LIB
+ && optab_libfunc (binoptab, wider_mode)))
+ && targetm.default_widening_p (mode, wider_mode, unsignedp))
{
rtx xop0 = op0, xop1 = op1;
int no_extend = 0;
@@ -1989,7 +1991,8 @@ expand_twoval_unop (optab unoptab, rtx o
{
FOR_EACH_WIDER_MODE (wider_mode, mode)
{
- if (optab_handler (unoptab, wider_mode) != CODE_FOR_nothing)
+ if (optab_handler (unoptab, wider_mode) != CODE_FOR_nothing
+ && targetm.default_widening_p (mode, wider_mode, unsignedp))
{
rtx t0 = gen_reg_rtx (wider_mode);
rtx t1 = gen_reg_rtx (wider_mode);
@@ -2070,7 +2073,8 @@ expand_twoval_binop (optab binoptab, rtx
{
FOR_EACH_WIDER_MODE (wider_mode, mode)
{
- if (optab_handler (binoptab, wider_mode) != CODE_FOR_nothing)
+ if (optab_handler (binoptab, wider_mode) != CODE_FOR_nothing
+ && targetm.default_widening_p (mode, wider_mode, unsignedp))
{
rtx t0 = gen_reg_rtx (wider_mode);
rtx t1 = gen_reg_rtx (wider_mode);
@@ -2169,7 +2173,9 @@ widen_leading (scalar_int_mode mode, rtx
FOR_EACH_WIDER_MODE (wider_mode_iter, mode)
{
scalar_int_mode wider_mode = wider_mode_iter.require ();
- if (optab_handler (unoptab, wider_mode) != CODE_FOR_nothing)
+ bool unsignedp = unoptab != clrsb_optab;
+ if (optab_handler (unoptab, wider_mode) != CODE_FOR_nothing
+ && targetm.default_widening_p (mode, wider_mode, unsignedp))
{
rtx xop0, temp;
rtx_insn *last;
@@ -2178,10 +2184,8 @@ widen_leading (scalar_int_mode mode, rtx
if (target == 0)
target = gen_reg_rtx (mode);
- xop0 = widen_operand (op0, wider_mode, mode,
- unoptab != clrsb_optab, false);
- temp = expand_unop (wider_mode, unoptab, xop0, NULL_RTX,
- unoptab != clrsb_optab);
+ xop0 = widen_operand (op0, wider_mode, mode, unsignedp, false);
+ temp = expand_unop (wider_mode, unoptab, xop0, NULL_RTX, unsignedp);
if (temp != 0)
temp = expand_binop
(wider_mode, sub_optab, temp,
@@ -2333,9 +2337,12 @@ widen_bswap (scalar_int_mode mode, rtx o
opt_scalar_int_mode wider_mode_iter;
FOR_EACH_WIDER_MODE (wider_mode_iter, mode)
- if (optab_handler (bswap_optab, wider_mode_iter.require ())
- != CODE_FOR_nothing)
- break;
+ {
+ machine_mode wider_mode = wider_mode_iter.require ();
+ if (optab_handler (bswap_optab, wider_mode) != CODE_FOR_nothing
+ && targetm.default_widening_p (mode, wider_mode, true))
+ break;
+ }
if (!wider_mode_iter.exists ())
return NULL_RTX;
@@ -2865,7 +2872,8 @@ expand_unop (machine_mode mode, optab un
if (CLASS_HAS_WIDER_MODES_P (mclass))
FOR_EACH_WIDER_MODE (wider_mode, mode)
{
- if (optab_handler (unoptab, wider_mode) != CODE_FOR_nothing)
+ if (optab_handler (unoptab, wider_mode) != CODE_FOR_nothing
+ && targetm.default_widening_p (mode, wider_mode, unsignedp))
{
rtx xop0 = op0;
rtx_insn *last = get_last_insn ();
@@ -3032,8 +3040,9 @@ expand_unop (machine_mode mode, optab un
{
FOR_EACH_WIDER_MODE (wider_mode, mode)
{
- if (optab_handler (unoptab, wider_mode) != CODE_FOR_nothing
- || optab_libfunc (unoptab, wider_mode))
+ if ((optab_handler (unoptab, wider_mode) != CODE_FOR_nothing
+ || optab_libfunc (unoptab, wider_mode))
+ && targetm.default_widening_p (mode, wider_mode, unsignedp))
{
rtx xop0 = op0;
rtx_insn *last = get_last_insn ();
Index: gcc/cse.c
===================================================================
--- gcc/cse.c (revision 259376)
+++ gcc/cse.c (working copy)
@@ -4885,6 +4885,9 @@ cse_insn (rtx_insn *insn)
if (GET_MODE_PRECISION (wider_mode) > BITS_PER_WORD)
break;
+ if (!targetm.default_widening_p (mode, wider_mode, false))
+ continue;
+
struct table_elt *const_elt
= lookup (src_const, HASH (src_const, wider_mode), wider_mode);
@@ -4924,6 +4927,9 @@ cse_insn (rtx_insn *insn)
if (GET_MODE_SIZE (tmode) > UNITS_PER_WORD)
break;
+ if (!targetm.default_widening_p (mode, tmode, false))
+ continue;
+
rtx inner = gen_lowpart (tmode, XEXP (src, 0));
struct table_elt *larger_elt;
@@ -4979,6 +4985,9 @@ cse_insn (rtx_insn *insn)
if (GET_MODE_SIZE (tmode) > UNITS_PER_WORD)
break;
+ if (!targetm.default_widening_p (mode, tmode, false))
+ continue;
+
PUT_MODE (memory_extend_rtx, tmode);
larger_elt = lookup (memory_extend_rtx,
HASH (memory_extend_rtx, tmode), tmode);
Index: gcc/combine.c
===================================================================
--- gcc/combine.c (revision 259376)
+++ gcc/combine.c (working copy)
@@ -12965,6 +12965,9 @@ simplify_comparison (enum rtx_code code,
|| (nonzero_bits (op1, tmode)
& ~GET_MODE_MASK (mode)) == 0)));
+ if (!targetm.default_widening_p (mode, tmode, zero_extended))
+ continue;
+
if (zero_extended
|| ((num_sign_bit_copies (op0, tmode)
> (unsigned int) (GET_MODE_PRECISION (tmode)
Index: gcc/var-tracking.c
===================================================================
--- gcc/var-tracking.c (revision 259376)
+++ gcc/var-tracking.c (working copy)
@@ -6347,10 +6347,14 @@ prepare_call_arguments (basic_block bb,
opt_scalar_int_mode mode_iter;
FOR_EACH_WIDER_MODE (mode_iter, mode)
{
+ machine_mode old_mode = mode;
mode = mode_iter.require ();
if (GET_MODE_BITSIZE (mode) > BITS_PER_WORD)
break;
+ if (!targetm.default_widening_p (old_mode, mode, false))
+ continue;
+
rtx reg = simplify_subreg (mode, x, GET_MODE (x), 0);
if (reg == NULL_RTX || !REG_P (reg))
continue;
Index: gcc/config/rs6000/rs6000.c
===================================================================
--- gcc/config/rs6000/rs6000.c (revision 259376)
+++ gcc/config/rs6000/rs6000.c (working copy)
@@ -1980,6 +1980,9 @@ static const struct attribute_spec rs600
#undef TARGET_STARTING_FRAME_OFFSET
#define TARGET_STARTING_FRAME_OFFSET rs6000_starting_frame_offset
+
+#undef TARGET_DEFAULT_WIDENING_P
+#define TARGET_DEFAULT_WIDENING_P rs6000_default_widening_p
/* Processor table. */
@@ -17150,6 +17153,29 @@ rs6000_init_builtins (void)
#endif
}
+/* Return true if FROM_MODE can be widened to TO_MODE automatically. UNSIGNEDP
+ says the conversion is unsigned.
+
+ On PowerPC, don't allow IBM extended double to widen to an IEEE 128-bit
+ floating point value or vice versa. */
+
+static bool
+rs6000_default_widening_p (machine_mode from_mode,
+ machine_mode to_mode,
+ bool unsignedp ATTRIBUTE_UNUSED)
+{
+ if (!TARGET_FLOAT128_TYPE)
+ return true;
+
+ if (FLOAT128_IEEE_P (from_mode) && FLOAT128_IBM_P (to_mode))
+ return false;
+
+ if (FLOAT128_IBM_P (from_mode) && FLOAT128_IEEE_P (to_mode))
+ return false;
+
+ return true;
+}
+
/* Returns the rs6000 builtin decl for CODE. */
static tree
Index: gcc/doc/tm.texi
===================================================================
--- gcc/doc/tm.texi (revision 259376)
+++ gcc/doc/tm.texi (working copy)
@@ -4315,6 +4315,11 @@ If this hook allows @code{val} to have a
@code{int8x8x3_t}s in registers rather than forcing them onto the stack.
@end deftypefn
+@deftypefn {Target Hook} bool TARGET_DEFAULT_WIDENING_P (machine_mode, @var{machine_mode}, @var{bool})
+Return true if GCC can automatically widen from @var{from_mode} to
+@var{to_mode}. Conversions are unsigned if @var{unsigned_p} is true.
+@end deftypefn
+
@deftypefn {Target Hook} bool TARGET_LIBGCC_FLOATING_MODE_SUPPORTED_P (scalar_float_mode @var{mode})
Define this to return nonzero if libgcc provides support for the
floating-point mode @var{mode}, which is known to pass
Index: gcc/doc/tm.texi.in
===================================================================
--- gcc/doc/tm.texi.in (revision 259376)
+++ gcc/doc/tm.texi.in (working copy)
@@ -3344,6 +3344,8 @@ stack.
@hook TARGET_ARRAY_MODE_SUPPORTED_P
+@hook TARGET_DEFAULT_WIDENING_P
+
@hook TARGET_LIBGCC_FLOATING_MODE_SUPPORTED_P
@hook TARGET_FLOATN_MODE
Index: gcc/testsuite/gcc.target/powerpc/pr85358.c
===================================================================
--- gcc/testsuite/gcc.target/powerpc/pr85358.c (revision 0)
+++ gcc/testsuite/gcc.target/powerpc/pr85358.c (revision 0)
@@ -0,0 +1,14 @@
+/* { dg-do compile { target { powerpc*-*-linux* && lp64 } } } */
+/* { dg-require-effective-target powerpc_p9vector_ok } */
+/* { dg-options "-mpower9-vector -mfloat128 -O2 -mabi=ieeelongdouble -Wno-psabi" } */
+
+/* Verify that __ibm128 does not get converted automatically to IEEE 128-bit on
+ machines with IEEE 128-bit hardware support. */
+
+__ibm128
+add (__ibm128 a, __ibm128 b)
+{
+ return a + b;
+}
+
+/* { dg-final { scan-assembler-not {\mxsaddqp\M} } } */
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