When I originally developed the IEEE 128-bit floating point support, the
emulation routines in libgcc did not raise errors on signalling NaNs. In the
course of adding full support for IEEE 128-bit floating point, we now have
added exception signaling support in the library. This means the C99/IEEE
built-in functions isgreater, isgreaterequal, isless, islessequal, and
islessgreater now will raise an error when you compare a signaling NaN. These
functions are mandated not to raise an error.
These patches add calls to __unordkf3 to validate that both arguments are
ordered before calling the ge/le/eq comparison function. I have done
bootstraps and make check on both little endian Power8 and big endian Power7
(both 32-bit and 64-bit tests done on the Power7 box) with no regressions. Are
these patches ok for the trunk?
In addition, since the glibc group needs this functionality to complete the
__float128 library support, I would like to get it into GCC 6.2 if it is still
possible. I know this is last minute, but this patch is important to the GLIBC
group, and it was only noticed recently. I will be starting the bootstrap and
regression test on the gcc6 branch shortly. If the patch works on gcc6, can I
commit it to the gcc6 branch ASAP, or will it have to wait for GCC 6.3?
[gcc]
2016-07-25 Michael Meissner <meiss...@linux.vnet.ibm.com>
PR target/71869
* config/rs6000/rs6000.c (rs6000_generate_compare): Rework
__float128 support when we don't have hardware support, so that
the IEEE built-in functions like isgreater, first call __unordkf3
to make sure neither operand is a NaN, and if both operands are
ordered, do the normal comparison.
[gcc/testsuite]
2016-07-25 Michael Meissner <meiss...@linux.vnet.ibm.com>
PR target/71869
* gcc.target/powerpc/float128-cmp.c: New test to make sure that
IEEE built-in functions first check to see if the arguments are
ordered.
--
Michael Meissner, IBM
IBM, M/S 2506R, 550 King Street, Littleton, MA 01460-6245, USA
email: meiss...@linux.vnet.ibm.com, phone: +1 (978) 899-4797
Index: gcc/config/rs6000/rs6000.c
===================================================================
--- gcc/config/rs6000/rs6000.c (revision 238730)
+++ gcc/config/rs6000/rs6000.c (working copy)
@@ -21755,8 +21755,8 @@ rs6000_generate_compare (rtx cmp, machin
else if (!TARGET_FLOAT128_HW && FLOAT128_VECTOR_P (mode))
{
rtx libfunc = NULL_RTX;
- bool uneq_or_ltgt = false;
- rtx dest = gen_reg_rtx (SImode);
+ bool check_nan = false;
+ rtx dest;
switch (code)
{
@@ -21783,21 +21783,23 @@ rs6000_generate_compare (rtx cmp, machin
case UNGE:
case UNGT:
- libfunc = optab_libfunc (le_optab, mode);
+ check_nan = true;
+ libfunc = optab_libfunc (ge_optab, mode);
code = (code == UNGE) ? GE : GT;
break;
case UNLE:
case UNLT:
- libfunc = optab_libfunc (ge_optab, mode);
+ check_nan = true;
+ libfunc = optab_libfunc (le_optab, mode);
code = (code == UNLE) ? LE : LT;
break;
case UNEQ:
case LTGT:
- libfunc = optab_libfunc (le_optab, mode);
- uneq_or_ltgt = true;
- code = (code = UNEQ) ? NE : EQ;
+ check_nan = true;
+ libfunc = optab_libfunc (eq_optab, mode);
+ code = (code = UNEQ) ? EQ : NE;
break;
default:
@@ -21805,21 +21807,56 @@ rs6000_generate_compare (rtx cmp, machin
}
gcc_assert (libfunc);
- dest = emit_library_call_value (libfunc, NULL_RTX, LCT_CONST,
- SImode, 2, op0, mode, op1, mode);
- /* If this is UNEQ or LTGT, we call __lekf2, which returns -1 for less
- than, 0 for equal, +1 for greater, and +2 for nan. We add 1, to give
- a value of 0..3, and then do and AND immediate of 1 to isolate whether
- it is 0/Nan (i.e. bottom bit is 0), or less than/greater than
- (i.e. bottom bit is 1). */
- if (uneq_or_ltgt)
- {
- rtx add_result = gen_reg_rtx (SImode);
- rtx and_result = gen_reg_rtx (SImode);
- emit_insn (gen_addsi3 (add_result, dest, GEN_INT (1)));
- emit_insn (gen_andsi3 (and_result, add_result, GEN_INT (1)));
- dest = and_result;
+ if (!check_nan)
+ dest = emit_library_call_value (libfunc, NULL_RTX, LCT_CONST,
+ SImode, 2, op0, mode, op1, mode);
+
+ /* The library signals an exception for signalling NaNs, so we need to
+ handle isgreater, etc. by first checking isordered. */
+ else
+ {
+ rtx ne_rtx, normal_dest, unord_dest;
+ rtx unord_func = optab_libfunc (unord_optab, mode);
+ rtx join_label = gen_label_rtx ();
+ rtx join_ref = gen_rtx_LABEL_REF (VOIDmode, join_label);
+ rtx unord_cmp = gen_reg_rtx (comp_mode);
+
+
+ /* Test for either value being a NaN. */
+ gcc_assert (unord_func);
+ unord_dest = emit_library_call_value (unord_func, NULL_RTX, LCT_CONST,
+ SImode, 2, op0, mode, op1,
+ mode);
+
+ /* Set value (0) if either value is a NaN, and jump to the join
+ label. */
+ dest = gen_reg_rtx (SImode);
+ emit_move_insn (dest, const1_rtx);
+ emit_insn (gen_rtx_SET (unord_cmp,
+ gen_rtx_COMPARE (comp_mode, unord_dest,
+ const0_rtx)));
+
+ ne_rtx = gen_rtx_NE (comp_mode, unord_cmp, const0_rtx);
+ emit_jump_insn (gen_rtx_SET (pc_rtx,
+ gen_rtx_IF_THEN_ELSE (VOIDmode, ne_rtx,
+ join_ref,
+ pc_rtx)));
+
+ /* Do the normal comparison, knowing that the values are not
+ NaNs. */
+ normal_dest = emit_library_call_value (libfunc, NULL_RTX, LCT_CONST,
+ SImode, 2, op0, mode, op1,
+ mode);
+
+ emit_insn (gen_cstoresi4 (dest,
+ gen_rtx_fmt_ee (code, SImode, normal_dest,
+ const0_rtx),
+ normal_dest, const0_rtx));
+
+ /* Join NaN and non-Nan paths. Compare dest against 0. */
+ emit_label (join_label);
+ code = NE;
}
emit_insn (gen_rtx_SET (compare_result,
Index: gcc/testsuite/gcc.target/powerpc/float128-cmp.c
===================================================================
--- gcc/testsuite/gcc.target/powerpc/float128-cmp.c (revision 0)
+++ gcc/testsuite/gcc.target/powerpc/float128-cmp.c (revision 0)
@@ -0,0 +1,17 @@
+/* { dg-do compile { target { powerpc*-*-linux* } } } */
+/* { dg-require-effective-target powerpc_float128_sw_ok } */
+/* { dg-skip-if "do not override -mcpu" { powerpc*-*-* } { "-mcpu=*" } {
"-mcpu=power7" } } */
+/* { dg-options "-O2 -mcpu=power7 -mfloat128" } */
+
+#ifndef __FLOAT128__
+#error "-mfloat128 is not supported."
+#endif
+
+int
+test_isgreater (__float128 a, __float128 b)
+{
+ return __builtin_isgreater (a, b);
+}
+
+/* { dg-final { scan-assembler "bl __\[gl\]ekf2" } } */
+/* { dg-final { scan-assembler "bl __unordkf2" } } */
