Normally Boolean options/flags in GCC take the values zero or one.
This patch tweaks flag_trapping_math to take the values 0 or 65535.
More accurately it introduces a new trapping_math_model enumeration in
flag-types.h, and uses this to allow front-ends to (potentially) control
which expressions may be constant folded at compile-time by the middle-end.
Floating point/language experts may recognize these flags (bits) as being
modelled upon (extended) FENV_ACCESS.
This instalment simply introduces the necessary infrastructure without
yet changing any functionality. The test "if (flag_trapping_math)" will
remain perfectly valid (but pessimistic). The goal is to allow time
for out-of-tree front-ends (modula-2, rust, etc.) to update themselves,
if required, and to confirm that this change doesn't introduce problems
for LTO, or elsewhere.
This patch has been tested on x86_64-pc-linux-gnu with "make bootstrap"
and "make -k check", all languages including Ada, with no new failures.
Ok for mainline?
2021-09-25 Roger Sayle <ro...@nextmovesoftware.com>
gcc/ChangeLog
* flag-types.h (trapping_math_model): New enumeration (of bits)
specifying possible floating-point (and integer) exceptions/traps.
* common.opt (ftrapping-math): Specify UInteger and initialize to
flag_trapping_math to TRAPPING_MATH_DEFAULT.
* toplev.c (process_options): The option -fsignaling-nans should
set flag_trapping_math to TRAPPING_MATH_DEFAULT.
gcc/ada/ChangeLog
* gcc-interface/misc.c (gnat_init_gcc_fp): Set flag_trapping_math
to TRAPPING_MATH_DEFAULT (instead of 1) if S'Machine_Overflow.
Roger
--
diff --git a/gcc/ada/gcc-interface/misc.c b/gcc/ada/gcc-interface/misc.c
index 96199bd..93cbc71 100644
--- a/gcc/ada/gcc-interface/misc.c
+++ b/gcc/ada/gcc-interface/misc.c
@@ -451,7 +451,7 @@ gnat_init_gcc_fp (void)
/* Assume that FP operations can trap if S'Machine_Overflow is true,
but don't override the user if not. */
if (Machine_Overflows_On_Target)
- flag_trapping_math = 1;
+ flag_trapping_math = TRAPPING_MATH_DEFAULT;
else if (!global_options_set.x_flag_trapping_math)
flag_trapping_math = 0;
}
diff --git a/gcc/common.opt b/gcc/common.opt
index b921f5e..314f9a7 100644
--- a/gcc/common.opt
+++ b/gcc/common.opt
@@ -2750,7 +2750,7 @@ generate them instead of using descriptors.
; (user-visible) trap. This is the case, for example, in nonstop
; IEEE 754 arithmetic.
ftrapping-math
-Common Var(flag_trapping_math) Init(1) Optimization SetByCombined
+Common Var(flag_trapping_math) Init(TRAPPING_MATH_DEFAULT) Optimization
SetByCombined UInteger
Assume floating-point operations can trap.
ftrapv
diff --git a/gcc/flag-types.h b/gcc/flag-types.h
index 5bd1f77..98b9ff0 100644
--- a/gcc/flag-types.h
+++ b/gcc/flag-types.h
@@ -481,6 +481,33 @@ enum openacc_privatization
OPENACC_PRIVATIZATION_NOISY
};
+/* Trapping math exception classes. */
+enum trapping_math_model
+{
+ TRAPPING_MATH_NONE = 0,
+ TRAPPING_MATH_QNANOP = 1UL << 0,
+ TRAPPING_MATH_SNANOP = 1UL << 1,
+ TRAPPING_MATH_QNANCMP = 1UL << 2,
+ TRAPPING_MATH_SNANCMP = 1UL << 3,
+ TRAPPING_MATH_INTCONV = 1UL << 4,
+ TRAPPING_MATH_SQRTNEG = 1UL << 5,
+ TRAPPING_MATH_LIBMFUN = 1UL << 6,
+ TRAPPING_MATH_FDIVZERO = 1UL << 7,
+ TRAPPING_MATH_IDIVZERO = 1UL << 8,
+ TRAPPING_MATH_FPDENORM = 1UL << 9,
+ TRAPPING_MATH_OVERFLOW = 1UL << 10,
+ TRAPPING_MATH_UNDERFLOW = 1UL << 11,
+ TRAPPING_MATH_INFDIVINF = 1UL << 12,
+ TRAPPING_MATH_INFSUBINF = 1UL << 13,
+ TRAPPING_MATH_INFMULZERO = 1UL << 14,
+ TRAPPING_MATH_ZERODIVZERO = 1UL << 15,
+
+ TRAPPING_MATH_DEFAULT = (1UL << 16) - 1,
+
+ TRAPPING_MATH_INEXACT = 1UL << 16,
+ TRAPPING_MATH_TRAPV = 1UL << 17
+};
+
#endif
#endif /* ! GCC_FLAG_TYPES_H */
diff --git a/gcc/toplev.c b/gcc/toplev.c
index 14d1335..6cd71cc 100644
--- a/gcc/toplev.c
+++ b/gcc/toplev.c
@@ -1664,7 +1664,7 @@ process_options (void)
/* The presence of IEEE signaling NaNs, implies all math can trap. */
if (flag_signaling_nans)
- flag_trapping_math = 1;
+ flag_trapping_math = TRAPPING_MATH_DEFAULT;
/* We cannot reassociate if we want traps or signed zeros. */
if (flag_associative_math && (flag_trapping_math || flag_signed_zeros))
