From 9b6e986e280f43e3df3baf7aae2069d599b5056c Mon Sep 17 00:00:00 2001 From: Peter Maydell Date: Mon, 24 Feb 2025 11:15:13 +0000 Subject: fpu: Make targets specify floatx80 default Inf at runtime MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Currently we hardcode at compile time whether the floatx80 default Infinity value has the explicit integer bit set or not (x86 sets it; m68k does not). To be able to compile softfloat once for all targets we'd like to move this setting to runtime. Define a new FloatX80Behaviour enum which is a set of flags that define the target's floatx80 handling. Initially we define just one flag, for whether the default Infinity has the Integer bit set or not, but we will expand this in future commits to cover the other floatx80 target specifics that we currently make compile-time settings. Define a new function floatx80_default_inf() which returns the appropriate default Infinity value of the given sign, and use it in the code that was previously directly using the compile-time constant floatx80_infinity_{low,high} values when packing an infinity into a floatx80. Since floatx80 is highly unlikely to be supported in any new architecture, and the existing code is generally written as "default to like x87, with an ifdef for m68k", we make the default value for the floatx80 behaviour flags be "what x87 does". This means we only need to change the m68k target to specify the behaviour flags. (Other users of floatx80 are the Arm NWFPE emulation, which is obsolete and probably not actually doing the right thing anyway, and the PPC xsrqpxp insn. Making the default be "like x87" avoids our needing to review and test for behaviour changes there.) We will clean up the remaining uses of the floatx80_infinity global constant in subsequent commits. Signed-off-by: Peter Maydell Reviewed-by: Richard Henderson Reviewed-by: Philippe Mathieu-Daudé Message-id: 20250224111524.1101196-2-peter.maydell@linaro.org Message-id: 20250217125055.160887-2-peter.maydell@linaro.org --- fpu/softfloat.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) (limited to 'fpu/softfloat.c') diff --git a/fpu/softfloat.c b/fpu/softfloat.c index f4fed9bfda..b12ad2b42a 100644 --- a/fpu/softfloat.c +++ b/fpu/softfloat.c @@ -1860,7 +1860,8 @@ static floatx80 floatx80_round_pack_canonical(FloatParts128 *p, case float_class_inf: /* x86 and m68k differ in the setting of the integer bit. */ - frac = floatx80_infinity_low; + frac = s->floatx80_behaviour & floatx80_default_inf_int_bit_is_zero ? + 0 : (1ULL << 63); exp = fmt->exp_max; break; @@ -5144,9 +5145,7 @@ floatx80 roundAndPackFloatx80(FloatX80RoundPrec roundingPrecision, bool zSign, ) { return packFloatx80( zSign, 0x7FFE, ~ roundMask ); } - return packFloatx80(zSign, - floatx80_infinity_high, - floatx80_infinity_low); + return floatx80_default_inf(zSign, status); } if ( zExp <= 0 ) { isTiny = status->tininess_before_rounding -- cgit 1.4.1