Propagate sNaN payload in quieting in the legacy-NaN mode as well. If clearing the quiet bit would produce infinity, then set the next lower trailing significand field bit, matching the SB-1 and BMIPS5000 hardware implementations. Some other MIPS FPU hardware implementations do produce the default qNaN bit pattern instead.
This reverts some changes made for semantics preservation with commit dc3ddf42 [MIPS: math-emu: Update sNaN quieting handlers], consequently bringing back most of the semantics from before commit fdffbafb [Lots of FPU bug fixes from Kjeld Borch Egevang.], except from the qNaN produced in the infinity case. Previously the default qNaN bit pattern was produced in that case. Signed-off-by: Maciej W. Rozycki <[email protected]> --- linux-mips-emu-snan-legacy.diff Index: linux-sfr-perf132-malta-el/arch/mips/math-emu/ieee754dp.c =================================================================== --- linux-sfr-perf132-malta-el.orig/arch/mips/math-emu/ieee754dp.c 2015-04-08 16:59:18.000000000 +0100 +++ linux-sfr-perf132-malta-el/arch/mips/math-emu/ieee754dp.c 2015-04-08 17:05:29.233752000 +0100 @@ -54,10 +54,13 @@ union ieee754dp __cold ieee754dp_nanxcpt assert(ieee754dp_issnan(r)); ieee754_setcx(IEEE754_INVALID_OPERATION); - if (ieee754_csr.nan2008) + if (ieee754_csr.nan2008) { DPMANT(r) |= DP_MBIT(DP_FBITS - 1); - else - r = ieee754dp_indef(); + } else { + DPMANT(r) &= ~DP_MBIT(DP_FBITS - 1); + if (!ieee754dp_isnan(r)) + DPMANT(r) |= DP_MBIT(DP_FBITS - 2); + } return r; } Index: linux-sfr-perf132-malta-el/arch/mips/math-emu/ieee754sp.c =================================================================== --- linux-sfr-perf132-malta-el.orig/arch/mips/math-emu/ieee754sp.c 2015-04-08 16:59:45.000000000 +0100 +++ linux-sfr-perf132-malta-el/arch/mips/math-emu/ieee754sp.c 2015-04-08 17:05:29.235752000 +0100 @@ -54,10 +54,13 @@ union ieee754sp __cold ieee754sp_nanxcpt assert(ieee754sp_issnan(r)); ieee754_setcx(IEEE754_INVALID_OPERATION); - if (ieee754_csr.nan2008) + if (ieee754_csr.nan2008) { SPMANT(r) |= SP_MBIT(SP_FBITS - 1); - else - r = ieee754sp_indef(); + } else { + SPMANT(r) &= ~SP_MBIT(SP_FBITS - 1); + if (!ieee754sp_isnan(r)) + SPMANT(r) |= SP_MBIT(SP_FBITS - 2); + } return r; } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
