17:17 Pet, 10.04.2020. Richard Henderson <richard.hender...@linaro.org> је написао/ла: > > On 4/10/20 2:38 AM, Aleksandar Markovic wrote: > > 17:55 Uto, 07.04.2020. Alex Bennée <alex.ben...@linaro.org > > <mailto:alex.ben...@linaro.org>> је написао/ла: > >> > >> From: Richard Henderson <richard.hender...@linaro.org > > <mailto:richard.hender...@linaro.org>> > >> > >> All other calls to normalize*Subnormal detect zero input before > >> the call -- this is the only outlier. This case can happen with > >> +0.0 + +0.0 = +0.0 or -0.0 + -0.0 = -0.0, so return a zero of > >> the correct sign. > >> > >> Reported-by: Coverity (CID 1421991) > >> Signed-off-by: Richard Henderson <richard.hender...@linaro.org > > <mailto:richard.hender...@linaro.org>> > >> Signed-off-by: Alex Bennée <alex.ben...@linaro.org > > <mailto:alex.ben...@linaro.org>> > >> Message-Id: <20200327232042.10008-1-richard.hender...@linaro.org > > <mailto:20200327232042.10008-1-richard.hender...@linaro.org>> > >> Message-Id: <20200403191150.863-8-alex.ben...@linaro.org > > <mailto:20200403191150.863-8-alex.ben...@linaro.org>> > >> > >> diff --git a/fpu/softfloat.c b/fpu/softfloat.c > >> index 301ce3b537b..ae6ba718540 100644 > >> --- a/fpu/softfloat.c > >> +++ b/fpu/softfloat.c > >> @@ -5856,6 +5856,9 @@ static floatx80 addFloatx80Sigs(floatx80 a, floatx80 b, > > flag zSign, > >> zSig1 = 0; > >> zSig0 = aSig + bSig; > >> if ( aExp == 0 ) { > >> + if (zSig0 == 0) { > >> + return packFloatx80(zSign, 0, 0); > >> + } > >> normalizeFloatx80Subnormal( zSig0, &zExp, &zSig0 ); > >> goto roundAndPack; > >> } > >> -- > >> 2.20.1 > >> > >> > > > > We in MIPS have extensive FP tests, that certainly include many cases of > > operations with +0 and -0. And they are all correct even before this patch. > > This is for the 80-bit extended-double type, only used on x86 and m68k. You > will not execute this path using MIPS. >
Thanks, Richard! First and foremost, may health be with you and all people of United States and all Americas!! Yes, the fact that m68k also uses 80-bit FP arithmetic was known to me. Though probably many people think 80-bit FP is limited to x86. I was just afraid of some strange way that other targets may end up using the function in question. But again, thanks for reassurances! > > Alex, from the commit message, it not clear if this is a fix of a bug (in which > > case a test example would be useful to have, and the assesment on what > > scenarios could be affected), or just a correction for some rare condition that > > practically for all intents and purposes was never triggered, or perhaps > > something third. > > This only avoids a Coverity out-of-range shift warning. > > Beforehand, we executed 0 << 64, got 0 as the result (regardless of whether or > not the host truncates the shift count), and constructed the correctly signed > fp zero in the end. > > There was more discussion about this in an earlier thread, associated with a > different patch for this same problem: > > https://lists.nongnu.org/archive/html/qemu-devel/2020-03/msg08278.html > OK. I didn't have a chance to read this pattivular thread. Thanks for the pointer! > > > Secondly, and not related to this patch only, I see more and more patches > > integrated into the main tree without "Reviewed-by:" tag. I don't think this is > > the best way an open source community works. In my personal opinion, this must > > stop. > > The only way to avoid this is to have more developers review code outside their > own bailiwick. The patch has been on the list for two weeks and was pinged > twice. > > Although why Alex didn't add his own R-b to my patch when merging it to his > branch, I don't know. > I also have a very similar impression as yours, that Alex in fact reviewed the patch (as if he implicitely gave R-B, but forgot to insert it in a hurry, given these hectic days around 5.0 final release). Best regards, and best wishes to all Sietlans, or wherever you happen to live! Aleksandar > > r~
