Am Donnerstag, 16. Oktober 2025, 10:49:56 Mitteleuropäische Sommerzeit schrieb Philippe Mathieu-Daudé: > On 9/10/25 22:51, Gabriel Brookman wrote: > > For the fmpyadd instruction on the hppa architecture, there is a bit > > used to specify whether the instruction is operating on a 32 bit or 64 > > bit floating point register. For most instructions, such a bit is 0 when > > operating on the smaller register and 1 when operating on the larger > > register. However, according to page 6-57 of the PA-RISC 1.1 Architecture > > and Instruction Set Reference Manual, this convention is reversed for the > > fmpyadd instruction specifically, meaning the bit is 1 for operations on > > 32 bit registers and 0 for 64 bit registers. Previously, QEMU decoded > > this operation as operating on the other size of register, leading to > > bugs when translating the fmpyadd instruction. This patch fixes that > > issue. > > > > Reported-by: Andreas Hüttel <[email protected]> > > Signed-off-by: Gabriel Brookman <[email protected]> > > Resolves: https://gitlab.com/qemu-project/qemu/-/issues/3096 > > --- > > Hi all, > > > > This patch fixes the decoding of the fmpyadd instruction on the hppa > > target, which uses an inverted bit convention to select between > > 32-bit and 64-bit floating-point registers. The issue was reported by > > Andreas Hüttel after observing incorrect behavior when running real > > binaries under that target. He kindly submitted a minimal reproducer > > which I was able to use to debug the issue. I used this reproducer > > to verify correct operation after my fix. > > > > Thanks, > > Gabriel > > > > Reported-by: Andreas Hüttel > > --- > > target/hppa/insns.decode | 8 ++++---- > > 1 file changed, 4 insertions(+), 4 deletions(-) > > Patch queued (including doc refs Andreas added). >
Thank you all! Will eventually help a lot here https://www.gentoo.org/downloads/#hppa (which is right now still blocked by an unrelated python bug) -- Andreas K. Hüttel [email protected] Gentoo Linux developer (council, toolchain, base-system, perl, libreoffice) -- PD Dr. Andreas K. Huettel Institute for Experimental and Applied Physics University of Regensburg 93040 Regensburg Germany tel. +49 151 241 67748 (mobile) tel. +49 941 943 1618 (office) e-mail [email protected] https://www.akhuettel.de/ https://www.akhuettel.de/group/
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