3: e8 fc ff ff ff call 4 <_Dmain+0x4> 8: d9 d0 fnop a: 5d pop ebp (http://dstress.kuehne.cn/run/a/asm_fnop_01.d)
I have a similar case that I reported on the users list together with a proposed fix (see https://sourceforge.net/p/valgrind/mailman/message/59283753/). The attached patch has a test for reproducing the issue and a fix for x86 and amd64 (that should also address bug 253446).
Created attachment 188561 [details] Add support for fnop instruction on x86 and amd64
*** Bug 253446 has been marked as a duplicate of this bug. ***
(In reply to Mark from comment #2) > Created attachment 188561 [details] > Add support for fnop instruction on x86 and amd64 Thanks, this looks good. Apologies this was never "implemented". At first I was afraid this needed some subtle floating point exception signaling. Which technically it does, but that is currently a known limitation according to the TODO at the top of the file - x87 FP Limitations: * no FP exceptions, except for handling stack over/underflow So this seems good to go, thanks for the testcases.
commit a615e4daebe2b7289beb66019493285cfc58c2bc Author: Mark <mark@zbuffer.de> Date: Sat Jan 17 17:22:59 2026 +0100 Add support for fnop instruction on x86 and amd64 This implements FNOP in guest_amd64_toIR.c and guest_x86_toIR.c by simply skipping the instruction. Which is OK for now since one of the x87 FP Limitations is no FP exceptions, except for handling stack over/underflow. Add fnop to none/tests/{amd64,x86}/insn_fpu.{def,stdout.exp}. Also update old 3_1_BUGSTATUS.txt to correct bug number. https://bugs.kde.org/show_bug.cgi?id=126256