eca30647fc
The x87 f2xm1 emulation is currently based around conversion to double. This is inherently unsuitable for a good emulation of any floatx80 operation, even before considering that it is a particularly naive implementation using double (computing with pow and then subtracting 1 rather than attempting a better emulation using expm1). Reimplement using the soft-float operations, including additions and multiplications with higher precision where appropriate to limit accumulation of errors. I considered reusing some of the m68k code for transcendental operations, but the instructions don't generally correspond exactly to x87 operations (for example, m68k has 2^x and e^x - 1, but not 2^x - 1); to avoid possible accumulation of errors from applying multiple such operations each rounding to floatx80 precision, I wrote a direct implementation of 2^x - 1 instead. It would be possible in principle to make the implementation more efficient by doing the intermediate operations directly with significands, signs and exponents and not packing / unpacking floatx80 format for each operation, but that would make it significantly more complicated and it's not clear that's worthwhile; the m68k emulation doesn't try to do that. A test is included with many randomly generated inputs. The assumption of the test is that the result in round-to-nearest mode should always be one of the two closest floating-point numbers to the mathematical value of 2^x - 1; the implementation aims to do somewhat better than that (about 70 correct bits before rounding). I haven't investigated how accurate hardware is. Signed-off-by: Joseph Myers <joseph@codesourcery.com> Message-Id: <alpine.DEB.2.21.2006112341010.18393@digraph.polyomino.org.uk> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> |
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| .. | ||
| system | ||
| hello-i386.c | ||
| Makefile.softmmu-target | ||
| Makefile.target | ||
| README | ||
| test-i386-code16.S | ||
| test-i386-f2xm1.c | ||
| test-i386-fbstp.c | ||
| test-i386-fisttp.c | ||
| test-i386-fldcst.c | ||
| test-i386-fp-exceptions.c | ||
| test-i386-fprem.c | ||
| test-i386-fscale.c | ||
| test-i386-fxam.c | ||
| test-i386-fxtract.c | ||
| test-i386-muldiv.h | ||
| test-i386-pcmpistri.c | ||
| test-i386-pseudo-denormal.c | ||
| test-i386-shift.h | ||
| test-i386-snan-convert.c | ||
| test-i386-ssse3.c | ||
| test-i386-vm86.S | ||
| test-i386.c | ||
| test-i386.h | ||
These are i386 specific guest programs test-i386 --------- This program executes most of the 16 bit and 32 bit x86 instructions and generates a text output, for comparison with the output obtained with a real CPU or another emulator. The Linux system call modify_ldt() is used to create x86 selectors to test some 16 bit addressing and 32 bit with segmentation cases. The Linux system call vm86() is used to test vm86 emulation. Various exceptions are raised to test most of the x86 user space exception reporting. linux-test ---------- This program tests various Linux system calls. It is used to verify that the system call parameters are correctly converted between target and host CPUs. test-i386-fprem --------------- test-mmap --------- sha1 ---- hello-i386 ----------