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> |
||
|---|---|---|
| .. | ||
| aarch64 | ||
| alpha | ||
| arm | ||
| cris | ||
| hppa | ||
| i386 | ||
| lm32 | ||
| m68k | ||
| minilib | ||
| mips | ||
| multiarch | ||
| openrisc | ||
| ppc | ||
| s390x | ||
| sh4 | ||
| sparc64 | ||
| x86_64 | ||
| xtensa | ||
| .gitignore | ||
| configure.sh | ||
| Makefile.prereqs | ||
| Makefile.qemu | ||
| Makefile.target | ||
| README | ||
This directory contains various interesting guest programs for regression testing. Tests are either multi-arch, meaning they can be built for all guest architectures that support linux-user executable, or they are architecture specific. CRIS ==== The testsuite for CRIS is in tests/tcg/cris. You can run it with "make test-cris". LM32 ==== The testsuite for LM32 is in tests/tcg/lm32. You can run it with "make test-lm32".