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a93e15aad1
The primary purpose of this change is to support programs compiled by GCC for the R5900 target and thereby run R5900 Linux distributions, for example Gentoo. GCC in version 7.3, by itself, by inspection of the GCC source code and inspection of the generated machine code, for the R5900 target, only emits two instructions that are specific to the R5900: the three- operand MULT and MULTU. GCC and libc also emit certain MIPS III instructions that are not part of the R5900 ISA. They are normally trapped and emulated by the Linux kernel, and therefore need to be treated accordingly by QEMU. A program compiled by GCC is taken to mean source code compiled by GCC under the restrictions above. One can, with the apparent limitations, with a bit of effort obtain a fully functioning operating system such as R5900 Gentoo. Strictly speaking, programs need not be compiled by GCC to make use of this change. Instructions and other facilities of the R5900 not implemented by this change are intended to signal provisional exceptions. One such example is the FPU that is not compliant with IEEE 754-1985 in system mode. It is therefore provisionally disabled. In user space the FPU is trapped and emulated by IEEE 754-1985 compliant software in the kernel, and this is handled accordingly by QEMU. Another example is the 93 multimedia instructions specific to the R5900 that generate provisional reserved instruction exception signals. One of the benefits of running a Linux distribution under QEMU is that programs can be compiled with a native compiler, where the host and target are the same, as opposed to a cross-compiler, where they are not the same. This is especially important in cases where the target hardware does not have the resources to run a native compiler. Problems with cross-compilation are often related to host and target differences in integer sizes, pointer sizes, endianness, machine code, ABI, etc. Sometimes cross-compilation is not even supported by the build script for a given package. One effective way to avoid those problems is to replace the cross-compiler with a native compiler. This change of compilation methods does not resolve the inherent problems with cross-compilation. The native compiler naturally replaces the cross-compiler, because one typically uses one or the other, and preferably the native compiler when the circumstances admit this. The native compiler is also a good test case for the R5900 QEMU user mode. Additionally, Gentoo is well- known for compiling and installing its packages from sources. This change has been tested with Gentoo compiled for R5900, including native compilation of several packages under QEMU. Backports commit ed4f49ba9bb56ebca6987b1083255daf6c89b5de from qemu. |
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| .. | ||
| accel | ||
| crypto | ||
| default-configs | ||
| docs | ||
| fpu | ||
| hw | ||
| include | ||
| qapi | ||
| qobject | ||
| qom | ||
| scripts | ||
| target | ||
| tcg | ||
| util | ||
| aarch64.h | ||
| aarch64eb.h | ||
| accel.c | ||
| arm.h | ||
| armeb.h | ||
| CODING_STYLE | ||
| configure | ||
| COPYING | ||
| COPYING.LIB | ||
| cpus.c | ||
| exec.c | ||
| gen_all_header.sh | ||
| glib_compat.c | ||
| HACKING | ||
| header_gen.py | ||
| ioport.c | ||
| LICENSE | ||
| m68k.h | ||
| Makefile | ||
| Makefile.objs | ||
| Makefile.target | ||
| memory.c | ||
| memory_ldst.inc.c | ||
| memory_mapping.c | ||
| mips.h | ||
| mips64.h | ||
| mips64el.h | ||
| mipsel.h | ||
| powerpc.h | ||
| qemu-timer.c | ||
| riscv32.h | ||
| riscv64.h | ||
| rules.mak | ||
| sparc.h | ||
| sparc64.h | ||
| unicorn_common.h | ||
| VERSION | ||
| vl.c | ||
| vl.h | ||
| x86_64.h | ||