From: Nathan Froyd <froy...@codesourcery.com>
This change addresses a problem where QEMU incorrectly traps on
floating-point MADD group instructions with SIGILL, at least while
emulating MIPS32r2 processors. These instructions use the COP1X major
opcode and include ones like:
madd.d $f2,$f4,$f2,$f6
Here's Nathan's original analysis of the problem:
"QEMU essentially does:
d = find_cpu (cpu_string) // get CPU definition
fpu_init (env, d) // initialize fpu state (init FCR0, basically)
cpu_reset (env)
...and the cpu_reset call clears all interesting state that fpu_init
setup, then proceeds to reinitialize all the CP0 registers...but not
FCR0."
I have verified this change with system emulation running the GDB test
suite for the mips-sde-elf target (o32, big endian, 24Kf CPU emulated),
there were 55 progressions and no regressions.
Signed-off-by: Maciej W. Rozycki <ma...@codesourcery.com>
---
Sent on behalf of Nathan, who's since left the company. Please apply.
Maciej
qemu-mips-fcr0.diff
Index: qemu-git-trunk/target-mips/translate.c
===================================================================
--- qemu-git-trunk.orig/target-mips/translate.c 2012-06-04 05:35:53.245610241
+0100
+++ qemu-git-trunk/target-mips/translate.c 2012-06-04 05:39:26.245563823
+0100
@@ -12776,6 +12776,7 @@ void cpu_state_reset(CPUMIPSState *env)
env->CP0_SRSConf3 = env->cpu_model->CP0_SRSConf3;
env->CP0_SRSConf4_rw_bitmask = env->cpu_model->CP0_SRSConf4_rw_bitmask;
env->CP0_SRSConf4 = env->cpu_model->CP0_SRSConf4;
+ env->active_fpu.fcr0 = env->cpu_model->CP1_fcr0;
env->insn_flags = env->cpu_model->insn_flags;
#if defined(CONFIG_USER_ONLY)
