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MIPS: Correct FCR0 initialization 

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 <macro@codesourcery.com>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
This commit is contained in:
Nathan Froyd 2012-06-07 15:04:14 +00:00 committed by Blue Swirl
parent 832a226b62
commit f1cb0951c5
1 changed files with 1 additions and 0 deletions
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1
target-mips/translate.c
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@ -12763,6 +12763,7 @@ 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)