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target/ppc: Bugfix FP when OE/UE are set 

When an overflow exception occurs and OE is set the intermediate result
should be adjusted (by subtracting from the exponent) to avoid rounding
to inf. The same applies to an underflow exceptionion and UE (but adding
to the exponent). To do this set the fp_status.rebias_overflow when OE
is set and fp_status.rebias_underflow when UE is set as the FPU will
recalculate in case of a overflow/underflow if the according rebias* is
set.

Signed-off-by: Lucas Mateus Castro (alqotel) <lucas.araujo@eldorado.org.br>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20220805141522.412864-3-lucas.araujo@eldorado.org.br>
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
master
Lucas Mateus Castro (alqotel) 2022-08-05 11:15:22 -03:00 committed by Daniel Henrique Barboza
parent c40da5c6fb
commit 08e185cadb
2 changed files with 2 additions and 2 deletions
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2
target/ppc/cpu.c
View File

@ -120,6 +120,8 @@ void ppc_store_fpscr(CPUPPCState *env, target_ulong val)
val |= FP_FEX;
}
env->fpscr = val;
env->fp_status.rebias_overflow = (FP_OE & env->fpscr) ? true : false;
env->fp_status.rebias_underflow = (FP_UE & env->fpscr) ? true : false;
if (tcg_enabled()) {
fpscr_set_rounding_mode(env);
}

2
target/ppc/fpu_helper.c
View File

@ -348,7 +348,6 @@ static inline int float_overflow_excp(CPUPPCState *env)
bool overflow_enabled = !!(env->fpscr & FP_OE);
if (overflow_enabled) {
/* XXX: should adjust the result */
/* Update the floating-point enabled exception summary */
env->fpscr |= FP_FEX;
/* We must update the target FPR before raising the exception */
@ -367,7 +366,6 @@ static inline void float_underflow_excp(CPUPPCState *env)
/* Update the floating-point exception summary */
env->fpscr |= FP_FX;
if (env->fpscr & FP_UE) {
/* XXX: should adjust the result */
/* Update the floating-point enabled exception summary */
env->fpscr |= FP_FEX;
/* We must update the target FPR before raising the exception */