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>

diff --git a/target/ppc/cpu.c b/target/ppc/cpu.c
index 401b6f9e630f9a7dac4ea52d34cacdd0936a9ccd..0ebac04bc465986fbceec8f433c0805f6a40d9f6 100644 (file)
--- a/target/ppc/cpu.c
+++ b/target/ppc/cpu.c
@@ -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);
     }

diff --git a/target/ppc/fpu_helper.c b/target/ppc/fpu_helper.c
index 7ab6beadad317cbcd066483a6b6cff8dba1f9230..0f045b70f82146aee82e75e5689564391f9a2324 100644 (file)
--- a/target/ppc/fpu_helper.c
+++ b/target/ppc/fpu_helper.c
@@ -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 */