[PULL,05/60] target/ppc: Bugfix FP when OE/UE are set

Commit Message

Daniel Henrique Barboza Aug. 31, 2022, 6:49 p.m. UTC

From: "Lucas Mateus Castro (alqotel)" <[e-mail]>

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) <[e-mail]>
Reviewed-by: Richard Henderson <[e-mail]>
Message-Id: <[e-mail]>
Signed-off-by: Daniel Henrique Barboza <[e-mail]>
---
 target/ppc/cpu.c        | 2 ++
 target/ppc/fpu_helper.c | 2 --
 2 files changed, 2 insertions(+), 2 deletions(-)

Patch

diff --git a/target/ppc/cpu.c b/target/ppc/cpu.c
index 401b6f9e63..0ebac04bc4 100644
--- 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 7ab6beadad..0f045b70f8 100644
--- 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 */