[PULL 10/17] target/ppc: Set result to QNaN for DENBCD when VXCVI occurs

[Daniel Henrique Barboza <danielhb413@gmail.com>]

From: Víctor Colombo <victor.colombo@eldorado.org.br>

According to the ISA, for instruction DENBCD:
"If an invalid BCD digit or sign code is detected in the source
operand, an invalid-operation exception (VXCVI) occurs."

In the Invalid Operation Exception section, there is the situation:
"When Invalid Operation Exception is disabled (VE=0) and Invalid
Operation occurs (...) If the operation is an (...) or format the
target FPR is set to a Quiet NaN". This was not being done in
QEMU.

This patch sets the result to QNaN when the instruction DENBCD causes
an Invalid Operation Exception.

Signed-off-by: Víctor Colombo <victor.colombo@eldorado.org.br>
Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Message-Id: <20220906125523.38765-5-victor.colombo@eldorado.org.br>
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
---
 target/ppc/dfp_helper.c | 26 ++++++++++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

diff --git a/target/ppc/dfp_helper.c b/target/ppc/dfp_helper.c
index be7aa5357a..cc024316d5 100644
--- a/target/ppc/dfp_helper.c
+++ b/target/ppc/dfp_helper.c
@@ -1147,6 +1147,26 @@ static inline uint8_t dfp_get_bcd_digit_128(ppc_vsr_t *t, unsigned n)
     return t->VsrD((n & 0x10) ? 0 : 1) >> ((n << 2) & 63) & 15;
 }
 
+static inline void dfp_invalid_op_vxcvi_64(struct PPC_DFP *dfp)
+{
+    /* TODO: fpscr is incorrectly not being saved to env */
+    dfp_set_FPSCR_flag(dfp, FP_VX | FP_VXCVI, FPSCR_VE);
+    if ((dfp->env->fpscr & FP_VE) == 0) {
+        dfp->vt.VsrD(1) = 0x7c00000000000000; /* QNaN */
+    }
+}
+
+
+static inline void dfp_invalid_op_vxcvi_128(struct PPC_DFP *dfp)
+{
+    /* TODO: fpscr is incorrectly not being saved to env */
+    dfp_set_FPSCR_flag(dfp, FP_VX | FP_VXCVI, FPSCR_VE);
+    if ((dfp->env->fpscr & FP_VE) == 0) {
+        dfp->vt.VsrD(0) = 0x7c00000000000000; /* QNaN */
+        dfp->vt.VsrD(1) = 0x0;
+    }
+}
+
 #define DFP_HELPER_ENBCD(op, size)                                           \
 void helper_##op(CPUPPCState *env, ppc_fprp_t *t, ppc_fprp_t *b,             \
                  uint32_t s)                                                 \
@@ -1173,7 +1193,8 @@ void helper_##op(CPUPPCState *env, ppc_fprp_t *t, ppc_fprp_t *b,             \
             sgn = 0;                                                         \
             break;                                                           \
         default:                                                             \
-            dfp_set_FPSCR_flag(&dfp, FP_VX | FP_VXCVI, FPSCR_VE);            \
+            dfp_invalid_op_vxcvi_##size(&dfp);                               \
+            set_dfp##size(t, &dfp.vt);                                       \
             return;                                                          \
         }                                                                    \
         }                                                                    \
@@ -1183,7 +1204,8 @@ void helper_##op(CPUPPCState *env, ppc_fprp_t *t, ppc_fprp_t *b,             \
         digits[(size) / 4 - n] = dfp_get_bcd_digit_##size(&dfp.vb,           \
                                                           offset++);         \
         if (digits[(size) / 4 - n] > 10) {                                   \
-            dfp_set_FPSCR_flag(&dfp, FP_VX | FP_VXCVI, FPSCR_VE);            \
+            dfp_invalid_op_vxcvi_##size(&dfp);                               \
+            set_dfp##size(t, &dfp.vt);                                       \
             return;                                                          \
         } else {                                                             \
             nonzero |= (digits[(size) / 4 - n] > 0);                         \
-- 
2.37.3