target/ppc: implement cbcdtd

Implements the Convert Binary Coded Decimal To Declets instruction.
Since libdecnumber doesn't expose the methods for direct conversion
(decDigitsToDPD, BCD2DPD, etc.), the BCD values are converted to
decimal32 format, from which the declets are extracted.

Where the behavior is undefined, we try to match the result observed in
a POWER9 DD2.3.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Matheus Ferst <matheus.ferst@eldorado.org.br>
Signed-off-by: Víctor Colombo <victor.colombo@eldorado.org.br>
Message-Id: <20220629162904.105060-11-victor.colombo@eldorado.org.br>
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>

diff --git a/target/ppc/dfp_helper.c b/target/ppc/dfp_helper.c
index 0d01ac3de0b700a1caf94861ba02e477ba554808..db9e994c8c26a875e5c15990b595c3aedff3ae5b 100644 (file)
--- a/target/ppc/dfp_helper.c
+++ b/target/ppc/dfp_helper.c
@@ -1391,3 +1391,42 @@ DFP_HELPER_SHIFT(DSCLI, 64, 1)
 DFP_HELPER_SHIFT(DSCLIQ, 128, 1)
 DFP_HELPER_SHIFT(DSCRI, 64, 0)
 DFP_HELPER_SHIFT(DSCRIQ, 128, 0)
+
+target_ulong helper_CBCDTD(target_ulong s)
+{
+    uint64_t res = 0;
+    uint32_t dec32;
+    uint8_t bcd[6];
+    int w, i, offs;
+    decNumber a;
+    decContext context;
+
+    decContextDefault(&context, DEC_INIT_DECIMAL32);
+
+    for (w = 1; w >= 0; w--) {
+        res <<= 32;
+        decNumberZero(&a);
+        /* Extract each BCD field of word "w" */
+        for (i = 5; i >= 0; i--) {
+            offs = 4 * (5 - i) + 32 * w;
+            bcd[i] = extract64(s, offs, 4);
+            if (bcd[i] > 9) {
+                /*
+                 * If the field value is greater than 9, the results are
+                 * undefined. We could use a fixed value like 0 or 9, but
+                 * an and with 9 seems to better match the hardware behavior.
+                 */
+                bcd[i] &= 9;
+            }
+        }
+
+        /* Create a decNumber with the BCD values and convert to decimal32 */
+        decNumberSetBCD(&a, bcd, 6);
+        decimal32FromNumber((decimal32 *)&dec32, &a, &context);
+
+        /* Extract the two declets from the decimal32 value */
+        res |= dec32 & 0xfffff;
+    }
+
+    return res;
+}

diff --git a/target/ppc/helper.h b/target/ppc/helper.h
index 84a41d85b00b22e6df0bd52dede2f67259f34286..583c8dd0c290a3c30e4437d1f17482ecc2ba0d2a 100644 (file)
--- a/target/ppc/helper.h
+++ b/target/ppc/helper.h
@@ -54,6 +54,7 @@ DEF_HELPER_3(sraw, tl, env, tl, tl)
 DEF_HELPER_FLAGS_2(CFUGED, TCG_CALL_NO_RWG_SE, i64, i64, i64)
 DEF_HELPER_FLAGS_2(PDEPD, TCG_CALL_NO_RWG_SE, i64, i64, i64)
 DEF_HELPER_FLAGS_2(PEXTD, TCG_CALL_NO_RWG_SE, i64, i64, i64)
+DEF_HELPER_FLAGS_1(CBCDTD, TCG_CALL_NO_RWG_SE, tl, tl)
 #if defined(TARGET_PPC64)
 DEF_HELPER_FLAGS_2(cmpeqb, TCG_CALL_NO_RWG_SE, i32, tl, tl)
 DEF_HELPER_FLAGS_1(popcntw, TCG_CALL_NO_RWG_SE, tl, tl)

diff --git a/target/ppc/insn32.decode b/target/ppc/insn32.decode
index af8ba9ca9b3e8fd554c3e3fa366a911be27fb7f2..65bcaf657fe5af7722fdc65d36f99681b2c35976 100644 (file)
--- a/target/ppc/insn32.decode
+++ b/target/ppc/insn32.decode
@@ -87,6 +87,9 @@
 &X_rc           rt ra rb rc:bool
 @X_rc           ...... rt:5 ra:5 rb:5 .......... rc:1           &X_rc
 
+&X_sa           rs ra
+@X_sa           ...... rs:5 ra:5 ..... .......... .             &X_sa
+
 %x_frtp         22:4 !function=times_2
 %x_frap         17:4 !function=times_2
 %x_frbp         12:4 !function=times_2
@@ -314,6 +317,7 @@ PEXTD           011111 ..... ..... ..... 0010111100 -   @X
 ## BCD Assist
 
 ADDG6S          011111 ..... ..... ..... - 001001010 -  @X
+CBCDTD          011111 ..... ..... ----- 0100111010 -   @X_sa
 
 ### Float-Point Load Instructions
 

diff --git a/target/ppc/translate/fixedpoint-impl.c.inc b/target/ppc/translate/fixedpoint-impl.c.inc
index 490e49cfc7c54ec17e4325b1bda3af25426c6754..892c9d25688653595e5c4180f8ef50f9a6939276 100644 (file)
--- a/target/ppc/translate/fixedpoint-impl.c.inc
+++ b/target/ppc/translate/fixedpoint-impl.c.inc
@@ -529,3 +529,10 @@ static bool trans_ADDG6S(DisasContext *ctx, arg_X *a)
 
     return true;
 }
+
+static bool trans_CBCDTD(DisasContext *ctx, arg_X_sa *a)
+{
+    REQUIRE_INSNS_FLAGS2(ctx, BCDA_ISA206);
+    gen_helper_CBCDTD(cpu_gpr[a->ra], cpu_gpr[a->rs]);
+    return true;
+}