[PULL v2 86/91] target/ppc: Rewrite trans_ADDG6S

[Richard Henderson]

Compute all carry bits in parallel instead of a loop.

Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 target/ppc/translate/fixedpoint-impl.c.inc | 44 +++++++++++-----------
 1 file changed, 23 insertions(+), 21 deletions(-)

diff --git a/target/ppc/translate/fixedpoint-impl.c.inc 
b/target/ppc/translate/fixedpoint-impl.c.inc
index 20ea484c3d..02d86b77a8 100644
--- a/target/ppc/translate/fixedpoint-impl.c.inc
+++ b/target/ppc/translate/fixedpoint-impl.c.inc
@@ -484,33 +484,35 @@ static bool trans_PEXTD(DisasContext *ctx, arg_X *a)
 
 static bool trans_ADDG6S(DisasContext *ctx, arg_X *a)
 {
-    const uint64_t carry_bits = 0x1111111111111111ULL;
-    TCGv t0, t1, carry, zero = tcg_constant_tl(0);
+    const target_ulong carry_bits = (target_ulong)-1 / 0xf;
+    TCGv in1, in2, carryl, carryh, tmp;
+    TCGv zero = tcg_constant_tl(0);
 
     REQUIRE_INSNS_FLAGS2(ctx, BCDA_ISA206);
 
-    t0 = tcg_temp_new();
-    t1 = tcg_const_tl(0);
-    carry = tcg_const_tl(0);
+    in1 = cpu_gpr[a->ra];
+    in2 = cpu_gpr[a->rb];
+    tmp = tcg_temp_new();
+    carryl = tcg_temp_new();
+    carryh = tcg_temp_new();
 
-    for (int i = 0; i < 16; i++) {
-        tcg_gen_shri_tl(t0, cpu_gpr[a->ra], i * 4);
-        tcg_gen_andi_tl(t0, t0, 0xf);
-        tcg_gen_add_tl(t1, t1, t0);
+    /* Addition with carry. */
+    tcg_gen_add2_tl(carryl, carryh, in1, zero, in2, zero);
+    /* Addition without carry. */
+    tcg_gen_xor_tl(tmp, in1, in2);
+    /* Difference between the two is carry in to each bit. */
+    tcg_gen_xor_tl(carryl, carryl, tmp);
 
-        tcg_gen_shri_tl(t0, cpu_gpr[a->rb], i * 4);
-        tcg_gen_andi_tl(t0, t0, 0xf);
-        tcg_gen_add_tl(t1, t1, t0);
+    /*
+     * The carry-out that we're looking for is the carry-in to
+     * the next nibble.  Shift the double-word down one nibble,
+     * which puts all of the bits back into one word.
+     */
+    tcg_gen_extract2_tl(carryl, carryl, carryh, 4);
 
-        tcg_gen_andi_tl(t1, t1, 0x10);
-        tcg_gen_setcond_tl(TCG_COND_NE, t1, t1, zero);
-
-        tcg_gen_shli_tl(t0, t1, i * 4);
-        tcg_gen_or_tl(carry, carry, t0);
-    }
-
-    tcg_gen_xori_tl(carry, carry, (target_long)carry_bits);
-    tcg_gen_muli_tl(cpu_gpr[a->rt], carry, 6);
+    /* Invert, isolate the carry bits, and produce 6's. */
+    tcg_gen_andc_tl(carryl, tcg_constant_tl(carry_bits), carryl);
+    tcg_gen_muli_tl(cpu_gpr[a->rt], carryl, 6);
     return true;
 }
 
-- 
2.34.1