tcg: Add helpers for clrsb

The number of actual invocations does not warrent an opcode,
and the backends generating it.  But at least we can eliminate
redundant helpers.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <rth@twiddle.net>

1 files changed, 28 insertions, 0 deletions

diff --git a/tcg/tcg-op.c b/tcg/tcg-op.c
index 2b520c1953..620e26897f 100644
--- a/tcg/tcg-op.c
+++ b/tcg/tcg-op.c
@@ -536,6 +536,20 @@ void tcg_gen_ctzi_i32(TCGv_i32 ret, TCGv_i32 arg1, uint32_t arg2)
     tcg_temp_free_i32(t);
 }
 
+void tcg_gen_clrsb_i32(TCGv_i32 ret, TCGv_i32 arg)
+{
+    if (TCG_TARGET_HAS_clz_i32) {
+        TCGv_i32 t = tcg_temp_new_i32();
+        tcg_gen_sari_i32(t, arg, 31);
+        tcg_gen_xor_i32(t, t, arg);
+        tcg_gen_clzi_i32(t, t, 32);
+        tcg_gen_subi_i32(ret, t, 1);
+        tcg_temp_free_i32(t);
+    } else {
+        gen_helper_clrsb_i32(ret, arg);
+    }
+}
+
 void tcg_gen_rotl_i32(TCGv_i32 ret, TCGv_i32 arg1, TCGv_i32 arg2)
 {
     if (TCG_TARGET_HAS_rot_i32) {
@@ -1846,6 +1860,20 @@ void tcg_gen_ctzi_i64(TCGv_i64 ret, TCGv_i64 arg1, uint64_t arg2)
     }
 }
 
+void tcg_gen_clrsb_i64(TCGv_i64 ret, TCGv_i64 arg)
+{
+    if (TCG_TARGET_HAS_clz_i64 || TCG_TARGET_HAS_clz_i32) {
+        TCGv_i64 t = tcg_temp_new_i64();
+        tcg_gen_sari_i64(t, arg, 63);
+        tcg_gen_xor_i64(t, t, arg);
+        tcg_gen_clzi_i64(t, t, 64);
+        tcg_gen_subi_i64(ret, t, 1);
+        tcg_temp_free_i64(t);
+    } else {
+        gen_helper_clrsb_i64(ret, arg);
+    }
+}
+
 void tcg_gen_rotl_i64(TCGv_i64 ret, TCGv_i64 arg1, TCGv_i64 arg2)
 {
     if (TCG_TARGET_HAS_rot_i64) {