From: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-Id: <20230823145542.79633-2-philmd@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
tcg/tcg-op.c | 27 +++++++++++++++++++--------
1 file changed, 19 insertions(+), 8 deletions(-)
diff --git a/tcg/tcg-op.c b/tcg/tcg-op.c
index b59a50a5a9..fc3a0ab7fc 100644
--- a/tcg/tcg-op.c
+++ b/tcg/tcg-op.c
@@ -1035,6 +1035,14 @@ void tcg_gen_ext16u_i32(TCGv_i32 ret, TCGv_i32 arg)
}
}
+/*
+ * bswap16_i32: 16-bit byte swap on the low bits of a 32-bit value.
+ *
+ * Byte pattern: xxab -> yyba
+ *
+ * With TCG_BSWAP_IZ, x == zero, else undefined.
+ * With TCG_BSWAP_OZ, y == zero, with TCG_BSWAP_OS y == sign, else undefined.
+ */
void tcg_gen_bswap16_i32(TCGv_i32 ret, TCGv_i32 arg, int flags)
{
/* Only one extension flag may be present. */
@@ -1046,22 +1054,25 @@ void tcg_gen_bswap16_i32(TCGv_i32 ret, TCGv_i32 arg, int flags)
TCGv_i32 t0 = tcg_temp_ebb_new_i32();
TCGv_i32 t1 = tcg_temp_ebb_new_i32();
- tcg_gen_shri_i32(t0, arg, 8);
+ /* arg = ..ab (IZ) xxab (!IZ) */
+ tcg_gen_shri_i32(t0, arg, 8); /* t0 = ...a (IZ) .xxa (!IZ) */
if (!(flags & TCG_BSWAP_IZ)) {
- tcg_gen_ext8u_i32(t0, t0);
+ tcg_gen_ext8u_i32(t0, t0); /* t0 = ...a */
}
if (flags & TCG_BSWAP_OS) {
- tcg_gen_shli_i32(t1, arg, 24);
- tcg_gen_sari_i32(t1, t1, 16);
+ tcg_gen_shli_i32(t1, arg, 24); /* t1 = b... */
+ tcg_gen_sari_i32(t1, t1, 16); /* t1 = ssb. */
} else if (flags & TCG_BSWAP_OZ) {
- tcg_gen_ext8u_i32(t1, arg);
- tcg_gen_shli_i32(t1, t1, 8);
+ tcg_gen_ext8u_i32(t1, arg); /* t1 = ...b */
+ tcg_gen_shli_i32(t1, t1, 8); /* t1 = ..b. */
} else {
- tcg_gen_shli_i32(t1, arg, 8);
+ tcg_gen_shli_i32(t1, arg, 8); /* t1 = xab. */
}
- tcg_gen_or_i32(ret, t0, t1);
+ tcg_gen_or_i32(ret, t0, t1); /* ret = ..ba (OZ) */
+ /* = ssba (OS) */
+ /* = xaba (no flag) */
tcg_temp_free_i32(t0);
tcg_temp_free_i32(t1);
}
--
2.34.1