tcg: Add flags argument to bswap opcodes

This will eventually simplify front-end usage, and will allow
backends to unset TCG_TARGET_HAS_MEMORY_BSWAP without loss of
optimization.

The argument is added during expansion, not currently exposed to the
front end translators.  The backends currently only support a flags
value of either TCG_BSWAP_IZ, or (TCG_BSWAP_IZ | TCG_BSWAP_OZ),
since they all require zero top bytes and leave them that way.
At the existing call sites we pass in (TCG_BSWAP_IZ | TCG_BSWAP_OZ),
except for the flags-ignored cases of a 32-bit swap of a 32-bit
value and or a 64-bit swap of a 64-bit value, where we pass 0.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

1 files changed, 12 insertions, 0 deletions

diff --git a/include/tcg/tcg.h b/include/tcg/tcg.h
index 2dad364240..899493701c 100644
--- a/include/tcg/tcg.h
+++ b/include/tcg/tcg.h
@@ -408,6 +408,18 @@ typedef TCGv_ptr TCGv_env;
 /* Used to align parameters.  See the comment before tcgv_i32_temp.  */
 #define TCG_CALL_DUMMY_ARG      ((TCGArg)0)
 
+/*
+ * Flags for the bswap opcodes.
+ * If IZ, the input is zero-extended, otherwise unknown.
+ * If OZ or OS, the output is zero- or sign-extended respectively,
+ * otherwise the high bits are undefined.
+ */
+enum {
+    TCG_BSWAP_IZ = 1,
+    TCG_BSWAP_OZ = 2,
+    TCG_BSWAP_OS = 4,
+};
+
 typedef enum TCGTempVal {
     TEMP_VAL_DEAD,
     TEMP_VAL_REG,