tcg: Document INDEX_mul[us]h_*

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

diff --git a/tcg/README b/tcg/README
index bb2ea5121bb51e86c244f9536c82a50748a72371..a5237a9edb6601b9fd2b62e086d4864d1fd37a9d 100644 (file)
--- a/tcg/README
+++ b/tcg/README
@@ -431,6 +431,14 @@ double-word product T0.  The later is returned in two single-word outputs.
 
 Similar to mulu2, except the two inputs T1 and T2 are signed.
 
+* mulsh_i32/i64 t0, t1, t2
+* muluh_i32/i64 t0, t1, t2
+
+Provide the high part of a signed or unsigned multiply, respectively.
+If mulu2/muls2 are not provided by the backend, the tcg-op generator
+can obtain the same results can be obtained by emitting a pair of
+opcodes, mul+muluh/mulsh.
+
 ********* Memory Barrier support
 
 * mb <$arg>