The input which overlaps the sign bit of the output can
have its input s_mask propagated to the output s_mask.

Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 tcg/optimize.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/tcg/optimize.c b/tcg/optimize.c
index 0f7c2c810e..b6a0bfe64e 100644
--- a/tcg/optimize.c
+++ b/tcg/optimize.c
@@ -1613,8 +1613,9 @@ static bool fold_deposit(OptContext *ctx, TCGOp *op)
     TempOptInfo *t2 = arg_info(op->args[2]);
     int ofs = op->args[3];
     int len = op->args[4];
+    int width;
     TCGOpcode and_opc;
-    uint64_t z_mask;
+    uint64_t z_mask, s_mask;
 
     if (t1->is_const && t2->is_const) {
         return tcg_opt_gen_movi(ctx, op, op->args[0],
@@ -1624,9 +1625,11 @@ static bool fold_deposit(OptContext *ctx, TCGOp *op)
     switch (ctx->type) {
     case TCG_TYPE_I32:
         and_opc = INDEX_op_and_i32;
+        width = 32;
         break;
     case TCG_TYPE_I64:
         and_opc = INDEX_op_and_i64;
+        width = 64;
         break;
     default:
         g_assert_not_reached();
@@ -1651,8 +1654,15 @@ static bool fold_deposit(OptContext *ctx, TCGOp *op)
         return fold_and(ctx, op);
     }
 
+    /* The s_mask from the top portion of the deposit is still valid. */
+    if (ofs + len == width) {
+        s_mask = t2->s_mask << ofs;
+    } else {
+        s_mask = t1->s_mask & ~MAKE_64BIT_MASK(0, ofs + len);
+    }
+
     z_mask = deposit64(t1->z_mask, ofs, len, t2->z_mask);
-    return fold_masks_z(ctx, op, z_mask);
+    return fold_masks_zs(ctx, op, z_mask, s_mask);
 }
 
 static bool fold_divide(OptContext *ctx, TCGOp *op)
-- 
2.43.0