[Qemu-devel] [PULL for-4.1 1/7] tcg: Fix constant folding of INDEX_op_extract2_i32

[Richard Henderson]

On a 64-bit host, discard any replications of the 32-bit
sign bit when performing the shift and merge.

Fixes: https://bugs.launchpad.net/bugs/1834496
Tested-by: Christophe Lyon <address@hidden>
Tested-by: Alex Bennée <address@hidden>
Reviewed-by: Alex Bennée <address@hidden>
Signed-off-by: Richard Henderson <address@hidden>
---
 tcg/optimize.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tcg/optimize.c b/tcg/optimize.c
index d7c71a6085..d2424de4af 100644
--- a/tcg/optimize.c
+++ b/tcg/optimize.c
@@ -1213,8 +1213,8 @@ void tcg_optimize(TCGContext *s)
                 if (opc == INDEX_op_extract2_i64) {
                     tmp = (v1 >> op->args[3]) | (v2 << (64 - op->args[3]));
                 } else {
-                    tmp = (v1 >> op->args[3]) | (v2 << (32 - op->args[3]));
-                    tmp = (int32_t)tmp;
+                    tmp = (int32_t)(((uint32_t)v1 >> op->args[3]) |
+                                    ((uint32_t)v2 << (32 - op->args[3])));
                 }
                 tcg_opt_gen_movi(s, op, op->args[0], tmp);
                 break;
-- 
2.17.1