On 26/10/23 03:39, Richard Henderson wrote:
A release build should simply accept and emit the subtract.
I'm not even sure if this is reasonable to keep for debug.
Not-Signed-off-by: Richard Henderson <richard.hender...@linaro.org>
---
tcg/tcg.c | 49 ++++++++++++++++++++++++++-------------
tcg/i386/tcg-target.c.inc | 13 ++++++++---
2 files changed, 43 insertions(+), 19 deletions(-)
diff --git a/tcg/tcg.c b/tcg/tcg.c
index a507c111cf..408647af7e 100644
--- a/tcg/tcg.c
+++ b/tcg/tcg.c
@@ -3618,23 +3618,40 @@ liveness_pass_1(TCGContext *s)
do_addsub2:
nb_iargs = 4;
nb_oargs = 2;
- /* Test if the high part of the operation is dead, but not
- the low part. The result can be optimized to a simple
- add or sub. This happens often for x86_64 guest when the
- cpu mode is set to 32 bit. */
- if (arg_temp(op->args[1])->state == TS_DEAD) {
- if (arg_temp(op->args[0])->state == TS_DEAD) {
- goto do_remove;
- }
- /* Replace the opcode and adjust the args in place,
- leaving 3 unused args at the end. */
- op->opc = opc = opc_new;
- op->args[1] = op->args[2];
- op->args[2] = op->args[4];
- /* Fall through and mark the single-word operation live. */
- nb_iargs = 2;
- nb_oargs = 1;
+ /*
+ * Test if the high part of the operation is dead, but the low
+ * part is still live. The result can be optimized to a simple
+ * add or sub.
+ */
+ if (arg_temp(op->args[1])->state != TS_DEAD) {
+ goto do_not_remove;
}
+ if (arg_temp(op->args[0])->state == TS_DEAD) {
+ goto do_remove;
+ }
+ /*
+ * Replace the opcode and adjust the args in place, leaving 3
+ * unused args at the end. Canonicalize subi to andi.
Typo s/andi/addi/.
+ */
+ op->args[1] = op->args[2];
+ {
+ TCGTemp *src2 = arg_temp(op->args[4]);
+ if (src2->kind == TEMP_CONST) {
+ if (opc_new == INDEX_op_sub_i32) {
+ src2 = tcg_constant_internal(TCG_TYPE_I32,
+ (int32_t)-src2->val);
+ opc_new = INDEX_op_add_i32;
+ } else if (opc_new == INDEX_op_sub_i64) {
+ src2 = tcg_constant_internal(TCG_TYPE_I64, -src2->val);
+ opc_new = INDEX_op_add_i64;
+ }
+ }
+ op->args[2] = temp_arg(src2);
+ }
+ op->opc = opc = opc_new;
+ /* Mark the single-word operation live. */
+ nb_iargs = 2;
+ nb_oargs = 1;
goto do_not_remove;
For tcg/tcg.c with your S-o-b and a reworded description:
Reviewed-by: Philippe Mathieu-Daudé <phi...@linaro.org>
