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.
+ */
+ 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;
case INDEX_op_mulu2_i32:
diff --git a/tcg/i386/tcg-target.c.inc b/tcg/i386/tcg-target.c.inc
index 0d97864174..39d03fa698 100644
--- a/tcg/i386/tcg-target.c.inc
+++ b/tcg/i386/tcg-target.c.inc
@@ -2544,8 +2544,14 @@ static inline void tcg_out_op(TCGContext *s, TCGOpcode
opc,
c = ARITH_ADD;
goto gen_arith;
OP_32_64(sub):
- c = ARITH_SUB;
- goto gen_arith;
+ /*
+ * Should have canonicalized all constants to add.
+ * Keep the constraint allowing any constant so that we catch this
+ * case without register allocation loading the constant first.
+ */
+ tcg_debug_assert(!const_a2);
+ tgen_arithr(s, ARITH_SUB + rexw, a0, a2);
+ break;
OP_32_64(and):
c = ARITH_AND;
goto gen_arith;
@@ -3325,7 +3331,6 @@ static TCGConstraintSetIndex tcg_target_op_def(TCGOpcode
op)
return C_O1_I2(r, r, re);
case INDEX_op_sub_i32:
- case INDEX_op_sub_i64:
case INDEX_op_mul_i32:
case INDEX_op_mul_i64:
case INDEX_op_or_i32:
@@ -3333,6 +3338,8 @@ static TCGConstraintSetIndex tcg_target_op_def(TCGOpcode
op)
case INDEX_op_xor_i32:
case INDEX_op_xor_i64:
return C_O1_I2(r, 0, re);
+ case INDEX_op_sub_i64:
+ return C_O1_I2(r, 0, ri);
case INDEX_op_and_i32:
case INDEX_op_and_i64:
--
2.34.1
