According to PR: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110751
As Richard and Richi suggested, we recognize uninitialized SSA_NAME and convert
it
into SCRATCH rtx if the target predicate allows SCRATCH.
It can help to reduce redundant data move instructions of targets like RISC-V.
Here we add the condition "insn_operand_matches (icode, opno, scratch)"
Then, we will only create scratch rtx that target allow scratch rtx in
predicate.
When the target doesn't allow scratch rtx in predicate, the later "else"
condtion
will create fresh pseudo for uninitialized SSA.
I have verify it in RISC-V port and it works well.
Bootstrap and Regression on X86 passed.
Ok for trunk ?
gcc/ChangeLog:
* internal-fn.cc (expand_fn_using_insn): Convert uninitialized SSA into
scratch.
---
gcc/internal-fn.cc | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/gcc/internal-fn.cc b/gcc/internal-fn.cc
index 0fd34359247..fe4d86b3dbd 100644
--- a/gcc/internal-fn.cc
+++ b/gcc/internal-fn.cc
@@ -243,10 +243,16 @@ expand_fn_using_insn (gcall *stmt, insn_code icode,
unsigned int noutputs,
tree rhs = gimple_call_arg (stmt, i);
tree rhs_type = TREE_TYPE (rhs);
rtx rhs_rtx = expand_normal (rhs);
+ rtx scratch = gen_rtx_SCRATCH (TYPE_MODE (rhs_type));
if (INTEGRAL_TYPE_P (rhs_type))
create_convert_operand_from (&ops[opno], rhs_rtx,
TYPE_MODE (rhs_type),
TYPE_UNSIGNED (rhs_type));
+ else if (TREE_CODE (rhs) == SSA_NAME
+ && SSA_NAME_IS_DEFAULT_DEF (rhs)
+ && VAR_P (SSA_NAME_VAR (rhs))
+ && insn_operand_matches (icode, opno, scratch))
+ create_input_operand (&ops[opno], scratch, TYPE_MODE (rhs_type));
else
create_input_operand (&ops[opno], rhs_rtx, TYPE_MODE (rhs_type));
opno += 1;
--
2.36.3
