[PATCH v1] RISC-V: Bugfix for merging undef tmp register for trunc

[pan2 . li]

From: Pan Li <pan2...@intel.com>

For trunc function autovec, there will be one step like below take MU
for the merge operand.

rtx tmp = gen_reg_rtx (vec_int_mode);
emit_vec_cvt_x_f_rtz (tmp, op_1, mask, vec_fp_mode);

The MU will leave the tmp (aka dest register) register unmasked elements
unchanged and it is undefined here. This patch would like to adjust the
MU to MA.

gcc/ChangeLog:

        * config/riscv/riscv-v.cc (emit_vec_cvt_x_f_rtz): Add insn type
        arg.
        (expand_vec_trunc): Take MA instead of MU for cvt_x_f_rtz.

Signed-off-by: Pan Li <pan2...@intel.com>
---
 gcc/config/riscv/riscv-v.cc | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/gcc/config/riscv/riscv-v.cc b/gcc/config/riscv/riscv-v.cc
index 91ad6a61fa8..fb6a4e561db 100644
--- a/gcc/config/riscv/riscv-v.cc
+++ b/gcc/config/riscv/riscv-v.cc
@@ -4144,12 +4144,20 @@ emit_vec_cvt_f_x (rtx op_dest, rtx op_src, rtx mask,
 
 static void
 emit_vec_cvt_x_f_rtz (rtx op_dest, rtx op_src, rtx mask,
-                     machine_mode vec_mode)
+                     insn_type type, machine_mode vec_mode)
 {
-  rtx cvt_x_ops[] = {op_dest, mask, op_dest, op_src};
   insn_code icode = code_for_pred (FIX, vec_mode);
 
-  emit_vlmax_insn (icode, UNARY_OP_TAMU, cvt_x_ops);
+  if (type & USE_VUNDEF_MERGE_P)
+    {
+      rtx cvt_x_ops[] = {op_dest, mask, op_src};
+      emit_vlmax_insn (icode, type, cvt_x_ops);
+    }
+  else
+    {
+      rtx cvt_x_ops[] = {op_dest, mask, op_dest, op_src};
+      emit_vlmax_insn (icode, type, cvt_x_ops);
+    }
 }
 
 void
@@ -4285,7 +4293,7 @@ expand_vec_trunc (rtx op_0, rtx op_1, machine_mode 
vec_fp_mode,
 
   /* Step-3: Convert to integer on mask, rounding to zero (aka truncate).  */
   rtx tmp = gen_reg_rtx (vec_int_mode);
-  emit_vec_cvt_x_f_rtz (tmp, op_1, mask, vec_fp_mode);
+  emit_vec_cvt_x_f_rtz (tmp, op_1, mask, UNARY_OP_TAMA, vec_fp_mode);
 
   /* Step-4: Convert to floating-point on mask for the rint result.  */
   emit_vec_cvt_f_x (op_0, tmp, mask, UNARY_OP_TAMU_FRM_DYN, vec_fp_mode);
-- 
2.34.1