[Bug target/119164] RISC-V: Extra FRM read/writes around call insns

[vineetg at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119164

--- Comment #2 from Vineet Gupta <vineetg at gcc dot gnu.org> ---
I tried to address the first issue by changing the helper called to identify
call as end of insn (in the presence of the label) - I hope that is the right
direction.

Anyways per IRC chat, someone suggested following

@@ -12144,9 +12144,7 @@ riscv_frm_mode_needed (rtx_insn *cur_insn, int code)

   if (CALL_P (cur_insn))
     {
-      rtx_insn *insn = next_nonnote_nondebug_insn_bb (cur_insn);
-      if (!insn)
+      if (BB_END (BLOCK_FOR_INSN (cur_insn)) == cur_insn)
        riscv_frm_emit_after_bb_end (cur_insn);

This started generating the FRM insn and with following fixup to
TARGET_MODE_AFTER hook, the test no longer generates extra frms.

@@ -12328,7 +12328,15 @@ riscv_frm_mode_after (rtx_insn *insn, int mode)


   if (reg_mentioned_p (gen_rtx_REG (SImode, FRM_REGNUM), PATTERN (insn)))
-    return get_attr_frm_mode (insn);
+    {
+      mode = get_attr_frm_mode (insn);
+      if (mode == riscv_vector::FRM_NONE)
+        {
+         rtx_insn *prev_insn = prev_nonnote_nondebug_insn_bb (insn);
+         if (prev_insn && CALL_P (prev_insn))
+           mode = riscv_vector::FRM_DYN;
+        }
+    }
   else
     return mode;