[PATCH] MIPS16: Mark $2/$3 as clobbered if GP is used

[PATCH] MIPS16: Mark $2/$3 as clobbered if GP is used

[YunQiang Su]

PR Target/84790.
The gp init sequence
        li      $2,%hi(_gp_disp)
        addiu   $3,$pc,%lo(_gp_disp)
        sll     $2,16
        addu    $2,$3
is generated directly in `mips_output_function_prologue`, and does
not appear in the RTL.

So the IRA/IPA passes are not aware that $2/$3 have been clobbered,
so they may be used for cross (local) function call.

Let's mark $2/$3 clobber both:
  - Just after the UNSPEC_GP RTL of a function;
  - Just after a function call.

Reported-by: Matthias Schiffer <mschiffer@universe-factory.net>
Origin-Patch-by: Felix Fietkau <nbd@nbd.name>.

gcc
	* config/mips/mips.cc(mips16_gp_pseudo_reg): Mark
	MIPS16_PIC_TEMP and MIPS_PROLOGUE_TEMP clobbered.
	(mips_emit_call_insn): Mark MIPS16_PIC_TEMP and
	MIPS_PROLOGUE_TEMP clobbered if MIPS16 and CALL_CLOBBERED_GP.
---
 gcc/config/mips/mips.cc | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/gcc/config/mips/mips.cc b/gcc/config/mips/mips.cc
index b63d40a357b..b478cddc8ad 100644
--- a/gcc/config/mips/mips.cc
+++ b/gcc/config/mips/mips.cc
@@ -3233,6 +3233,9 @@ mips_emit_call_insn (rtx pattern, rtx orig_addr, rtx addr, bool lazy_p)
     {
       rtx post_call_tmp_reg = gen_rtx_REG (word_mode, POST_CALL_TMP_REG);
       clobber_reg (&CALL_INSN_FUNCTION_USAGE (insn), post_call_tmp_reg);
+      clobber_reg (&CALL_INSN_FUNCTION_USAGE (insn), MIPS16_PIC_TEMP);
+      clobber_reg (&CALL_INSN_FUNCTION_USAGE (insn),
+			MIPS_PROLOGUE_TEMP (word_mode));
     }
 
   return insn;
@@ -3329,7 +3332,13 @@ mips16_gp_pseudo_reg (void)
       rtx set = gen_load_const_gp (cfun->machine->mips16_gp_pseudo_rtx);
       rtx_insn *insn = emit_insn_after (set, scan);
       INSN_LOCATION (insn) = 0;
-
+      /* NewABI support hasn't been implement.  NewABI should generate RTL
+	 sequence instead of ASM sequence directly.  */
+      if (mips_current_loadgp_style () == LOADGP_OLDABI)
+	{
+	  emit_clobber (MIPS16_PIC_TEMP);
+	  emit_clobber (MIPS_PROLOGUE_TEMP (Pmode));
+	}
       pop_topmost_sequence ();
     }
 
-- 
2.39.2