RISC-V: Don't clobber retval when __builtin_eh_return called.

	gcc/
	* config/riscv/riscv-protos.h (riscv_expand_epilogue): Change bool arg
	to int.
	* config/riscv/riscv.c (riscv_for_each_saved_reg): New args epilogue
	and maybe_eh_return.  Change regno to unsigned int.  Use new args to
	handle EH_RETURN_DATA_REGNO registers properly.
	(riscv_expand_prologue): Pass new args to riscv_for_each_saved_reg.
	(riscv_expand_epilogue): Update comment.  Change argument name and
	type.  Update code to use new name and type.  Pass new args to
	riscv_for_each_saved_reg.  Only use EH_RETURN_STACKADJ_RTX when
	EXCEPTION_RETURN.
	* config/riscv/riscv.md (NORMAL_RETURN): New.
	(SIBCALL_RETURN, EXCEPTION_RETURN): New.
	(epilogue, sibcall_epilogue): Update riscv_expand_epilogue arg.
	(eh_return): Call gen_eh_return_internal and emit barrier.
	(eh_return_internal): Call riscv_expand_epilogue.

From-SVN: r261176

gcc/ChangeLog

+2018-06-04  Jim Wilson  <jimw@sifive.com>
+
+	* config/riscv/riscv-protos.h (riscv_expand_epilogue): Change bool arg
+	to int.
+	* config/riscv/riscv.c (riscv_for_each_saved_reg): New args epilogue
+	and maybe_eh_return.  Change regno to unsigned int.  Use new args to
+	handle EH_RETURN_DATA_REGNO registers properly.
+	(riscv_expand_prologue): Pass new args to riscv_for_each_saved_reg.
+	(riscv_expand_epilogue): Update comment.  Change argument name and
+	type.  Update code to use new name and type.  Pass new args to
+	riscv_for_each_saved_reg.  Only use EH_RETURN_STACKADJ_RTX when
+	EXCEPTION_RETURN.
+	* config/riscv/riscv.md (NORMAL_RETURN): New.
+	(SIBCALL_RETURN, EXCEPTION_RETURN): New.
+	(epilogue, sibcall_epilogue): Update riscv_expand_epilogue arg.
+	(eh_return): Call gen_eh_return_internal and emit barrier.
+	(eh_return_internal): Call riscv_expand_epilogue.
+
 2018-06-04  Eric Botcazou  <ebotcazou@adacore.com>
 
 	* gimple-ssa-store-merging.c (struct merged_store_group): Move up

gcc/config/riscv/riscv-protos.h

@@ -66,7 +66,7 @@ extern bool riscv_expand_block_move (rtx, rtx, rtx);
 extern rtx riscv_return_addr (int, rtx);
 extern HOST_WIDE_INT riscv_initial_elimination_offset (int, int);
 extern void riscv_expand_prologue (void);
-extern void riscv_expand_epilogue (bool);
+extern void riscv_expand_epilogue (int);
 extern bool riscv_epilogue_uses (unsigned int);
 extern bool riscv_can_use_return_insn (void);
 extern rtx riscv_function_value (const_tree, const_tree, enum machine_mode);

gcc/config/riscv/riscv.c

@@ -3502,23 +3502,45 @@ riscv_save_restore_reg (machine_mode mode, int regno,
    of the frame.  */
 
 static void
-riscv_for_each_saved_reg (HOST_WIDE_INT sp_offset, riscv_save_restore_fn fn)
+riscv_for_each_saved_reg (HOST_WIDE_INT sp_offset, riscv_save_restore_fn fn,
+			  bool epilogue, bool maybe_eh_return)
 {
   HOST_WIDE_INT offset;
 
   /* Save the link register and s-registers. */
   offset = cfun->machine->frame.gp_sp_offset - sp_offset;
-  for (int regno = GP_REG_FIRST; regno <= GP_REG_LAST; regno++)
+  for (unsigned int regno = GP_REG_FIRST; regno <= GP_REG_LAST; regno++)
     if (BITSET_P (cfun->machine->frame.mask, regno - GP_REG_FIRST))
       {
-	riscv_save_restore_reg (word_mode, regno, offset, fn);
+	bool handle_reg = TRUE;
+
+	/* If this is a normal return in a function that calls the eh_return
+	   builtin, then do not restore the eh return data registers as that
+	   would clobber the return value.  But we do still need to save them
+	   in the prologue, and restore them for an exception return, so we
+	   need special handling here.  */
+	if (epilogue && !maybe_eh_return && crtl->calls_eh_return)
+	  {
+	    unsigned int i, regnum;
+
+	    for (i = 0; (regnum = EH_RETURN_DATA_REGNO (i)) != INVALID_REGNUM;
+		 i++)
+	      if (regno == regnum)
+		{
+		  handle_reg = FALSE;
+		  break;
+		}
+	  }
+
+	if (handle_reg)
+	  riscv_save_restore_reg (word_mode, regno, offset, fn);
 	offset -= UNITS_PER_WORD;
       }
 
   /* This loop must iterate over the same space as its companion in
      riscv_compute_frame_info.  */
   offset = cfun->machine->frame.fp_sp_offset - sp_offset;
-  for (int regno = FP_REG_FIRST; regno <= FP_REG_LAST; regno++)
+  for (unsigned int regno = FP_REG_FIRST; regno <= FP_REG_LAST; regno++)
     if (BITSET_P (cfun->machine->frame.fmask, regno - FP_REG_FIRST))
       {
 	machine_mode mode = TARGET_DOUBLE_FLOAT ? DFmode : SFmode;
@@ -3694,7 +3716,7 @@ riscv_expand_prologue (void)
 			    GEN_INT (-step1));
       RTX_FRAME_RELATED_P (emit_insn (insn)) = 1;
       size -= step1;
-      riscv_for_each_saved_reg (size, riscv_save_reg);
+      riscv_for_each_saved_reg (size, riscv_save_reg, false, false);
     }
 
   frame->mask = mask; /* Undo the above fib.  */
@@ -3756,11 +3778,11 @@ riscv_adjust_libcall_cfi_epilogue ()
   return dwarf;
 }
 
-/* Expand an "epilogue" or "sibcall_epilogue" pattern; SIBCALL_P
-   says which.  */
+/* Expand an "epilogue", "sibcall_epilogue", or "eh_return_internal" pattern;
+   style says which.  */
 
 void
-riscv_expand_epilogue (bool sibcall_p)
+riscv_expand_epilogue (int style)
 {
   /* Split the frame into two.  STEP1 is the amount of stack we should
      deallocate before restoring the registers.  STEP2 is the amount we
@@ -3771,7 +3793,8 @@ riscv_expand_epilogue (bool sibcall_p)
   unsigned mask = frame->mask;
   HOST_WIDE_INT step1 = frame->total_size;
   HOST_WIDE_INT step2 = 0;
-  bool use_restore_libcall = !sibcall_p && riscv_use_save_libcall (frame);
+  bool use_restore_libcall = ((style == NORMAL_RETURN)
+			      && riscv_use_save_libcall (frame));
   rtx ra = gen_rtx_REG (Pmode, RETURN_ADDR_REGNUM);
   rtx insn;
 
@@ -3781,14 +3804,14 @@ riscv_expand_epilogue (bool sibcall_p)
 
   if (cfun->machine->naked_p)
     {
-      gcc_assert (!sibcall_p);
+      gcc_assert (style == NORMAL_RETURN);
 
       emit_jump_insn (gen_return ());
 
       return;
     }
 
-  if (!sibcall_p && riscv_can_use_return_insn ())
+  if ((style == NORMAL_RETURN) && riscv_can_use_return_insn ())
     {
       emit_jump_insn (gen_return ());
       return;
@@ -3863,7 +3886,8 @@ riscv_expand_epilogue (bool sibcall_p)
     frame->mask = 0; /* Temporarily fib that we need not save GPRs.  */
 
   /* Restore the registers.  */
-  riscv_for_each_saved_reg (frame->total_size - step2, riscv_restore_reg);
+  riscv_for_each_saved_reg (frame->total_size - step2, riscv_restore_reg,
+			    true, style == EXCEPTION_RETURN);
 
   if (use_restore_libcall)
     {
@@ -3902,14 +3926,14 @@ riscv_expand_epilogue (bool sibcall_p)
     }
 
   /* Add in the __builtin_eh_return stack adjustment. */
-  if (crtl->calls_eh_return)
+  if ((style == EXCEPTION_RETURN) && crtl->calls_eh_return)
     emit_insn (gen_add3_insn (stack_pointer_rtx, stack_pointer_rtx,
 			      EH_RETURN_STACKADJ_RTX));
 
   /* Return from interrupt.  */
   if (cfun->machine->interrupt_handler_p)
     emit_insn (gen_riscv_mret ());
-  else if (!sibcall_p)
+  else if (style != SIBCALL_RETURN)
     emit_jump_insn (gen_simple_return_internal (ra));
 }
 

gcc/config/riscv/riscv.md

@@ -73,6 +73,10 @@
    (S0_REGNUM			8)
    (S1_REGNUM			9)
    (S2_REGNUM			18)
+
+   (NORMAL_RETURN		0)
+   (SIBCALL_RETURN		1)
+   (EXCEPTION_RETURN		2)
 ])
 
 (include "predicates.md")
@@ -2036,7 +2040,7 @@
   [(const_int 2)]
   ""
 {
-  riscv_expand_epilogue (false);
+  riscv_expand_epilogue (NORMAL_RETURN);
   DONE;
 })
 
@@ -2044,7 +2048,7 @@
   [(const_int 2)]
   ""
 {
-  riscv_expand_epilogue (true);
+  riscv_expand_epilogue (SIBCALL_RETURN);
   DONE;
 })
 
@@ -2086,6 +2090,9 @@
     emit_insn (gen_eh_set_lr_di (operands[0]));
   else
     emit_insn (gen_eh_set_lr_si (operands[0]));
+
+  emit_jump_insn (gen_eh_return_internal ());
+  emit_barrier ();
   DONE;
 })
 
@@ -2114,6 +2121,14 @@
   DONE;
 })
 
+(define_insn_and_split "eh_return_internal"
+  [(eh_return)]
+  ""
+  "#"
+  "epilogue_completed"
+  [(const_int 0)]
+  "riscv_expand_epilogue (EXCEPTION_RETURN); DONE;")
+
 ;;
 ;;  ....................
 ;;