From 806973409adc48c8ca701d55fdbad897b0e31c78 Mon Sep 17 00:00:00 2001
From: Dominik Vogt <vogt@linux.vnet.ibm.com>
Date: Fri, 11 Dec 2015 11:33:23 +0100
Subject: [PATCH] S/390: Allow to use r1 to r4 as literal pool base
 pointer.

The old code only considered r5 and r13.
---
 gcc/config/s390/s390.c | 61 +++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 48 insertions(+), 13 deletions(-)

diff --git a/gcc/config/s390/s390.c b/gcc/config/s390/s390.c
index bc6f05b..c45b992 100644
--- a/gcc/config/s390/s390.c
+++ b/gcc/config/s390/s390.c
@@ -9506,6 +9506,26 @@ s390_frame_info (void)
 				  & ~(STACK_BOUNDARY / BITS_PER_UNIT - 1));
 }
 
+/* Returns the register number that is used as a temp register in the prologue.
+ */
+static int
+s390_get_prologue_temp_regno (void)
+{
+  if (!has_hard_reg_initial_val (Pmode, RETURN_REGNUM)
+      && !crtl->is_leaf
+      && !TARGET_TPF_PROFILING)
+    return RETURN_REGNUM;
+  if (cfun_save_high_fprs_p)
+    /* Needs an address register.  */
+    return 1;
+  else if (TARGET_BACKCHAIN)
+    /* Does not need an address register.  */
+    return 0;
+
+  /* No temp register needed.  */
+  return -1;
+}
+
 /* Generate frame layout.  Fills in register and frame data for the current
    function in cfun->machine.  This routine can be called multiple times;
    it will re-do the complete frame layout every time.  */
@@ -9543,10 +9563,24 @@ s390_init_frame_layout (void)
 	 as base register to avoid save/restore overhead.  */
       if (!base_used)
 	cfun->machine->base_reg = NULL_RTX;
-      else if (crtl->is_leaf && !df_regs_ever_live_p (5))
-	cfun->machine->base_reg = gen_rtx_REG (Pmode, 5);
       else
-	cfun->machine->base_reg = gen_rtx_REG (Pmode, BASE_REGNUM);
+	{
+	  int br = 0;
+
+	  if (crtl->is_leaf)
+	    {
+	      int temp_regno;
+
+	      temp_regno = s390_get_prologue_temp_regno ();
+	      /* Prefer r5 (most likely to be free).  */
+	      for (br = 5;
+		   br >= 1 && (br == temp_regno || df_regs_ever_live_p (br));
+		   br--)
+		;
+	    }
+	  cfun->machine->base_reg =
+	    gen_rtx_REG (Pmode, (br > 0) ? br : BASE_REGNUM);
+	}
 
       s390_register_info ();
       s390_frame_info ();
@@ -10385,19 +10419,16 @@ s390_emit_prologue (void)
 {
   rtx insn, addr;
   rtx temp_reg;
+  int temp_regno;
   int i;
   int offset;
   int next_fpr = 0;
 
-  /* Choose best register to use for temp use within prologue.
-     See below for why TPF must use the register 1.  */
-
-  if (!has_hard_reg_initial_val (Pmode, RETURN_REGNUM)
-      && !crtl->is_leaf
-      && !TARGET_TPF_PROFILING)
-    temp_reg = gen_rtx_REG (Pmode, RETURN_REGNUM);
-  else
-    temp_reg = gen_rtx_REG (Pmode, 1);
+  /* If new uses of temp_reg are introduced into the prologue, be sure to
+     update the conditions in s390_get_prologue_temp_regno().  Otherwise the
+     prologue might overwrite the literal pool pointer in r1.  */
+  temp_regno = s390_get_prologue_temp_regno ();
+  temp_reg = (temp_regno >= 0) ? gen_rtx_REG (Pmode, temp_regno) : NULL_RTX;
 
   s390_save_gprs_to_fprs ();
 
@@ -10551,7 +10582,10 @@ s390_emit_prologue (void)
 
       /* Save incoming stack pointer into temp reg.  */
       if (TARGET_BACKCHAIN || next_fpr)
-	insn = emit_insn (gen_move_insn (temp_reg, stack_pointer_rtx));
+	{
+	  gcc_assert (temp_regno >= 0);
+	  insn = emit_insn (gen_move_insn (temp_reg, stack_pointer_rtx));
+	}
 
       /* Subtract frame size from stack pointer.  */
 
@@ -10606,6 +10640,7 @@ s390_emit_prologue (void)
 
   if (cfun_save_high_fprs_p && next_fpr)
     {
+      gcc_assert (temp_regno >= 1);
       /* If the stack might be accessed through a different register
 	 we have to make sure that the stack pointer decrement is not
 	 moved below the use of the stack slots.  */
-- 
2.3.0