or1k: Fix issue with set_got clobbering LR (r9)

When compiling glibc we found that the GOT register was being allocated
r9 when the instruction was still set_got_tmp.  That is a problem
because r9 is the Link Register (LR) in OpenRISC which is used/clobbered
in set_got.  We cannot use r9 as the GOT register.  Also, we cannot
simply say set_got_tmp clobbers r9 as this is the reason for having the
temporary set_got_tmp.

Fix by using a register class constraint that does not allow r9 during
register allocation.

gcc/ChangeLog:

        * config/or1k/constraints.md (t): New constraint.
        * config/or1k/or1k.h (GOT_REGS): New register class.
        * config/or1k/or1k.md (set_got_tmp, set_got): Use t contraint.

From-SVN: r275242

gcc/ChangeLog

+2019-08-31  Stafford Horne  <shorne@gmail.com>
+
+	* config/or1k/constraints.md (t): New constraint.
+	* config/or1k/or1k.h (GOT_REGS): New register class.
+	* config/or1k/or1k.md (set_got_tmp, set_got): Use t contraint.
+
 2019-08-30  Jim Wilson  <jimw@sifive.com>
 
 	* config/riscv/riscv.c (riscv_option_override): If -msave-restore

gcc/config/or1k/constraints.md

@@ -25,6 +25,7 @@
 ; We use:
 ;  c - sibcall registers
 ;  d - double pair base registers (excludes r0, r30 and r31 which overflow)
+;  t - got address registers (excludes LR (r9) which is clobbered by set_got)
 ;  I - constant signed 16-bit
 ;  K - constant unsigned 16-bit
 ;  M - constant signed 16-bit shifted left 16-bits (l.movhi)
@@ -36,6 +37,9 @@
 (define_register_constraint "d" "DOUBLE_REGS"
   "Registers which can be used for double reg pairs.")
 
+(define_register_constraint "t" "GOT_REGS"
+  "Registers which can be used to store the Global Offset Table (GOT) address.")
+
 ;; Immediates
 (define_constraint "I"
   "A signed 16-bit immediate in the range -32768 to 32767."

gcc/config/or1k/or1k.h

@@ -190,6 +190,7 @@ enum reg_class
   NO_REGS,
   SIBCALL_REGS,
   DOUBLE_REGS,
+  GOT_REGS,
   GENERAL_REGS,
   FLAG_REGS,
   ALL_REGS,
@@ -202,6 +203,7 @@ enum reg_class
   "NO_REGS", 			\
   "SIBCALL_REGS",		\
   "DOUBLE_REGS",		\
+  "GOT_REGS",			\
   "GENERAL_REGS",		\
   "FLAG_REGS",			\
   "ALL_REGS" }
@@ -215,6 +217,7 @@ enum reg_class
 { { 0x00000000, 0x00000000 },	\
   { SIBCALL_REGS_MASK,   0 },	\
   { 0x7f7ffffe, 0x00000000 },	\
+  { 0xfffffdff, 0x00000000 },	\
   { 0xffffffff, 0x00000003 },	\
   { 0x00000000, 0x00000004 },	\
   { 0xffffffff, 0x00000007 }	\

gcc/config/or1k/or1k.md

@@ -706,7 +706,7 @@
 ;; set_got pattern below.  This works because the set_got_tmp insn is the
 ;; first insn in the stream and that it isn't moved during RA.
 (define_insn "set_got_tmp"
-  [(set (match_operand:SI 0 "register_operand" "=r")
+  [(set (match_operand:SI 0 "register_operand" "=t")
 	(unspec_volatile:SI [(const_int 0)] UNSPECV_SET_GOT))]
   ""
 {
@@ -715,7 +715,7 @@
 
 ;; The insn to initialize the GOT.
 (define_insn "set_got"
-  [(set (match_operand:SI 0 "register_operand" "=r")
+  [(set (match_operand:SI 0 "register_operand" "=t")
 	(unspec:SI [(const_int 0)] UNSPEC_SET_GOT))
    (clobber (reg:SI LR_REGNUM))]
   ""