[RS6000] PC-relative TLS support

Supporting TLS for -mpcrel turns out to be relatively simple.  The
existing TLSGD and TLSLD unspecs happily can have their GOT pointer
reg element replaced with zero, refelecting the fact that optimisation
of calls to __tls_get_addr when pc-rel won't use the GOT pointer.
Some other insns also can be reused, and just a few added.

	* config/rs6000/predicates.md (unspec_tls): Allow const0_rtx for got
	element of unspec vec.
	* config/rs6000/rs6000.c (rs6000_legitimize_tls_address): Support
	PC-relative TLS.
	* config/rs6000/rs6000.md (UNSPEC_TLSTLS_PCREL): New unspec.
	(tls_gd_pcrel, tls_ld_pcrel): New insns.
	(tls_dtprel, tls_tprel): Set attr prefixed when tls_size is not 16.
	(tls_got_tprel_pcrel, tls_tls_pcrel): New insns.

From-SVN: r278076

4 files changed, 72 insertions, 8 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 4fdb911ab8b..4a38e5459b4 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,5 +1,16 @@
 2019-11-12  Alan Modra  <amodra@gmail.com>
 
+	* config/rs6000/predicates.md (unspec_tls): Allow const0_rtx for got
+	element of unspec vec.
+	* config/rs6000/rs6000.c (rs6000_legitimize_tls_address): Support
+	PC-relative TLS.
+	* config/rs6000/rs6000.md (UNSPEC_TLSTLS_PCREL): New unspec.
+	(tls_gd_pcrel, tls_ld_pcrel): New insns.
+	(tls_dtprel, tls_tprel): Set attr prefixed when tls_size is not 16.
+	(tls_got_tprel_pcrel, tls_tls_pcrel): New insns.
+
+2019-11-12  Alan Modra  <amodra@gmail.com>
+
 	* config/rs6000/rs6000.opt (mtls-markers): Delete.
 	* config/rs6000/rs6000.h (TARGET_TLS_MARKERS): Don't define.
 	(IS_NOMARK_TLSGETADDR): Likewise.
diff --git a/gcc/config/rs6000/predicates.md b/gcc/config/rs6000/predicates.md
index b5c510f99f2..f4ecc4193ef 100644
--- a/gcc/config/rs6000/predicates.md
+++ b/gcc/config/rs6000/predicates.md
@@ -986,9 +986,9 @@
   if (CONST_INT_P (op))
     return 1;
   if (XINT (op, 1) == UNSPEC_TLSGD)
-    return REG_P (XVECEXP (op, 0, 1));
+    return REG_P (XVECEXP (op, 0, 1)) || XVECEXP (op, 0, 1) == const0_rtx;
   if (XINT (op, 1) == UNSPEC_TLSLD)
-    return REG_P (XVECEXP (op, 0, 0));
+    return REG_P (XVECEXP (op, 0, 0)) || XVECEXP (op, 0, 0) == const0_rtx;
   return 0;
 })
 
diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index 892ee94032f..32101b77ea3 100644
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -8518,7 +8518,8 @@ rs6000_legitimize_tls_address (rtx addr, enum tls_model model)
     return rs6000_legitimize_tls_address_aix (addr, model);
 
   dest = gen_reg_rtx (Pmode);
-  if (model == TLS_MODEL_LOCAL_EXEC && rs6000_tls_size == 16)
+  if (model == TLS_MODEL_LOCAL_EXEC
+      && (rs6000_tls_size == 16 || rs6000_pcrel_p (cfun)))
     {
       rtx tlsreg;
 
@@ -8565,7 +8566,9 @@ rs6000_legitimize_tls_address (rtx addr, enum tls_model model)
 	 them in the .got section.  So use a pointer to the .got section,
 	 not one to secondary TOC sections used by 64-bit -mminimal-toc,
 	 or to secondary GOT sections used by 32-bit -fPIC.  */
-      if (TARGET_64BIT)
+      if (rs6000_pcrel_p (cfun))
+	got = const0_rtx;
+      else if (TARGET_64BIT)
 	got = gen_rtx_REG (Pmode, 2);
       else
 	{
@@ -8628,7 +8631,7 @@ rs6000_legitimize_tls_address (rtx addr, enum tls_model model)
 	  rtx uns = gen_rtx_UNSPEC (Pmode, vec, UNSPEC_TLS_GET_ADDR);
 	  set_unique_reg_note (get_last_insn (), REG_EQUAL, uns);
 
-	  if (rs6000_tls_size == 16)
+	  if (rs6000_tls_size == 16 || rs6000_pcrel_p (cfun))
 	    {
 	      if (TARGET_64BIT)
 		insn = gen_tls_dtprel_64 (dest, tmp1, addr);
@@ -8669,7 +8672,14 @@ rs6000_legitimize_tls_address (rtx addr, enum tls_model model)
 	  else
 	    insn = gen_tls_got_tprel_32 (tmp2, got, addr);
 	  emit_insn (insn);
-	  if (TARGET_64BIT)
+	  if (rs6000_pcrel_p (cfun))
+	    {
+	      if (TARGET_64BIT)
+		insn = gen_tls_tls_pcrel_64 (dest, tmp2, addr);
+	      else
+		insn = gen_tls_tls_pcrel_32 (dest, tmp2, addr);
+	    }
+	  else if (TARGET_64BIT)
 	    insn = gen_tls_tls_64 (dest, tmp2, addr);
 	  else
 	    insn = gen_tls_tls_32 (dest, tmp2, addr);
diff --git a/gcc/config/rs6000/rs6000.md b/gcc/config/rs6000/rs6000.md
index 0fc0f952611..cbfe38bef94 100644
--- a/gcc/config/rs6000/rs6000.md
+++ b/gcc/config/rs6000/rs6000.md
@@ -86,6 +86,7 @@
    UNSPEC_TLSTPRELLO
    UNSPEC_TLSGOTTPREL
    UNSPEC_TLSTLS
+   UNSPEC_TLSTLS_PCREL
    UNSPEC_FIX_TRUNC_TF		; fadd, rounding towards zero
    UNSPEC_STFIWX
    UNSPEC_POPCNTB
@@ -9495,6 +9496,15 @@
 
 ;; TLS support.
 
+(define_insn "*tls_gd_pcrel<bits>"
+  [(set (match_operand:P 0 "gpc_reg_operand" "=b")
+	(unspec:P [(match_operand:P 1 "rs6000_tls_symbol_ref" "")
+		   (const_int 0)]
+		  UNSPEC_TLSGD))]
+  "HAVE_AS_TLS && TARGET_ELF"
+  "la %0,%1@got@tlsgd@pcrel"
+  [(set_attr "prefixed" "yes")])
+
 (define_insn_and_split "*tls_gd<bits>"
   [(set (match_operand:P 0 "gpc_reg_operand" "=b")
 	(unspec:P [(match_operand:P 1 "rs6000_tls_symbol_ref" "")
@@ -9535,6 +9545,14 @@
   "HAVE_AS_TLS && TARGET_ELF && TARGET_CMODEL != CMODEL_SMALL"
   "addi %0,%1,%2@got@tlsgd@l")
 
+(define_insn "*tls_ld_pcrel<bits>"
+  [(set (match_operand:P 0 "gpc_reg_operand" "=b")
+	(unspec:P [(const_int 0)]
+		  UNSPEC_TLSLD))]
+  "HAVE_AS_TLS && TARGET_ELF"
+  "la %0,%&@got@tlsld@pcrel"
+  [(set_attr "prefixed" "yes")])
+
 (define_insn_and_split "*tls_ld<bits>"
   [(set (match_operand:P 0 "gpc_reg_operand" "=b")
 	(unspec:P [(match_operand:P 1 "gpc_reg_operand" "b")]
@@ -9578,7 +9596,11 @@
 		   (match_operand:P 2 "rs6000_tls_symbol_ref" "")]
 		  UNSPEC_TLSDTPREL))]
   "HAVE_AS_TLS"
-  "addi %0,%1,%2@dtprel")
+  "addi %0,%1,%2@dtprel"
+  [(set (attr "prefixed")
+	(if_then_else (match_test "rs6000_tls_size == 16")
+		      (const_string "no")
+		      (const_string "yes")))])
 
 (define_insn "tls_dtprel_ha_<bits>"
   [(set (match_operand:P 0 "gpc_reg_operand" "=r")
@@ -9642,7 +9664,11 @@
 		   (match_operand:P 2 "rs6000_tls_symbol_ref" "")]
 		  UNSPEC_TLSTPREL))]
   "HAVE_AS_TLS"
-  "addi %0,%1,%2@tprel")
+  "addi %0,%1,%2@tprel"
+  [(set (attr "prefixed")
+	(if_then_else (match_test "rs6000_tls_size == 16")
+		      (const_string "no")
+		      (const_string "yes")))])
 
 (define_insn "tls_tprel_ha_<bits>"
   [(set (match_operand:P 0 "gpc_reg_operand" "=r")
@@ -9660,6 +9686,15 @@
   "HAVE_AS_TLS"
   "addi %0,%1,%2@tprel@l")
 
+(define_insn "*tls_got_tprel_pcrel_<bits>"
+  [(set (match_operand:P 0 "gpc_reg_operand" "=b")
+	(unspec:P [(const_int 0)
+		   (match_operand:P 1 "rs6000_tls_symbol_ref" "")]
+		  UNSPEC_TLSGOTTPREL))]
+  "HAVE_AS_TLS"
+  "<ptrload> %0,%1@got@tprel@pcrel"
+  [(set_attr "prefixed" "yes")])
+
 ;; "b" output constraint here and on tls_tls input to support linker tls
 ;; optimization.  The linker may edit the instructions emitted by a
 ;; tls_got_tprel/tls_tls pair to addis,addi.
@@ -9703,6 +9738,14 @@
   "HAVE_AS_TLS && TARGET_CMODEL != CMODEL_SMALL"
   "<ptrload> %0,%2@got@tprel@l(%1)")
 
+(define_insn "tls_tls_pcrel_<bits>"
+  [(set (match_operand:P 0 "gpc_reg_operand" "=r")
+	(unspec:P [(match_operand:P 1 "gpc_reg_operand" "b")
+		   (match_operand:P 2 "rs6000_tls_symbol_ref" "")]
+		  UNSPEC_TLSTLS_PCREL))]
+  "TARGET_ELF && HAVE_AS_TLS"
+  "add %0,%1,%2@tls@pcrel")
+
 (define_insn "tls_tls_<bits>"
   [(set (match_operand:P 0 "gpc_reg_operand" "=r")
 	(unspec:P [(match_operand:P 1 "gpc_reg_operand" "b")