rs6000: Make CSE'ing __tls_get_addr calls possible

CSE does not consider calls, not even const calls.  This patch puts a
REG_EQUAL note on the pseudo we assign the __tls_get_addr result to,
so that those pseudos can be CSE'd and the extra calls deleted as dead
code.

CSE should really handle const calls directly, but it is stage 4.


	* config/rs6000/rs6000.c (rs6000_legitimize_tls_address): Add REG_EQUAL
	notes for the result of the __tls_get_addr calls.
	* config/rs6000/rs6000.md (unspec UNSPEC_TLS_GET_ADDR): New.

From-SVN: r269902

gcc/ChangeLog

-2019-03-26  Jeff Law  <law@redhat.com>
+2019-03-24  Segher Boessenkool  <segher@kernel.crashing.org>
+
+	* config/rs6000/rs6000.c (rs6000_legitimize_tls_address): Add REG_EQUAL
+	notes for the result of the __tls_get_addr calls.
+	* config/rs6000/rs6000.md (unspec UNSPEC_TLS_GET_ADDR): New.
+
+2019-03-24  Jeff Law  <law@redhat.com>
 
 	* config/bfin/bfin.md (movpdi): Fix length for alternative 1.
 

gcc/config/rs6000/rs6000.c

@@ -8785,6 +8785,11 @@ rs6000_legitimize_tls_address (rtx addr, enum tls_model model)
 	  else
 	    emit_library_call_value (tga, dest, LCT_CONST, Pmode);
 	  global_tlsarg = NULL_RTX;
+
+	  /* Make a note so that the result of this call can be CSEd.  */
+	  rtvec vec = gen_rtvec (1, copy_rtx (arg));
+	  rtx uns = gen_rtx_UNSPEC (Pmode, vec, UNSPEC_TLS_GET_ADDR);
+	  set_unique_reg_note (get_last_insn (), REG_EQUAL, uns);
 	}
       else if (model == TLS_MODEL_LOCAL_DYNAMIC)
 	{
@@ -8803,6 +8808,11 @@ rs6000_legitimize_tls_address (rtx addr, enum tls_model model)
 	    emit_library_call_value (tga, tmp1, LCT_CONST, Pmode);
 	  global_tlsarg = NULL_RTX;
 
+	  /* Make a note so that the result of this call can be CSEd.  */
+	  rtvec vec = gen_rtvec (1, copy_rtx (arg));
+	  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 (TARGET_64BIT)

gcc/config/rs6000/rs6000.md

@@ -79,6 +79,7 @@
    UNSPEC_MPIC_CORRECT		; macho_correct_pic
    UNSPEC_TLSGD
    UNSPEC_TLSLD
+   UNSPEC_TLS_GET_ADDR
    UNSPEC_MOVESI_FROM_CR
    UNSPEC_MOVESI_TO_CR
    UNSPEC_TLSDTPREL