[PATCH] use use_reg in several backends

[Nathan Froyd]

Several places in the compiler could be usefully modified to use use_reg
instead of hand-building EXPR_LISTs.  This patch makes such changes.

Since this patch implements equivalent functionality with an existing
function call, I believe it counts as obvious.

Tested by building cc1 for appropriate targets.  Will commit in a day or
two after giving maintainers a chance for comments.

-Nathan

        * config/alpha/alpha.c (alpha_emit_xfloating_libcall): Call use_reg.
        * config/xtensa/xtensa.c (xtensa_call_tls_desc): Likewise.
        * config/sparc/sparc.c (sparc_legitimize_tls_address): Likewise.

diff --git a/gcc/config/alpha/alpha.c b/gcc/config/alpha/alpha.c
index 8aabeb2..d34042e 100644
--- a/gcc/config/alpha/alpha.c
+++ b/gcc/config/alpha/alpha.c
@@ -2999,7 +2999,7 @@ alpha_emit_xfloating_libcall (rtx func, rtx target, rtx 
operands[],
        }
 
       emit_move_insn (reg, operands[i]);
-      usage = alloc_EXPR_LIST (0, gen_rtx_USE (VOIDmode, reg), usage);
+      use_reg (&usage, reg);
     }
 
   switch (GET_MODE (target))
diff --git a/gcc/config/xtensa/xtensa.c b/gcc/config/xtensa/xtensa.c
index 5623cc1..fe70270 100644
--- a/gcc/config/xtensa/xtensa.c
+++ b/gcc/config/xtensa/xtensa.c
@@ -1872,9 +1872,7 @@ xtensa_call_tls_desc (rtx sym, rtx *retp)
   emit_insn (gen_tls_arg (arg, sym));
   emit_move_insn (a10, arg);
   call_insn = emit_call_insn (gen_tls_call (a10, fn, sym, const1_rtx));
-  CALL_INSN_FUNCTION_USAGE (call_insn)
-    = gen_rtx_EXPR_LIST (VOIDmode, gen_rtx_USE (VOIDmode, a10),
-                        CALL_INSN_FUNCTION_USAGE (call_insn));
+  use_reg (&CALL_INSN_FUNCTION_USAGE (call_insn), a10);
   insns = get_insns ();
   end_sequence ();

diff --git a/gcc/config/sparc/sparc.c b/gcc/config/sparc/sparc.c
index 1e7ce53..ecb4d25 100644
--- a/gcc/config/sparc/sparc.c
+++ b/gcc/config/sparc/sparc.c
@@ -3308,9 +3308,7 @@ sparc_legitimize_tls_address (rtx addr)
            insn = emit_call_insn (gen_tgd_call64 (o0, sparc_tls_get_addr (),
                                                   addr, const1_rtx));
          }
-        CALL_INSN_FUNCTION_USAGE (insn)
-         = gen_rtx_EXPR_LIST (VOIDmode, gen_rtx_USE (VOIDmode, o0),
-                              CALL_INSN_FUNCTION_USAGE (insn));
+       use_reg (&CALL_INSN_FUNCTION_USAGE (insn), o0);
        insn = get_insns ();
        end_sequence ();
        emit_libcall_block (insn, ret, o0, addr);
@@ -3338,9 +3336,7 @@ sparc_legitimize_tls_address (rtx addr)
            insn = emit_call_insn (gen_tldm_call64 (o0, sparc_tls_get_addr (),
                                                    const1_rtx));
          }
-        CALL_INSN_FUNCTION_USAGE (insn)
-         = gen_rtx_EXPR_LIST (VOIDmode, gen_rtx_USE (VOIDmode, o0),
-                              CALL_INSN_FUNCTION_USAGE (insn));
+       use_reg (&CALL_INSN_FUNCTION_USAGE (insn), o0);
        insn = get_insns ();
        end_sequence ();
        emit_libcall_block (insn, temp3, o0,