[amdgcn] Use first lane of v1 for zero offset

Use v1 instead of v0 when a zero-valued VGPR is needed.  This frees up
v0 for other purposes.

2019-11-15  Kwok Cheung Yeung  <kcy@codesourcery.com>

	gcc/
	* config/gcn/gcn.c (gcn_expand_prologue): Remove initialization and
	prologue use of v0.
	(print_operand_address): Use v1 for zero vector offset.

From-SVN: r278297

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 619afc5..1e32d49 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+2019-11-15  Kwok Cheung Yeung  <kcy@codesourcery.com>
+
+       gcc/
+       * config/gcn/gcn.c (gcn_expand_prologue): Remove initialization and
+       prologue use of v0.
+       (print_operand_address): Use v1 for zero vector offset.
+
 2019-11-15  Richard Sandiford  <richard.sandiford@arm.com>
 
        PR tree-optimization/92515

diff --git a/gcc/config/gcn/gcn.c b/gcc/config/gcn/gcn.c
index f12d06d..4f72758 100644 (file)
--- a/gcc/config/gcn/gcn.c
+++ b/gcc/config/gcn/gcn.c
@@ -2803,15 +2803,6 @@ gcn_expand_prologue ()
                                     cfun->machine->args.
                                     reg[PRIVATE_SEGMENT_WAVE_OFFSET_ARG]);
 
-      if (TARGET_GCN5_PLUS)
-       {
-         /* v0 is reserved for constant zero so that "global"
-            memory instructions can have a nul-offset without
-            causing reloads.  */
-         emit_insn (gen_vec_duplicatev64si
-                    (gen_rtx_REG (V64SImode, VGPR_REGNO (0)), const0_rtx));
-       }
-
       if (cfun->machine->args.requested & (1 << FLAT_SCRATCH_INIT_ARG))
        {
          rtx fs_init_lo =
@@ -2870,8 +2861,6 @@ gcn_expand_prologue ()
                  gen_int_mode (LDS_SIZE, SImode));
 
   emit_insn (gen_prologue_use (gen_rtx_REG (SImode, M0_REG)));
-  if (TARGET_GCN5_PLUS)
-    emit_insn (gen_prologue_use (gen_rtx_REG (SImode, VGPR_REGNO (0))));
 
   if (cfun && cfun->machine && !cfun->machine->normal_function && flag_openmp)
     {
@@ -5327,9 +5316,9 @@ print_operand_address (FILE *file, rtx mem)
              /* The assembler requires a 64-bit VGPR pair here, even though
                 the offset should be only 32-bit.  */
              if (vgpr_offset == NULL_RTX)
-               /* In this case, the vector offset is zero, so we use v0,
-                  which is initialized by the kernel prologue to zero.  */
-               fprintf (file, "v[0:1]");
+               /* In this case, the vector offset is zero, so we use the first
+                  lane of v1, which is initialized to zero.  */
+               fprintf (file, "v[1:2]");
              else if (REG_P (vgpr_offset)
                       && VGPR_REGNO_P (REGNO (vgpr_offset)))
                {