bpf: improve memmove inlining [PR122140]

The BPF backend inline memmove expansion was broken for certain
constructs.  This patch addresses the two underlying issues:
1. Off-by-one in the "backwards" unrolled move loop offset.
2. Poor use of temporary register for the generated move loop, which
   could result in some of the loads performing the move to be optimized
   away when the source and destination of the memmove are based off of
   the same pointer.

gcc/

	PR target/122140
	* config/bpf/bpf.cc (bpf_expand_cpymem): Fix off-by-one offset
	in backwards loop.  Improve src and dest addrs used for the
	branch condition.
	(emit_move_loop): Improve emitted set insns and remove the
	explict temporary register.

diff --git a/gcc/config/bpf/bpf.cc b/gcc/config/bpf/bpf.cc
index a28018b3367214b255712fd0ada0e333b0b2036a..39168f689aca5cbb62d553817b63ed66d17688e6 100644 (file)
--- a/gcc/config/bpf/bpf.cc
+++ b/gcc/config/bpf/bpf.cc
@@ -1252,13 +1252,11 @@ static void
 emit_move_loop (rtx src, rtx dst, machine_mode mode, int offset, int inc,
                unsigned iters, unsigned remainder)
 {
-  rtx reg = gen_reg_rtx (mode);
-
   /* First copy in chunks as large as alignment permits.  */
   for (unsigned int i = 0; i < iters; i++)
     {
-      emit_move_insn (reg, adjust_address (src, mode, offset));
-      emit_move_insn (adjust_address (dst, mode, offset), reg);
+      emit_insn (gen_rtx_SET (adjust_address (dst, mode, offset),
+                             adjust_address (src, mode, offset)));
       offset += inc;
     }
 
@@ -1266,22 +1264,22 @@ emit_move_loop (rtx src, rtx dst, machine_mode mode, int offset, int inc,
      used above.  */
   if (remainder & 4)
     {
-      emit_move_insn (reg, adjust_address (src, SImode, offset));
-      emit_move_insn (adjust_address (dst, SImode, offset), reg);
+      emit_insn (gen_rtx_SET (adjust_address (dst, SImode, offset),
+                             adjust_address (src, SImode, offset)));
       offset += (inc < 0 ? -4 : 4);
       remainder -= 4;
     }
   if (remainder & 2)
     {
-      emit_move_insn (reg, adjust_address (src, HImode, offset));
-      emit_move_insn (adjust_address (dst, HImode, offset), reg);
+      emit_insn (gen_rtx_SET (adjust_address (dst, HImode, offset),
+                             adjust_address (src, HImode, offset)));
       offset += (inc < 0 ? -2 : 2);
       remainder -= 2;
     }
   if (remainder & 1)
     {
-      emit_move_insn (reg, adjust_address (src, QImode, offset));
-      emit_move_insn (adjust_address (dst, QImode, offset), reg);
+      emit_insn (gen_rtx_SET (adjust_address (dst, QImode, offset),
+                             adjust_address (src, QImode, offset)));
     }
 }
 
@@ -1351,13 +1349,13 @@ bpf_expand_cpymem (rtx *operands, bool is_move)
       fwd_label = gen_label_rtx ();
       done_label = gen_label_rtx ();
 
-      rtx dst_addr = copy_to_mode_reg (Pmode, XEXP (dst, 0));
-      rtx src_addr = copy_to_mode_reg (Pmode, XEXP (src, 0));
+      rtx src_addr = force_operand (XEXP (src, 0), NULL_RTX);
+      rtx dst_addr = force_operand (XEXP (dst, 0), NULL_RTX);
       emit_cmp_and_jump_insns (src_addr, dst_addr, GEU, NULL_RTX, Pmode,
                               true, fwd_label, profile_probability::even ());
 
       /* Emit the "backwards" unrolled loop.  */
-      emit_move_loop (src, dst, mode, size_bytes, -inc, iters, remainder);
+      emit_move_loop (src, dst, mode, (size_bytes - 1), -inc, iters, remainder);
       emit_jump_insn (gen_jump (done_label));
       emit_barrier ();