i386: Fix infinite loop under -mrelax-cmpxchg-loop [PR 103069]

For -mrelax-cmpxchg-loop which relaxes atomic_fetch_<logic> loops,
there is a missing set to %eax when compare fails, which would result
in infinite loop in some benchmark. Add set to %eax to avoid it.

gcc/ChangeLog:

	PR target/103069
	* config/i386/i386-expand.cc (ix86_expand_cmpxchg_loop):
	  Add missing set to target_val at pause label.

diff --git a/gcc/config/i386/i386-expand.cc b/gcc/config/i386/i386-expand.cc
index 677059b..68978ef 100644 (file)
--- a/gcc/config/i386/i386-expand.cc
+++ b/gcc/config/i386/i386-expand.cc
@@ -23405,6 +23405,7 @@ ix86_expand_cmpxchg_loop (rtx *ptarget_bool, rtx target_val,
 
     /* If mem is not expected, pause and loop back.  */
     emit_label (cmp_label);
+    emit_move_insn (target_val, new_mem);
     emit_insn (gen_pause ());
     emit_jump_insn (gen_jump (loop_label));
     emit_barrier ();