diff mbox series

[5/6] x86: adjust NOP generation after potential non-insn

Message ID 6186c042-e778-470f-a995-1522aca041ea@suse.com
State Unresolved
Headers
Series correct and further utilize x86'es last-insn tracking |

Checks

Context Check Description
snail/binutils-gdb-check warning Git am fail log

Commit Message

Jan Beulich Nov. 24, 2023, 9:05 a.m. UTC 
  Just like avoiding to do certain transformations potentially affected by
stand-alone prefixes or direct data emission, also avoid emitting
optimized NOPs right afterwards; insert a plain old NOP first in such
cases.
diff mbox series

Patch

--- a/gas/config/tc-i386.c
+++ b/gas/config/tc-i386.c
@@ -1529,6 +1529,14 @@  i386_generate_nops (fragS *fragP, char *
   else if (fragP->fr_type != rs_machine_dependent)
     fragP->fr_var = count;
 
+  /* Emit a plain NOP first when the last thing we saw may not have been
+     a proper instruction (e.g. a stand-alone prefix or .byte).  */
+  if (!fragP->tc_frag_data.last_insn_normal)
+    {
+      *where++ = 0x90;
+      --count;
+    }
+
   if ((count / max_single_nop_size) > max_number_of_nops)
     {
       /* Generate jump over NOPs.  */
--- a/gas/config/tc-i386.h
+++ b/gas/config/tc-i386.h
@@ -321,6 +321,7 @@  struct i386_tc_frag_data
   unsigned int branch_type : 3;
   unsigned int cpunop : 1;
   unsigned int isanop : 1;
+  unsigned int last_insn_normal : 1;
 };
 
 /* We need to emit the right NOP pattern in .align frags.  This is
@@ -347,7 +348,10 @@  struct i386_tc_frag_data
      (FRAGP)->tc_frag_data.cmp_size = 0;			\
      (FRAGP)->tc_frag_data.classified = 0;			\
      (FRAGP)->tc_frag_data.branch_type = 0;			\
-     (FRAGP)->tc_frag_data.mf_type = 0;			\
+     (FRAGP)->tc_frag_data.mf_type = 0;				\
+     (FRAGP)->tc_frag_data.last_insn_normal			\
+	= (seg_info(now_seg)->tc_segment_info_data.last_insn.kind \
+	   == last_insn_other);					\
    }								\
  while (0)