x86-64: special case LEA when determining signedness of displacement

LEA behavior without a 64-bit destination is independent of address size
- in particular LEA with 32-bit addressing and 64-bit destination is the
same as LEA with 64-bit addressing and 32-bit destination. IOW checking
merely i.prefix[ADDR_PREFIX] is insufficient. This also means wrong
relocation types (R_X86_64_32S when R_X86_64_32 is needed) were used so
far in such cases.

Note that in one case in build_modrm_byte() the 64-bit check came too
early altogether, and hence gets dropped in favor of the one included in
the new helper. This is benign to non-64-bit code from all I can tell,
but the failure to clear disp16 could have been a latent problem.

diff --git a/gas/ChangeLog b/gas/ChangeLog
index aeacaa6b0fb34e72f504b39147e9428dda7fa02c..7fe07770b61a6815c2d4bc8825f9126d4db75d5a 100644 (file)
--- a/gas/ChangeLog
+++ b/gas/ChangeLog
@@ -1,3 +1,10 @@
+2021-04-23  Jan Beulich  <jbeulich@suse.com>
+
+       * config/tc-i386.c (want_disp32): New.
+       (md_assemble): Use it.
+       (optimize_disp): Likewise.
+       (build_modrm_byte): Likewise.
+
 2021-04-23  Jan Beulich  <jbeulich@suse.com>
 
        * config/tc-i386.c (i386_finalize_displacement): Move Disp32S

diff --git a/gas/config/tc-i386.c b/gas/config/tc-i386.c
index 8098f5045f941313746a5fd11bbdf16cb00451f0..dc1ee881a203075b6283ae88ab248a8bd66de659 100644 (file)
--- a/gas/config/tc-i386.c
+++ b/gas/config/tc-i386.c
@@ -3555,6 +3555,16 @@ tc_i386_fix_adjustable (fixS *fixP ATTRIBUTE_UNUSED)
   return 1;
 }
 
+static INLINE bool
+want_disp32 (const insn_template *t)
+{
+  return flag_code != CODE_64BIT
+        || i.prefix[ADDR_PREFIX]
+        || (t->base_opcode == 0x8d
+            && t->opcode_modifier.opcodespace == SPACE_BASE
+            && !i.types[1].bitfield.qword);
+}
+
 static int
 intel_float_operand (const char *mnemonic)
 {
@@ -4740,7 +4750,7 @@ md_assemble (char *line)
   if (i.imm_operands)
     optimize_imm ();
 
-  if (i.disp_operands && flag_code == CODE_64BIT && !i.prefix[ADDR_PREFIX])
+  if (i.disp_operands && !want_disp32 (current_templates->start))
     {
       for (j = 0; j < i.operands; ++j)
        {
@@ -5748,7 +5758,7 @@ optimize_disp (void)
 #ifdef BFD64
            else if (flag_code == CODE_64BIT)
              {
-               if (i.prefix[ADDR_PREFIX]
+               if (want_disp32 (current_templates->start)
                    && fits_in_unsigned_long (op_disp))
                  i.types[op].bitfield.disp32 = 1;
 
@@ -8108,7 +8118,7 @@ build_modrm_byte (void)
                  i.types[op].bitfield.disp8 = 0;
                  i.types[op].bitfield.disp16 = 0;
                  i.types[op].bitfield.disp64 = 0;
-                 if (flag_code != CODE_64BIT || i.prefix[ADDR_PREFIX])
+                 if (want_disp32 (&i.tm))
                    {
                      /* Must be 32 bit */
                      i.types[op].bitfield.disp32 = 1;
@@ -8159,7 +8169,7 @@ build_modrm_byte (void)
                      i.rm.regmem = ESCAPE_TO_TWO_BYTE_ADDRESSING;
                      i.sib.base = NO_BASE_REGISTER;
                      i.sib.index = NO_INDEX_REGISTER;
-                     newdisp = (!i.prefix[ADDR_PREFIX] ? disp32s : disp32);
+                     newdisp = (want_disp32(&i.tm) ? disp32 : disp32s);
                    }
                  else if ((flag_code == CODE_16BIT)
                           ^ (i.prefix[ADDR_PREFIX] != 0))
@@ -8188,7 +8198,7 @@ build_modrm_byte (void)
                  i.types[op].bitfield.disp8 = 0;
                  i.types[op].bitfield.disp16 = 0;
                  i.types[op].bitfield.disp64 = 0;
-                 if (flag_code != CODE_64BIT || i.prefix[ADDR_PREFIX])
+                 if (want_disp32 (&i.tm))
                    {
                      /* Must be 32 bit */
                      i.types[op].bitfield.disp32 = 1;
@@ -8263,12 +8273,11 @@ build_modrm_byte (void)
            }
          else /* i.base_reg and 32/64 bit mode  */
            {
-             if (flag_code == CODE_64BIT
-                 && operand_type_check (i.types[op], disp))
+             if (operand_type_check (i.types[op], disp))
                {
                  i.types[op].bitfield.disp16 = 0;
                  i.types[op].bitfield.disp64 = 0;
-                 if (i.prefix[ADDR_PREFIX] == 0)
+                 if (!want_disp32 (&i.tm))
                    {
                      i.types[op].bitfield.disp32 = 0;
                      i.types[op].bitfield.disp32s = 1;