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PATCH: Support .quad for x32

H.J. Lu hjl.tools@gmail.com
Tue Mar 29 12:51:00 GMT 2011 
On Tue, Mar 29, 2011 at 1:35 AM, Jan Beulich <JBeulich@novell.com> wrote:
>>>> On 29.03.11 at 00:51, "H.J. Lu" <hongjiu.lu@intel.com> wrote:
>> Hi,
>>
>> For this testcase:
>>
>> ---
>> union U
>> {
>>   int *m;
>>   double d;
>> };
>>
>> extern int xxxx;
>>
>> int
>> foo (union U u)
>> {
>>   union U v = { &xxxx};
>>   return u.d == v.d;
>> }
>> ---
>>
>> We can generate
>>
>> foo:
>> .LFB0:
>>       .cfi_startproc
>>       movq    %rdi, -8(%rsp)
>>       movsd   .LC0(%rip), %xmm1
>>       movsd   -8(%rsp), %xmm0
>>       movl    $1, %eax
>>       ucomisd %xmm1, %xmm0
>>       jp      .L3
>>       jne     .L3
>>       rep
>>       ret
>>       .p2align 4,,10
>>       .p2align 3
>> .L3:
>>       xorl    %eax, %eax
>>       .p2align 4,,9
>>       ret
>>       .cfi_endproc
>> .LFE0:
>>       .size   foo, .-foo
>>       .section        .rodata.cst8,"aM",@progbits,8
>>       .align 8
>> .LC0:
>>       .quad   xxxx
>
> Looks more like a compiler bug than something that needs fixing in

Reload generates 64bit symbol address in constant pool.  I decided it
is a nice optimization for x32.  Otherwise, we have to do it like ia32. See:

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47958

> binutils. If programming in assembly, using .quad may be intended

handle_quad has

  if (x86_elf_abi != X86_64_X32_ABI)
    {
      cons (nbytes);
      return;
    }

It only applies to x32.

> to generate wider than 32-bit relocs (e.g. when xxxx is a
> constant in another translation unit). Yes, with the bogus tying
> of the 32-bit ABI to the ELF object bit size (thus causing only
> 32-bit relocation forms to be used) that's sort of difficult to
> achieve, but not impossible (global constant with less than 32 bits
> plus addend with less than 32 bits).
>
> Additionally, I think the change isn't correct either:
>
>> I checked in this patch to allow .quad for x32.
>>
>>
...
>
> ... but then you zero-extend only the last one?
>

Thanks for noticing it.  I checked in this patch to fix it.

-- 
H.J.
----
diff --git a/gas/ChangeLog b/gas/ChangeLog
index 7c5b705..4275767 100644
--- a/gas/ChangeLog
+++ b/gas/ChangeLog
@@ -1,3 +1,8 @@
+2011-03-29  H.J. Lu  <hongjiu.lu@intel.com>
+
+	* config/tc-i386.c (handle_quad): Properly handle multiple
+	operands.
+
 2011-03-29  Mike Frysinger  <vapier@gentoo.org>

 	* config/bfin-parse.y (BYTEUNPACK): Return yyerror when dest
diff --git a/gas/config/tc-i386.c b/gas/config/tc-i386.c
index 624c78a..aa345b5 100644
--- a/gas/config/tc-i386.c
+++ b/gas/config/tc-i386.c
@@ -9182,19 +9182,19 @@ handle_quad (int nbytes)
       if (exp.X_op != O_constant)
 	nbytes = 4;
       emit_expr (&exp, (unsigned int) nbytes);
+      /* Zero-extends to 8 bytes if not constant.  */
+      if (nbytes == 4)
+	{
+	  memset (&exp, '\0', sizeof (exp));
+	  exp.X_op = O_constant;
+	  emit_expr (&exp, nbytes);
+	}
+      nbytes = 8;
     }
   while (*input_line_pointer++ == ',');

   input_line_pointer--;		/* Put terminator back into stream.  */

   demand_empty_rest_of_line ();
-
-  /* Zero-extends to 8 bytes if not constant.  */
-  if (nbytes == 4)
-    {
-      memset (&exp, '\0', sizeof (exp));
-      exp.X_op = O_constant;
-      emit_expr (&exp, nbytes);
-    }
 }
 #endif /* OBJ_ELF || OBJ_MAYBE_ELF */
diff --git a/gas/testsuite/ChangeLog b/gas/testsuite/ChangeLog
index 2101e9f..51502ee 100644
--- a/gas/testsuite/ChangeLog
+++ b/gas/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2011-03-29  H.J. Lu  <hongjiu.lu@intel.com>
+
+	* gas/i386/ilp32/quad.d: Add tests for multiple operands.
+	* gas/i386/ilp32/quad.s: Likewise.
+
 2011-03-29  Mike Frysinger  <vapier@gentoo.org>

 	* gas/bfin/expected_errors.s: Add invalid BYTEUNPACK insn tests.
diff --git a/gas/testsuite/gas/i386/ilp32/quad.d
b/gas/testsuite/gas/i386/ilp32/quad.d
index d3e6ff8..6f8a6c6 100644
--- a/gas/testsuite/gas/i386/ilp32/quad.d
+++ b/gas/testsuite/gas/i386/ilp32/quad.d
@@ -7,8 +7,12 @@ RELOCATION RECORDS FOR \[.data\]:
 OFFSET +TYPE +VALUE
 0+ R_X86_64_32 +foo
 0+10 R_X86_64_32 +bar
+0+20 R_X86_64_32 +foo
+0+30 R_X86_64_32 +bar


 Contents of section .data:
  0000 00000000 00000000 efcdab90 78674512  ............xgE.
  0010 00000000 00000000 ffffffff ffffffff  ................
+ 0020 00000000 00000000 efcdab90 78674512  ............xgE.
+ 0030 00000000 00000000 ffffffff ffffffff  ................
diff --git a/gas/testsuite/gas/i386/ilp32/quad.s
b/gas/testsuite/gas/i386/ilp32/quad.s
index e96653a..a14304d 100644
--- a/gas/testsuite/gas/i386/ilp32/quad.s
+++ b/gas/testsuite/gas/i386/ilp32/quad.s
@@ -3,3 +3,4 @@
 	.quad 0x1245677890abcdef
 	.quad bar
 	.quad -1
+	.quad foo, 0x1245677890abcdef, bar, -1
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