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[i386,MPX,2/X] Pointers Checker [21/25] Size relocation

Message ID 20131120123259.GA53216@msticlxl57.ims.intel.com
State New
Headers show

Commit Message

Ilya Enkovich Nov. 20, 2013, 12:32 p.m. UTC 
On 20 Nov 09:49, Uros Bizjak wrote:
> On Tue, Nov 19, 2013 at 9:43 PM, Ilya Enkovich <enkovich.gnu@gmail.com> wrote:
> 
> >> > Here is a patch to add size relocation and instruction to obtain object's size in i386 target.
> >>
> >> +(define_insn "move_size_reloc_<mode>"
> >> +  [(set (match_operand:SWI48 0 "register_operand" "=r")
> >> +        (match_operand:<MODE> 1 "size_relocation" "Z"))]
> >> +  ""
> >> +{
> >> +  return "mov{<imodesuffix>}\t{%1, %0|%0, %1}";
> >>
> >> Please don't change x86_64_immediate_operand just to use "Z"
> >> constraint The predicate is used in a couple of other places that for
> >> sure don't accept your change.
> >>
> >> Better write this insn in an explicit way (see for example
> >> tls_initial_exec_64_sun). Something like:
> >>
> >> (define_insn "move_size_reloc_<mode>"
> >>   [(set (match_operand:SWI48 0 "register_operand" "=r")
> >>     (unspec:SWI48
> >>      [(match_operand 1 "symbolic_operand" "..." )]
> >>      UNSPEC_SIZEOF))]
> >>   ""
> >>   "mov{<imodesuffix>}\t{%a1@SIZE, %0|%0, %a1@SIZE}")
> >>
> >> You will probably need to define new operand 1 predicate and constraint.
> >>
> >> Uros.
> >
> > Hi, Uros!  Thanks for comments!  Here is what I got trying to follow your suggestion.  Does it look better?
> 
> You actually don't need any operand modifiers in the insn template. Simply use:
> 
> "mov{<imodesuffix>}\t{%1@SIZE, %0|%0, %1@SIZE}"
> 
> and you will automatically get
> 
> "movl $zzz, %eax" or "mov %eax, OFFSET FLAT: zzz".
> 
> Since your pattern allows only symbolic_operand, there is no reload,
> so you can avoid the constraint alltogether.
> 
> BTW: Did you consider various -mcmodel=... options? For DImode moves,
> you should check x86_64_zext_immediate_operand predicate and output
> either "movl $zzz, %eax" or "movabs $zzz, %rax". There is no movq with
> 64bit immediate. Please see movdi pattern.
> 
> Uros.

Yep, for large objects it may work wrongly. Does anyone use static objects >4Gb? :)

Large address does not mean large object but seems we have to be conservative here. I added  x86_64_zext_immediate_operand check with additional CM_KERNEL check because in this model object size should always fit 32 bits.

Thanks,
Ilya
--

gcc/

2013-11-19  Ilya Enkovich  <ilya.enkovich@intel.com>

	* config/i386/i386.md (UNSPEC_SIZEOF): New.
	(move_size_reloc_<mode>): New.
	* config/i386/predicates.md (symbol_operand): New.
diff mbox

Patch

diff --git a/gcc/config/i386/constraints.md b/gcc/config/i386/constraints.md
index 7289ae4..b29fadb 100644
--- a/gcc/config/i386/constraints.md
+++ b/gcc/config/i386/constraints.md
@@ -241,6 +241,7 @@ 
 ;;   s - address with no segment register
 ;;   i - address with no index and no rip
 ;;   b - address with no base and no rip
+;;   S - symbol reference
 
 (define_address_constraint "Tv"
   "VSIB address operand"
diff --git a/gcc/config/i386/i386.md b/gcc/config/i386/i386.md
index e23b3b6..772c09d 100644
--- a/gcc/config/i386/i386.md
+++ b/gcc/config/i386/i386.md
@@ -79,6 +79,7 @@ 
   UNSPEC_PLTOFF
   UNSPEC_MACHOPIC_OFFSET
   UNSPEC_PCREL
+  UNSPEC_SIZEOF
 
   ;; Prologue support
   UNSPEC_STACK_ALLOC
@@ -18446,6 +18447,22 @@ 
   "bndstx\t{%2, %3|%3, %2}"
   [(set_attr "type" "mpxst")])
 
+(define_insn "move_size_reloc_<mode>"
+  [(set (match_operand:SWI48 0 "register_operand" "=r")
+	(unspec:<MODE>
+	 [(match_operand:<MODE> 1 "symbol_operand")]
+	 UNSPEC_SIZEOF))]
+  ""
+{
+  if (GET_MODE (operands[0]) == SImode)
+    return "mov{l}\t{%1@SIZE, %k0|%k0, %1@SIZE}";
+  else if (x86_64_zext_immediate_operand (operands[1], VOIDmode)
+	   || ix86_cmodel == CM_KERNEL)
+    return "mov{q}\t{%1@SIZE, %0|%0, %1@SIZE}";
+  else
+    return "movabs{q}\t{%1@SIZE, %0|%0, %1@SIZE}";
+})
+
 (include "mmx.md")
 (include "sse.md")
 (include "sync.md")
diff --git a/gcc/config/i386/predicates.md b/gcc/config/i386/predicates.md
index 66ac52f..5c758ab 100644
--- a/gcc/config/i386/predicates.md
+++ b/gcc/config/i386/predicates.md
@@ -119,6 +119,10 @@ 
        (match_test "TARGET_64BIT")
        (match_test "REGNO (op) > BX_REG")))
 
+;; Return true if VALUE is symbol reference
+(define_predicate "symbol_operand"
+  (match_code "symbol_ref"))
+
 ;; Return true if VALUE can be stored in a sign extended immediate field.
 (define_predicate "x86_64_immediate_operand"
   (match_code "const_int,symbol_ref,label_ref,const")