On 15 Apr 14:07, Ilya Enkovich wrote:
> 2015-04-14 8:22 GMT+03:00 Jeff Law <l...@redhat.com>:
> > On 03/15/2015 02:30 PM, Richard Sandiford wrote:
> >>
> >> Ilya Enkovich <enkovich....@gmail.com> writes:
> >>>
> >>> This patch allows propagation of loop invariants for i386 if propagated
> >>> value is a constant to be used in address operand. Bootstrapped and
> >>> tested on x86_64-unknown-linux-gnu. OK for trunk or stage 1?
> >>
> >>
> >> Is it necessary for this to be a target hook? The concept doesn't seem
> >> particularly target-specific. We should only propagate into the address
> >> if the new cost is no greater than the old cost, but if the address
> >> meets that condition and if propagating at this point in the pipeline is
> >> a win on x86, then wouldn't it be a win for other targets too?
> >
> > I agree with Richard here. I can't see a strong reason why this should be a
> > target hook.
> >
> > Perhaps part of the issue here is the address costing metrics may not have
> > enough context to make good decisions. In which case what context do they
> > need?
>
> At this point I don't insist on a target hook. The main reasoning was
> to not affect other targets. If we extend propagation for non constant
> values different aspects may appear. E.g. possible register pressure
> changes may significantly affect ia32. I just wanted to have an
> instrument to play with a propagation on x86 not affecting other
> targets. I don't have an opportunity to test possible performance
> implications on non-x86 targets. Don't expect (significant)
> regressions there but who knows...
>
> I'll remove the hook from this patch. Will probably introduce it later
> if some target specific cases are found.
>
> Thanks,
> Ilya
>
> >
> > Jeff
Here is a version with no hook. Bootstrapped and tested on
x86_64-unknown-linux-gnu. Is it OK for trunk?
Thanks,
Ilya
--
gcc/
2015-04-17 Ilya Enkovich <ilya.enkov...@intel.com>
PR target/65103
* fwprop.c (forward_propagate_into): Propagate loop
invariants if a target says so.
gcc/testsuite/
2015-04-17 Ilya Enkovich <ilya.enkov...@intel.com>
PR target/65103
* gcc.target/i386/pr65103-2.c: New.
diff --git a/gcc/fwprop.c b/gcc/fwprop.c
index fc64ec9..82ebd01 100644
--- a/gcc/fwprop.c
+++ b/gcc/fwprop.c
@@ -1365,8 +1365,18 @@ forward_propagate_into (df_ref use)
if (DF_REF_IS_ARTIFICIAL (def))
return false;
- /* Do not propagate loop invariant definitions inside the loop. */
- if (DF_REF_BB (def)->loop_father != DF_REF_BB (use)->loop_father)
+ def_insn = DF_REF_INSN (def);
+ if (multiple_sets (def_insn))
+ return false;
+ def_set = single_set (def_insn);
+ if (!def_set)
+ return false;
+
+ /* Do not propagate loop invariant definitions inside the loop.
+ Allow address constant propagation. */
+ if (DF_REF_BB (def)->loop_father != DF_REF_BB (use)->loop_father
+ && (DF_REF_TYPE (use) == DF_REF_REG_USE
+ || GET_CODE (SET_SRC (def_set)) != CONST))
return false;
/* Check if the use is still present in the insn! */
@@ -1379,13 +1389,6 @@ forward_propagate_into (df_ref use)
if (!reg_mentioned_p (DF_REF_REG (use), parent))
return false;
- def_insn = DF_REF_INSN (def);
- if (multiple_sets (def_insn))
- return false;
- def_set = single_set (def_insn);
- if (!def_set)
- return false;
-
/* Only try one kind of propagation. If two are possible, we'll
do it on the following iterations. */
if (forward_propagate_and_simplify (use, def_insn, def_set)
diff --git a/gcc/testsuite/gcc.target/i386/pr65103-2.c
b/gcc/testsuite/gcc.target/i386/pr65103-2.c
new file mode 100644
index 0000000..b7a32f7
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr65103-2.c
@@ -0,0 +1,24 @@
+/* { dg-do compile { target ia32 } } */
+/* { dg-require-effective-target pie } */
+/* { dg-options "-O2 -fPIE" } */
+/* { dg-final { scan-assembler-not "GOTOFF," } } */
+
+typedef struct S
+{
+ int a;
+ int b;
+} S;
+struct S gs;
+
+extern int compute ( struct S * );
+
+int test( void )
+{
+ int t = -1;
+ while (t)
+ {
+ gs.a++;
+ t = compute (&gs);
+ }
+ return 0;
+}
