On Thu, 11 Jul 2019 at 01:48, Richard Sandiford
<richard.sandif...@arm.com> wrote:
>
> Prathamesh Kulkarni <prathamesh.kulka...@linaro.org> writes:
> > Hi,
> > For following test-case:
> >
> > typedef double v4df __attribute__ ((vector_size (32)));
> > void foo(v4df);
> >
> > int
> > main ()
> > {
> > volatile v4df x1;
> > x1 = (v4df) { 10.0, 20.0, 30.0, 40.0 };
> > foo (x1);
> > return 0;
> > }
> >
> > Compiling with -msve-vector-bits=256, the compiler goes into infinite
> > recursion and eventually segfaults due to stack overflow.
> >
> > This happens during expansion of:
> > x1.0_1 ={v} x1;
> >
> > aarch64_expand_sve_mem_move calls aarch64_emit_sve_pred_move with
> > dest = (reg:VNx2DF 93) and
> > src = (mem/u/c:VNx2DF
> > (plus:DI (reg/f:DI 94) (const_int 32 [0x20])) [0 S32 A128])
> >
> > aarch64_emit_sve_pred_move calls expand_insn with above ops.
> > Eventually we hit EXPAND_INPUT case in maybe_legitimize_operand for
> > src (opno == 2)
> >
> > Since the operand is marked with volatile, and volatile_ok is set to false,
> > insn_operand_matches return false and we call:
> > op->value = copy_to_mode_reg (mode, op->value);
> > break;
> >
> > copy_to_mode_reg however, creates a fresh register and calls emit_move_insn:
> > rtx temp = gen_reg_rtx (mode);
> > if (x != temp)
> > emit_move_insn (temp, x);
> >
> > and we again end up in aarch64_emit_sve_pred_move, with dest assigned
> > the new register and src remaining unchanged, and thus the cycle continues.
> >
> > As suggested by Richard, the attached patch temporarily sets volatile_ok to
> > true
> > using RAII class volatile_ok_temp in aarch64_emit_sve_pred_move which
> > avoids the recursion.
> >
> > Bootstrap + tested on x86_64-unknown-linux-gnu, aarch64-linux-gnu.
> > Cross-testing with SVE in progress.
> > OK to commit ?
> >
> > Thanks,
> > Prathamesh
> >
> > 2019-07-09 Prathamesh Kulkarni <prathamesh.kulka...@linaro.org>
> >
> > PR target/90723
> > * recog.h (volatile_ok_temp): New class.
> > * config/aarch64/aarch64.c (aarch64_emit_sve_pred_move): Set
> > volatile_ok temporarily to true using volatile_ok_temp.
> > * expr.c (emit_block_move_via_cpymem): Likewise.
> > * optabs.c (maybe_legitimize_operand): Likewise.
>
> I'm the last person who should be suggesting names, but how about
> temporary_volatile_ok? Putting "temp" after the name IMO makes it
> sound too much like it's describing the RAII object rather than the
> value of volatile_ok itself.
>
> > diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
> > index 5a923ca006b..50afba1a2b6 100644
> > --- a/gcc/config/aarch64/aarch64.c
> > +++ b/gcc/config/aarch64/aarch64.c
> > @@ -3457,6 +3457,7 @@ aarch64_emit_sve_pred_move (rtx dest, rtx pred, rtx
> > src)
> > create_output_operand (&ops[0], dest, mode);
> > create_input_operand (&ops[1], pred, GET_MODE(pred));
> > create_input_operand (&ops[2], src, mode);
> > + volatile_ok_temp v(true);
>
> Missing space before "(". Same for later uses.
>
> > [...]
> > diff --git a/gcc/recog.h b/gcc/recog.h
> > index 75cbbdc10ad..8a8eaf7e0c3 100644
> > --- a/gcc/recog.h
> > +++ b/gcc/recog.h
> > @@ -186,6 +186,22 @@ skip_alternative (const char *p)
> > /* Nonzero means volatile operands are recognized. */
> > extern int volatile_ok;
> >
> > +/* RAII class for temporarily setting volatile_ok. */
> > +
> > +class volatile_ok_temp
> > +{
> > +public:
> > + volatile_ok_temp(int value): save_volatile_ok (volatile_ok)
>
> Missing space before "(" and before ":".
>
> > + {
> > + volatile_ok = value;
> > + }
> > +
> > + ~volatile_ok_temp() { volatile_ok = save_volatile_ok; }
>
> Missing space before "(".
>
> > +
> > +private:
> > + int save_volatile_ok;
>
> For extra safety we should probably have a private copy constructor
> (declaration only, no implementation). We're still C++03 and so can't
> use "= delete".
Thanks for the suggestions.
Does the attached version look OK ?
Thanks,
Prathamesh
>
> Thanks,
> Richard
>
>
> > +};
> > +
> > /* Set by constrain_operands to the number of the alternative that
> > matched. */
> > extern int which_alternative;
2019-07-11 Prathamesh Kulkarni <prathamesh.kulka...@linaro.org>
PR target/90723
* recog.h (temporary_volatile_ok): New class.
* config/aarch64/aarch64.c (aarch64_emit_sve_pred_move): Set
volatile_ok temporarily to true using temporary_volatile_ok.
* expr.c (emit_block_move_via_cpymem): Likewise.
* optabs.c (maybe_legitimize_operand): Likewise.
diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index 5a923ca006b..abdf4b1c87a 100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -3457,6 +3457,7 @@ aarch64_emit_sve_pred_move (rtx dest, rtx pred, rtx src)
create_output_operand (&ops[0], dest, mode);
create_input_operand (&ops[1], pred, GET_MODE(pred));
create_input_operand (&ops[2], src, mode);
+ temporary_volatile_ok v (true);
expand_insn (code_for_aarch64_pred_mov (mode), 3, ops);
}
diff --git a/gcc/expr.c b/gcc/expr.c
index 4acf250dd3c..795a56d88a6 100644
--- a/gcc/expr.c
+++ b/gcc/expr.c
@@ -1732,8 +1732,6 @@ emit_block_move_via_cpymem (rtx x, rtx y, rtx size,
unsigned int align,
unsigned HOST_WIDE_INT max_size,
unsigned HOST_WIDE_INT probable_max_size)
{
- int save_volatile_ok = volatile_ok;
-
if (expected_align < align)
expected_align = align;
if (expected_size != -1)
@@ -1745,7 +1743,7 @@ emit_block_move_via_cpymem (rtx x, rtx y, rtx size,
unsigned int align,
}
/* Since this is a move insn, we don't care about volatility. */
- volatile_ok = 1;
+ temporary_volatile_ok v (true);
/* Try the most limited insn first, because there's no point
including more than one in the machine description unless
@@ -1809,14 +1807,10 @@ emit_block_move_via_cpymem (rtx x, rtx y, rtx size,
unsigned int align,
create_fixed_operand (&ops[8], NULL);
}
if (maybe_expand_insn (code, nops, ops))
- {
- volatile_ok = save_volatile_ok;
- return true;
- }
+ return true;
}
}
- volatile_ok = save_volatile_ok;
return false;
}
diff --git a/gcc/optabs.c b/gcc/optabs.c
index 18ca7370917..187a3d3621d 100644
--- a/gcc/optabs.c
+++ b/gcc/optabs.c
@@ -7202,17 +7202,15 @@ maybe_legitimize_operand (enum insn_code icode,
unsigned int opno,
struct expand_operand *op)
{
machine_mode mode, imode;
- bool old_volatile_ok, result;
mode = op->mode;
switch (op->type)
{
case EXPAND_FIXED:
- old_volatile_ok = volatile_ok;
- volatile_ok = true;
- result = maybe_legitimize_operand_same_code (icode, opno, op);
- volatile_ok = old_volatile_ok;
- return result;
+ {
+ temporary_volatile_ok v (true);
+ return maybe_legitimize_operand_same_code (icode, opno, op);
+ }
case EXPAND_OUTPUT:
gcc_assert (mode != VOIDmode);
diff --git a/gcc/recog.h b/gcc/recog.h
index 75cbbdc10ad..8a8c9125ff2 100644
--- a/gcc/recog.h
+++ b/gcc/recog.h
@@ -186,6 +186,23 @@ skip_alternative (const char *p)
/* Nonzero means volatile operands are recognized. */
extern int volatile_ok;
+/* RAII class for temporarily setting volatile_ok. */
+
+class temporary_volatile_ok
+{
+public:
+ temporary_volatile_ok (int value): save_volatile_ok (volatile_ok)
+ {
+ volatile_ok = value;
+ }
+
+ ~temporary_volatile_ok () { volatile_ok = save_volatile_ok; }
+
+private:
+ temporary_volatile_ok (const temporary_volatile_ok&);
+ int save_volatile_ok;
+};
+
/* Set by constrain_operands to the number of the alternative that
matched. */
extern int which_alternative;
