Re: [RFC PATCH] __builtin_escape/__builtin_bless
Am Dienstag, den 04.02.2020, 15:01 +0100 schrieb Richard Biener:
> On Sat, Feb 1, 2020 at 1:04 AM Uecker, Martin
> wrote:
> >
> >
> >
> > Hi Richard and Joseph,
> >
> > for discussion: here is my simple patch
> > for __builtin_escape/__builtin_bless.
> >
> > Maybe it does something stupid.
>
> I'd use an internal function once the frontend inserts the calls,
> we shouldn't expose those to the user.
Ok. I thought it might be useful for testing...
> I expect the builtins to show as quite invasive with their
> data dependence blocking many optimizations.
Yes, I wondering about the impact of this on
optimization and whether this could be made
more light-weight somehow.
Do you think it is worth investigating
the use of some other kind of marker?
> Any reason that __builtin_escape is not marked as const?
Conceptually, letting something escape (or marking
it "exposed" according to the formal semantics
in the PVNI proposal) is a side-effect.
Practically, if I mark it constant, I think the
problem was that it was getting optimized away
completely.
> Do you try to prevent code motion of it so flow-sensitive
> "escape" analysis can be used?
If I don't miss something important, there is
no flow-sensitive analysis done in GCC.
> But nothing prevents hoisting of the bless call
> across the escape one.
With flow-sensitive analysis, this would be
incorrect.
Martin
> >
> > diff --git a/gcc/builtins.c b/gcc/builtins.c
> > index e4a8694054e..d0046135213 100644
> > --- a/gcc/builtins.c
> > +++ b/gcc/builtins.c
> > @@ -6014,6 +6014,31 @@ expand_builtin_unreachable (void)
> > emit_barrier ();
> > }
> >
> > +
> > +static rtx
> > +expand_builtin_escape (tree exp, rtx target)
> > +{
> > + if (call_expr_nargs (exp) < 1)
> > +return const0_rtx;
> > +
> > + target = expand_expr (CALL_EXPR_ARG (exp, 0), target, Pmode,
> > + EXPAND_NORMAL);
> > +
> > + return target;
> > +}
> > +
> > +static rtx
> > +expand_builtin_bless (tree exp, rtx target)
> > +{
> > + if (call_expr_nargs (exp) < 1)
> > +return const0_rtx;
> > +
> > + target = expand_expr (CALL_EXPR_ARG (exp, 0), target, Pmode,
> > + EXPAND_NORMAL);
> > +
> > + return target;
> > +}
> > +
> > /* Expand EXP, a call to fabs, fabsf or fabsl.
> > Return NULL_RTX if a normal call should be emitted rather than
> > expanding
> > the function inline. If convenient, the result should be
> > placed
> > @@ -8304,6 +8329,12 @@ expand_builtin (tree exp, rtx target, rtx
> > subtarget, machine_mode mode,
> > expand_builtin_unreachable ();
> > return const0_rtx;
> >
> > +case BUILT_IN_ESCAPE:
> > + return expand_builtin_escape (exp, target);
> > +
> > +case BUILT_IN_BLESS:
> > + return expand_builtin_bless (exp, target);
> > +
> > CASE_FLT_FN (BUILT_IN_SIGNBIT):
> > case BUILT_IN_SIGNBITD32:
> > case BUILT_IN_SIGNBITD64:
> > diff --git a/gcc/builtins.def b/gcc/builtins.def
> > index fa8b0641ab1..9264a0fdaab 100644
> > --- a/gcc/builtins.def
> > +++ b/gcc/builtins.def
> > @@ -865,6 +865,8 @@ DEF_EXT_LIB_BUILTIN(BUILT_IN_EXECVP,
> > "execvp", BT_FN_INT_CONST_STRING_PT
> > DEF_EXT_LIB_BUILTIN(BUILT_IN_EXECVE, "execve",
> > BT_FN_INT_CONST_STRING_PTR_CONST_STRING_PTR_CONST_STRING,
> > ATTR_NOTHROW_LIST)
> > DEF_LIB_BUILTIN(BUILT_IN_EXIT, "exit", BT_FN_VOID_INT,
> > ATTR_NORETURN_NOTHROW_LIST)
> > DEF_GCC_BUILTIN(BUILT_IN_EXPECT, "expect",
> > BT_FN_LONG_LONG_LONG, ATTR_CONST_NOTHROW_LEAF_LIST)
> > +DEF_GCC_BUILTIN(BUILT_IN_ESCAPE, "escape", BT_FN_PTR_PTR,
> > ATTR_NOTHROW_LEAF_LIST)
> > +DEF_GCC_BUILTIN(BUILT_IN_BLESS, "bless", BT_FN_PTR_PTR,
> > ATTR_CONST_NOTHROW_LEAF_LIST)
> > DEF_GCC_BUILTIN(BUILT_IN_EXPECT_WITH_PROBABILITY,
> > "expect_with_probability", BT_FN_LONG_LONG_LONG_DOUBLE,
> > ATTR_CONST_NOTHROW_LEAF_LIST)
> > DEF_GCC_BUILTIN(BUILT_IN_ASSUME_ALIGNED, "assume_aligned",
> > BT_FN_PTR_CONST_PTR_SIZE_VAR, ATTR_CONST_NOTHROW_LEAF_LIST)
> > DEF_GCC_BUILTIN(BUILT_IN_EXTEND_POINTER, "extend_pointer",
> > BT_FN_UNWINDWORD_PTR, ATTR_CONST_NOTHROW_LEAF_LIST)
> > diff --git a/gcc/testsuite/gcc.dg/alias-17.c
> > b/gcc/testsuite/gcc.dg/alias-17.c
> > new file mode 100644
> > index 000..c375e4027ca
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.dg/alias-17.c
> > @@ -0,0 +1,29 @@
> > +/* { dg-do run } */
> > +/* { dg-options "-O1" } */
> > +
> > +
> > +static
> > +int test(int a, int b, int c)
> > +{
> > + int x, y;
> > + int d = (&x < &y) ? 1 : -1;
> > + if (a) __builtin_escape(&y);
> > + y = 0; //!
> > + int *q = &x;
> > + q += d;
> > + int *r = q;
> > + if (b) r = __builtin_bless(q);
> > + *(c ? r : q) = 1;
> > + return y;
> > +}
> > +
> > +int main()
> > +{
> > + if (0 != test(0, 0, 1)) __builtin_abort();
> > + if (0 != test(0, 1, 0)) __builtin_abort();
> > + if (0 != test(0, 1, 1)) __built
Re: [RFC PATCH] __builtin_escape/__builtin_bless
On Sat, Feb 1, 2020 at 1:04 AM Uecker, Martin
wrote:
>
>
>
> Hi Richard and Joseph,
>
> for discussion: here is my simple patch
> for __builtin_escape/__builtin_bless.
>
> Maybe it does something stupid.
I'd use an internal function once the frontend inserts the calls,
we shouldn't expose those to the user.
I expect the builtins to show as quite invasive with their
data dependence blocking many optimizations. Any reason
that __builtin_escape is not marked as const? Do you try
to prevent code motion of it so flow-sensitive "escape" analysis
can be used? But nothing prevents hoisting of the bless call
across the escape one.
Richard.
>
> Best,
> Martin
>
>
> diff --git a/gcc/builtins.c b/gcc/builtins.c
> index e4a8694054e..d0046135213 100644
> --- a/gcc/builtins.c
> +++ b/gcc/builtins.c
> @@ -6014,6 +6014,31 @@ expand_builtin_unreachable (void)
>emit_barrier ();
> }
>
> +
> +static rtx
> +expand_builtin_escape (tree exp, rtx target)
> +{
> + if (call_expr_nargs (exp) < 1)
> +return const0_rtx;
> +
> + target = expand_expr (CALL_EXPR_ARG (exp, 0), target, Pmode,
> + EXPAND_NORMAL);
> +
> + return target;
> +}
> +
> +static rtx
> +expand_builtin_bless (tree exp, rtx target)
> +{
> + if (call_expr_nargs (exp) < 1)
> +return const0_rtx;
> +
> + target = expand_expr (CALL_EXPR_ARG (exp, 0), target, Pmode,
> + EXPAND_NORMAL);
> +
> + return target;
> +}
> +
> /* Expand EXP, a call to fabs, fabsf or fabsl.
> Return NULL_RTX if a normal call should be emitted rather than expanding
> the function inline. If convenient, the result should be placed
> @@ -8304,6 +8329,12 @@ expand_builtin (tree exp, rtx target, rtx subtarget,
> machine_mode mode,
>expand_builtin_unreachable ();
>return const0_rtx;
>
> +case BUILT_IN_ESCAPE:
> + return expand_builtin_escape (exp, target);
> +
> +case BUILT_IN_BLESS:
> + return expand_builtin_bless (exp, target);
> +
> CASE_FLT_FN (BUILT_IN_SIGNBIT):
> case BUILT_IN_SIGNBITD32:
> case BUILT_IN_SIGNBITD64:
> diff --git a/gcc/builtins.def b/gcc/builtins.def
> index fa8b0641ab1..9264a0fdaab 100644
> --- a/gcc/builtins.def
> +++ b/gcc/builtins.def
> @@ -865,6 +865,8 @@ DEF_EXT_LIB_BUILTIN(BUILT_IN_EXECVP, "execvp",
> BT_FN_INT_CONST_STRING_PT
> DEF_EXT_LIB_BUILTIN(BUILT_IN_EXECVE, "execve",
> BT_FN_INT_CONST_STRING_PTR_CONST_STRING_PTR_CONST_STRING, ATTR_NOTHROW_LIST)
> DEF_LIB_BUILTIN(BUILT_IN_EXIT, "exit", BT_FN_VOID_INT,
> ATTR_NORETURN_NOTHROW_LIST)
> DEF_GCC_BUILTIN(BUILT_IN_EXPECT, "expect", BT_FN_LONG_LONG_LONG,
> ATTR_CONST_NOTHROW_LEAF_LIST)
> +DEF_GCC_BUILTIN(BUILT_IN_ESCAPE, "escape", BT_FN_PTR_PTR,
> ATTR_NOTHROW_LEAF_LIST)
> +DEF_GCC_BUILTIN(BUILT_IN_BLESS, "bless", BT_FN_PTR_PTR,
> ATTR_CONST_NOTHROW_LEAF_LIST)
> DEF_GCC_BUILTIN(BUILT_IN_EXPECT_WITH_PROBABILITY,
> "expect_with_probability", BT_FN_LONG_LONG_LONG_DOUBLE,
> ATTR_CONST_NOTHROW_LEAF_LIST)
> DEF_GCC_BUILTIN(BUILT_IN_ASSUME_ALIGNED, "assume_aligned",
> BT_FN_PTR_CONST_PTR_SIZE_VAR, ATTR_CONST_NOTHROW_LEAF_LIST)
> DEF_GCC_BUILTIN(BUILT_IN_EXTEND_POINTER, "extend_pointer",
> BT_FN_UNWINDWORD_PTR, ATTR_CONST_NOTHROW_LEAF_LIST)
> diff --git a/gcc/testsuite/gcc.dg/alias-17.c b/gcc/testsuite/gcc.dg/alias-17.c
> new file mode 100644
> index 000..c375e4027ca
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/alias-17.c
> @@ -0,0 +1,29 @@
> +/* { dg-do run } */
> +/* { dg-options "-O1" } */
> +
> +
> +static
> +int test(int a, int b, int c)
> +{
> + int x, y;
> + int d = (&x < &y) ? 1 : -1;
> + if (a) __builtin_escape(&y);
> + y = 0; //!
> + int *q = &x;
> + q += d;
> + int *r = q;
> + if (b) r = __builtin_bless(q);
> + *(c ? r : q) = 1;
> + return y;
> +}
> +
> +int main()
> +{
> + if (0 != test(0, 0, 1)) __builtin_abort();
> + if (0 != test(0, 1, 0)) __builtin_abort();
> + if (0 != test(0, 1, 1)) __builtin_abort();
> + if (0 != test(1, 0, 1)) __builtin_abort();
> +// if (0 != test(1, 1, 0)) __builtin_abort();
> + if (0 == test(1, 1, 1)) __builtin_abort();
> + return 0;
> +}
> diff --git a/gcc/tree-ssa-alias.c b/gcc/tree-ssa-alias.c
> index 670676f20c3..d5befff71a6 100644
> --- a/gcc/tree-ssa-alias.c
> +++ b/gcc/tree-ssa-alias.c
> @@ -2462,6 +2462,8 @@ ref_maybe_used_by_call_p_1 (gcall *call, ao_ref *ref,
> bool tbaa_p)
> }
>
> /* The following builtins do not read from memory. */
> + case BUILT_IN_ESCAPE:
> + case BUILT_IN_BLESS:
> case BUILT_IN_FREE:
> case BUILT_IN_MALLOC:
> case BUILT_IN_POSIX_MEMALIGN:
> diff --git a/gcc/tree-ssa-ccp.c b/gcc/tree-ssa-ccp.c
> index be6647db894..53a38a04ebb 100644
> --- a/gcc/tree-ssa-ccp.c
> +++ b/gcc/tree-ssa-ccp.c
> @@ -1963,6 +1963,8 @@ evaluate_stmt (gimple *stmt)
> break;
>
> /* These built
[RFC PATCH] __builtin_escape/__builtin_bless
Hi Richard and Joseph,
for discussion: here is my simple patch
for __builtin_escape/__builtin_bless.
Maybe it does something stupid.
Best,
Martin
diff --git a/gcc/builtins.c b/gcc/builtins.c
index e4a8694054e..d0046135213 100644
--- a/gcc/builtins.c
+++ b/gcc/builtins.c
@@ -6014,6 +6014,31 @@ expand_builtin_unreachable (void)
emit_barrier ();
}
+
+static rtx
+expand_builtin_escape (tree exp, rtx target)
+{
+ if (call_expr_nargs (exp) < 1)
+return const0_rtx;
+
+ target = expand_expr (CALL_EXPR_ARG (exp, 0), target, Pmode,
+ EXPAND_NORMAL);
+
+ return target;
+}
+
+static rtx
+expand_builtin_bless (tree exp, rtx target)
+{
+ if (call_expr_nargs (exp) < 1)
+return const0_rtx;
+
+ target = expand_expr (CALL_EXPR_ARG (exp, 0), target, Pmode,
+ EXPAND_NORMAL);
+
+ return target;
+}
+
/* Expand EXP, a call to fabs, fabsf or fabsl.
Return NULL_RTX if a normal call should be emitted rather than expanding
the function inline. If convenient, the result should be placed
@@ -8304,6 +8329,12 @@ expand_builtin (tree exp, rtx target, rtx subtarget,
machine_mode mode,
expand_builtin_unreachable ();
return const0_rtx;
+case BUILT_IN_ESCAPE:
+ return expand_builtin_escape (exp, target);
+
+case BUILT_IN_BLESS:
+ return expand_builtin_bless (exp, target);
+
CASE_FLT_FN (BUILT_IN_SIGNBIT):
case BUILT_IN_SIGNBITD32:
case BUILT_IN_SIGNBITD64:
diff --git a/gcc/builtins.def b/gcc/builtins.def
index fa8b0641ab1..9264a0fdaab 100644
--- a/gcc/builtins.def
+++ b/gcc/builtins.def
@@ -865,6 +865,8 @@ DEF_EXT_LIB_BUILTIN(BUILT_IN_EXECVP, "execvp",
BT_FN_INT_CONST_STRING_PT
DEF_EXT_LIB_BUILTIN(BUILT_IN_EXECVE, "execve",
BT_FN_INT_CONST_STRING_PTR_CONST_STRING_PTR_CONST_STRING, ATTR_NOTHROW_LIST)
DEF_LIB_BUILTIN(BUILT_IN_EXIT, "exit", BT_FN_VOID_INT,
ATTR_NORETURN_NOTHROW_LIST)
DEF_GCC_BUILTIN(BUILT_IN_EXPECT, "expect", BT_FN_LONG_LONG_LONG,
ATTR_CONST_NOTHROW_LEAF_LIST)
+DEF_GCC_BUILTIN(BUILT_IN_ESCAPE, "escape", BT_FN_PTR_PTR,
ATTR_NOTHROW_LEAF_LIST)
+DEF_GCC_BUILTIN(BUILT_IN_BLESS, "bless", BT_FN_PTR_PTR,
ATTR_CONST_NOTHROW_LEAF_LIST)
DEF_GCC_BUILTIN(BUILT_IN_EXPECT_WITH_PROBABILITY,
"expect_with_probability", BT_FN_LONG_LONG_LONG_DOUBLE,
ATTR_CONST_NOTHROW_LEAF_LIST)
DEF_GCC_BUILTIN(BUILT_IN_ASSUME_ALIGNED, "assume_aligned",
BT_FN_PTR_CONST_PTR_SIZE_VAR, ATTR_CONST_NOTHROW_LEAF_LIST)
DEF_GCC_BUILTIN(BUILT_IN_EXTEND_POINTER, "extend_pointer",
BT_FN_UNWINDWORD_PTR, ATTR_CONST_NOTHROW_LEAF_LIST)
diff --git a/gcc/testsuite/gcc.dg/alias-17.c b/gcc/testsuite/gcc.dg/alias-17.c
new file mode 100644
index 000..c375e4027ca
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/alias-17.c
@@ -0,0 +1,29 @@
+/* { dg-do run } */
+/* { dg-options "-O1" } */
+
+
+static
+int test(int a, int b, int c)
+{
+ int x, y;
+ int d = (&x < &y) ? 1 : -1;
+ if (a) __builtin_escape(&y);
+ y = 0; //!
+ int *q = &x;
+ q += d;
+ int *r = q;
+ if (b) r = __builtin_bless(q);
+ *(c ? r : q) = 1;
+ return y;
+}
+
+int main()
+{
+ if (0 != test(0, 0, 1)) __builtin_abort();
+ if (0 != test(0, 1, 0)) __builtin_abort();
+ if (0 != test(0, 1, 1)) __builtin_abort();
+ if (0 != test(1, 0, 1)) __builtin_abort();
+// if (0 != test(1, 1, 0)) __builtin_abort();
+ if (0 == test(1, 1, 1)) __builtin_abort();
+ return 0;
+}
diff --git a/gcc/tree-ssa-alias.c b/gcc/tree-ssa-alias.c
index 670676f20c3..d5befff71a6 100644
--- a/gcc/tree-ssa-alias.c
+++ b/gcc/tree-ssa-alias.c
@@ -2462,6 +2462,8 @@ ref_maybe_used_by_call_p_1 (gcall *call, ao_ref *ref,
bool tbaa_p)
}
/* The following builtins do not read from memory. */
+ case BUILT_IN_ESCAPE:
+ case BUILT_IN_BLESS:
case BUILT_IN_FREE:
case BUILT_IN_MALLOC:
case BUILT_IN_POSIX_MEMALIGN:
diff --git a/gcc/tree-ssa-ccp.c b/gcc/tree-ssa-ccp.c
index be6647db894..53a38a04ebb 100644
--- a/gcc/tree-ssa-ccp.c
+++ b/gcc/tree-ssa-ccp.c
@@ -1963,6 +1963,8 @@ evaluate_stmt (gimple *stmt)
break;
/* These builtins return their first argument, unmodified. */
+ case BUILT_IN_ESCAPE:
+ case BUILT_IN_BLESS:
case BUILT_IN_MEMCPY:
case BUILT_IN_MEMMOVE:
case BUILT_IN_MEMSET:
diff --git a/gcc/tree-ssa-structalias.c b/gcc/tree-ssa-structalias.c
index 416a26c996c..003349c7278 100644
--- a/gcc/tree-ssa-structalias.c
+++ b/gcc/tree-ssa-structalias.c
@@ -4381,6 +4381,24 @@ find_func_aliases_for_builtin_call (struct function *fn,
gcall *t)
in the alias-oracle query functions explicitly! */
switch (DECL_FUNCTION_CODE (fndecl))
{
+ case BUILT_IN_ESCAPE:
+ {
+ make_escape_constraint (gimple_call_arg (t, 0));
+ return true;
+ }
+ case BUILT_IN_BLESS:
+ {
+
