Re: [PATCH] Check precision in STRIP_NOPS when possible (take 2)

[Richard Guenther <richard dot guenther at gmail dot com>]

On Thu, Jun 11, 2009 at 3:37 AM, Adam Nemet<anemet@caviumnetworks.com> wrote:
> This is the current version of the patch based on the thread in:
>
> ?http://gcc.gnu.org/ml/gcc-patches/2009-06/msg00711.html
>
> Eric, Bootstrapping and testing Ada succeeded with the additional assert.
> Later however I've found that C++ created nop_expr on aggregate types for
> reinterpret_cast. ?Thus the code falls back on the old TYPE_MODE equality for
> aggregate types.
>
> There were some other cases that required special handling; I tried to comment
> them appropriately in the code. ?To summarize I use precision for
> INTEGERAL_TYPE_P, POINTER_TYPE_P, OFFSET_TYPE and FLOAT_TYPE_P.
>
> Boostrapped and regtested on x86_64-linux including Ada.
>
> Further comments? ?OK to install?
>
> Adam
>
>
> ? ? ? ?* tree.c (tree_nop_conversion, tree_sign_nop_conversion): New
> ? ? ? ?functions.
> ? ? ? ?* tree.h (STRIP_NOPS, STRIP_SIGN_NOPS): Use them.
>
> testsuite/
> ? ? ? ?* gcc.c-torture/execute/bitfld-5.c: New test.
>
> Index: tree.h
> ===================================================================
> --- tree.h ? ? ?(revision 148091)
> +++ tree.h ? ? ?(working copy)
> @@ -964,29 +964,17 @@ extern void omp_clause_range_check_faile
> ? case NOP_EXPR: ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? \
> ? case CONVERT_EXPR
>
> -/* Given an expression as a tree, strip any NON_LVALUE_EXPRs and NOP_EXPRs
> - ? that don't change the machine mode. ?*/
> +/* Given an expression as a tree, strip any conversion that generates no
> + ? instruction. ?*/
>
> -#define STRIP_NOPS(EXP) ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?\
> - ?while ((CONVERT_EXPR_P (EXP) ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? \
> - ? ? ? ? || TREE_CODE (EXP) == NON_LVALUE_EXPR) ? ? ? ? ? ? ? ?\
> - ? ? ? ?&& TREE_OPERAND (EXP, 0) != error_mark_node ? ? ? ? ? ?\
> - ? ? ? ?&& (TYPE_MODE (TREE_TYPE (EXP)) ? ? ? ? ? ? ? ? ? ? ? ?\
> - ? ? ? ? ? ?== TYPE_MODE (TREE_TYPE (TREE_OPERAND (EXP, 0))))) \
> +#define STRIP_NOPS(EXP) ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?\
> + ?while (tree_nop_conversion (EXP)) ? ? ? ? ? ?\
> ? ? (EXP) = TREE_OPERAND (EXP, 0)
>
> ?/* Like STRIP_NOPS, but don't let the signedness change either. ?*/
>
> -#define STRIP_SIGN_NOPS(EXP) \
> - ?while ((CONVERT_EXPR_P (EXP) ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? \
> - ? ? ? ? || TREE_CODE (EXP) == NON_LVALUE_EXPR) ? ? ? ? ? ? ? ?\
> - ? ? ? ?&& TREE_OPERAND (EXP, 0) != error_mark_node ? ? ? ? ? ?\
> - ? ? ? ?&& (TYPE_MODE (TREE_TYPE (EXP)) ? ? ? ? ? ? ? ? ? ? ? ?\
> - ? ? ? ? ? ?== TYPE_MODE (TREE_TYPE (TREE_OPERAND (EXP, 0)))) ?\
> - ? ? ? ?&& (TYPE_UNSIGNED (TREE_TYPE (EXP)) ? ? ? ? ? ? ? ? ? ?\
> - ? ? ? ? ? ?== TYPE_UNSIGNED (TREE_TYPE (TREE_OPERAND (EXP, 0)))) \
> - ? ? ? ?&& (POINTER_TYPE_P (TREE_TYPE (EXP)) ? ? ? ? ? ? ? ? ? \
> - ? ? ? ? ? ?== POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND (EXP, 0))))) \
> +#define STRIP_SIGN_NOPS(EXP) ? ? ? ? ? ? ? ? ? ?\
> + ?while (tree_sign_nop_conversion (EXP)) ? ? ? ?\
> ? ? (EXP) = TREE_OPERAND (EXP, 0)
>
> ?/* Like STRIP_NOPS, but don't alter the TREE_TYPE either. ?*/
> @@ -4628,6 +4616,8 @@ extern bool stdarg_p (tree);
> ?extern bool prototype_p (tree);
> ?extern bool auto_var_in_fn_p (const_tree, const_tree);
> ?extern tree build_low_bits_mask (tree, unsigned);
> +extern bool tree_nop_conversion (const_tree);
> +extern bool tree_sign_nop_conversion (const_tree);
>
> ?/* In cgraph.c */
> ?extern void change_decl_assembler_name (tree, tree);
> Index: tree.c
> ===================================================================
> --- tree.c ? ? ?(revision 148091)
> +++ tree.c ? ? ?(working copy)
> @@ -9437,5 +9437,80 @@ list_equal_p (const_tree t1, const_tree
> ? return !t1 && !t2;
> ?}
>
> +/* Return true iff conversion in EXP generates no instruction. ?*/
> +
> +bool
> +tree_nop_conversion (const_tree exp)
> +{
> + ?tree outer_type, inner_type;
> +
> + ?if (!CONVERT_EXPR_P (exp)
> + ? ? ?&& TREE_CODE (exp) != NON_LVALUE_EXPR)
> + ? ?return false;
> + ?if (TREE_OPERAND (exp, 0) == error_mark_node)
> + ? ?return false;

ok, but ...

> + ?/* Ignore qualifiers. ?*/
> + ?outer_type = TYPE_MAIN_VARIANT (TREE_TYPE (exp));
> + ?inner_type = TYPE_MAIN_VARIANT (TREE_TYPE (TREE_OPERAND (exp, 0)));
> +
> + ?if (outer_type == inner_type)
> + ? ?return true;
> +
> + ?/* Conversion to void does not yield a value. ?*/
> + ?if (outer_type == void_type_node)
> + ? ?return false;
> +
> + ?/* C++ casts a void_zero_node to a pointer type for the dummy
> + ? ? object. ?*/
> + ?if (inner_type == void_type_node)
> + ? ?return false;

what's all this about?  The mode check will deal with it properly.

> + ?/* Use precision rather then machine mode when we can, which gives
> + ? ? the correct answer even for submode (bit-field) types. ?*/
> + ?if (INTEGRAL_TYPE_P (outer_type)
> + ? ? ?|| POINTER_TYPE_P (outer_type)
> + ? ? ?|| TREE_CODE (outer_type) == OFFSET_TYPE
> + ? ? ?|| FLOAT_TYPE_P (outer_type))
> + ? ?{
> +#ifdef ENABLE_CHECKING
> + ? ? ?/* Don't allow conversion between float and integral+ types. ?*/
> + ? ? ?gcc_assert ((INTEGRAL_TYPE_P (outer_type)
> + ? ? ? ? ? ? ? ? ?|| POINTER_TYPE_P (outer_type)
> + ? ? ? ? ? ? ? ? ?|| TREE_CODE (outer_type) == OFFSET_TYPE)
> + ? ? ? ? ? ? ? ? == ((INTEGRAL_TYPE_P (inner_type)
> + ? ? ? ? ? ? ? ? ? ? ?|| POINTER_TYPE_P (inner_type)
> + ? ? ? ? ? ? ? ? ? ? ?|| TREE_CODE (inner_type) == OFFSET_TYPE)));
> +#endif
> +
> + ? ? ?return TYPE_PRECISION (outer_type) == TYPE_PRECISION (inner_type);
> + ? ?}

Just do

  if ((INTEGRAL_TYPE_P (outer_type_p)
      || POINTER_TYPE_P (outer_type_p)
      || TREE_CODE (outer_type_p) == OFFSET_TYPE)
      && (INTEGRAL_TYPE_P (inner_type)
             || ...))
    return TYPE_PRECISION (outer_Type) == TYPE_RECISION (inner_type);

> + ?/* Aggregate types have no precision so we fall back on the machine
> + ? ? mode. ?The C++ front-end creates NOP_EXPR of aggregate types for
> + ? ? example for reinterpret_cast. ?*/
> + ?else if (AGGREGATE_TYPE_P (outer_type))
> + ? ?return TYPE_MODE (outer_type) == TYPE_MODE (inner_type);
> + ?else
> + ? ?gcc_unreachable ();

no if's necessary, just fall back to mode comparisions.

Please fold the follow-up patch and this into one and resent
for double-checking.

Thx,
Richard.


> +}
> +
> +/* Return true iff conversion in EXP generates no instruction. ?Don't
> + ? consider conversions changing the signedness. ?*/
> +
> +bool
> +tree_sign_nop_conversion (const_tree exp)
> +{
> + ?tree outer_type, inner_type;
> +
> + ?if (!tree_nop_conversion (exp))
> + ? ?return false;
> +
> + ?outer_type = TREE_TYPE (exp);
> + ?inner_type = TREE_TYPE (TREE_OPERAND (exp, 0));
> +
> + ?return (TYPE_UNSIGNED (outer_type) == TYPE_UNSIGNED (inner_type)
> + ? ? ? ? && POINTER_TYPE_P (outer_type) == POINTER_TYPE_P (inner_type));
> +}
> +
>
> ?#include "gt-tree.h"
> Index: testsuite/gcc.c-torture/execute/bitfld-5.c
> ===================================================================
> --- testsuite/gcc.c-torture/execute/bitfld-5.c ?(revision 0)
> +++ testsuite/gcc.c-torture/execute/bitfld-5.c ?(revision 0)
> @@ -0,0 +1,35 @@
> +/* See http://gcc.gnu.org/ml/gcc/2009-06/msg00072.html. ?*/
> +
> +extern void abort (void);
> +
> +struct s
> +{
> + ?unsigned long long a:2;
> + ?unsigned long long b:40;
> + ?unsigned long long c:22;
> +};
> +
> +__attribute__ ((noinline)) void
> +g (unsigned long long a, unsigned long long b)
> +{
> + ?asm ("");
> + ?if (a != b)
> + ? ?abort ();
> +}
> +
> +__attribute__ ((noinline)) void
> +f (struct s s, unsigned long long b)
> +{
> + ?asm ("");
> + ?g (((unsigned long long) (s.b-8)) + 8, b);
> +}
> +
> +int
> +main ()
> +{
> + ?struct s s = {1, 10, 3};
> + ?struct s t = {1, 2, 3};
> + ?f (s, 10);
> + ?f (t, 0x10000000002);
> + ?return 0;
> +}
>