[PATCH V6] Optimize '(X - N * M) / N' to 'X / N - M' if valid

Richard Biener rguenther@suse.de
Fri Sep 1 12:28:51 GMT 2023


On Fri, 1 Sep 2023, Jiufu Guo wrote:

> Hi,
> 
> Integer expression "(X - N * M) / N" can be optimized to "X / N - M" with
> the below conditions:
> 1. There is no wrap/overflow/underflow.
>    wrap/overflow/underflow breaks the arithmetic operation.
> 2. "X - N * M" and "X" are not of opposite sign.
>    Here, the operation "/" would be "trunc_div", the fractional part is
>    discarded towards zero. If "X - N * M" and "X" are in different signs,
>    then trunc_div discards the fractional parts (of /N) in different
>    directions.
> 
> Compare the previous version:
> https://gcc.gnu.org/pipermail/gcc-patches/2023-July/624801.html
> This patch adds comments and update the pattern on "(t + C)" to be more
> tight.
> 
> Bootstrap & regtest pass on ppc64{,le} and x86_64.
> Is this patch ok for trunk?
> 
> BR,
> Jeff (Jiufu Guo)
> 
> 	PR tree-optimization/108757
> 
> gcc/ChangeLog:
> 
> 	* match.pd ((X - N * M) / N): New pattern.
> 	((X + N * M) / N): New pattern.
> 	((X + C) div_rshift N): New pattern.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* gcc.dg/pr108757-1.c: New test.
> 	* gcc.dg/pr108757-2.c: New test.
> 	* gcc.dg/pr108757.h: New test.
> 
> ---
>  gcc/match.pd                      |  78 ++++++++++
>  gcc/testsuite/gcc.dg/pr108757-1.c |  18 +++
>  gcc/testsuite/gcc.dg/pr108757-2.c |  19 +++
>  gcc/testsuite/gcc.dg/pr108757.h   | 233 ++++++++++++++++++++++++++++++
>  4 files changed, 348 insertions(+)
>  create mode 100644 gcc/testsuite/gcc.dg/pr108757-1.c
>  create mode 100644 gcc/testsuite/gcc.dg/pr108757-2.c
>  create mode 100644 gcc/testsuite/gcc.dg/pr108757.h
> 
> diff --git a/gcc/match.pd b/gcc/match.pd
> index fa598d5ca2e470f9cc3b82469e77d743b12f107e..863bc7299cdefc622a7806a4d32e37268c50d453 100644
> --- a/gcc/match.pd
> +++ b/gcc/match.pd
> @@ -959,6 +959,84 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
>  #endif
>     ))))
>  
> +#if GIMPLE
> +(for div (trunc_div exact_div)
> + /* Simplify (X + M*N) / N -> X / N + M.  */
> + (simplify
> +  (div (plus:c@4 @0 (mult:c@3 @1 @2)) @2)
> +  (with {value_range vr0, vr1, vr2, vr3, vr4;}
> +  (if (INTEGRAL_TYPE_P (type)
> +       && get_range_query (cfun)->range_of_expr (vr1, @1)
> +       && get_range_query (cfun)->range_of_expr (vr2, @2)
> +       /* "N*M" doesn't overflow.  */
> +       && range_op_handler (MULT_EXPR).overflow_free_p (vr1, vr2)
> +       && get_range_query (cfun)->range_of_expr (vr0, @0)
> +       && get_range_query (cfun)->range_of_expr (vr3, @3)
> +       /* "X+(N*M)" doesn't overflow.  */
> +       && range_op_handler (PLUS_EXPR).overflow_free_p (vr0, vr3)
> +       && get_range_query (cfun)->range_of_expr (vr4, @4)
> +       /* "X+N*M" is not with opposite sign as "X".  */
> +       && (TYPE_UNSIGNED (type)
> +	   || (vr0.nonnegative_p () && vr4.nonnegative_p ())
> +	   || (vr0.nonpositive_p () && vr4.nonpositive_p ())))
> +  (plus (div @0 @2) @1))))
> +
> + /* Simplify (X - M*N) / N -> X / N - M.  */
> + (simplify
> +  (div (minus@4 @0 (mult:c@3 @1 @2)) @2)
> +  (with {value_range vr0, vr1, vr2, vr3, vr4;}
> +  (if (INTEGRAL_TYPE_P (type)
> +       && get_range_query (cfun)->range_of_expr (vr1, @1)
> +       && get_range_query (cfun)->range_of_expr (vr2, @2)
> +       /* "N * M" doesn't overflow.  */
> +       && range_op_handler (MULT_EXPR).overflow_free_p (vr1, vr2)
> +       && get_range_query (cfun)->range_of_expr (vr0, @0)
> +       && get_range_query (cfun)->range_of_expr (vr3, @3)
> +       /* "X - (N*M)" doesn't overflow.  */
> +       && range_op_handler (MINUS_EXPR).overflow_free_p (vr0, vr3)
> +       && get_range_query (cfun)->range_of_expr (vr4, @4)
> +       /* "X-N*M" is not with opposite sign as "X".  */
> +       && (TYPE_UNSIGNED (type)
> +	   || (vr0.nonnegative_p () && vr4.nonnegative_p ())
> +	   || (vr0.nonpositive_p () && vr4.nonpositive_p ())))
> +  (minus (div @0 @2) @1)))))
> +
> +/* Simplify
> +   (X + C) / N -> X / N + C / N where C is multiple of N.
> +   (X + C) >> N -> X >> N + C>>N if low N bits of C is 0.  */
> +(for op (trunc_div exact_div rshift)
> + (simplify
> +  (op (plus@3 @0 INTEGER_CST@1) INTEGER_CST@2)
> +   (with
> +    {
> +      wide_int c = wi::to_wide (@1);
> +      wide_int n = wi::to_wide (@2);
> +      bool shift = op == RSHIFT_EXPR;
> +      #define plus_op1(v) (shift ? wi::rshift (v, n, TYPE_SIGN (type)) \
> +				 : wi::div_trunc (v, n, TYPE_SIGN (type)))
> +      #define exact_mod(v) (shift ? wi::ctz (v) >= n.to_shwi () \
> +				  : wi::multiple_of_p (v, n, TYPE_SIGN (type)))

please indent these full left

> +      value_range vr0, vr1, vr3;
> +    }
> +    (if (INTEGRAL_TYPE_P (type)
> +	 && get_range_query (cfun)->range_of_expr (vr0, @0))
> +     (if (exact_mod (c)
> +	  && get_range_query (cfun)->range_of_expr (vr1, @1)
> +	  /* "X+C" doesn't overflow.  */
> +	  && range_op_handler (PLUS_EXPR).overflow_free_p (vr0, vr1)
> +	  && get_range_query (cfun)->range_of_expr (vr3, @3)
> +	  /* "X+C" and "X" are not of opposite sign.  */
> +	  && (TYPE_UNSIGNED (type)
> +	      || (vr0.nonnegative_p () && vr3.nonnegative_p ())
> +	      || (vr0.nonpositive_p () && vr3.nonpositive_p ())))
> +       (plus (op @0 @2) { wide_int_to_tree (type, plus_op1 (c)); })
> +       (if (TYPE_UNSIGNED (type) && c.sign_mask () < 0
> +	    && exact_mod (-c)
> +	    /* unsigned "X-(-C)" doesn't underflow.  */
> +	    && wi::geu_p (vr0.lower_bound (), -c))
> +	 (plus (op @0 @2) { wide_int_to_tree (type, -plus_op1 (-c)); })))))))

and #undef them here again.

OK with that change.

Thanks,
Richard.

> +#endif
> +
>  (for op (negate abs)
>   /* Simplify cos(-x) and cos(|x|) -> cos(x).  Similarly for cosh.  */
>   (for coss (COS COSH)
> diff --git a/gcc/testsuite/gcc.dg/pr108757-1.c b/gcc/testsuite/gcc.dg/pr108757-1.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..7908f4bdcb8e225fe311b668efbe8f6db525b4d5
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/pr108757-1.c
> @@ -0,0 +1,18 @@
> +/* PR tree-optimization/108757 */
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-tree-optimized" } */
> +
> +#include <limits.h>
> +#define N 5
> +#define M 3
> +#define GAP 0
> +typedef unsigned int UINT;
> +typedef int INT;
> +#define UMAX UINT_MAX
> +#define IMAX INT_MAX
> +#define IMIN INT_MIN
> +#include "pr108757.h"
> +
> +/* { dg-final { scan-tree-dump-not " = x_\[0-9\]+\\(D\\) \\+ " "optimized" } } *
> +/* { dg-final { scan-tree-dump-not " = x_\[0-9\]+\\(D\\) \\- " "optimized" } } */
> +/* { dg-final { scan-tree-dump-not " = b_\[0-9\]+ \\+ " "optimized" } } */
> diff --git a/gcc/testsuite/gcc.dg/pr108757-2.c b/gcc/testsuite/gcc.dg/pr108757-2.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..82bebd09944f0be2e0690c604723bfe6182acec3
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/pr108757-2.c
> @@ -0,0 +1,19 @@
> +/* PR tree-optimization/108757 */
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-tree-optimized -fwrapv" } */
> +
> +#include <limits.h>
> +#define N 4
> +#define M 3
> +#define GAP 2
> +typedef unsigned int UINT;
> +typedef int INT;
> +#define UMAX UINT_MAX
> +#define IMAX INT_MAX
> +#define IMIN INT_MIN
> +#include "pr108757.h"
> +
> +/* { dg-final { scan-tree-dump-times " = x_\[0-9\]+\\(D\\) \\+ " 16 "optimized" } } */
> +/* { dg-final { scan-tree-dump-times " = x_\[0-9\]+\\(D\\) \\- " 3 "optimized" } } */
> +/* { dg-final { scan-tree-dump-times " \\+ x_\[0-9\]+\\(D\\)" 3 "optimized" } } */
> +
> diff --git a/gcc/testsuite/gcc.dg/pr108757.h b/gcc/testsuite/gcc.dg/pr108757.h
> new file mode 100644
> index 0000000000000000000000000000000000000000..5550199c1ef952f54eaa83087cec25e992057c34
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/pr108757.h
> @@ -0,0 +1,233 @@
> +#define NOINLINE __attribute__ ((noinline))
> +UINT NOINLINE
> +opt_u1 (UINT x)
> +{
> +  if (x < (M * N) - GAP)
> +    return 0;
> +  UINT a = x - (M * N);
> +  UINT b = a / N;
> +  return b + M;
> +}
> +
> +UINT NOINLINE
> +opt_u2 (UINT x)
> +{
> +  if (x > (UMAX - (M * N) + GAP))
> +    return 0;
> +  UINT a = x + (M * N);
> +  UINT b = a / N;
> +  return b - M;
> +}
> +
> +INT NOINLINE
> +opt_s1 (INT x)
> +{
> +  if (x < (M * N) - GAP)
> +    return 0;
> +  INT a = x - (M * N);
> +  INT b = a / N;
> +  return b + M;
> +}
> +
> +INT NOINLINE
> +opt_s2 (INT x)
> +{
> +  if (x < IMIN + (M * N) - GAP || x > 0)
> +    return 0;
> +  INT a = x - (M * N);
> +  INT b = a / N;
> +  return b + M;
> +}
> +
> +INT NOINLINE
> +opt_s3 (INT x)
> +{
> +  if (x < (M * N) - GAP)
> +    return 0;
> +  INT a = x - (M * N);
> +  INT b = a / -N;
> +  return b + -M;
> +}
> +
> +INT NOINLINE
> +opt_s4 (INT x)
> +{
> +  if (x < IMIN + (M * N) - GAP || x > 0)
> +    return 0;
> +  INT a = x - (M * N);
> +  INT b = a / -N;
> +  return b + -M;
> +}
> +
> +INT NOINLINE
> +opt_s5 (INT x)
> +{
> +  if (x > (-M * N) + GAP)
> +    return 0;
> +  INT a = x - (-M * N);
> +  INT b = a / N;
> +  return b + -M;
> +}
> +
> +INT NOINLINE
> +opt_s6 (INT x)
> +{
> +  if (x > IMAX - (M * N) + GAP || x < 0)
> +    return 0;
> +  INT a = x - (-M * N);
> +  INT b = a / N;
> +  return b + -M;
> +}
> +
> +INT NOINLINE
> +opt_s7 (INT x)
> +{
> +  if (x > (M * -N) + GAP)
> +    return 0;
> +  INT a = x - (M * -N);
> +  INT b = a / -N;
> +  return b + M;
> +}
> +
> +INT NOINLINE
> +opt_s8 (INT x)
> +{
> +  if (x > IMAX - (M * N) + GAP || x < 0)
> +    return 0;
> +  INT a = x - (M * -N);
> +  INT b = a / -N;
> +  return b + M;
> +}
> +
> +UINT NOINLINE
> +opt_u3 (UINT x)
> +{
> +  if (x < (M << N) - GAP)
> +    return 0;
> +  UINT a = x - (M << N);
> +  UINT b = a >> N;
> +  return b + M;
> +}
> +
> +UINT NOINLINE
> +opt_u4 (UINT x)
> +{
> +  if (x > (UMAX - (M << N)) + GAP)
> +    return 0;
> +  UINT a = x + (M << N);
> +  UINT b = a >> N;
> +  return b - M;
> +}
> +
> +INT NOINLINE
> +opt_s9 (INT x)
> +{
> +  if (x < (M << N) - GAP)
> +    return 0;
> +  INT a = x - (M << N);
> +  INT b = a >> N;
> +  return b + M;
> +}
> +
> +INT NOINLINE
> +opt_s10 (INT x)
> +{
> +  if (x < IMIN + (M << N) - GAP || x > 0)
> +    return 0;
> +  INT a = x - (M << N);
> +  INT b = a >> N;
> +  return b + M;
> +}
> +
> +INT NOINLINE
> +opt_s11 (INT x)
> +{
> +  if (x > (-M << N) + GAP)
> +    return 0;
> +  INT a = x - (-M << N);
> +  INT b = a >> N;
> +  return b + -M;
> +}
> +
> +INT NOINLINE
> +opt_s12 (INT x)
> +{
> +  if (x > IMAX - (M << N) + GAP || x < 0)
> +    return 0;
> +  INT a = x - (-M << N);
> +  INT b = a >> N;
> +  return b + -M;
> +}
> +
> +UINT NOINLINE
> +opt_u5 (UINT x, UINT n, UINT m)
> +{
> +  if (n > N || m > M)
> +    return 0;
> +  if (x < (M*N) - GAP)
> +    return 0;
> +  UINT a = x - (m * n);
> +  UINT b = a / n;
> +  return b + m;
> +}
> +
> +UINT NOINLINE
> +opt_u6 (UINT x, UINT n, UINT m)
> +{
> +  if (n > N || m > M)
> +    return 0;
> +  if (x > (UMAX - M*N) + GAP)
> +    return 0;
> +  UINT a = x + (m * n);
> +  UINT b = a / n;
> +  return b - m;
> +}
> +
> +INT NOINLINE
> +opt_s13 (INT x, INT n, INT m)
> +{
> +  if (n > N || m > M || n < 0 || m < 0)
> +    return 0;
> +  if (x < (M*N) - GAP)
> +    return 0;
> +  INT a = x - (m * n);
> +  INT b = a / n;
> +  return b + m;
> +}
> +
> +INT NOINLINE
> +opt_s14 (INT x, INT n, INT m)
> +{
> +  if (n > N || m > M || n < 0 || m < 0)
> +    return 0;
> +  if (x > -M*N + GAP)
> +    return 0;
> +  INT a = x + (m * n);
> +  INT b = a / n;
> +  return b - m;
> +}
> +
> +INT
> +opt_s15 (INT x, INT n, INT m)
> +{
> +  if (n > 0 || m > 0 || n < -N || m < -M)
> +    return 0;
> +  if (x < (M*N) - GAP)
> +    return 0;
> +  INT a = x - (m * n);
> +  INT b = a / n;
> +  return b + m;
> +}
> +
> +INT NOINLINE
> +opt_s16 (INT x, INT n, INT m)
> +{
> +  if (n > 0 || m > 0 || n < -N || m < -M)
> +    return 0;
> +  if (x < 0 || x > (IMAX - M*N) + GAP)
> +    return 0;
> +  INT a = x + (m * n);
> +  INT b = a / n;
> +  return b - m;
> +}
> +
> 

-- 
Richard Biener <rguenther@suse.de>
SUSE Software Solutions Germany GmbH,
Frankenstrasse 146, 90461 Nuernberg, Germany;
GF: Ivo Totev, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg)


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