On Wed, 17 May 2023, Jiufu Guo wrote: > Hi, > > This patch tries to optimize "(X - N * M) / N + M" to "X / N".
But if that's valid why not make the transform simpler and transform (X - N * M) / N to X / N - M instead? You use the same optimize_x_minus_NM_div_N_plus_M validator for the division and shift variants but the overflow rules are different, so I'm not sure that's warranted. I'd also prefer to not split out the validator to a different file - iff then the appropriate file is fold-const.cc, not gimple-match-head.cc (I see we're a bit inconsistent here, for pure gimple matches gimple-fold.cc would be another place). Since you use range information why is the transform restricted to constant M? Richard. > As per the discussions in PR108757, we know this transformation is valid > only under some conditions. > For C code, "/" towards zero (trunc_div), and "X - N * M" > maybe wrap/overflow/underflow. So, it is valid that "X - N * M" does > not cross zero and does not wrap/overflow/underflow. > > This patch also handles the case when "N" is the power of 2, where > "(X - N * M) / N" is "(X - N * M) >> log2(N)". > > Bootstrap & regtest pass on ppc64{,le} and x86_64. > Is this ok for trunk? > > BR, > Jeff (Jiufu) > > PR tree-optimization/108757 > > gcc/ChangeLog: > > * gimple-match-head.cc (optimize_x_minus_NM_div_N_plus_M): New function. > * match.pd ((X - N * M) / N + M): 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/gimple-match-head.cc | 54 ++++++++++ > gcc/match.pd | 22 ++++ > gcc/testsuite/gcc.dg/pr108757-1.c | 17 ++++ > gcc/testsuite/gcc.dg/pr108757-2.c | 18 ++++ > gcc/testsuite/gcc.dg/pr108757.h | 160 ++++++++++++++++++++++++++++++ > 5 files changed, 271 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/gimple-match-head.cc b/gcc/gimple-match-head.cc > index b08cd891a13..680a4cb2fc6 100644 > --- a/gcc/gimple-match-head.cc > +++ b/gcc/gimple-match-head.cc > @@ -224,3 +224,57 @@ optimize_successive_divisions_p (tree divisor, tree > inner_div) > } > return true; > } > + > +/* Return true if "(X - N * M) / N + M" can be optimized into "X / N". > + Otherwise return false. > + > + For unsigned, > + If sign bit of M is 0 (clz is 0), valid range is [N*M, MAX]. > + If sign bit of M is 1, valid range is [0, MAX - N*(-M)]. > + > + For signed, > + If N*M > 0, valid range: [MIN+N*M, 0] + [N*M, MAX] > + If N*M < 0, valid range: [MIN, -(-N*M)] + [0, MAX - (-N*M)]. */ > + > +static bool > +optimize_x_minus_NM_div_N_plus_M (tree x, wide_int n, wide_int m, tree type) > +{ > + wide_int max = wi::max_value (type); > + signop sgn = TYPE_SIGN (type); > + wide_int nm; > + wi::overflow_type ovf; > + if (TYPE_UNSIGNED (type) && wi::clz (m) == 0) > + nm = wi::mul (n, -m, sgn, &ovf); > + else > + nm = wi::mul (n, m, sgn, &ovf); > + > + if (ovf != wi::OVF_NONE) > + return false; > + > + value_range vr0; > + if (!get_range_query (cfun)->range_of_expr (vr0, x) || vr0.varying_p () > + || vr0.undefined_p ()) > + return false; > + > + wide_int wmin0 = vr0.lower_bound (); > + wide_int wmax0 = vr0.upper_bound (); > + wide_int min = wi::min_value (type); > + > + /* unsigned */ > + if ((TYPE_UNSIGNED (type))) > + /* M > 0 (clz != 0): [N*M, MAX], M < 0 : [0, MAX-N*(-M)] */ > + return wi::clz (m) != 0 ? wi::ge_p (wmin0, nm, sgn) > + : wi::le_p (wmax0, max - nm, sgn); > + > + /* signed, N*M > 0 */ > + else if (wi::gt_p (nm, 0, sgn)) > + /* [N*M, MAX] or [MIN+N*M, 0] */ > + return wi::ge_p (wmin0, nm, sgn) > + || (wi::ge_p (wmin0, min + nm, sgn) && wi::le_p (wmax0, 0, sgn)); > + > + /* signed, N*M < 0 */ > + /* [MIN, N*M] or [0, MAX + N*M]*/ > + else > + return wi::le_p (wmax0, nm, sgn) > + || (wi::ge_p (wmin0, 0, sgn) && wi::le_p (wmax0, max - (-nm), sgn)); > +} > diff --git a/gcc/match.pd b/gcc/match.pd > index ceae1c34abc..1aaa5530577 100644 > --- a/gcc/match.pd > +++ b/gcc/match.pd > @@ -881,6 +881,28 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) > #endif > )))) > > +#if GIMPLE > +/* Simplify ((t + -N*M) / N + M) -> t / N. */ > +(for div (trunc_div exact_div) > + (simplify > + (plus (div (plus @0 INTEGER_CST@1) INTEGER_CST@2) INTEGER_CST@3) > + (with {wide_int n = wi::to_wide (@2); wide_int m = wi::to_wide (@3);} > + (if (INTEGRAL_TYPE_P (type) > + && n * m == -wi::to_wide (@1) > + && optimize_x_minus_NM_div_N_plus_M (@0, n, m, type)) > + (div @0 @2))))) > + > +/* Simplify ((t + -(M<<N)) >> N + M) -> t >> N. */ > +(simplify > + (plus (rshift (plus @0 INTEGER_CST@1) INTEGER_CST@2) INTEGER_CST@3) > + (with {wide_int n = wi::to_wide (@2); wide_int m = wi::to_wide (@3);} > + (if (INTEGRAL_TYPE_P (type) > + && (m << n) == -wi::to_wide (@1) > + && optimize_x_minus_NM_div_N_plus_M (@0, > + wi::one (TYPE_PRECISION (type)) << n, m, type)) > + (rshift @0 @2)))) > +#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 00000000000..349318a7c82 > --- /dev/null > +++ b/gcc/testsuite/gcc.dg/pr108757-1.c > @@ -0,0 +1,17 @@ > +/* PR tree-optimization/108757 */ > +/* { dg-do compile } */ > +/* { dg-options "-O2 -fdump-tree-optimized" } */ > + > +#include <limits.h> > +#define N 4 > +#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 " = 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 00000000000..7302e9c606c > --- /dev/null > +++ b/gcc/testsuite/gcc.dg/pr108757-2.c > @@ -0,0 +1,18 @@ > +/* PR tree-optimization/108757 */ > +/* { dg-do compile } */ > +/* { dg-options "-O2 -fdump-tree-optimized" } */ > + > +#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 " = b_\[0-9\] \\+ " 16 "optimized" } } > */ > + > diff --git a/gcc/testsuite/gcc.dg/pr108757.h b/gcc/testsuite/gcc.dg/pr108757.h > new file mode 100644 > index 00000000000..9e12d106aad > --- /dev/null > +++ b/gcc/testsuite/gcc.dg/pr108757.h > @@ -0,0 +1,160 @@ > +#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; > +} > -- Richard Biener <rguent...@suse.de> SUSE Software Solutions Germany GmbH, Frankenstrasse 146, 90461 Nuernberg, Germany; GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman; HRB 36809 (AG Nuernberg)