Re: Use nonzero bits to refine range in split_constant_offset (PR 81635)
On Thu, Feb 8, 2018 at 1:09 PM, Richard Sandiford wrote: > Richard Biener writes: >> On Fri, Feb 2, 2018 at 3:12 PM, Richard Sandiford >> wrote: >>> Index: gcc/tree-data-ref.c >>> === >>> --- gcc/tree-data-ref.c 2018-02-02 14:03:53.964530009 + >>> +++ gcc/tree-data-ref.c 2018-02-02 14:03:54.184521826 + >>> @@ -721,7 +721,13 @@ split_constant_offset_1 (tree type, tree >>> if (TREE_CODE (tmp_var) != SSA_NAME) >>> return false; >>> wide_int var_min, var_max; >>> - if (get_range_info (tmp_var, &var_min, &var_max) != >>> VR_RANGE) >>> + value_range_type vr_type = get_range_info (tmp_var, >>> &var_min, >>> + &var_max); >>> + wide_int var_nonzero = get_nonzero_bits (tmp_var); >>> + signop sgn = TYPE_SIGN (itype); >>> + if (intersect_range_with_nonzero_bits (vr_type, &var_min, >>> + &var_max, >>> var_nonzero, >>> + sgn) != VR_RANGE) >> >> Above it looks like we could go from VR_RANGE to VR_UNDEFINED. >> I'm not sure if the original range-info might be useful in this case - >> if it may be >> can we simply use only the range info if it was VR_RANGE? > > I think we only drop to VR_UNDEFINED if we have contradictory > information: nonzero bits says some bits must be clear, but the range > only contains values for which the bits are set. In that case I think > we should either be conservative and not use the information, or be > aggressive and say that we have undefined behaviour, so overflow is OK. > > It seems a bit of a fudge to go back to the old range when we know it's > false, and use it to allow the split some times and not others. Fine. > Thanks, > Richard > >> >> Ok otherwise. >> Thanks, >> Richard. >> >>> return false; >>> >>> /* See whether the range of OP0 (i.e. TMP_VAR + TMP_OFF) >>> @@ -729,7 +735,6 @@ split_constant_offset_1 (tree type, tree >>>operations done in ITYPE. The addition must overflow >>>at both ends of the range or at neither. */ >>> bool overflow[2]; >>> - signop sgn = TYPE_SIGN (itype); >>> unsigned int prec = TYPE_PRECISION (itype); >>> wide_int woff = wi::to_wide (tmp_off, prec); >>> wide_int op0_min = wi::add (var_min, woff, sgn, >>> &overflow[0]); >>> Index: gcc/testsuite/gcc.dg/vect/bb-slp-pr81635-3.c >>> === >>> --- /dev/null 2018-02-02 09:03:36.168354735 + >>> +++ gcc/testsuite/gcc.dg/vect/bb-slp-pr81635-3.c2018-02-02 >>> 14:03:54.183521863 + >>> @@ -0,0 +1,62 @@ >>> +/* { dg-do compile } */ >>> +/* { dg-additional-options "-fno-tree-loop-vectorize" } */ >>> +/* { dg-require-effective-target vect_double } */ >>> +/* { dg-require-effective-target lp64 } */ >>> + >>> +void >>> +f1 (double *p, double *q, unsigned int n) >>> +{ >>> + p = (double *) __builtin_assume_aligned (p, sizeof (double) * 2); >>> + q = (double *) __builtin_assume_aligned (q, sizeof (double) * 2); >>> + for (unsigned int i = 0; i < n; i += 4) >>> +{ >>> + double a = q[i] + p[i]; >>> + double b = q[i + 1] + p[i + 1]; >>> + q[i] = a; >>> + q[i + 1] = b; >>> +} >>> +} >>> + >>> +void >>> +f2 (double *p, double *q, unsigned int n) >>> +{ >>> + p = (double *) __builtin_assume_aligned (p, sizeof (double) * 2); >>> + q = (double *) __builtin_assume_aligned (q, sizeof (double) * 2); >>> + for (unsigned int i = 0; i < n; i += 2) >>> +{ >>> + double a = q[i] + p[i]; >>> + double b = q[i + 1] + p[i + 1]; >>> + q[i] = a; >>> + q[i + 1] = b; >>> +} >>> +} >>> + >>> +void >>> +f3 (double *p, double *q, unsigned int n) >>> +{ >>> + p = (double *) __builtin_assume_aligned (p, sizeof (double) * 2); >>> + q = (double *) __builtin_assume_aligned (q, sizeof (double) * 2); >>> + for (unsigned int i = 0; i < n; i += 6) >>> +{ >>> + double a = q[i] + p[i]; >>> + double b = q[i + 1] + p[i + 1]; >>> + q[i] = a; >>> + q[i + 1] = b; >>> +} >>> +} >>> + >>> +void >>> +f4 (double *p, double *q, unsigned int start, unsigned int n) >>> +{ >>> + p = (double *) __builtin_assume_aligned (p, sizeof (double) * 2); >>> + q = (double *) __builtin_assume_aligned (q, sizeof (double) * 2); >>> + for (unsigned int i = start & -2; i < n; i += 2) >>> +{ >>> + double a = q[i] + p[i]; >>> + double b = q[i + 1] + p[i + 1]; >>> + q[i] = a; >>> + q[i + 1] = b; >>> +} >>> +} >>> + >>> +/* { dg-final { scan-tree-dump-times "basic block vectorized" 4 "slp1" } } >>> */ >>> Index: gcc/testsuite/gcc.dg/vect/bb-slp-pr81635-4.c >>> =
Re: Use nonzero bits to refine range in split_constant_offset (PR 81635)
Richard Biener writes: > On Fri, Feb 2, 2018 at 3:12 PM, Richard Sandiford > wrote: >> Index: gcc/tree-data-ref.c >> === >> --- gcc/tree-data-ref.c 2018-02-02 14:03:53.964530009 + >> +++ gcc/tree-data-ref.c 2018-02-02 14:03:54.184521826 + >> @@ -721,7 +721,13 @@ split_constant_offset_1 (tree type, tree >> if (TREE_CODE (tmp_var) != SSA_NAME) >> return false; >> wide_int var_min, var_max; >> - if (get_range_info (tmp_var, &var_min, &var_max) != VR_RANGE) >> + value_range_type vr_type = get_range_info (tmp_var, &var_min, >> + &var_max); >> + wide_int var_nonzero = get_nonzero_bits (tmp_var); >> + signop sgn = TYPE_SIGN (itype); >> + if (intersect_range_with_nonzero_bits (vr_type, &var_min, >> + &var_max, var_nonzero, >> + sgn) != VR_RANGE) > > Above it looks like we could go from VR_RANGE to VR_UNDEFINED. > I'm not sure if the original range-info might be useful in this case - > if it may be > can we simply use only the range info if it was VR_RANGE? I think we only drop to VR_UNDEFINED if we have contradictory information: nonzero bits says some bits must be clear, but the range only contains values for which the bits are set. In that case I think we should either be conservative and not use the information, or be aggressive and say that we have undefined behaviour, so overflow is OK. It seems a bit of a fudge to go back to the old range when we know it's false, and use it to allow the split some times and not others. Thanks, Richard > > Ok otherwise. > Thanks, > Richard. > >> return false; >> >> /* See whether the range of OP0 (i.e. TMP_VAR + TMP_OFF) >> @@ -729,7 +735,6 @@ split_constant_offset_1 (tree type, tree >>operations done in ITYPE. The addition must overflow >>at both ends of the range or at neither. */ >> bool overflow[2]; >> - signop sgn = TYPE_SIGN (itype); >> unsigned int prec = TYPE_PRECISION (itype); >> wide_int woff = wi::to_wide (tmp_off, prec); >> wide_int op0_min = wi::add (var_min, woff, sgn, >> &overflow[0]); >> Index: gcc/testsuite/gcc.dg/vect/bb-slp-pr81635-3.c >> === >> --- /dev/null 2018-02-02 09:03:36.168354735 + >> +++ gcc/testsuite/gcc.dg/vect/bb-slp-pr81635-3.c2018-02-02 >> 14:03:54.183521863 + >> @@ -0,0 +1,62 @@ >> +/* { dg-do compile } */ >> +/* { dg-additional-options "-fno-tree-loop-vectorize" } */ >> +/* { dg-require-effective-target vect_double } */ >> +/* { dg-require-effective-target lp64 } */ >> + >> +void >> +f1 (double *p, double *q, unsigned int n) >> +{ >> + p = (double *) __builtin_assume_aligned (p, sizeof (double) * 2); >> + q = (double *) __builtin_assume_aligned (q, sizeof (double) * 2); >> + for (unsigned int i = 0; i < n; i += 4) >> +{ >> + double a = q[i] + p[i]; >> + double b = q[i + 1] + p[i + 1]; >> + q[i] = a; >> + q[i + 1] = b; >> +} >> +} >> + >> +void >> +f2 (double *p, double *q, unsigned int n) >> +{ >> + p = (double *) __builtin_assume_aligned (p, sizeof (double) * 2); >> + q = (double *) __builtin_assume_aligned (q, sizeof (double) * 2); >> + for (unsigned int i = 0; i < n; i += 2) >> +{ >> + double a = q[i] + p[i]; >> + double b = q[i + 1] + p[i + 1]; >> + q[i] = a; >> + q[i + 1] = b; >> +} >> +} >> + >> +void >> +f3 (double *p, double *q, unsigned int n) >> +{ >> + p = (double *) __builtin_assume_aligned (p, sizeof (double) * 2); >> + q = (double *) __builtin_assume_aligned (q, sizeof (double) * 2); >> + for (unsigned int i = 0; i < n; i += 6) >> +{ >> + double a = q[i] + p[i]; >> + double b = q[i + 1] + p[i + 1]; >> + q[i] = a; >> + q[i + 1] = b; >> +} >> +} >> + >> +void >> +f4 (double *p, double *q, unsigned int start, unsigned int n) >> +{ >> + p = (double *) __builtin_assume_aligned (p, sizeof (double) * 2); >> + q = (double *) __builtin_assume_aligned (q, sizeof (double) * 2); >> + for (unsigned int i = start & -2; i < n; i += 2) >> +{ >> + double a = q[i] + p[i]; >> + double b = q[i + 1] + p[i + 1]; >> + q[i] = a; >> + q[i + 1] = b; >> +} >> +} >> + >> +/* { dg-final { scan-tree-dump-times "basic block vectorized" 4 "slp1" } } >> */ >> Index: gcc/testsuite/gcc.dg/vect/bb-slp-pr81635-4.c >> === >> --- /dev/null 2018-02-02 09:03:36.168354735 + >> +++ gcc/testsuite/gcc.dg/vect/bb-slp-pr81635-4.c2018-02-02 >> 14:03:54.183521863 + >> @@ -0,0 +1,47
Re: Use nonzero bits to refine range in split_constant_offset (PR 81635)
On Fri, Feb 2, 2018 at 3:12 PM, Richard Sandiford wrote: > This patch is part 2 of the fix for PR 81635. It means that > split_constant_offset can handle loops like: > > for (unsigned int i = 0; i < n; i += 4) > { > a[i] = ...; > a[i + 1] = ...; > } > > CCP records that "i" must have its low 2 bits clear, but we don't > include this information in the range of "i", which remains [0, +INF]. > I tried making set_nonzero_bits update the range info in the same > way that set_range_info updates the nonzero bits, but it regressed > cases like vrp117.c and made some other tests worse. > > vrp117.c has a multiplication by 10, so CCP can infer that the low bit > of the result is clear. If we included that in the range, the range > would go from [-INF, +INF] to [-INF, not-quite-+INF]. However, > the multiplication is also known to overflow in all cases, so VRP > saturates the result to [INT_MAX, INT_MAX]. This obviously creates a > contradiction with the nonzero bits, and intersecting the new saturated > range with an existing not-quite-+INF range would make us drop to > VR_UNDEFINED. We're prepared to fold a comparison with an [INT_MAX, > INT_MAX] value but not with a VR_UNDEFINED value. > > The other problems were created when intersecting [-INF, not-quite-+INF] > with a useful VR_ANTI_RANGE like ~[-1, 1]. The intersection would > keep the former range rather than the latter. > > The patch therefore keeps the adjustment local to split_constant_offset > for now, but adds a helper routine so that it's easy to move this later. > > Tested on aarch64-linux-gnu, x86_64-linux-gnu and powerpc64le-linux-gnu. > OK to install? > > Richard > > > 2018-02-02 Richard Sandiford > > gcc/ > PR tree-optimization/81635 > * wide-int.h (wi::round_down_for_mask, wi::round_up_for_mask): > Declare. > * wide-int.cc (wi::round_down_for_mask, wi::round_up_for_mask) > (test_round_for_mask): New functions. > (wide_int_cc_tests): Call test_round_for_mask. > * tree-vrp.h (intersect_range_with_nonzero_bits): Declare. > * tree-vrp.c (intersect_range_with_nonzero_bits): New function. > * tree-data-ref.c (split_constant_offset_1): Use it to refine the > range returned by get_range_info. > > gcc/testsuite/ > PR tree-optimization/81635 > * gcc.dg/vect/bb-slp-pr81635-3.c: New test. > * gcc.dg/vect/bb-slp-pr81635-4.c: Likewise. > > Index: gcc/wide-int.h > === > --- gcc/wide-int.h 2018-02-02 14:03:53.964530009 + > +++ gcc/wide-int.h 2018-02-02 14:03:54.185521788 + > @@ -3308,6 +3308,8 @@ gt_pch_nx (trailing_wide_ints *, voi >wide_int set_bit_in_zero (unsigned int, unsigned int); >wide_int insert (const wide_int &x, const wide_int &y, unsigned int, >unsigned int); > + wide_int round_down_for_mask (const wide_int &, const wide_int &); > + wide_int round_up_for_mask (const wide_int &, const wide_int &); > >template >T mask (unsigned int, bool); > Index: gcc/wide-int.cc > === > --- gcc/wide-int.cc 2018-02-02 14:03:53.964530009 + > +++ gcc/wide-int.cc 2018-02-02 14:03:54.185521788 + > @@ -2132,6 +2132,70 @@ wi::only_sign_bit_p (const wide_int_ref >return only_sign_bit_p (x, x.precision); > } > > +/* Return VAL if VAL has no bits set outside MASK. Otherwise round VAL > + down to the previous value that has no bits set outside MASK. > + This rounding wraps for signed values if VAL is negative and > + the top bit of MASK is clear. > + > + For example, round_down_for_mask (6, 0xf1) would give 1 and > + round_down_for_mask (24, 0xf1) would give 17. */ > + > +wide_int > +wi::round_down_for_mask (const wide_int &val, const wide_int &mask) > +{ > + /* Get the bits in VAL that are outside the mask. */ > + wide_int extra_bits = wi::bit_and_not (val, mask); > + if (extra_bits == 0) > +return val; > + > + /* Get a mask that includes the top bit in EXTRA_BITS and is all 1s > + below that bit. */ > + unsigned int precision = val.get_precision (); > + wide_int lower_mask = wi::mask (precision - wi::clz (extra_bits), > + false, precision); > + > + /* Clear the bits that aren't in MASK, but ensure that all bits > + in MASK below the top cleared bit are set. */ > + return (val & mask) | (mask & lower_mask); > +} > + > +/* Return VAL if VAL has no bits set outside MASK. Otherwise round VAL > + up to the next value that has no bits set outside MASK. The rounding > + wraps if there are no suitable values greater than VAL. > + > + For example, round_up_for_mask (6, 0xf1) would give 16 and > + round_up_for_mask (24, 0xf1) would give 32. */ > + > +wide_int > +wi::round_up_for_mask (const wide_int &val, const wide_int &mask) > +{ > + /* Get the bits in VAL that are outside the
Use nonzero bits to refine range in split_constant_offset (PR 81635)
This patch is part 2 of the fix for PR 81635. It means that split_constant_offset can handle loops like: for (unsigned int i = 0; i < n; i += 4) { a[i] = ...; a[i + 1] = ...; } CCP records that "i" must have its low 2 bits clear, but we don't include this information in the range of "i", which remains [0, +INF]. I tried making set_nonzero_bits update the range info in the same way that set_range_info updates the nonzero bits, but it regressed cases like vrp117.c and made some other tests worse. vrp117.c has a multiplication by 10, so CCP can infer that the low bit of the result is clear. If we included that in the range, the range would go from [-INF, +INF] to [-INF, not-quite-+INF]. However, the multiplication is also known to overflow in all cases, so VRP saturates the result to [INT_MAX, INT_MAX]. This obviously creates a contradiction with the nonzero bits, and intersecting the new saturated range with an existing not-quite-+INF range would make us drop to VR_UNDEFINED. We're prepared to fold a comparison with an [INT_MAX, INT_MAX] value but not with a VR_UNDEFINED value. The other problems were created when intersecting [-INF, not-quite-+INF] with a useful VR_ANTI_RANGE like ~[-1, 1]. The intersection would keep the former range rather than the latter. The patch therefore keeps the adjustment local to split_constant_offset for now, but adds a helper routine so that it's easy to move this later. Tested on aarch64-linux-gnu, x86_64-linux-gnu and powerpc64le-linux-gnu. OK to install? Richard 2018-02-02 Richard Sandiford gcc/ PR tree-optimization/81635 * wide-int.h (wi::round_down_for_mask, wi::round_up_for_mask): Declare. * wide-int.cc (wi::round_down_for_mask, wi::round_up_for_mask) (test_round_for_mask): New functions. (wide_int_cc_tests): Call test_round_for_mask. * tree-vrp.h (intersect_range_with_nonzero_bits): Declare. * tree-vrp.c (intersect_range_with_nonzero_bits): New function. * tree-data-ref.c (split_constant_offset_1): Use it to refine the range returned by get_range_info. gcc/testsuite/ PR tree-optimization/81635 * gcc.dg/vect/bb-slp-pr81635-3.c: New test. * gcc.dg/vect/bb-slp-pr81635-4.c: Likewise. Index: gcc/wide-int.h === --- gcc/wide-int.h 2018-02-02 14:03:53.964530009 + +++ gcc/wide-int.h 2018-02-02 14:03:54.185521788 + @@ -3308,6 +3308,8 @@ gt_pch_nx (trailing_wide_ints *, voi wide_int set_bit_in_zero (unsigned int, unsigned int); wide_int insert (const wide_int &x, const wide_int &y, unsigned int, unsigned int); + wide_int round_down_for_mask (const wide_int &, const wide_int &); + wide_int round_up_for_mask (const wide_int &, const wide_int &); template T mask (unsigned int, bool); Index: gcc/wide-int.cc === --- gcc/wide-int.cc 2018-02-02 14:03:53.964530009 + +++ gcc/wide-int.cc 2018-02-02 14:03:54.185521788 + @@ -2132,6 +2132,70 @@ wi::only_sign_bit_p (const wide_int_ref return only_sign_bit_p (x, x.precision); } +/* Return VAL if VAL has no bits set outside MASK. Otherwise round VAL + down to the previous value that has no bits set outside MASK. + This rounding wraps for signed values if VAL is negative and + the top bit of MASK is clear. + + For example, round_down_for_mask (6, 0xf1) would give 1 and + round_down_for_mask (24, 0xf1) would give 17. */ + +wide_int +wi::round_down_for_mask (const wide_int &val, const wide_int &mask) +{ + /* Get the bits in VAL that are outside the mask. */ + wide_int extra_bits = wi::bit_and_not (val, mask); + if (extra_bits == 0) +return val; + + /* Get a mask that includes the top bit in EXTRA_BITS and is all 1s + below that bit. */ + unsigned int precision = val.get_precision (); + wide_int lower_mask = wi::mask (precision - wi::clz (extra_bits), + false, precision); + + /* Clear the bits that aren't in MASK, but ensure that all bits + in MASK below the top cleared bit are set. */ + return (val & mask) | (mask & lower_mask); +} + +/* Return VAL if VAL has no bits set outside MASK. Otherwise round VAL + up to the next value that has no bits set outside MASK. The rounding + wraps if there are no suitable values greater than VAL. + + For example, round_up_for_mask (6, 0xf1) would give 16 and + round_up_for_mask (24, 0xf1) would give 32. */ + +wide_int +wi::round_up_for_mask (const wide_int &val, const wide_int &mask) +{ + /* Get the bits in VAL that are outside the mask. */ + wide_int extra_bits = wi::bit_and_not (val, mask); + if (extra_bits == 0) +return val; + + /* Get a mask that is all 1s above the top bit in EXTRA_BITS. */ + unsigned int precision = val.get_precision (); + wide_int upper_mask = wi::mask (precision - w