Hello,
On Wed, 16 Sep 2020, Richard Biener wrote:
> This removes the canonicalization of X + -CST to X - CST to facilitate
> SLP vectorization analysis where we currently treat the added testcase
> as two-operation plus blend vectorization opportunity. While there
> may be the possibility to avoid this in the vectorizer itself the
> canonicalization is somewhat premature - it's motivation is that
> a FP constant of both signs is common and thus canonicalizing to
> positive values optimizes constant pool. But if you mix, say,
> x * -7.1 and x - 7.1 this backfires - this instead looks like
> a local optimization to be applied in RTL CSE or even LRA
> load inheritance. I filed PR97071 for this.
>
> Bootstrapped and tested on x86_64-unknown-linux-gnu, any objections?
You need to adjust the comments, this will be very confusing in a couple
years:
/* We want to canonicalize to positive real constants. Pretend
that only negative ones can be easily negated. */
return true;
Ciao,
Michael.
>
> Thanks,
> Richard.
>
> 2020-09-16 Richard Biener <rguent...@suse.de>
>
> * fold-const.c (fold_binary_loc): Remove condition
> on REAL_CST for A - B -> A + (-B) transform.
> (negate_expr_p): Remove condition on REAL_CST.
> * match.pd (negate_expr_p): Likewise.
> (X + -C -> X - C): Remove.
>
> * gcc.dg/vect/slp-49.c: New testcase.
> * gcc.dg/tree-ssa/pr90356-1.c: Adjust.
> * gcc.dg/tree-ssa/pr90356-3.c: Likewise.
> * gcc.dg/tree-ssa/pr90356-4.c: Likewise.
> * gcc.target/i386/pr54855-3.c: Likewise.
> * gfortran.dg/reassoc_1.f90: Likewise.
> * gfortran.dg/reassoc_2.f90: Likewise.
> ---
> gcc/fold-const.c | 7 ++-----
> gcc/match.pd | 11 +----------
> gcc/testsuite/gcc.dg/tree-ssa/pr90356-1.c | 4 ++--
> gcc/testsuite/gcc.dg/tree-ssa/pr90356-3.c | 2 +-
> gcc/testsuite/gcc.dg/tree-ssa/pr90356-4.c | 2 +-
> gcc/testsuite/gcc.dg/vect/slp-49.c | 15 +++++++++++++++
> gcc/testsuite/gcc.target/i386/pr54855-3.c | 2 +-
> gcc/testsuite/gfortran.dg/reassoc_1.f90 | 2 +-
> gcc/testsuite/gfortran.dg/reassoc_2.f90 | 2 +-
> 9 files changed, 25 insertions(+), 22 deletions(-)
> create mode 100644 gcc/testsuite/gcc.dg/vect/slp-49.c
>
> diff --git a/gcc/fold-const.c b/gcc/fold-const.c
> index 0cc80adf632..ec369169a4c 100644
> --- a/gcc/fold-const.c
> +++ b/gcc/fold-const.c
> @@ -401,7 +401,7 @@ negate_expr_p (tree t)
> case REAL_CST:
> /* We want to canonicalize to positive real constants. Pretend
> that only negative ones can be easily negated. */
> - return REAL_VALUE_NEGATIVE (TREE_REAL_CST (t));
> + return true;
>
> case COMPLEX_CST:
> return negate_expr_p (TREE_REALPART (t))
> @@ -10962,10 +10962,7 @@ fold_binary_loc (location_t loc, enum tree_code
> code, tree type,
> /* A - B -> A + (-B) if B is easily negatable. */
> if (negate_expr_p (op1)
> && ! TYPE_OVERFLOW_SANITIZED (type)
> - && ((FLOAT_TYPE_P (type)
> - /* Avoid this transformation if B is a positive REAL_CST. */
> - && (TREE_CODE (op1) != REAL_CST
> - || REAL_VALUE_NEGATIVE (TREE_REAL_CST (op1))))
> + && (FLOAT_TYPE_P (type)
> || INTEGRAL_TYPE_P (type)))
> return fold_build2_loc (loc, PLUS_EXPR, type,
> fold_convert_loc (loc, type, arg0),
> diff --git a/gcc/match.pd b/gcc/match.pd
> index 7d63bb973cb..9f14d50ae2d 100644
> --- a/gcc/match.pd
> +++ b/gcc/match.pd
> @@ -1307,8 +1307,7 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
> (negate @0)
> (if (!TYPE_OVERFLOW_SANITIZED (type))))
> (match negate_expr_p
> - REAL_CST
> - (if (REAL_VALUE_NEGATIVE (TREE_REAL_CST (t)))))
> + REAL_CST)
> /* VECTOR_CST handling of non-wrapping types would recurse in unsupported
> ways. */
> (match negate_expr_p
> @@ -3326,14 +3325,6 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
>
> /* Canonicalization of binary operations. */
>
> -/* Convert X + -C into X - C. */
> -(simplify
> - (plus @0 REAL_CST@1)
> - (if (REAL_VALUE_NEGATIVE (TREE_REAL_CST (@1)))
> - (with { tree tem = const_unop (NEGATE_EXPR, type, @1); }
> - (if (!TREE_OVERFLOW (tem) || !flag_trapping_math)
> - (minus @0 { tem; })))))
> -
> /* Convert x+x into x*2. */
> (simplify
> (plus @0 @0)
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr90356-1.c
> b/gcc/testsuite/gcc.dg/tree-ssa/pr90356-1.c
> index c3a15ea21af..ac95ec56810 100644
> --- a/gcc/testsuite/gcc.dg/tree-ssa/pr90356-1.c
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/pr90356-1.c
> @@ -2,8 +2,8 @@
> /* { dg-do compile } */
> /* { dg-options "-O2 -fno-rounding-math -fsignaling-nans -fsigned-zeros
> -fdump-tree-optimized" } */
> /* { dg-final { scan-tree-dump-times "x_\[0-9]*.D. \\+ 0.0;" 12 "optimized"
> } } */
> -/* { dg-final { scan-tree-dump-times "y_\[0-9]*.D. - 0.0;" 4 "optimized" } }
> */
> -/* { dg-final { scan-tree-dump-times " \[+-] 0.0;" 16 "optimized" } } */
> +/* { dg-final { scan-tree-dump-times "y_\[0-9]*.D. \\+ -0.0;" 4 "optimized"
> } } */
> +/* { dg-final { scan-tree-dump-times " \\+ -?0.0;" 16 "optimized" } } */
>
> double f1 (double x) { return (x + 0.0) + 0.0; }
> double f2 (double y) { return (y + (-0.0)) + (-0.0); }
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr90356-3.c
> b/gcc/testsuite/gcc.dg/tree-ssa/pr90356-3.c
> index e658130c69f..951971b95ee 100644
> --- a/gcc/testsuite/gcc.dg/tree-ssa/pr90356-3.c
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/pr90356-3.c
> @@ -1,6 +1,6 @@
> /* PR tree-optimization/90356 */
> /* { dg-do compile } */
> /* { dg-options "-O2 -frounding-math -fsignaling-nans -fsigned-zeros
> -fdump-tree-optimized" } */
> -/* { dg-final { scan-tree-dump-times " \[+-] 0.0;" 32 "optimized" } } */
> +/* { dg-final { scan-tree-dump-times " \\+ -?0.0;" 32 "optimized" } } */
>
> #include "pr90356-1.c"
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr90356-4.c
> b/gcc/testsuite/gcc.dg/tree-ssa/pr90356-4.c
> index 126cd10928b..3459ddba356 100644
> --- a/gcc/testsuite/gcc.dg/tree-ssa/pr90356-4.c
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/pr90356-4.c
> @@ -1,6 +1,6 @@
> /* PR tree-optimization/90356 */
> /* { dg-do compile } */
> /* { dg-options "-O2 -frounding-math -fno-signaling-nans -fsigned-zeros
> -fdump-tree-optimized" } */
> -/* { dg-final { scan-tree-dump-times " \[+-] 0.0;" 32 "optimized" } } */
> +/* { dg-final { scan-tree-dump-times " \\+ -?0.0;" 32 "optimized" } } */
>
> #include "pr90356-1.c"
> diff --git a/gcc/testsuite/gcc.dg/vect/slp-49.c
> b/gcc/testsuite/gcc.dg/vect/slp-49.c
> new file mode 100644
> index 00000000000..4b3ec77b99d
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/vect/slp-49.c
> @@ -0,0 +1,15 @@
> +/* { dg-do compile } */
> +/* { dg-require-effective-target vect_double } */
> +
> +void foo (double *x)
> +{
> + for (int i = 0; i < 1024; ++i)
> + {
> + x[2*i] += 1.0;
> + x[2*i+1] -= 2.0;
> + }
> +}
> +
> +/* { dg-final { scan-tree-dump "loop vectorized" "vect" } } */
> +/* The loop should be SLPed with uniform plus. */
> +/* { dg-final { scan-tree-dump-not "VEC_PERM" "vect" } } */
> diff --git a/gcc/testsuite/gcc.target/i386/pr54855-3.c
> b/gcc/testsuite/gcc.target/i386/pr54855-3.c
> index 3c15dfc93d1..802d6882e43 100644
> --- a/gcc/testsuite/gcc.target/i386/pr54855-3.c
> +++ b/gcc/testsuite/gcc.target/i386/pr54855-3.c
> @@ -1,6 +1,6 @@
> /* { dg-do compile } */
> /* { dg-options "-O2 -msse2 -mfpmath=sse" } */
> -/* { dg-final { scan-assembler-times "subsd" 1 } } */
> +/* { dg-final { scan-assembler-times "addsd" 1 } } */
> /* { dg-final { scan-assembler-not "movapd" } } */
> /* { dg-final { scan-assembler-not "movsd" } } */
>
> diff --git a/gcc/testsuite/gfortran.dg/reassoc_1.f90
> b/gcc/testsuite/gfortran.dg/reassoc_1.f90
> index e3d84c4ffd9..19b47fc7ce6 100644
> --- a/gcc/testsuite/gfortran.dg/reassoc_1.f90
> +++ b/gcc/testsuite/gfortran.dg/reassoc_1.f90
> @@ -9,4 +9,4 @@ end
>
> ! We need an explicit +5 and -5, and an intermediate ((bla)) expression
> ! (the reassoc barrier). Make use of "." matching lineends.
> -! { dg-final { scan-tree-dump "\\\+ 5.*\\\)\\\).* - 5" "optimized" } }
> +! { dg-final { scan-tree-dump "\\\+ 5.*\\\)\\\).* \\\+ -5" "optimized" } }
> diff --git a/gcc/testsuite/gfortran.dg/reassoc_2.f90
> b/gcc/testsuite/gfortran.dg/reassoc_2.f90
> index 3e323eb0134..62361619932 100644
> --- a/gcc/testsuite/gfortran.dg/reassoc_2.f90
> +++ b/gcc/testsuite/gfortran.dg/reassoc_2.f90
> @@ -12,4 +12,4 @@ function test(a)
> test = d
> end
>
> -! { dg-final { scan-tree-dump "- 5" "optimized" } }
> +! { dg-final { scan-tree-dump "\\\+ -5" "optimized" } }
>
