[Bug middle-end/109986] missing fold (~a | b) ^ a => ~(a & b)
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109986 Andrew Pinski changed: What|Removed |Added Status|NEW |RESOLVED Target Milestone|--- |14.0 Resolution|--- |FIXED --- Comment #7 from Andrew Pinski --- Fixed, I will file some bool ones in a few minutes.
[Bug middle-end/109986] missing fold (~a | b) ^ a => ~(a & b)
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109986 Gabriel Ravier changed: What|Removed |Added CC||gabravier at gmail dot com --- Comment #6 from Gabriel Ravier --- Seems to be fixed on trunk, except that I've noticed that the f0 example does some weird operations on BPF, but that seems like a separate issue.
[Bug middle-end/109986] missing fold (~a | b) ^ a => ~(a & b)
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109986 --- Comment #5 from Ivan Sorokin --- (In reply to CVS Commits from comment #4) > commit r14-2751-g2a3556376c69a1fb588dcf25225950575e42784f > Author: Drew Ross > Co-authored-by: Jakub Jelinek Thank you!
[Bug middle-end/109986] missing fold (~a | b) ^ a => ~(a & b)
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109986 --- Comment #4 from CVS Commits --- The master branch has been updated by Jakub Jelinek : https://gcc.gnu.org/g:2a3556376c69a1fb588dcf25225950575e42784f commit r14-2751-g2a3556376c69a1fb588dcf25225950575e42784f Author: Drew Ross Date: Mon Jul 24 17:51:28 2023 +0200 match.pd: Implement missed optimization (~X | Y) ^ X -> ~(X & Y) [PR109986] Adds a simplification for (~X | Y) ^ X to be folded into ~(X & Y). Also adds the macro bitwise_equal_p for generic and gimple which returns true iff EXPR1 and EXPR2 have the same value. This helps to reduce the number of nop_converts necessary to match the pattern. PR middle-end/109986 gcc/ChangeLog: * generic-match-head.cc (bitwise_equal_p): New macro. * gimple-match-head.cc (bitwise_equal_p): New macro. (gimple_nop_convert): Declare. (gimple_bitwise_equal_p): Helper for bitwise_equal_p. * match.pd ((~X | Y) ^ X -> ~(X & Y)): New simplification. gcc/testsuite/ChangeLog: * gcc.c-torture/execute/pr109986.c: New test. * gcc.dg/tree-ssa/pr109986.c: New test. Co-authored-by: Jakub Jelinek
[Bug middle-end/109986] missing fold (~a | b) ^ a => ~(a & b)
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109986 --- Comment #3 from Ivan Sorokin --- I tried to investigate why GCC is able to simplify `(a | b) ^ a` and `(a | ~b) ^ a` from comment 2, but not similarly looking `(~a | b) ^ a` from comment 0. `(a | b) ^ a` matches the following pattern from match.pd: /* (X | Y) ^ X -> Y & ~ X*/ (simplify (bit_xor:c (convert1? (bit_ior:c @@0 @1)) (convert2? @0)) (if (tree_nop_conversion_p (type, TREE_TYPE (@0))) (convert (bit_and @1 (bit_not @0) `(a | ~b) ^ a` matches another pattern: /* (~X | C) ^ D -> (X | C) ^ (~D ^ C) if (~D ^ C) can be simplified. */ (simplify (bit_xor:c (bit_ior:cs (bit_not:s @0) @1) @2) (bit_xor (bit_ior @0 @1) (bit_xor! (bit_not! @2) @1))) With substitution `X = b, C = a, D = a` it gives: (b | a) ^ (~a ^ a) (b | a) ^ -1 ~(b | a) `(~a | b) ^ a` is not simplifiable by this pattern because it requires that `~D ^ C` is simplifiable further, but `~a ^ b` is not. In any case, even if it were applicable it would produce `(a | b) ^ (~a ^ b)` which has more operations than the original expression.
[Bug middle-end/109986] missing fold (~a | b) ^ a => ~(a & b)
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109986
Andrew Pinski changed:
What|Removed |Added
Keywords||missed-optimization
Last reconfirmed||2023-05-26
Status|UNCONFIRMED |NEW
Severity|normal |enhancement
Ever confirmed|0 |1
--- Comment #2 from Andrew Pinski ---
GCC does handle:
int f0(int a, int b)
{
return (a | b) ^ a;
}
And:
int f1(int a, int b)
{
return (a | ~b) ^ a;
}
[Bug middle-end/109986] missing fold (~a | b) ^ a => ~(a & b)
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109986
--- Comment #1 from Ivan Sorokin ---
(In reply to Ivan Sorokin from comment #0)
> int foo(int a, int b)
> {
> return (~a | b) ^ a;
> }
>
> This can be optimized to `return ~(a | b);`. This transformation is done by
> LLVM, but not by GCC.
Correction: it can be optimized to `return ~(a & b);`.
