[Bug tree-optimization/110992] [13/14 Regression] missed VRP optimization due to transformation of `a & -zero_one_valued_p` into `a * zero_one_valued_p`
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110992 Xi Ruoyao changed: What|Removed |Added CC||xry111 at gcc dot gnu.org See Also||https://gcc.gnu.org/bugzill ||a/show_bug.cgi?id=26 --- Comment #14 from Xi Ruoyao --- (In reply to Jeffrey A. Law from comment #13) > So like the other bug involving multiplies against objects with a known > range [0,1], we should very seriously consider turning the multiply into a > conditional move. ie x * b where b is known to have the range [0,1] we can > turn that into > > dest = b ? x : 0 > > Some processors that don't have generalized conditional moves do have > conditional zero instructions. ie, zicond on RISC-V. It's PR26.
[Bug tree-optimization/110992] [13/14 Regression] missed VRP optimization due to transformation of `a & -zero_one_valued_p` into `a * zero_one_valued_p`
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110992 Jeffrey A. Law changed: What|Removed |Added CC||rzinsly at ventanamicro dot com --- Comment #13 from Jeffrey A. Law --- So like the other bug involving multiplies against objects with a known range [0,1], we should very seriously consider turning the multiply into a conditional move. ie x * b where b is known to have the range [0,1] we can turn that into dest = b ? x : 0 Some processors that don't have generalized conditional moves do have conditional zero instructions. ie, zicond on RISC-V.
[Bug tree-optimization/110992] [13/14 Regression] missed VRP optimization due to transformation of `a & -zero_one_valued_p` into `a * zero_one_valued_p`
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110992 Jeffrey A. Law changed: What|Removed |Added CC||law at gcc dot gnu.org Priority|P3 |P2
[Bug tree-optimization/110992] [13/14 Regression] missed VRP optimization due to transformation of `a & -zero_one_valued_p` into `a * zero_one_valued_p`
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110992 Andrew Pinski changed: What|Removed |Added URL|https://gcc.gnu.org/piperma | |il/gcc-patches/2023-Septemb | |er/630651.html | Status|ASSIGNED|NEW Keywords|patch | Assignee|pinskia at gcc dot gnu.org |unassigned at gcc dot gnu.org --- Comment #12 from Andrew Pinski --- Not working on this. a Ranger/VRP person should fix this instead ...
[Bug tree-optimization/110992] [13/14 Regression] missed VRP optimization due to transformation of `a & -zero_one_valued_p` into `a * zero_one_valued_p`
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110992 Andrew Pinski changed: What|Removed |Added Keywords||patch URL||https://gcc.gnu.org/piperma ||il/gcc-patches/2023-Septemb ||er/630651.html --- Comment #11 from Andrew Pinski --- Patch posted: https://gcc.gnu.org/pipermail/gcc-patches/2023-September/630651.html
[Bug tree-optimization/110992] [13/14 Regression] missed VRP optimization due to transformation of `a & -zero_one_valued_p` into `a * zero_one_valued_p`
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110992
--- Comment #10 from Andrew Pinski ---
This is what I came up with in the end:
/* (a * b@[0,1]) == CST
->
CST == 0 ? (a == CST | b == 0) : (a == CST & b != 0)
(a * b@[0,1]) != CST
->
CST != 0 ? (a != CST | b == 0) : (a != CST & b != 0) */
(for cmp (ne eq)
(simplify
(cmp (mult:cs @0 zero_one_valued_p@1) INTEGER_CST@2)
(if ((cmp == EQ_EXPR) ^ (wi::to_wide (@2) != 0))
(bit_ior
(cmp @0 @2)
(convert (bit_xor @1 { build_one_cst (TREE_TYPE (@1)); })))
(bit_and (cmp @0 @2) (convert @1)
This allows more than just CST == 0 even. I will write up some testcases now
...
[Bug tree-optimization/110992] [13/14 Regression] missed VRP optimization due to transformation of `a & -zero_one_valued_p` into `a * zero_one_valued_p`
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110992
--- Comment #9 from Andrew Pinski ---
This is what I have so far:
/* Transform (a * { 0 or 1 }) != 0 into {0 or 1} != 0 & (a != 0) */
/* Transform (a * { 0 or 1 }) == 0 into ({0 or 1} == 0) | (a == 0) */
(for cmp (ne eq)
bit_op (bit_and bit_ior)
(simplify
(cmp (mult:cs @0 zero_one_valued_p@1) integer_zerop@2)
(bit_op (cmp @1 { build_zero_cst (TREE_TYPE (@1)); })
(cmp @0 @2
/* zero_one_valued_p != 0 -> (cast)zero_one_valued_p */
(simplify
(ne zero_one_valued_p@0 integer_zerop)
(convert @0))
[Bug tree-optimization/110992] [13/14 Regression] missed VRP optimization due to transformation of `a & -zero_one_valued_p` into `a * zero_one_valued_p`
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110992 --- Comment #8 from Andrew Pinski --- (In reply to Andrew Pinski from comment #7) > Actually we should transform it into > ((convert)zero_one_valued_p) & (a != 0) > > Or ^1 for the == 0 case ... > > This should allow for better code I think. Or better yet: (((Convert)cmp) & b) != 0 Into cmp & (b!=0) Icmp for == 0. Now I have seen that before too.
[Bug tree-optimization/110992] [13/14 Regression] missed VRP optimization due to transformation of `a & -zero_one_valued_p` into `a * zero_one_valued_p`
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110992 --- Comment #7 from Andrew Pinski --- Actually we should transform it into ((convert)zero_one_valued_p) & (a != 0) Or ^1 for the == 0 case ... This should allow for better code I think.
[Bug tree-optimization/110992] [13/14 Regression] missed VRP optimization due to transformation of `a & -zero_one_valued_p` into `a * zero_one_valued_p`
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110992
Andrew Pinski changed:
What|Removed |Added
Status|NEW |ASSIGNED
Assignee|unassigned at gcc dot gnu.org |pinskia at gcc dot
gnu.org
--- Comment #6 from Andrew Pinski ---
One way of fixing this is:
/* Transform (a * { 0 or 1 }) !=/== 0 into (a & { 0 or 1 }) !=/== 0. */
(for cmp (ne eq)
(simplify
(cmp (mult:cs @0 zero_one_valued_p@1) integer_zerop@2)
(cmp (bit_and @0 @1) @2)))
That is (a*zero_one_valued_p)!=0 transform it into (a & zero_one_valued_p) != 0
if the multiply was single use.
That is how I am going to fix this.
[Bug tree-optimization/110992] [13/14 Regression] missed VRP optimization due to transformation of `a & -zero_one_valued_p` into `a * zero_one_valued_p`
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110992
Andrew Pinski changed:
What|Removed |Added
Target Milestone|14.0|13.3
Summary|[14 Regression] Dead Code |[13/14 Regression] missed
|Elimination Regression at |VRP optimization due to
|-O3 since |transformation of `a &
|r14-1654-g7ceed7e3e29 |-zero_one_valued_p` into `a
||* zero_one_valued_p`
--- Comment #5 from Andrew Pinski ---
Hmm, I think this is a ranger issue really.
Take:
```
int f(unsigned b, short c)
{
int bt = b;
int bt1 = bt;
int t = bt1 & -(c!=0);
// int t = bt1 * (c!=0);
if (!t) return 0;
foo(bt == 0);
return 0;
}
```
That `bt == 0` should be figured out that is 0 there. We could figure that out
in GCC 12 even. But in GCC 13+ we could not.
That is traced back to r13-793-g8fb94fc6097c but really the ranger should
figure out if you have a*b != 0, then both a and b should be non-zero ...
But currently that is not support
It looks like we only handle `a & b` that way ...
