https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83072
Bug ID: 83072
Summary: Late VRP optimization
Product: gcc
Version: 8.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: glisse at gcc dot gnu.org
Target Milestone: ---
Before r254954, cmpmul-1.c was optimized during EVRP:
int f(int a, int b, int c){
c |= 1;
a *= c;
b *= c;
return a == b;
}
After that revision, the range deduced for c|1 contains zero (we may want to
revisit that at some point, but that's a separate issue), so I changed the
testcase to
int f(int a, int b, int c){
if(c==0)__builtin_unreachable();
a *= c;
b *= c;
return a == b;
}
which is only optimized during forwprop3, after __builtin_unreachable() is
removed. Since EVRP knows how to perform this optimization, it may be worth
investigating why it fails to perform it in this case.
