https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90401
Bug ID: 90401
Summary: Missed propagation of by-ref constant argument to
callee function
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: ipa
Assignee: unassigned at gcc dot gnu.org
Reporter: fxue at os dot amperecomputing.com
CC: marxin at gcc dot gnu.org
Target Milestone: ---
Created attachment 46318
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=46318&action=edit
The case that ipa_cp is failed on by_ref constant argument
IPA-cp can not identify a constant by-ref argument to a function, if value
definition of the argument is not in same basic block where the callsite lies
in. In Fortran, this is very common that a constant function argument is placed
in a local variable instead of literal constant.
The following is a C++ case, compiling option is "-O3 -fno-inline", here using
"-fno-inline" to give a change for ipa-cp on small function.
If we move the statement "int a = 1" from inside conditional block to begin of
function, ipa-cp fails to do function versioning on "callee()".
int data;
int callee(int &v)
{
if (v < 2) {
return 0;
} else {
data = v;
return 1;
}
}
int caller(int c, int &r)
{
// int a = 1; <----. /* ipa-cp on callee(), failed */
|
if (c) { |
// int a = 1; -----' /* ipa-cp on callee(), ok */
return callee(a);
} else {
r = 1;
return callee(r);
}
}
