https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71558
Bug ID: 71558
Summary: missed optimization for type short, char and floating
point types
Product: gcc
Version: 6.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: denis.campredon at gmail dot com
Target Milestone: ---
for the following code gcc should produce the same code for fun and fun2, but
fail for shorts and char with -01 and higher. It also fails for floating types
with -0fast
-----------------
#define optimize(type) \
type fun(type i, type j) \
{ \
return i + j; \
} \
type fun2(type i, type j) \
{ \
if (j == 0) \
return i; \
else if (i == 0) \
return j; \
else \
return i + j; \
}
optimize(int);
optimize(char);
optimize(short);
--------------------
For all types the optimization is no longer performed if any type is different
from the other
--------------------
int fun2(unsigned i, int j)
{
if (i == 0)
return j;
else if (j == 0)
return i;
else
return i + j;
}
--------------------
And if we are testing if both i and j are 0 the optimization is no longer
performed
------------------
int fun2(int i, int j)
{
if (i == 0 && j == 0)
return j; //or "return i + j;" or "return 0;" or "return i;"
if (i == 0)
return j;
else if (j == 0)
return i;
else
return i + j;
}
-------------------
It also fails if one replace the addition with a subtraction or a
multiplication (with changed return values.)
