http://llvm.org/bugs/show_bug.cgi?id=6212
Summary: Clang misses optimisation on if vs else if
Product: libraries
Version: trunk
Platform: PC
OS/Version: All
Status: NEW
Severity: normal
Priority: P2
Component: Scalar Optimizations
AssignedTo: [email protected]
ReportedBy: [email protected]
CC: [email protected]
int test1(int mainType, int subType)
{
if(mainType == 7)
{
subType = 4;
}
else if(mainType == 9)
{
subType = 6;
}
else if(mainType == 11)
{
subType = 9;
}
return subType;
}
int test2(int mainType, int subType)
{
if(mainType == 7)
{
subType = 4;
}
if(mainType == 9)
{
subType = 6;
}
if(mainType == 11)
{
subType = 9;
}
return subType;
}
Clang generates more efficient code in the second case than the first, because
the first is transformed into a switch which then gets expanded to longer code
by the code generator.
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