https://bugs.llvm.org/show_bug.cgi?id=39333
Bug ID: 39333
Summary: Redundant jump table index xoring
Product: libraries
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: Scalar Optimizations
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
template<int> int foo();
typedef int (*int_fun)();
int_fun get_fun(unsigned int x)
{
switch(x&3)
{
case 0: return foo<0>;
case 1: return foo<1>;
case 2: return foo<2>;
case 3: return foo<3>;
}
return 0;
}
Current (SVN, X86-64, -O3):
get_fun(unsigned int):
and edi, 3
xor edi, 2
mov rax, qword ptr [8*rdi + .Lswitch.table.get_fun(unsigned int)]
ret
Prefered:
get_fun(unsigned int):
and edi, 3
mov rax, QWORD PTR CSWTCH.1[0+rdi*8]
ret
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