and num operands in the User class. this allows us to embed the operands
directly in the subclasses if possible. For example, for binary operators
we store the two operands in the derived class.
The has several effects:
1. it improves locality because the operands and instruction are together
2. it makes accesses to operands faster (one less load) if you access them
through the derived class pointer. For example this:
Value *GetBinaryOperatorOp(BinaryOperator *I, int i) {
return I->getOperand(i);
}
Was compiled to:
_Z19GetBinaryOperatorOpPN4llvm14BinaryOperatorEi:
movl 4(%esp), %edx
movl 8(%esp), %eax
sall $4, %eax
movl 24(%edx), %ecx
addl %ecx, %eax
movl (%eax), %eax
ret
and is now compiled to:
_Z19GetBinaryOperatorOpPN4llvm14BinaryOperatorEi:
movl 8(%esp), %eax
movl 4(%esp), %edx
sall $4, %eax
addl %edx, %eax
movl 44(%eax), %eax
ret
Accesses through "Instruction*" are unmodified.
3. This reduces memory consumption (by about 3%) by eliminating 1 word of
vector overhead and a malloc header on a seperate object.
4. This speeds up gccas about 10% (both debug and release builds) on
large things (such as 176.gcc). For example, it takes a debug build
from 172.9 -> 155.6s and a release gccas from 67.7 -> 61.8s
llvm-svn: 19883
Operands are maintained as a vector<Use> in the User class, and operator
iterators are provided as before. Getting an operand no longer requires
a virtual function call.
WARNING: getOperand(x) where x >= getNumOperands() will now assert instead
of returning null!
llvm-svn: 149
