mwilliams
412dce677f
While debugging a sandbox crash, I spent some time looking at a huge sequnce of conditional masks, compares and branches that didnt seem to belong in the code I was debugging. Finally realized that it was a reffiness check. It looked way too complicated, so I investigated. Part of the problem was that we were avoiding a malloc in the case of a zero param function at the expense of an extra check. Instead, this diff always sets up at least 64 bits worth of m_refBitVec. But by using the space set aside for the pointer in Func::m_shared it avoids a malloc for any function with fewer than 65 arguments, and avoids the numParams check for the first 64 parameters. In addition, the existing code was spitting out a generic test for the guard condition - (mask & bits) == value - where mask and value are known constants. Since the most common case is that value == 0 (all the parameters are expected to be by value), we can usually omit the compare. In addition, since most functions only have a small number of parameters, we can usually get away with 8 bit, or 32 bit operations. The result is that for a typical function (fewer than 64 args, args expected to be by value) the reffiness guard is now test <mask>, Func::m_refBitVec[0] jne exit Rather than: move <mask>, reg1 xor reg2, reg2 cmp 1, Func::m_numParams jnl ok test AttrVarArgs, Func::m_attrs jne exit jmp done ok: load reg3, Func::m_refBitVec[0] and mask, reg3 cmp reg3, reg2 jne exit done:
5 linhas
28 B
Plaintext
5 linhas
28 B
Plaintext
......
|
|
++++++
|
|
******
|
|
******
|