6502/llvm-6502
1
0
Fork 0
mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2024-07-21 02:29:22 +00:00
Code Issues Projects Releases Wiki Activity

Update a bunch of stale comments that dated from when this folled the

Browse Source 
very first (and worst) placement algorithm. These should now more
accurately reflect the reality of the pass.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@159185 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chandler Carruth 2012-06-26 05:16:37 +00:00
parent 952caee4f6
commit c04f816afd
1 changed files with 11 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

25
lib/CodeGen/MachineBlockPlacement.cpp
View File

@ -63,17 +63,13 @@ namespace {
///
/// This is the datastructure representing a chain of consecutive blocks that
/// are profitable to layout together in order to maximize fallthrough
/// probabilities. We also can use a block chain to represent a sequence of
/// basic blocks which have some external (correctness) requirement for
/// sequential layout.
/// probabilities and code locality. We also can use a block chain to represent
/// a sequence of basic blocks which have some external (correctness)
/// requirement for sequential layout.
///
/// Eventually, the block chains will form a directed graph over the function.
/// We provide an SCC-supporting-iterator in order to quicky build and walk the
/// SCCs of block chains within a function.
///
/// The block chains also have support for calculating and caching probability
/// information related to the chain itself versus other chains. This is used
/// for ranking during the final layout of block chains.
/// Chains can be built around a single basic block and can be merged to grow
/// them. They participate in a block-to-chain mapping, which is updated
/// automatically as chains are merged together.
class BlockChain {
/// \brief The sequence of blocks belonging to this chain.
///
@ -179,10 +175,11 @@ class MachineBlockPlacement : public MachineFunctionPass {
/// \brief Allocator and owner of BlockChain structures.
///
/// We build BlockChains lazily by merging together high probability BB
/// sequences according to the "Algo2" in the paper mentioned at the top of
/// the file. To reduce malloc traffic, we allocate them using this slab-like
/// allocator, and destroy them after the pass completes.
/// We build BlockChains lazily while processing the loop structure of
/// a function. To reduce malloc traffic, we allocate them using this
/// slab-like allocator, and destroy them after the pass completes. An
/// important guarantee is that this allocator produces stable pointers to
/// the chains.
SpecificBumpPtrAllocator<BlockChain> ChainAllocator;
/// \brief Function wide BasicBlock to BlockChain mapping.