maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity

add a debugging option to help track down j-t problems. 

llvm-svn: 60514
This commit is contained in:
Chris Lattner 2008-12-04 00:07:59 +00:00
parent ba3fdfcbff
commit 75c2661d24
1 changed files with 14 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
llvm/lib/Transforms/Scalar/JumpThreading.cpp
View File

@ -36,6 +36,11 @@ Threshold("jump-threading-threshold",
cl::desc("Max block size to duplicate for jump threading"), cl::desc("Max block size to duplicate for jump threading"),
cl::init(6), cl::Hidden); cl::init(6), cl::Hidden);
static cl::opt<int>
DebugIterations("jump-threading-debug",
cl::desc("Stop jump threading after N iterations"),
cl::init(-1), cl::Hidden);
namespace { namespace {
/// This pass performs 'jump threading', which looks at blocks that have /// This pass performs 'jump threading', which looks at blocks that have
/// multiple predecessors and multiple successors. If one or more of the /// multiple predecessors and multiple successors. If one or more of the
@ -104,11 +109,15 @@ bool JumpThreading::runOnFunction(Function &F) {
// If the block is trivially dead, zap it. This eliminates the successor // If the block is trivially dead, zap it. This eliminates the successor
// edges which simplifies the CFG. // edges which simplifies the CFG.
if (pred_begin(BB) == pred_end(BB) && if (pred_begin(BB) == pred_end(BB) &&
BB != &BB->getParent()->getEntryBlock()) { BB != &BB->getParent()->getEntryBlock() &&
DebugIterations != 0) {
DOUT << " JT: Deleting dead block '" << BB->getNameStart() DOUT << " JT: Deleting dead block '" << BB->getNameStart()
<< "' with terminator: " << *BB->getTerminator(); << "' with terminator: " << *BB->getTerminator();
DeleteDeadBlock(BB); DeleteDeadBlock(BB);
Changed = true; Changed = true;
if (DebugIterations != -1)
DebugIterations = DebugIterations-1;
} }
} }
AnotherIteration = Changed; AnotherIteration = Changed;
@ -183,6 +192,10 @@ static unsigned getJumpThreadDuplicationCost(const BasicBlock *BB) {
/// ProcessBlock - If there are any predecessors whose control can be threaded /// ProcessBlock - If there are any predecessors whose control can be threaded
/// through to a successor, transform them now. /// through to a successor, transform them now.
bool JumpThreading::ProcessBlock(BasicBlock *BB) { bool JumpThreading::ProcessBlock(BasicBlock *BB) {
if (DebugIterations == 0) return false;
if (DebugIterations != -1)
DebugIterations = DebugIterations-1;
// If this block has a single predecessor, and if that pred has a single // If this block has a single predecessor, and if that pred has a single
// successor, merge the blocks. This encourages recursive jump threading // successor, merge the blocks. This encourages recursive jump threading
// because now the condition in this block can be threaded through // because now the condition in this block can be threaded through