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

teach LVI to infer edge information from switch instructions. 

This allows JT to eliminate a ton of infeasible edges when
handling code like the templates in PatternMatch.h

llvm-svn: 88869
This commit is contained in:
Chris Lattner 2009-11-15 20:02:12 +00:00
parent b0c0a0df3e
commit 7735878591
1 changed files with 24 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

30
llvm/lib/Analysis/LazyValueInfo.cpp
View File

@ -403,8 +403,10 @@ LVILatticeVal LVIQuery::getBlockValue(BasicBlock *BB) {
}
/// getEdgeValue - This method
/// getEdgeValue - This method attempts to infer more complex
LVILatticeVal LVIQuery::getEdgeValue(BasicBlock *BBFrom, BasicBlock *BBTo) {
// TODO: Handle more complex conditionals. If (v == 0 || v2 < 1) is false, we
// know that v != 0.
if (BranchInst *BI = dyn_cast<BranchInst>(BBFrom->getTerminator())) {
// If this is a conditional branch and only one successor goes to BBTo, then
// we maybe able to infer something from the condition.
@ -433,11 +435,27 @@ LVILatticeVal LVIQuery::getEdgeValue(BasicBlock *BBFrom, BasicBlock *BBTo) {
}
}
}
// TODO: Info from switch.
// TODO: Handle more complex conditionals. If (v == 0 || v2 < 1) is false, we
// know that v != 0.
// If the edge was formed by a switch on the value, then we may know exactly
// what it is.
if (SwitchInst *SI = dyn_cast<SwitchInst>(BBFrom->getTerminator())) {
// If BBTo is the default destination of the switch, we don't know anything.
// Given a more powerful range analysis we could know stuff.
if (SI->getCondition() == Val && SI->getDefaultDest() != BBTo) {
// We only know something if there is exactly one value that goes from
// BBFrom to BBTo.
unsigned NumEdges = 0;
ConstantInt *EdgeVal = 0;
for (unsigned i = 1, e = SI->getNumSuccessors(); i != e; ++i) {
if (SI->getSuccessor(i) != BBTo) continue;
if (NumEdges++) break;
EdgeVal = SI->getCaseValue(i);
}
assert(EdgeVal && "Missing successor?");
if (NumEdges == 1)
return LVILatticeVal::get(EdgeVal);
}
}
// Otherwise see if the value is known in the block.
return getBlockValue(BBFrom);