6502/llvm-6502
1
0
Fork 0
mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2025-01-09 10:31:14 +00:00
Code Issues Projects Releases Wiki Activity

Be more strict about detecting multi-use blocks for isolation.

Browse Source 
When a block has exactly two uses and the register is both live-in and live-out,
don't isolate the block. We would be inserting two copies, so we haven't really
made any progress.

If the live-in and live-out values separate into disconnected components after
splitting, we would be making progress. We can't detect that for now.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@117169 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jakob Stoklund Olesen 2010-10-22 22:48:56 +00:00
parent 432a8142ef
commit 2bfb324684
1 changed files with 29 additions and 28 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

57
lib/CodeGen/SplitKit.cpp
View File

@ -289,34 +289,6 @@ const MachineLoop *SplitAnalysis::getBestSplitLoop() {
return Best;
}
/// getMultiUseBlocks - if curli has more than one use in a basic block, it
/// may be an advantage to split curli for the duration of the block.
bool SplitAnalysis::getMultiUseBlocks(BlockPtrSet &Blocks) {
// If curli is local to one block, there is no point to splitting it.
if (usingBlocks_.size() <= 1)
return false;
// Add blocks with multiple uses.
for (BlockCountMap::iterator I = usingBlocks_.begin(), E = usingBlocks_.end();
I != E; ++I)
switch (I->second) {
case 0:
case 1:
continue;
case 2: {
// It doesn't pay to split a 2-instr block if it redefines curli.
VNInfo *VN1 = curli_->getVNInfoAt(lis_.getMBBStartIdx(I->first));
VNInfo *VN2 =
curli_->getVNInfoAt(lis_.getMBBEndIdx(I->first).getPrevIndex());
// live-in and live-out with a different value.
if (VN1 && VN2 && VN1 != VN2)
continue;
} // Fall through.
default:
Blocks.insert(I->first);
}
return !Blocks.empty();
}
//===----------------------------------------------------------------------===//
// LiveIntervalMap
//===----------------------------------------------------------------------===//
@ -946,6 +918,35 @@ void SplitEditor::splitAroundLoop(const MachineLoop *Loop) {
// Single Block Splitting
//===----------------------------------------------------------------------===//
/// getMultiUseBlocks - if curli has more than one use in a basic block, it
/// may be an advantage to split curli for the duration of the block.
bool SplitAnalysis::getMultiUseBlocks(BlockPtrSet &Blocks) {
// If curli is local to one block, there is no point to splitting it.
if (usingBlocks_.size() <= 1)
return false;
// Add blocks with multiple uses.
for (BlockCountMap::iterator I = usingBlocks_.begin(), E = usingBlocks_.end();
I != E; ++I)
switch (I->second) {
case 0:
case 1:
continue;
case 2: {
// When there are only two uses and curli is both live in and live out,
// we don't really win anything by isolating the block since we would be
// inserting two copies.
// The remaing register would still have two uses in the block. (Unless it
// separates into disconnected components).
if (lis_.isLiveInToMBB(*curli_, I->first) &&
lis_.isLiveOutOfMBB(*curli_, I->first))
continue;
} // Fall through.
default:
Blocks.insert(I->first);
}
return !Blocks.empty();
}
/// splitSingleBlocks - Split curli into a separate live interval inside each
/// basic block in Blocks.
void SplitEditor::splitSingleBlocks(const SplitAnalysis::BlockPtrSet &Blocks) {