From 2d6d86be84ee355223ccd20b7f87a0c9971c50c9 Mon Sep 17 00:00:00 2001 From: Jakob Stoklund Olesen Date: Fri, 5 Aug 2011 22:20:45 +0000 Subject: Split around single instructions to enable register class inflation. Normally, we don't create a live range for a single instruction in a basic block, the spiller does that anyway. However, when splitting a live range that belongs to a proper register sub-class, inserting these extra COPY instructions completely remove the constraints from the remainder interval, and it may be allocated from the larger super-class. The spiller will mop up these small live ranges if we end up spilling anyway. It calls them snippets. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@136989 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/CodeGen/SplitKit.cpp | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) (limited to 'lib/CodeGen/SplitKit.cpp') diff --git a/lib/CodeGen/SplitKit.cpp b/lib/CodeGen/SplitKit.cpp index e6bcfcdfe3..cc85771d3d 100644 --- a/lib/CodeGen/SplitKit.cpp +++ b/lib/CodeGen/SplitKit.cpp @@ -1087,6 +1087,24 @@ void SplitEditor::finish(SmallVectorImpl *LRMap) { // Single Block Splitting //===----------------------------------------------------------------------===// +bool SplitAnalysis::shouldSplitSingleBlock(const BlockInfo &BI, + bool SingleInstrs) const { + // Always split for multiple instructions. + if (!BI.isOneInstr()) + return true; + // Don't split for single instructions unless explicitly requested. + if (!SingleInstrs) + return false; + // Splitting a live-through range always makes progress. + if (BI.LiveIn && BI.LiveOut) + return true; + // No point in isolating a copy. It has no register class constraints. + if (LIS.getInstructionFromIndex(BI.FirstInstr)->isCopyLike()) + return false; + // Finally, don't isolate an end point that was created by earlier splits. + return isOriginalEndpoint(BI.FirstInstr); +} + /// 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) { -- cgit v1.2.3-18-g5258