From 70c245e92dc7bad7588a542abc84a138a2eacc60 Mon Sep 17 00:00:00 2001 From: Stanislav Mekhanoshin Date: Wed, 1 Feb 2017 01:18:36 +0000 Subject: [PATCH] Fix regalloc assignment of overlapping registers SplitEditor::defFromParent() can create a register copy. If register is a tuple of other registers and not all lanes are used a copy will be done on a full tuple regardless. Later register unit for an unused lane will be considered free and another overlapping register tuple can be assigned to a different value even though first register is live at that point. That is because interference only look at liveness info, while full register copy clobbers all lanes, even unused. This patch fixes copy to only cover used lanes. Differential Revision: https://reviews.llvm.org/D29105 llvm-svn: 293728 --- llvm/lib/CodeGen/SplitKit.cpp | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) diff --git a/llvm/lib/CodeGen/SplitKit.cpp b/llvm/lib/CodeGen/SplitKit.cpp index 1c6a84e53944..689992403550 100644 --- a/llvm/lib/CodeGen/SplitKit.cpp +++ b/llvm/lib/CodeGen/SplitKit.cpp @@ -522,6 +522,27 @@ VNInfo *SplitEditor::defFromParent(unsigned RegIdx, Def = LIS.getSlotIndexes() ->insertMachineInstrInMaps(*CopyMI, Late) .getRegSlot(); + if (LI->hasSubRanges()) { + LaneBitmask LM = LaneBitmask::getNone(); + for (LiveInterval::SubRange &S : LI->subranges()) + LM |= S.LaneMask; + + if (MRI.getMaxLaneMaskForVReg(LI->reg) != LM) { + // Find subreg for the lane mask. + unsigned SubIdx = 0; + for (unsigned I = 1, E = TRI.getNumSubRegIndices(); I < E; ++I) { + if (TRI.getSubRegIndexLaneMask(I) == LM) { + SubIdx = I; + break; + } + } + if (SubIdx == 0) + report_fatal_error("Cannot find subreg index to cover all alive lanes"); + CopyMI->getOperand(0).setSubReg(SubIdx); + CopyMI->getOperand(1).setSubReg(SubIdx); + CopyMI->getOperand(0).setIsUndef(true); + } + } ++NumCopies; }