From 54cfeda74574ee167fc1261ddc71d64ee94add11 Mon Sep 17 00:00:00 2001 From: Jakob Stoklund Olesen Date: Fri, 5 Aug 2011 18:47:07 +0000 Subject: Fix liveness computations in BranchFolding. The old code would look at kills and defs in one pass over the instruction operands, causing problems with this code: %R0, %CPSR = tLSLri %R5, 2, pred:14, pred:%noreg %R0, %CPSR = tADDrr %R4, %R0, pred:14, %pred:%noreg The last instruction kills and redefines %R0, so it is still live after the instruction. This caused a register scavenger crash when compiling 483.xalancbmk for armv6. I am not including a test case because it requires too much bad luck to expose this old bug. First you need to convince the register allocator to use %R0 twice on the tADDrr instruction, then you have to convince BranchFolding to do something that causes it to run the register scavenger on he bad block. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@136973 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/CodeGen/BranchFolding.cpp | 29 ++++++++++++++++------------- 1 file changed, 16 insertions(+), 13 deletions(-) diff --git a/lib/CodeGen/BranchFolding.cpp b/lib/CodeGen/BranchFolding.cpp index 99090a8269..75288b0934 100644 --- a/lib/CodeGen/BranchFolding.cpp +++ b/lib/CodeGen/BranchFolding.cpp @@ -1624,26 +1624,29 @@ bool BranchFolder::HoistCommonCodeInSuccs(MachineBasicBlock *MBB) { if (!TIB->isSafeToMove(TII, 0, DontMoveAcrossStore)) break; + // Remove kills from LocalDefsSet, these registers had short live ranges. + for (unsigned i = 0, e = TIB->getNumOperands(); i != e; ++i) { + MachineOperand &MO = TIB->getOperand(i); + if (!MO.isReg() || !MO.isUse() || !MO.isKill()) + continue; + unsigned Reg = MO.getReg(); + if (!Reg || !LocalDefsSet.count(Reg)) + continue; + for (const unsigned *OR = TRI->getOverlaps(Reg); *OR; ++OR) + LocalDefsSet.erase(*OR); + } + // Track local defs so we can update liveins. for (unsigned i = 0, e = TIB->getNumOperands(); i != e; ++i) { MachineOperand &MO = TIB->getOperand(i); - if (!MO.isReg()) + if (!MO.isReg() || !MO.isDef() || MO.isDead()) continue; unsigned Reg = MO.getReg(); if (!Reg) continue; - if (MO.isDef()) { - if (!MO.isDead()) { - LocalDefs.push_back(Reg); - LocalDefsSet.insert(Reg); - for (const unsigned *SR = TRI->getSubRegisters(Reg); *SR; ++SR) - LocalDefsSet.insert(*SR); - } - } else if (MO.isKill() && LocalDefsSet.count(Reg)) { - LocalDefsSet.erase(Reg); - for (const unsigned *SR = TRI->getSubRegisters(Reg); *SR; ++SR) - LocalDefsSet.erase(*SR); - } + LocalDefs.push_back(Reg); + for (const unsigned *OR = TRI->getOverlaps(Reg); *OR; ++OR) + LocalDefsSet.insert(*OR); } HasDups = true;; -- cgit v1.2.3