From 44500e3d538a250d8591e708b62741cde0bdc249 Mon Sep 17 00:00:00 2001 From: Chris Lattner Date: Thu, 15 Jun 2006 22:21:53 +0000 Subject: [PATCH] Teach the local allocator to know that live-in values (e.g. arguments) are live at function entry. This prevents it from using arg registers for other purposes before the arguments are used. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@28809 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/CodeGen/RegAllocLocal.cpp | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) diff --git a/lib/CodeGen/RegAllocLocal.cpp b/lib/CodeGen/RegAllocLocal.cpp index e3921e4ed38..55d412960c2 100644 --- a/lib/CodeGen/RegAllocLocal.cpp +++ b/lib/CodeGen/RegAllocLocal.cpp @@ -491,6 +491,26 @@ void RA::AllocateBasicBlock(MachineBasicBlock &MBB) { // loop over each instruction MachineBasicBlock::iterator MII = MBB.begin(); const TargetInstrInfo &TII = *TM->getInstrInfo(); + + // If this is the first basic block in the machine function, add live-in + // registers as active. + if (&MBB == &*MF->begin()) { + for (MachineFunction::livein_iterator I = MF->livein_begin(), + E = MF->livein_end(); I != E; ++I) { + unsigned Reg = I->first; + PhysRegsEverUsed[Reg] = true; + PhysRegsUsed[Reg] = 0; // It is free and reserved now + PhysRegsUseOrder.push_back(Reg); + for (const unsigned *AliasSet = RegInfo->getAliasSet(Reg); + *AliasSet; ++AliasSet) { + PhysRegsUseOrder.push_back(*AliasSet); + PhysRegsUsed[*AliasSet] = 0; // It is free and reserved now + PhysRegsEverUsed[*AliasSet] = true; + } + } + } + + // Otherwise, sequentially allocate each instruction in the MBB. while (MII != MBB.end()) { MachineInstr *MI = MII++; const TargetInstrDescriptor &TID = TII.get(MI->getOpcode());