diff options
| -rw-r--r-- | lib/Target/ARM/ARMConstantIslandPass.cpp | 44 |
1 files changed, 35 insertions, 9 deletions
diff --git a/lib/Target/ARM/ARMConstantIslandPass.cpp b/lib/Target/ARM/ARMConstantIslandPass.cpp index 55a0cc0f44..65abff0b95 100644 --- a/lib/Target/ARM/ARMConstantIslandPass.cpp +++ b/lib/Target/ARM/ARMConstantIslandPass.cpp @@ -52,6 +52,10 @@ static cl::opt<bool> AdjustJumpTableBlocks("arm-adjust-jump-tables", cl::Hidden, cl::init(true), cl::desc("Adjust basic block layout to better use TB[BH]")); +static cl::opt<bool> +AlignConstantIslands("arm-align-constant-island", cl::Hidden, + cl::desc("Align constant islands in code")); + /// UnknownPadding - Return the worst case padding that could result from /// unknown offset bits. This does not include alignment padding caused by /// known offset bits. @@ -487,8 +491,18 @@ void ARMConstantIslands::DoInitialPlacement(MachineFunction &MF, MachineBasicBlock *BB = MF.CreateMachineBasicBlock(); MF.push_back(BB); - // Mark the basic block as 4-byte aligned as required by the const-pool. - BB->setAlignment(2); + // MachineConstantPool measures alignment in bytes. We measure in log2(bytes). + unsigned MaxAlign = Log2_32(MF.getConstantPool()->getConstantPoolAlignment()); + + // Mark the basic block as required by the const-pool. + // If AlignConstantIslands isn't set, use 4-byte alignment for everything. + BB->setAlignment(AlignConstantIslands ? MaxAlign : 2); + + // Order the entries in BB by descending alignment. That ensures correct + // alignment of all entries as long as BB is sufficiently aligned. Keep + // track of the insertion point for each alignment. We are going to bucket + // sort the entries as they are created. + SmallVector<MachineBasicBlock::iterator, 8> InsPoint(MaxAlign + 1, BB->end()); // Add all of the constants from the constant pool to the end block, use an // identity mapping of CPI's to CPE's. @@ -498,23 +512,35 @@ void ARMConstantIslands::DoInitialPlacement(MachineFunction &MF, const TargetData &TD = *MF.getTarget().getTargetData(); for (unsigned i = 0, e = CPs.size(); i != e; ++i) { unsigned Size = TD.getTypeAllocSize(CPs[i].getType()); - // Verify that all constant pool entries are a multiple of 4 bytes. If not, - // we would have to pad them out or something so that instructions stay - // aligned. - assert((Size & 3) == 0 && "CP Entry not multiple of 4 bytes!"); + assert(Size >= 4 && "Too small constant pool entry"); + unsigned Align = CPs[i].getAlignment(); + assert(isPowerOf2_32(Align) && "Invalid alignment"); + // Verify that all constant pool entries are a multiple of their alignment. + // If not, we would have to pad them out so that instructions stay aligned. + assert((Size % Align) == 0 && "CP Entry not multiple of 4 bytes!"); + + // Insert CONSTPOOL_ENTRY before entries with a smaller alignment. + unsigned LogAlign = Log2_32(Align); + MachineBasicBlock::iterator InsAt = InsPoint[LogAlign]; MachineInstr *CPEMI = - BuildMI(BB, DebugLoc(), TII->get(ARM::CONSTPOOL_ENTRY)) + BuildMI(*BB, InsAt, DebugLoc(), TII->get(ARM::CONSTPOOL_ENTRY)) .addImm(i).addConstantPoolIndex(i).addImm(Size); CPEMIs.push_back(CPEMI); + // Ensure that future entries with higher alignment get inserted before + // CPEMI. This is bucket sort with iterators. + for (unsigned a = LogAlign + 1; a < MaxAlign; ++a) + if (InsPoint[a] == InsAt) + InsPoint[a] = CPEMI; + // Add a new CPEntry, but no corresponding CPUser yet. std::vector<CPEntry> CPEs; CPEs.push_back(CPEntry(CPEMI, i)); CPEntries.push_back(CPEs); ++NumCPEs; - DEBUG(dbgs() << "Moved CPI#" << i << " to end of function as #" << i - << "\n"); + DEBUG(dbgs() << "Moved CPI#" << i << " to end of function\n"); } + DEBUG(BB->dump()); } /// BBHasFallthrough - Return true if the specified basic block can fallthrough |