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Compute some alignment information for each basic block.

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These fields are not used for anything yet.

llvm-svn: 146017
This commit is contained in:
Jakob Stoklund Olesen 2011-12-07 04:17:35 +00:00
parent e74e55c372
commit 90c2c87a91
1 changed files with 48 additions and 14 deletions
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62
lib/Target/ARM/ARMConstantIslandPass.cpp
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@ -82,8 +82,17 @@ namespace {
/// will both be ==2 mod 4).
unsigned Size;
BasicBlockInfo() : Offset(0), Size(0) {}
BasicBlockInfo(unsigned o, unsigned s) : Offset(o), Size(s) {}
/// Unalign - When non-zero, the block contains instructions (inline asm)
/// of unknown size. The real size may be smaller than Size bytes by a
/// multiple of 1 << Unalign.
uint8_t Unalign;
/// PostAlign - When non-zero, the block terminator contains a .align
/// directive, so the end of the block is aligned to 1 << PostAlign
/// bytes.
uint8_t PostAlign;
BasicBlockInfo() : Offset(0), Size(0), Unalign(0), PostAlign(0) {}
/// Compute the offset immediately following this block.
unsigned postOffset() const { return Offset + Size; }
@ -234,6 +243,7 @@ namespace {
MachineBasicBlock *AdjustJTTargetBlockForward(MachineBasicBlock *BB,
MachineBasicBlock *JTBB);
void ComputeBlockSize(const MachineBasicBlock *MBB);
unsigned GetOffsetOf(MachineInstr *MI) const;
void dumpBBs();
void verify(MachineFunction &MF);
@ -507,11 +517,16 @@ void ARMConstantIslands::InitialFunctionScan(MachineFunction &MF,
HasInlineAsm = true;
}
BBInfo.clear();
BBInfo.resize(MF.getNumBlockIDs());
// Now go back through the instructions and build up our data structures.
unsigned Offset = 0;
for (MachineFunction::iterator MBBI = MF.begin(), E = MF.end();
MBBI != E; ++MBBI) {
MachineBasicBlock &MBB = *MBBI;
BasicBlockInfo &BBI = BBInfo[MBB.getNumber()];
BBI.Offset = Offset;
// If this block doesn't fall through into the next MBB, then this is
// 'water' that a constant pool island could be placed.
@ -526,6 +541,11 @@ void ARMConstantIslands::InitialFunctionScan(MachineFunction &MF,
// Add instruction size to MBBSize.
MBBSize += TII->GetInstSizeInBytes(I);
// For inline asm, GetInstSizeInBytes returns a conservative estimate.
// The actual size may be smaller, but still a multiple of the instr size.
if (I->isInlineAsm())
BBI.Unalign = isThumb ? 1 : 2;
int Opc = I->getOpcode();
if (I->getDesc().isBranch()) {
bool isCond = false;
@ -543,6 +563,7 @@ void ARMConstantIslands::InitialFunctionScan(MachineFunction &MF,
// is aligned. That is held in Offset+MBBSize, which already has
// 2 added in for the size of the mov pc instruction.
MF.EnsureAlignment(2U);
BBI.PostAlign = 2;
if ((Offset+MBBSize)%4 != 0 || HasInlineAsm)
// FIXME: Add a pseudo ALIGN instruction instead.
MBBSize += 2; // padding
@ -673,11 +694,33 @@ void ARMConstantIslands::InitialFunctionScan(MachineFunction &MF,
((Offset%4) != 0 || HasInlineAsm))
MBBSize += 2;
BBInfo.push_back(BasicBlockInfo(Offset, MBBSize));
BBI.Size = MBBSize;
Offset += MBBSize;
}
}
/// ComputeBlockSize - Compute the size and some alignment information for MBB.
/// This function updates BBInfo directly.
void ARMConstantIslands::ComputeBlockSize(const MachineBasicBlock *MBB) {
BasicBlockInfo &BBI = BBInfo[MBB->getNumber()];
BBI.Size = 0;
BBI.Unalign = 0;
BBI.PostAlign = 0;
for (MachineBasicBlock::const_iterator I = MBB->begin(), E = MBB->end();
I != E; ++I) {
BBI.Size += TII->GetInstSizeInBytes(I);
// For inline asm, GetInstSizeInBytes returns a conservative estimate.
// The actual size may be smaller, but still a multiple of the instr size.
if (I->isInlineAsm())
BBI.Unalign = isThumb ? 1 : 2;
}
// tBR_JTr contains a .align 2 directive.
if (!MBB->empty() && MBB->back().getOpcode() == ARM::tBR_JTr)
BBI.PostAlign = 2;
}
/// GetOffsetOf - Return the current offset of the specified machine instruction
/// from the start of the function. This offset changes as stuff is moved
/// around inside the function.
@ -798,23 +841,14 @@ MachineBasicBlock *ARMConstantIslands::SplitBlockBeforeInstr(MachineInstr *MI) {
// the new jump we added. (It should be possible to do this without
// recounting everything, but it's very confusing, and this is rarely
// executed.)
unsigned OrigBBSize = 0;
for (MachineBasicBlock::iterator I = OrigBB->begin(), E = OrigBB->end();
I != E; ++I)
OrigBBSize += TII->GetInstSizeInBytes(I);
BBInfo[OrigBBI].Size = OrigBBSize;
ComputeBlockSize(OrigBB);
// ...and adjust BBOffsets for NewBB accordingly.
BBInfo[NewBBI].Offset = BBInfo[OrigBBI].postOffset();
// Figure out how large the NewMBB is. As the second half of the original
// block, it may contain a tablejump.
unsigned NewBBSize = 0;
for (MachineBasicBlock::iterator I = NewBB->begin(), E = NewBB->end();
I != E; ++I)
NewBBSize += TII->GetInstSizeInBytes(I);
// Set the size of NewBB in BBSizes. It does not include any padding now.
BBInfo[NewBBI].Size = NewBBSize;
ComputeBlockSize(NewBB);
MachineInstr* ThumbJTMI = prior(NewBB->end());
if (ThumbJTMI->getOpcode() == ARM::tBR_JTr) {