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- Added Thumb constpool island support.

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- Islands are inserted right after the user MI since thumb LDR cannot encode
  negative offset.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@33690 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng 2007-01-31 02:22:22 +00:00
parent 4c16069a44
commit 0c61584d05
1 changed files with 17 additions and 24 deletions
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41
lib/Target/ARM/ARMConstantIslandPass.cpp
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@ -112,7 +112,7 @@ namespace {
std::vector<MachineInstr*> &CPEMIs);
void InitialFunctionScan(MachineFunction &Fn,
const std::vector<MachineInstr*> &CPEMIs);
void SplitBlockBeforeInstr(MachineInstr *MI);
MachineBasicBlock *SplitBlockBeforeInstr(MachineInstr *MI);
void UpdateForInsertedWaterBlock(MachineBasicBlock *NewBB);
bool HandleConstantPoolUser(MachineFunction &Fn, CPUser &U);
bool BBIsInBranchRange(MachineInstr *MI, MachineBasicBlock *BB, unsigned D);
@ -406,8 +406,8 @@ void ARMConstantIslands::UpdateForInsertedWaterBlock(MachineBasicBlock *NewBB) {
/// Split the basic block containing MI into two blocks, which are joined by
/// an unconditional branch. Update datastructures and renumber blocks to
/// account for this change.
void ARMConstantIslands::SplitBlockBeforeInstr(MachineInstr *MI) {
/// account for this change and returns the newly created block.
MachineBasicBlock *ARMConstantIslands::SplitBlockBeforeInstr(MachineInstr *MI) {
MachineBasicBlock *OrigBB = MI->getParent();
bool isThumb = AFI->isThumbFunction();
@ -453,6 +453,8 @@ void ARMConstantIslands::SplitBlockBeforeInstr(MachineInstr *MI) {
// We removed instructions from UserMBB, subtract that off from its size.
// Add 2 or 4 to the block to count the unconditional branch we added to it.
BBSizes[OrigBB->getNumber()] -= NewBBSize - (isThumb ? 2 : 4);
return NewBB;
}
/// HandleConstantPoolUser - Analyze the specified user, checking to see if it
@ -475,33 +477,25 @@ bool ARMConstantIslands::HandleConstantPoolUser(MachineFunction &Fn, CPUser &U){
// User before the CPE.
if (CPEOffset-UserOffset <= U.MaxDisp)
return false;
} else {
} else if (!AFI->isThumbFunction()) {
// Thumb LDR cannot encode negative offset.
if (UserOffset-CPEOffset <= U.MaxDisp)
return false;
}
// Solution guaranteed to work: split the user's MBB right before the user and
// Solution guaranteed to work: split the user's MBB right after the user and
// insert a clone the CPE into the newly created water.
// If the user isn't at the start of its MBB, or if there is a fall-through
// into the user's MBB, split the MBB before the User.
MachineBasicBlock *UserMBB = UserMI->getParent();
if (&UserMBB->front() != UserMI ||
UserMBB == &Fn.front() || // entry MBB of function.
BBHasFallthrough(prior(MachineFunction::iterator(UserMBB)))) {
// TODO: Search for the best place to split the code. In practice, using
// loop nesting information to insert these guys outside of loops would be
// sufficient.
SplitBlockBeforeInstr(UserMI);
// UserMI's BB may have changed.
UserMBB = UserMI->getParent();
}
MachineInstr *NextMI = next(MachineBasicBlock::iterator(UserMI));
// TODO: Search for the best place to split the code. In practice, using
// loop nesting information to insert these guys outside of loops would be
// sufficient.
MachineBasicBlock *NewBB = SplitBlockBeforeInstr(NextMI);
// Okay, we know we can put an island before UserMBB now, do it!
MachineBasicBlock *NewIsland = new MachineBasicBlock();
Fn.getBasicBlockList().insert(UserMBB, NewIsland);
Fn.getBasicBlockList().insert(NewBB, NewIsland);
// Update internal data structures to account for the newly inserted MBB.
UpdateForInsertedWaterBlock(NewIsland);
@ -528,7 +522,6 @@ bool ARMConstantIslands::HandleConstantPoolUser(MachineFunction &Fn, CPUser &U){
DEBUG(std::cerr << " Moved CPE to #" << ID << " CPI=" << CPI << "\t"
<< *UserMI);
return true;
}