Changes in directory llvm/lib/CodeGen:
BranchFolding.cpp updated: 1.8 -> 1.9
---
Log message:
disable some objectionable code, maybe we can bring this pass to life
---
Diffs of the changes: (+42 -7)
BranchFolding.cpp | 49 ++++++++++++++++++++++++++++++++++++++++++-------
1 files changed, 42 insertions(+), 7 deletions(-)
Index: llvm/lib/CodeGen/BranchFolding.cpp
diff -u llvm/lib/CodeGen/BranchFolding.cpp:1.8
llvm/lib/CodeGen/BranchFolding.cpp:1.9
--- llvm/lib/CodeGen/BranchFolding.cpp:1.8 Thu Apr 21 17:33:33 2005
+++ llvm/lib/CodeGen/BranchFolding.cpp Fri Oct 13 15:43:10 2006
@@ -94,11 +94,7 @@
I->getOperand(i).setMachineBasicBlock(New);
}
- // If BB falls through into Old, insert an unconditional branch to New.
- MachineFunction::iterator BBSucc = BB; ++BBSucc;
- if (BBSucc != BB->getParent()->end() && &*BBSucc == Old)
- TII.insertGoto(*BB, *New);
-
+ // Update the successor information.
std::vector<MachineBasicBlock*> Succs(BB->succ_begin(), BB->succ_end());
for (int i = Succs.size()-1; i >= 0; --i)
if (Succs[i] == Old) {
@@ -110,7 +106,7 @@
bool BranchFolder::OptimizeBlock(MachineFunction::iterator MBB,
const TargetInstrInfo &TII) {
- // If this block is empty, make everyone use it's fall-through, not the block
+ // If this block is empty, make everyone use its fall-through, not the block
// explicitly.
if (MBB->empty()) {
if (MBB->pred_empty()) return false;
@@ -124,6 +120,43 @@
return true;
}
+#if 0
+
+ if (MBB->pred_size() == 1) {
+ // If this block has a single predecessor, and if that block has a single
+ // successor, merge this block into that block.
+ MachineBasicBlock *Pred = *MBB->pred_begin();
+ if (Pred->succ_size() == 1) {
+ // Delete all of the terminators from end of the pred block. NOTE, this
+ // assumes that terminators do not have side effects!
+ // FIXME: This doesn't work for FP_REG_KILL.
+
+ while (!Pred->empty() && TII.isTerminatorInstr(Pred->back().getOpcode()))
+ Pred->pop_back();
+
+ // Splice the instructions over.
+ Pred->splice(Pred->end(), MBB, MBB->begin(), MBB->end());
+
+ // If MBB does not end with a barrier, add a goto instruction to the end.
+ if (Pred->empty() || !TII.isBarrier(Pred->back().getOpcode()))
+ TII.insertGoto(*Pred, *next(MBB));
+
+ // Update the CFG now.
+ Pred->removeSuccessor(Pred->succ_begin());
+ while (!MBB->succ_empty()) {
+ Pred->addSuccessor(*(MBB->succ_end()-1));
+ MBB->removeSuccessor(MBB->succ_end()-1);
+ }
+ return true;
+ }
+ }
+
+ // If BB falls through into Old, insert an unconditional branch to New.
+ MachineFunction::iterator BBSucc = BB; ++BBSucc;
+ if (BBSucc != BB->getParent()->end() && &*BBSucc == Old)
+ TII.insertGoto(*BB, *New);
+
+
if (MBB->pred_size() == 1) {
// If this block has a single predecessor, and if that block has a single
// successor, merge this block into that block.
@@ -131,6 +164,8 @@
if (Pred->succ_size() == 1) {
// Delete all of the terminators from end of the pred block. NOTE, this
// assumes that terminators do not have side effects!
+ // FIXME: This doesn't work for FP_REG_KILL.
+
while (!Pred->empty() && TII.isTerminatorInstr(Pred->back().getOpcode()))
Pred->pop_back();
@@ -199,6 +234,6 @@
}
}
}
-
+#endif
return false;
}
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