[llvm-commits] [llvm] r132798 - /llvm/trunk/lib/CodeGen/TailDuplication.cpp
Rafael Espindola
rafael.espindola at gmail.com
Thu Jun 9 12:54:42 PDT 2011
Author: rafael
Date: Thu Jun 9 14:54:42 2011
New Revision: 132798
URL: http://llvm.org/viewvc/llvm-project?rev=132798&view=rev
Log:
Refactor some checks into shouldTailDuplicate. Update comments.
No functionality change.
Modified:
llvm/trunk/lib/CodeGen/TailDuplication.cpp
Modified: llvm/trunk/lib/CodeGen/TailDuplication.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/TailDuplication.cpp?rev=132798&r1=132797&r2=132798&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/TailDuplication.cpp (original)
+++ llvm/trunk/lib/CodeGen/TailDuplication.cpp Thu Jun 9 14:54:42 2011
@@ -91,6 +91,8 @@
SmallVector<MachineBasicBlock*, 8> &TDBBs,
SmallSetVector<MachineBasicBlock*, 8> &Succs);
bool TailDuplicateBlocks(MachineFunction &MF);
+ bool shouldTailDuplicate(const MachineFunction &MF,
+ MachineBasicBlock &TailBB);
bool TailDuplicate(MachineBasicBlock *TailBB, MachineFunction &MF,
SmallVector<MachineBasicBlock*, 8> &TDBBs,
SmallVector<MachineInstr*, 16> &Copies);
@@ -184,10 +186,6 @@
if (NumTails == TailDupLimit)
break;
- // Only duplicate blocks that end with unconditional branches.
- if (MBB->canFallThrough())
- continue;
-
// Save the successors list.
SmallSetVector<MachineBasicBlock*, 8> Succs(MBB->succ_begin(),
MBB->succ_end());
@@ -450,14 +448,15 @@
}
}
-/// TailDuplicate - If it is profitable, duplicate TailBB's contents in each
-/// of its predecessors.
+/// shouldTailDuplicate - Determine if it is profitable to duplicate this block.
bool
-TailDuplicatePass::TailDuplicate(MachineBasicBlock *TailBB, MachineFunction &MF,
- SmallVector<MachineBasicBlock*, 8> &TDBBs,
- SmallVector<MachineInstr*, 16> &Copies) {
- // Set the limit on the number of instructions to duplicate, with a default
- // of one less than the tail-merge threshold. When optimizing for size,
+TailDuplicatePass::shouldTailDuplicate(const MachineFunction &MF,
+ MachineBasicBlock &TailBB) {
+ // Only duplicate blocks that end with unconditional branches.
+ if (TailBB.canFallThrough())
+ return false;
+
+ // Set the limit on the cost to duplicate. When optimizing for size,
// duplicate only one, because one branch instruction can be eliminated to
// compensate for the duplication.
unsigned MaxDuplicateCount;
@@ -468,12 +467,12 @@
MaxDuplicateCount = TailDuplicateSize;
if (PreRegAlloc) {
- if (TailBB->empty())
+ if (TailBB.empty())
return false;
- const TargetInstrDesc &TID = TailBB->back().getDesc();
+ const TargetInstrDesc &TID = TailBB.back().getDesc();
// Pre-regalloc tail duplication hurts compile time and doesn't help
- // much except for indirect branches and returns.
- if (!TID.isIndirectBranch() && !TID.isReturn())
+ // much except for indirect branches.
+ if (!TID.isIndirectBranch())
return false;
// If the target has hardware branch prediction that can handle indirect
// branches, duplicating them can often make them predictable when there
@@ -484,15 +483,15 @@
}
// Don't try to tail-duplicate single-block loops.
- if (TailBB->isSuccessor(TailBB))
+ if (TailBB.isSuccessor(&TailBB))
return false;
// Check the instructions in the block to determine whether tail-duplication
// is invalid or unlikely to be profitable.
unsigned InstrCount = 0;
bool HasCall = false;
- for (MachineBasicBlock::iterator I = TailBB->begin();
- I != TailBB->end(); ++I) {
+ for (MachineBasicBlock::const_iterator I = TailBB.begin(); I != TailBB.end();
+ ++I) {
// Non-duplicable things shouldn't be tail-duplicated.
if (I->getDesc().isNotDuplicable()) return false;
// Do not duplicate 'return' instructions if this is a pre-regalloc run.
@@ -512,6 +511,18 @@
if (InstrCount > 1 && (PreRegAlloc && HasCall))
return false;
+ return true;
+}
+
+/// TailDuplicate - If it is profitable, duplicate TailBB's contents in each
+/// of its predecessors.
+bool
+TailDuplicatePass::TailDuplicate(MachineBasicBlock *TailBB, MachineFunction &MF,
+ SmallVector<MachineBasicBlock*, 8> &TDBBs,
+ SmallVector<MachineInstr*, 16> &Copies) {
+ if (!shouldTailDuplicate(MF, *TailBB))
+ return false;
+
DEBUG(dbgs() << "\n*** Tail-duplicating BB#" << TailBB->getNumber() << '\n');
// Iterate through all the unique predecessors and tail-duplicate this
More information about the llvm-commits
mailing list