Add a late optimization to BranchFolding that hoist common instruction sequences
at the start of basic blocks to their common predecessor. It's actually quite
common (e.g. about 50 times in JM/lencod) and has shown to be a nice code size
benefit. e.g.
pushq %rax
testl %edi, %edi
jne LBB0_2
## BB#1:
xorb %al, %al
popq %rdx
ret
LBB0_2:
xorb %al, %al
callq _foo
popq %rdx
ret
=>
pushq %rax
xorb %al, %al
testl %edi, %edi
je LBB0_2
## BB#1:
callq _foo
LBB0_2:
popq %rdx
ret
rdar://9145558
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@131172 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/BranchFolding.h b/lib/CodeGen/BranchFolding.h
index 15dfa7f..4daf4ec 100644
--- a/lib/CodeGen/BranchFolding.h
+++ b/lib/CodeGen/BranchFolding.h
@@ -19,11 +19,10 @@
class RegScavenger;
class TargetInstrInfo;
class TargetRegisterInfo;
- template<typename T> class SmallVectorImpl;
class BranchFolder {
public:
- explicit BranchFolder(bool defaultEnableTailMerge);
+ explicit BranchFolder(bool defaultEnableTailMerge, bool CommonHoist);
bool OptimizeFunction(MachineFunction &MF,
const TargetInstrInfo *tii,
@@ -85,6 +84,7 @@
std::vector<SameTailElt> SameTails;
bool EnableTailMerge;
+ bool EnableHoistCommonCode;
const TargetInstrInfo *TII;
const TargetRegisterInfo *TRI;
MachineModuleInfo *MMI;
@@ -110,6 +110,9 @@
bool OptimizeBlock(MachineBasicBlock *MBB);
void RemoveDeadBlock(MachineBasicBlock *MBB);
bool OptimizeImpDefsBlock(MachineBasicBlock *MBB);
+
+ bool HoistCommonCode(MachineFunction &MF);
+ bool HoistCommonCodeInSuccs(MachineBasicBlock *MBB);
};
}