Generate PPC early conditional returns

PowerPC has a conditional branch to the link register (return) instruction: BCLR.
This should be used any time when we'd otherwise have a conditional branch to a
return. This adds a small pass, PPCEarlyReturn, which runs just prior to the
branch selection pass (and, importantly, after block placement) to generate
these conditional returns when possible. It will also eliminate unconditional
branches to returns (these happen rarely; most of the time these have already
been tail duplicated by the time PPCEarlyReturn is invoked). This is a nice
optimization for small functions that do not maintain a stack frame.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179026 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 2 insertions, 1 deletions

diff --git a/lib/Target/PowerPC/PPC.h b/lib/Target/PowerPC/PPC.h
index 446b6854fb..b4be51a8ca 100644
--- a/lib/Target/PowerPC/PPC.h
+++ b/lib/Target/PowerPC/PPC.h
@@ -31,6 +31,7 @@ namespace llvm {
   class MCInst;
 
   FunctionPass *createPPCCTRLoops();
+  FunctionPass *createPPCEarlyReturnPass();
   FunctionPass *createPPCBranchSelectionPass();
   FunctionPass *createPPCISelDag(PPCTargetMachine &TM);
   FunctionPass *createPPCJITCodeEmitterPass(PPCTargetMachine &TM,
@@ -40,7 +41,7 @@ namespace llvm {
 
   /// \brief Creates an PPC-specific Target Transformation Info pass.
   ImmutablePass *createPPCTargetTransformInfoPass(const PPCTargetMachine *TM);
-  
+
   namespace PPCII {
     
   /// Target Operand Flag enum.