Implement PPCInstrInfo::FoldImmediate

There are certain PPC instructions into which we can fold a zero immediate
operand. We can detect such cases by looking at the register class required
by the using operand (so long as it is not otherwise constrained).

llvm-svn: 178961

1 files changed, 2 insertions, 0 deletions

diff --git a/llvm/lib/Target/PowerPC/PPCRegisterInfo.cpp b/llvm/lib/Target/PowerPC/PPCRegisterInfo.cpp
index 1d61a3a8eac..3f5f6c26ffa 100644
--- a/llvm/lib/Target/PowerPC/PPCRegisterInfo.cpp
+++ b/llvm/lib/Target/PowerPC/PPCRegisterInfo.cpp
@@ -76,6 +76,8 @@ PPCRegisterInfo::PPCRegisterInfo(const PPCSubtarget &ST,
 const TargetRegisterClass *
 PPCRegisterInfo::getPointerRegClass(const MachineFunction &MF, unsigned Kind)
                                                                        const {
+  // Note that PPCInstrInfo::FoldImmediate also directly uses this Kind value
+  // when it checks for ZERO folding.
   if (Kind == 1) {
     if (Subtarget.isPPC64())
       return &PPC::G8RC_NOX0RegClass;