Fix a significant code quality regression I introduced on PPC64 quite

a while ago.  We now produce:

_foo:
	mflr r0
	std r0, 16(r1)
	ld r2, 16(r1)
	std r2, 0(r3)
	ld r0, 16(r1)
	mtlr r0
	blr 

instead of:

_foo:
	mflr r0
	std r0, 16(r1)
	lis r0, 0
	ori r0, r0, 16
	ldx r2, r1, r0
	std r2, 0(r3)
	ld r0, 16(r1)
	mtlr r0
	blr 

for:

void foo(void **X) {
  *X = __builtin_return_address(0);
}

on ppc64.

llvm-svn: 44701

llvm/lib/Target/PowerPC/PPCRegisterInfo.cpp

@@ -817,7 +817,7 @@ void PPCRegisterInfo::eliminateFrameIndex(MachineBasicBlock::iterator II,
   // clear can be encoded.  This is extremely uncommon, because normally you
   // only "std" to a stack slot that is at least 4-byte aligned, but it can
   // happen in invalid code.
-  if (isInt16(Offset) && (!isIXAddr || (isIXAddr & 3) == 0)) {
+  if (isInt16(Offset) && (!isIXAddr || (Offset & 3) == 0)) {
     if (isIXAddr)
       Offset >>= 2;    // The actual encoded value has the low two bits zero.
     MI.getOperand(OffsetOperandNo).ChangeToImmediate(Offset);

llvm/test/CodeGen/PowerPC/retaddr.ll

@@ -1,5 +1,6 @@
 ; RUN: llvm-as < %s | llc -march=ppc32 | grep mflr
 ; RUN: llvm-as < %s | llc -march=ppc32 | grep lwz
+; RUN: llvm-as < %s | llc -march=ppc64 | grep {ld r., 16(r1)}
 
 target triple = "powerpc-apple-darwin8"