Add testcase for legalizing ISD::CTTZ efficiently. On PPC, ctlz(int) is

now codegen'd as this:

        addi r2, r3, -1
        andc r2, r2, r3
        cntlzw r2, r2
        subfic r3, r2, 32
        blr

llvm-svn: 21881

llvm/test/Regression/CodeGen/PowerPC/cttz.ll

@@ -0,0 +1,12 @@
+; Make sure this testcase does not use ctpop
+; RUN: llvm-as < %s | llc -march=ppc32 | grep -i 'cntlzw'
+
+declare int %llvm.cttz(int)
+
+implementation   ; Functions:
+
+int %bar(int %x) {
+entry:
+	%tmp.1 = call int %llvm.cttz( int %x ) 
+	ret int %tmp.1
+}