[PowerPC] Fix a crash in POWER 9 setb peephole

[qiucf]

Summary

Variable InnerIsSel references FalseRes, while FalseRes might be zext/sext. So InnerIsSel should reference SetOrSelCC, otherwise a crash will happen.

[steven.zhang]

LGTM, thank you for fixing this.

llvm/lib/Target/PowerPC/PPCISelDAGToDAG.cpp

static bool mayUseP9Setb(SDNode *N, const ISD::CondCode &CC, SelectionDAG *DAG,
   int64_t TrueResVal = TrueConst->getSExtValue();
   if ((TrueResVal < -1 || TrueResVal > 1) ||
       (TrueResVal == -1 && FalseRes.getOpcode() != ISD::ZERO_EXTEND) ||
       (TrueResVal == 1 && FalseRes.getOpcode() != ISD::SIGN_EXTEND) ||
       (TrueResVal == 0 &&
        (FalseRes.getOpcode() != ISD::SELECT_CC || CC != ISD::SETEQ)))
     return false;
 
-  bool InnerIsSel = FalseRes.getOpcode() == ISD::SELECT_CC;
-  SDValue SetOrSelCC = InnerIsSel ? FalseRes : FalseRes.getOperand(0);
+  SDValue SetOrSelCC = FalseRes.getOpcode() == ISD::SELECT_CC
+                           ? FalseRes
+                           : FalseRes.getOperand(0);
+  bool InnerIsSel = SetOrSelCC.getOpcode() == ISD::SELECT_CC;
   if (SetOrSelCC.getOpcode() != ISD::SETCC &&
       SetOrSelCC.getOpcode() != ISD::SELECT_CC)
     return false;
 
   // Without this setb optimization, the outer SELECT_CC will be manually
   // selected to SELECT_CC_I4/SELECT_CC_I8 Pseudo, then expand-isel-pseudos pass
   // transforms pseudo instruction to isel instruction. When there are more than
   // one use for result like zext/sext, with current optimization we only see

llvm/test/CodeGen/PowerPC/ppc64-P9-setb.ll

define i64 @setbn3(float %a, float %b) {
   %t3 = zext i1 %t2 to i64
   %t4 = select i1 %t1, i64 -1, i64 %t3
   ret i64 %t4
 ; CHECK-LABEL: setbn3:
 ; CHECK-NOT: {{\<setb\>}}
 ; CHECK: isel
 ; CHECK: blr
 }
+
+; Verify this case doesn't crash
+define void @setbn4(i128 %0, i32* %sel.out) {
+entry:
+; CHECK-LABEL: setbn4:
+; CHECK-NOT: {{\<setb\>}}
+; CHECK: isel
+; CHECK: blr
+  %c1 = icmp ult i128 %0, 5192296858534827628530496329220096
+  %c2 = icmp ugt i128 %0, 5192296858534827628530496329220096
+  %ext = zext i1 %c2 to i32
+  %sel = select i1 %c1, i32 -1, i32 %ext
+  store i32 %sel, i32* %sel.out, align 4
+  ret void
+}