[SystemZ] Fix invalid codegen using RISBMux on out-of-range bits

Before using the 32-bit RISBMux set of instructions we need to
verify that the input bits are actually within range of the 32-bit
instruction.  This fixer PR35289.

llvm-svn: 318177

1 files changed, 9 insertions, 1 deletions

diff --git a/llvm/lib/Target/SystemZ/SystemZISelDAGToDAG.cpp b/llvm/lib/Target/SystemZ/SystemZISelDAGToDAG.cpp
index 6ad8932caaa..802af1ae861 100644
--- a/llvm/lib/Target/SystemZ/SystemZISelDAGToDAG.cpp
+++ b/llvm/lib/Target/SystemZ/SystemZISelDAGToDAG.cpp
@@ -992,7 +992,15 @@ bool SystemZDAGToDAGISel::tryRISBGZero(SDNode *N) {
   if (Subtarget->hasMiscellaneousExtensions())
     Opcode = SystemZ::RISBGN;
   EVT OpcodeVT = MVT::i64;
-  if (VT == MVT::i32 && Subtarget->hasHighWord()) {
+  if (VT == MVT::i32 && Subtarget->hasHighWord() &&
+      // We can only use the 32-bit instructions if all source bits are
+      // in the low 32 bits without wrapping, both after rotation (because
+      // of the smaller range for Start and End) and before rotation
+      // (because the input value is truncated).
+      RISBG.Start >= 32 && RISBG.End >= RISBG.Start &&
+      ((RISBG.Start + RISBG.Rotate) & 63) >= 32 &&
+      ((RISBG.End + RISBG.Rotate) & 63) >=
+      ((RISBG.Start + RISBG.Rotate) & 63)) {
     Opcode = SystemZ::RISBMux;
     OpcodeVT = MVT::i32;
     RISBG.Start &= 31;