1 files changed, 13 insertions, 6 deletions
diff --git a/llvm/lib/Target/AArch64/AArch64FastISel.cpp b/llvm/lib/Target/AArch64/AArch64FastISel.cpp
index 179fe4dd7ff..7ee8c47930a 100644
--- a/llvm/lib/Target/AArch64/AArch64FastISel.cpp
+++ b/llvm/lib/Target/AArch64/AArch64FastISel.cpp
@@ -2694,8 +2694,11 @@ bool AArch64FastISel::SelectTrunc(const Instruction *I) {
   bool SrcIsKill = hasTrivialKill(Op);
 
   // If we're truncating from i64 to a smaller non-legal type then generate an
-  // AND.  Otherwise, we know the high bits are undefined and a truncate doesn't
-  // generate any code.
+  // AND. Otherwise, we know the high bits are undefined and a truncate only
+  // generate a COPY. We cannot mark the source register also as result
+  // register, because this can incorrectly transfer the kill flag onto the
+  // source register.
+  unsigned ResultReg;
   if (SrcVT == MVT::i64) {
     uint64_t Mask = 0;
     switch (DestVT.SimpleTy) {
@@ -2716,12 +2719,16 @@ bool AArch64FastISel::SelectTrunc(const Instruction *I) {
     unsigned Reg32 = FastEmitInst_extractsubreg(MVT::i32, SrcReg, SrcIsKill,
                                                 AArch64::sub_32);
     // Create the AND instruction which performs the actual truncation.
-    unsigned ANDReg = emitAND_ri(MVT::i32, Reg32, /*IsKill=*/true, Mask);
-    assert(ANDReg && "Unexpected AND instruction emission failure.");
-    SrcReg = ANDReg;
+    ResultReg = emitAND_ri(MVT::i32, Reg32, /*IsKill=*/true, Mask);
+    assert(ResultReg && "Unexpected AND instruction emission failure.");
+  } else {
+    ResultReg = createResultReg(&AArch64::GPR32RegClass);
+    BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc,
+            TII.get(TargetOpcode::COPY), ResultReg)
+        .addReg(SrcReg, getKillRegState(SrcIsKill));
   }
 
-  UpdateValueMap(I, SrcReg);
+  UpdateValueMap(I, ResultReg);
   return true;
 }