1 files changed, 6 insertions, 2 deletions
diff --git a/llvm/lib/CodeGen/CodeGenPrepare.cpp b/llvm/lib/CodeGen/CodeGenPrepare.cpp
index 373064d..fd55ef2 100644
--- a/llvm/lib/CodeGen/CodeGenPrepare.cpp
+++ b/llvm/lib/CodeGen/CodeGenPrepare.cpp
@@ -6131,7 +6131,8 @@ bool CodeGenPrepare::optimizeSelectInst(SelectInst *SI) {
   // Into:
   //    start:
   //       %cmp = cmp uge i32 %a, %b
-  //       br i1 %cmp, label %select.true, label %select.false
+  //       %cmp.frozen = freeze %cmp
+  //       br i1 %cmp.frozen, label %select.true, label %select.false
   //    select.true:
   //       br label %select.end
   //    select.false:
@@ -6139,6 +6140,7 @@ bool CodeGenPrepare::optimizeSelectInst(SelectInst *SI) {
   //    select.end:
   //       %sel = phi i32 [ %c, %select.true ], [ %d, %select.false ]
   //
+  // %cmp should be freezed, otherwise it may introduce undefined behavior.
   // In addition, we may sink instructions that produce %c or %d from
   // the entry block into the destination(s) of the new branch.
   // If the true or false blocks do not contain a sunken instruction, that
@@ -6217,7 +6219,9 @@ bool CodeGenPrepare::optimizeSelectInst(SelectInst *SI) {
     TT = TrueBlock;
     FT = FalseBlock;
   }
-  IRBuilder<>(SI).CreateCondBr(SI->getCondition(), TT, FT, SI);
+  IRBuilder<> IB(SI);
+  auto CondFr = IB.CreateFreeze(SI->getCondition(), SI->getName() + ".frozen");
+  IB.CreateCondBr(CondFr, TT, FT, SI);
 
   SmallPtrSet<const Instruction *, 2> INS;
   INS.insert(ASI.begin(), ASI.end());