1 files changed, 28 insertions, 6 deletions
diff --git a/clang/lib/CodeGen/CGExprScalar.cpp b/clang/lib/CodeGen/CGExprScalar.cpp
index 418f23bd1a97..e47701915f2f 100644
--- a/clang/lib/CodeGen/CGExprScalar.cpp
+++ b/clang/lib/CodeGen/CGExprScalar.cpp
@@ -2063,11 +2063,25 @@ Value *ScalarExprEmitter::VisitCastExpr(CastExpr *CE) {
     // perform the bitcast.
     if (const auto *FixedSrc = dyn_cast<llvm::FixedVectorType>(SrcTy)) {
       if (const auto *ScalableDst = dyn_cast<llvm::ScalableVectorType>(DstTy)) {
+        // If we are casting a fixed i8 vector to a scalable 16 x i1 predicate
+        // vector, use a vector insert and bitcast the result.
+        bool NeedsBitCast = false;
+        auto PredType = llvm::ScalableVectorType::get(Builder.getInt1Ty(), 16);
+        llvm::Type *OrigType = DstTy;
+        if (ScalableDst == PredType &&
+            FixedSrc->getElementType() == Builder.getInt8Ty()) {
+          DstTy = llvm::ScalableVectorType::get(Builder.getInt8Ty(), 2);
+          ScalableDst = dyn_cast<llvm::ScalableVectorType>(DstTy);
+          NeedsBitCast = true;
+        }
         if (FixedSrc->getElementType() == ScalableDst->getElementType()) {
           llvm::Value *UndefVec = llvm::UndefValue::get(DstTy);
           llvm::Value *Zero = llvm::Constant::getNullValue(CGF.CGM.Int64Ty);
-          return Builder.CreateInsertVector(DstTy, UndefVec, Src, Zero,
-                                            "castScalableSve");
+          llvm::Value *Result = Builder.CreateInsertVector(
+              DstTy, UndefVec, Src, Zero, "castScalableSve");
+          if (NeedsBitCast)
+            Result = Builder.CreateBitCast(Result, OrigType);
+          return Result;
         }
       }
     }
@@ -2077,6 +2091,15 @@ Value *ScalarExprEmitter::VisitCastExpr(CastExpr *CE) {
     // perform the bitcast.
     if (const auto *ScalableSrc = dyn_cast<llvm::ScalableVectorType>(SrcTy)) {
       if (const auto *FixedDst = dyn_cast<llvm::FixedVectorType>(DstTy)) {
+        // If we are casting a scalable 16 x i1 predicate vector to a fixed i8
+        // vector, bitcast the source and use a vector extract.
+        auto PredType = llvm::ScalableVectorType::get(Builder.getInt1Ty(), 16);
+        if (ScalableSrc == PredType &&
+            FixedDst->getElementType() == Builder.getInt8Ty()) {
+          SrcTy = llvm::ScalableVectorType::get(Builder.getInt8Ty(), 2);
+          ScalableSrc = dyn_cast<llvm::ScalableVectorType>(SrcTy);
+          Src = Builder.CreateBitCast(Src, SrcTy);
+        }
         if (ScalableSrc->getElementType() == FixedDst->getElementType()) {
           llvm::Value *Zero = llvm::Constant::getNullValue(CGF.CGM.Int64Ty);
           return Builder.CreateExtractVector(DstTy, Src, Zero, "castFixedSve");
@@ -2087,10 +2110,9 @@ Value *ScalarExprEmitter::VisitCastExpr(CastExpr *CE) {
     // Perform VLAT <-> VLST bitcast through memory.
     // TODO: since the llvm.experimental.vector.{insert,extract} intrinsics
     //       require the element types of the vectors to be the same, we
-    //       need to keep this around for casting between predicates, or more
-    //       generally for bitcasts between VLAT <-> VLST where the element
-    //       types of the vectors are not the same, until we figure out a better
-    //       way of doing these casts.
+    //       need to keep this around for bitcasts between VLAT <-> VLST where
+    //       the element types of the vectors are not the same, until we figure
+    //       out a better way of doing these casts.
     if ((isa<llvm::FixedVectorType>(SrcTy) &&
          isa<llvm::ScalableVectorType>(DstTy)) ||
         (isa<llvm::ScalableVectorType>(SrcTy) &&