Merge commit '57384aeb3743' from llvm.org/main into next

Author: git apple-llvm automerger

llvm/lib/IR/ConstantFold.cpp

@@ -295,6 +295,13 @@ static Constant *ExtractConstantBytes(Constant *C, unsigned ByteStart,
   }
 }
 
+static Constant *foldMaybeUndesirableCast(unsigned opc, Constant *V,
+                                          Type *DestTy) {
+  return ConstantExpr::isDesirableCastOp(opc)
+             ? ConstantExpr::getCast(opc, V, DestTy)
+             : ConstantFoldCastInstruction(opc, V, DestTy);
+}
+
 Constant *llvm::ConstantFoldCastInstruction(unsigned opc, Constant *V,
                                             Type *DestTy) {
   if (isa<PoisonValue>(V))
@@ -320,7 +327,7 @@ Constant *llvm::ConstantFoldCastInstruction(unsigned opc, Constant *V,
     if (CE->isCast()) {
       // Try hard to fold cast of cast because they are often eliminable.
       if (unsigned newOpc = foldConstantCastPair(opc, CE, DestTy))
-        return ConstantExpr::getCast(newOpc, CE->getOperand(0), DestTy);
+        return foldMaybeUndesirableCast(newOpc, CE->getOperand(0), DestTy);
     } else if (CE->getOpcode() == Instruction::GetElementPtr &&
                // Do not fold addrspacecast (gep 0, .., 0). It might make the
                // addrspacecast uncanonicalized.
@@ -357,18 +364,22 @@ Constant *llvm::ConstantFoldCastInstruction(unsigned opc, Constant *V,
     Type *DstEltTy = DestVecTy->getElementType();
     // Fast path for splatted constants.
     if (Constant *Splat = V->getSplatValue()) {
+      Constant *Res = foldMaybeUndesirableCast(opc, Splat, DstEltTy);
+      if (!Res)
+        return nullptr;
       return ConstantVector::getSplat(
-          cast<VectorType>(DestTy)->getElementCount(),
-          ConstantExpr::getCast(opc, Splat, DstEltTy));
+          cast<VectorType>(DestTy)->getElementCount(), Res);
     }
     SmallVector<Constant *, 16> res;
     Type *Ty = IntegerType::get(V->getContext(), 32);
     for (unsigned i = 0,
                   e = cast<FixedVectorType>(V->getType())->getNumElements();
          i != e; ++i) {
-      Constant *C =
-        ConstantExpr::getExtractElement(V, ConstantInt::get(Ty, i));
-      res.push_back(ConstantExpr::getCast(opc, C, DstEltTy));
+      Constant *C = ConstantExpr::getExtractElement(V, ConstantInt::get(Ty, i));
+      Constant *Casted = foldMaybeUndesirableCast(opc, C, DstEltTy);
+      if (!Casted)
+        return nullptr;
+      res.push_back(Casted);
     }
     return ConstantVector::get(res);
   }

llvm/test/CodeGen/AArch64/arm64-codegen-prepare-extload.ll

@@ -338,7 +338,8 @@ entry:
 ; OPTALL: [[LD:%[a-zA-Z_0-9-]+]] = load i16, ptr %addr
 ;
 ; OPT-NEXT: [[SEXT:%[a-zA-Z_0-9-]+]] = sext i16 [[LD]] to i32
-; OPT-NEXT: [[RES:%[a-zA-Z_0-9-]+]] = add nuw nsw i32 [[SEXT]], zext (i1 icmp ne (ptr getelementptr inbounds ([2 x i32], ptr @c, i64 0, i64 1), ptr @a) to i32)
+; OPT-NEXT: [[SEXT2:%[a-zA-Z_0-9-]+]] = sext i16 zext (i1 icmp ne (ptr getelementptr inbounds ([2 x i32], ptr @c, i64 0, i64 1), ptr @a) to i16) to i32
+; OPT-NEXT: [[RES:%[a-zA-Z_0-9-]+]] = add nuw nsw i32 [[SEXT]], [[SEXT2]]
 ;
 ; DISABLE-NEXT: [[ADD:%[a-zA-Z_0-9-]+]] = add nuw nsw i16 [[LD]], zext (i1 icmp ne (ptr getelementptr inbounds ([2 x i32], ptr @c, i64 0, i64 1), ptr @a) to i16)
 ; DISABLE-NEXT: [[RES:%[a-zA-Z_0-9-]+]] = sext i16 [[ADD]] to i32

llvm/test/CodeGen/X86/codegen-prepare-extload.ll

@@ -546,7 +546,8 @@ define i32 @promotionOfArgEndsUpInValue(ptr %addr) {
 ; OPT-NEXT:  entry:
 ; OPT-NEXT:    [[VAL:%.*]] = load i16, ptr [[ADDR]], align 2
 ; OPT-NEXT:    [[CONV3:%.*]] = sext i16 [[VAL]] to i32
-; OPT-NEXT:    [[ADD:%.*]] = add nuw nsw i32 [[CONV3]], zext (i1 icmp ne (ptr getelementptr inbounds ([2 x i32], ptr @c, i64 0, i64 1), ptr @a) to i32)
+; OPT-NEXT:    [[PROMOTED:%.*]] = sext i16 zext (i1 icmp ne (ptr getelementptr inbounds ([2 x i32], ptr @c, i64 0, i64 1), ptr @a) to i16) to i32
+; OPT-NEXT:    [[ADD:%.*]] = add nuw nsw i32 [[CONV3]], [[PROMOTED]]
 ; OPT-NEXT:    ret i32 [[ADD]]
 ;
 ; DISABLE-LABEL: define i32 @promotionOfArgEndsUpInValue(