[ConstantFold][SVE] Fix constand fold for vector call.

[huihuiz]

Summary

Do not iterate on scalable vectors.

[huihuiz]

Current upstream crash with: llvm/lib/IR/Value.cpp:408: void llvm::Value::doRAUW(llvm::Value *, llvm::Value::ReplaceMetadataUses): Assertion `New->getType() == getType() && "replaceAllUses of value with new value of different type!"' failed.

test.ll

declare <vscale x 16 x i8> @llvm.sadd.sat.nxv16i8(<vscale x 16 x i8>, <vscale x 16 x i8>)

define <vscale x 16 x i8> @sqadd_i8_low() {
  %r =  call <vscale x 16 x i8> @llvm.sadd.sat.nxv16i8(<vscale x 16 x i8> undef, <vscale x 16 x i8> undef)
  ret <vscale x 16 x i8> %r
}

run: opt -S test.ll -constprop -o -

[sdesmalen]

LGTM!

llvm/lib/Analysis/ConstantFolding.cpp

static Constant *ConstantFoldVectorCall(StringRef Name,
                                         ArrayRef<Constant *> Operands,
                                         const DataLayout &DL,
                                         const TargetLibraryInfo *TLI,
                                         const CallBase *Call) {
   SmallVector<Constant *, 4> Result(VTy->getNumElements());
   SmallVector<Constant *, 4> Lane(Operands.size());
   Type *Ty = VTy->getElementType();
 
+  // Do not iterate on scalable vector. The number of elements is unknown at
+  // compile-time.
+  if (VTy->getVectorIsScalable())
+    return nullptr;
+
   if (IntrinsicID == Intrinsic::masked_load) {
     auto *SrcPtr = Operands[0];
     auto *Mask = Operands[2];
     auto *Passthru = Operands[3];
 
     Constant *VecData = ConstantFoldLoadFromConstPtr(SrcPtr, VTy, DL);
 
     SmallVector<Constant *, 32> NewElements;

llvm/test/Analysis/ConstantFolding/vscale.ll

 
 define <vscale x 4 x i32> @select() {
 ; CHECK-LABEL: @select(
 ; CHECK-NEXT:    ret <vscale x 4 x i32> undef
 ;
   %r = select <vscale x 4 x i1> undef, <vscale x 4 x i32> zeroinitializer, <vscale x 4 x i32> undef
   ret <vscale x 4 x i32> %r
 }
+
+declare <vscale x 16 x i8> @llvm.sadd.sat.nxv16i8(<vscale x 16 x i8>, <vscale x 16 x i8>)
+
+define <vscale x 16 x i8> @call() {
+; CHECK-LABEL: @call(
+; CHECK-NEXT:    [[R:%.*]] = call <vscale x 16 x i8> @llvm.sadd.sat.nxv16i8(<vscale x 16 x i8> undef, <vscale x 16 x i8> undef)
+; CHECK-NEXT:    ret <vscale x 16 x i8> [[R]]
+;
+  %r =  call <vscale x 16 x i8> @llvm.sadd.sat.nxv16i8(<vscale x 16 x i8> undef, <vscale x 16 x i8> undef)
+  ret <vscale x 16 x i8> %r
+}