[PATCH] D74386: [SVE] Update API ConstantVector::getSplat() to use ElementCount.

[Huihui Zhang via Phabricator via llvm-commits]

huihuiz added inline comments.


================
Comment at: llvm/lib/CodeGen/CodeGenPrepare.cpp:6542
 
-    unsigned End = getTransitionType()->getVectorNumElements();
+    auto EC = getTransitionType()->getVectorElementCount();
     if (UseSplat)
----------------
efriedma wrote:
> Please write out the type ElementCount.
> 
> This is unfortunately turning the explicit assertion if the type is scalable into a later verifier failure in the case where it isn't a splat.  Please either fix it properly, or change it so the non-splat codepath still asserts.
Good catch! Thanks Eli!

Going with assert for non-splat codepath for scalable vector.

We should implement like:

```
UndefValue *UndefVal = UndefValue::get(getTransitionType());
Type *I32Ty = Type::getInt32Ty(getTransitionType()->getContext());
return ConstantExpr::getInsertElement(UndefVal, Val, ConstantInt::get(I32Ty, ExtractIdx));
```

But current target lowering will reject scalable vector earlier while checking isTypeLegal(EVT VT). 

I am adding a test to check this. So we get assert once target lowering is ready. Then I can bring in this implementation and check for its correctness.

```
define void @simpleOneInstructionPromotion(<vscale x 2 x i32>* %addr1, i32* %dest) {
  %in1 = load <vscale x 2 x i32>, <vscale x 2 x i32>* %addr1, align 8
  %extract = extractelement <vscale x 2 x i32> %in1, i32 1
  %out = or i32 %extract, 1
  store i32 %out, i32* %dest, align 4
  ret void
}

```


Repository:
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  https://reviews.llvm.org/D74386/new/

https://reviews.llvm.org/D74386