[LV] Add initial support for vectorizing literal struct return values (#109833)

This patch adds initial support for vectorizing literal struct return
values. Currently, this is limited to the case where the struct is
homogeneous (all elements have the same type) and not packed. The users
of the call also must all be `extractvalue` instructions.

The intended use case for this is vectorizing intrinsics such as:

```
declare { float, float } @llvm.sincos.f32(float %x)
```

Mapping them to structure-returning library calls such as:

```
declare { <4 x float>, <4 x float> } @Sleef_sincosf4_u10advsimd(<4 x float>)
```

Or their widened form (such as `@llvm.sincos.v4f32` in this case).

Implementing this required two main changes:

1. Supporting widening `extractvalue`
2. Adding support for vectorized struct types in LV
  * This is mostly limited to parts of the cost model and scalarization

Since the supported use case is narrow, the required changes are
relatively small.

1 files changed, 3 insertions, 10 deletions

diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp
index e3599315e224..420cbc5384ce 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp
@@ -954,7 +954,7 @@ bool LoopVectorizationLegality::canVectorizeInstrs() {
       if (CI && !VFDatabase::getMappings(*CI).empty())
         VecCallVariantsFound = true;
 
-      auto CanWidenInstructionTy = [this](Instruction const &Inst) {
+      auto CanWidenInstructionTy = [](Instruction const &Inst) {
         Type *InstTy = Inst.getType();
         if (!isa<StructType>(InstTy))
           return canVectorizeTy(InstTy);
@@ -962,15 +962,8 @@ bool LoopVectorizationLegality::canVectorizeInstrs() {
         // For now, we only recognize struct values returned from calls where
         // all users are extractvalue as vectorizable. All element types of the
         // struct must be types that can be widened.
-        if (isa<CallInst>(Inst) && canWidenCallReturnType(InstTy) &&
-            all_of(Inst.users(), IsaPred<ExtractValueInst>)) {
-          // TODO: Remove the `StructVecCallFound` flag once vectorizing calls
-          // with struct returns is supported.
-          StructVecCallFound = true;
-          return true;
-        }
-
-        return false;
+        return isa<CallInst>(Inst) && canWidenCallReturnType(InstTy) &&
+               all_of(Inst.users(), IsaPred<ExtractValueInst>);
       };
 
       // Check that the instruction return type is vectorizable.