[1/11][IR] Permit load/store/alloca for struct of the same scalable vector type

This patch-set aims to simplify the existing RVV segment load/store
intrinsics to use a type that represents a tuple of vectors instead.

To achieve this, first we need to relax the current limitation for an
aggregate type to be a target of load/store/alloca when the aggregate
type contains homogeneous scalable vector types. Then to adjust the
prolog of an LLVM function during lowering to clang. Finally we
re-define the RVV segment load/store intrinsics to use the tuple types.

The pull request under the RVV intrinsic specification is
riscv-non-isa/rvv-intrinsic-doc#198

---

This is the 1st patch of the patch-set. This patch is originated from
D98169.

This patch allows aggregate type (StructType) that contains homogeneous
scalable vector types to be a target of load/store/alloca. The RFC of
this patch was posted in LLVM Discourse.

https://discourse.llvm.org/t/rfc-ir-permit-load-store-alloca-for-struct-of-the-same-scalable-vector-type/69527

The main changes in this patch are:

Extend `StructLayout::StructSize` from `uint64_t` to `TypeSize` to
accommodate an expression of scalable size.

Allow `StructType:isSized` to also return true for homogeneous
scalable vector types.

Let `Type::isScalableTy` return true when `Type` is `StructType`
and contains scalable vectors

Extra description is added in the LLVM Language Reference Manual on the
relaxation of this patch.

Authored-by: Hsiangkai Wang <kai.wang@sifive.com>
Co-Authored-by: eop Chen <eop.chen@sifive.com>

Reviewed By: craig.topper, nikic

Differential Revision: https://reviews.llvm.org/D146872

1 files changed, 57 insertions, 6 deletions

diff --git a/llvm/lib/CodeGen/Analysis.cpp b/llvm/lib/CodeGen/Analysis.cpp
index b957944..2065bfb 100644
--- a/llvm/lib/CodeGen/Analysis.cpp
+++ b/llvm/lib/CodeGen/Analysis.cpp
@@ -79,8 +79,8 @@ unsigned llvm::ComputeLinearIndex(Type *Ty,
 void llvm::ComputeValueVTs(const TargetLowering &TLI, const DataLayout &DL,
                            Type *Ty, SmallVectorImpl<EVT> &ValueVTs,
                            SmallVectorImpl<EVT> *MemVTs,
-                           SmallVectorImpl<uint64_t> *Offsets,
-                           uint64_t StartingOffset) {
+                           SmallVectorImpl<TypeSize> *Offsets,
+                           TypeSize StartingOffset) {
   // Given a struct type, recursively traverse the elements.
   if (StructType *STy = dyn_cast<StructType>(Ty)) {
     // If the Offsets aren't needed, don't query the struct layout. This allows
@@ -92,7 +92,8 @@ void llvm::ComputeValueVTs(const TargetLowering &TLI, const DataLayout &DL,
                                       EE = STy->element_end();
          EI != EE; ++EI) {
       // Don't compute the element offset if we didn't get a StructLayout above.
-      uint64_t EltOffset = SL ? SL->getElementOffset(EI - EB) : 0;
+      TypeSize EltOffset = SL ? SL->getElementOffset(EI - EB)
+                              : TypeSize::get(0, StartingOffset.isScalable());
       ComputeValueVTs(TLI, DL, *EI, ValueVTs, MemVTs, Offsets,
                       StartingOffset + EltOffset);
     }
@@ -101,7 +102,7 @@ void llvm::ComputeValueVTs(const TargetLowering &TLI, const DataLayout &DL,
   // Given an array type, recursively traverse the elements.
   if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
     Type *EltTy = ATy->getElementType();
-    uint64_t EltSize = DL.getTypeAllocSize(EltTy).getFixedValue();
+    TypeSize EltSize = DL.getTypeAllocSize(EltTy);
     for (unsigned i = 0, e = ATy->getNumElements(); i != e; ++i)
       ComputeValueVTs(TLI, DL, EltTy, ValueVTs, MemVTs, Offsets,
                       StartingOffset + i * EltSize);
@@ -120,12 +121,62 @@ void llvm::ComputeValueVTs(const TargetLowering &TLI, const DataLayout &DL,
 
 void llvm::ComputeValueVTs(const TargetLowering &TLI, const DataLayout &DL,
                            Type *Ty, SmallVectorImpl<EVT> &ValueVTs,
-                           SmallVectorImpl<uint64_t> *Offsets,
-                           uint64_t StartingOffset) {
+                           SmallVectorImpl<TypeSize> *Offsets,
+                           TypeSize StartingOffset) {
   return ComputeValueVTs(TLI, DL, Ty, ValueVTs, /*MemVTs=*/nullptr, Offsets,
                          StartingOffset);
 }
 
+void llvm::ComputeValueVTs(const TargetLowering &TLI, const DataLayout &DL,
+                           Type *Ty, SmallVectorImpl<EVT> &ValueVTs,
+                           SmallVectorImpl<TypeSize> *Offsets,
+                           uint64_t StartingOffset) {
+  TypeSize Offset = TypeSize::get(StartingOffset, Ty->isScalableTy());
+  return ComputeValueVTs(TLI, DL, Ty, ValueVTs, Offsets, Offset);
+}
+
+void llvm::ComputeValueVTs(const TargetLowering &TLI, const DataLayout &DL,
+                           Type *Ty, SmallVectorImpl<EVT> &ValueVTs,
+                           SmallVectorImpl<uint64_t> *FixedOffsets,
+                           uint64_t StartingOffset) {
+  TypeSize Offset = TypeSize::get(StartingOffset, Ty->isScalableTy());
+  SmallVector<TypeSize, 4> Offsets;
+  if (FixedOffsets)
+    ComputeValueVTs(TLI, DL, Ty, ValueVTs, &Offsets, Offset);
+  else
+    ComputeValueVTs(TLI, DL, Ty, ValueVTs, nullptr, Offset);
+
+  if (FixedOffsets)
+    for (TypeSize Offset : Offsets)
+      FixedOffsets->push_back(Offset.getKnownMinValue());
+}
+
+void llvm::ComputeValueVTs(const TargetLowering &TLI, const DataLayout &DL,
+                           Type *Ty, SmallVectorImpl<EVT> &ValueVTs,
+                           SmallVectorImpl<EVT> *MemVTs,
+                           SmallVectorImpl<TypeSize> *Offsets,
+                           uint64_t StartingOffset) {
+  TypeSize Offset = TypeSize::get(StartingOffset, Ty->isScalableTy());
+  return ComputeValueVTs(TLI, DL, Ty, ValueVTs, MemVTs, Offsets, Offset);
+}
+
+void llvm::ComputeValueVTs(const TargetLowering &TLI, const DataLayout &DL,
+                           Type *Ty, SmallVectorImpl<EVT> &ValueVTs,
+                           SmallVectorImpl<EVT> *MemVTs,
+                           SmallVectorImpl<uint64_t> *FixedOffsets,
+                           uint64_t StartingOffset) {
+  TypeSize Offset = TypeSize::get(StartingOffset, Ty->isScalableTy());
+  SmallVector<TypeSize, 4> Offsets;
+  if (FixedOffsets)
+    ComputeValueVTs(TLI, DL, Ty, ValueVTs, MemVTs, &Offsets, Offset);
+  else
+    ComputeValueVTs(TLI, DL, Ty, ValueVTs, MemVTs, nullptr, Offset);
+
+  if (FixedOffsets)
+    for (TypeSize Offset : Offsets)
+      FixedOffsets->push_back(Offset.getKnownMinValue());
+}
+
 void llvm::computeValueLLTs(const DataLayout &DL, Type &Ty,
                             SmallVectorImpl<LLT> &ValueTys,
                             SmallVectorImpl<uint64_t> *Offsets,