[SCEV] Fix SCEV analysis for scalable target types.

[sdesmalen]

Summary

These scalable opaque target types need to be handled in a similar way to
scalable vector types.

[sdesmalen]

Refactored to use Type::isScalableTy()

[sdesmalen]

This was addressed by D144624

llvm/include/llvm/Analysis/ScalarEvolution.h

public:
   const SCEV *getOne(Type *Ty) { return getConstant(Ty, 1); }
 
   /// Return a SCEV for the constant -1 of a specific type.
   const SCEV *getMinusOne(Type *Ty) {
     return getConstant(Ty, -1, /*isSigned=*/true);
   }
 
   /// Return an expression for sizeof ScalableTy that is type IntTy, where
-  /// ScalableTy is a scalable vector type.
-  const SCEV *getSizeOfScalableVectorExpr(Type *IntTy,
-                                          ScalableVectorType *ScalableTy);
+  /// ScalableTy is a scalable vector type or an AArch64 predicate-as-counter
+  /// (opaque) type.
+  const SCEV *getSizeOfScalableTypeExpr(Type *IntTy, Type *ScalableTy);
 
   /// Return an expression for the alloc size of AllocTy that is type IntTy
   const SCEV *getSizeOfExpr(Type *IntTy, Type *AllocTy);
 
   /// Return an expression for the store size of StoreTy that is type IntTy
   const SCEV *getStoreSizeOfExpr(Type *IntTy, Type *StoreTy);
 
   /// Return an expression for offsetof on the given field with type IntTy

llvm/lib/Analysis/ScalarEvolution.cpp

 
 const SCEV *ScalarEvolution::getUMinExpr(SmallVectorImpl<const SCEV *> &Ops,
                                          bool Sequential) {
   return Sequential ? getSequentialMinMaxExpr(scSequentialUMinExpr, Ops)
                     : getMinMaxExpr(scUMinExpr, Ops);
 }
 
 const SCEV *
-ScalarEvolution::getSizeOfScalableVectorExpr(Type *IntTy,
-                                             ScalableVectorType *ScalableTy) {
+ScalarEvolution::getSizeOfScalableTypeExpr(Type *IntTy, Type *ScalableTy) {
+  assert(ScalableTy->isScalableTy() && "Expected a scalable type");
   Constant *NullPtr = Constant::getNullValue(ScalableTy->getPointerTo());
   Constant *One = ConstantInt::get(IntTy, 1);
   Constant *GEP = ConstantExpr::getGetElementPtr(ScalableTy, NullPtr, One);
   // Note that the expression we created is the final expression, we don't
   // want to simplify it any further Also, if we call a normal getSCEV(),
   // we'll end up in an endless recursion. So just create an SCEVUnknown.
   return getUnknown(ConstantExpr::getPtrToInt(GEP, IntTy));
 }
 
 const SCEV *ScalarEvolution::getSizeOfExpr(Type *IntTy, Type *AllocTy) {
-  if (auto *ScalableAllocTy = dyn_cast<ScalableVectorType>(AllocTy))
-    return getSizeOfScalableVectorExpr(IntTy, ScalableAllocTy);
+  if (AllocTy->isScalableTy())
+    return getSizeOfScalableTypeExpr(IntTy, AllocTy);
+
   // We can bypass creating a target-independent constant expression and then
   // folding it back into a ConstantInt. This is just a compile-time
   // optimization.
   return getConstant(IntTy, getDataLayout().getTypeAllocSize(AllocTy));
 }
 
 const SCEV *ScalarEvolution::getStoreSizeOfExpr(Type *IntTy, Type *StoreTy) {
-  if (auto *ScalableStoreTy = dyn_cast<ScalableVectorType>(StoreTy))
-    return getSizeOfScalableVectorExpr(IntTy, ScalableStoreTy);
+  if (StoreTy->isScalableTy())
+    return getSizeOfScalableTypeExpr(IntTy, StoreTy);
+
   // We can bypass creating a target-independent constant expression and then
   // folding it back into a ConstantInt. This is just a compile-time
   // optimization.
   return getConstant(IntTy, getDataLayout().getTypeStoreSize(StoreTy));
 }
 
 const SCEV *ScalarEvolution::getOffsetOfExpr(Type *IntTy,
                                              StructType *STy,

llvm/test/Analysis/LoopAccessAnalysis/scalable-target-ext.ll

+; RUN: opt  -passes='print<access-info>' -disable-output < %s 2>&1 | FileCheck %s
+
+; Test that loop-access analysis and SCEV analysis work on a loop that has
+; a PHI node with a scalable target type.
+
+; CHECK:      Loop access info in function 'test_scev_analysis':
+; CHECK-NEXT:   loop.body:
+; CHECK-NEXT:     Memory dependences are safe with run-time checks
+; CHECK-NEXT:     Dependences:
+; CHECK-NEXT:     Run-time memory checks:
+; CHECK-NEXT:     Check 0:
+; CHECK-NEXT:       Comparing group ([[G1:[a-z0-9]+]]):
+; CHECK-NEXT:         %iptr.gep = getelementptr i64, ptr %iptr, i64 %ind
+; CHECK-NEXT:       Against group ([[G2:[a-z0-9]+]]):
+; CHECK-NEXT:       ptr %pptr
+; CHECK-NEXT:     Grouped accesses:
+; CHECK-NEXT:       Group [[G1]]:
+; CHECK-NEXT:         (Low: %iptr High: (8 + (8 * %N) + %iptr))
+; CHECK-NEXT:           Member: {%iptr,+,8}<%loop.body>
+; CHECK-NEXT:       Group [[G2]]:
+; CHECK-NEXT:         (Low: %pptr High: (sizeof(target("aarch64.svcount")) + %pptr))
+; CHECK-NEXT:           Member: %pptr
+; CHECK-EMPTY:
+; CHECK-NEXT:     Non vectorizable stores to invariant address were not found in loop.
+; CHECK-NEXT:     SCEV assumptions:
+; CHECK-EMPTY:
+; CHECK-NEXT:     Expressions re-written:
+
+define target("aarch64.svcount") @test_scev_analysis(target("aarch64.svcount") %val0,
+                                                     target("aarch64.svcount") %val1,
+                                                     ptr %iptr, ptr %pptr, i64 %N) nounwind {
+entry:
+  br label %loop.body
+
+loop.body:
+  %ind = phi i64 [0, %entry], [%ind.next, %loop.body]
+  %phi = phi target("aarch64.svcount") [%val0, %entry], [%val1, %loop.body]
+  %iptr.gep = getelementptr i64, ptr %iptr, i64 %ind
+  store i64 %ind, ptr %iptr.gep
+  store target("aarch64.svcount") %phi, ptr %pptr
+  %ind.next = add i64 %ind, 1
+  %i1 = icmp eq i64 %ind, %N
+  br i1 %i1, label %loop.exit, label %loop.body
+
+loop.exit:
+  ret target("aarch64.svcount") %phi
+}