[SeparateConstOffsetFromGEP] Remove TypeSize error when collecting constant indices.

[arsenm]

llvm/lib/Transforms/Scalar/SeparateConstOffsetFromGEP.cpp

1014

Is there not a way to directly check isScalable on the type without going through getTypeAllocSize?

[arsenm]

llvm/lib/Transforms/Scalar/SeparateConstOffsetFromGEP.cpp

1014

Looks like we're missing isScalableVectorTy, it should be there

[paulwalker-arm]

Updated to check for scalable vector types rather that scalable sizes.

[paulwalker-arm]

llvm/lib/Transforms/Scalar/SeparateConstOffsetFromGEP.cpp

1014

I guess I was trying to be future proof. However, currently scalable vectors cannot be in arrays and struct support is purely in register and thus cannot be indexed via getelementptr.

If this changes then the same TypeSize error will be triggered as was the case for the scenario this patch fixes.

[arsenm]

llvm/lib/Transforms/Scalar/SeparateConstOffsetFromGEP.cpp

1014

I don't see how that could change. Even then there should be a predicate for that. I'd prefer to stick to a direct type check

llvm/lib/Transforms/Scalar/SeparateConstOffsetFromGEP.cpp

 int64_t
 SeparateConstOffsetFromGEP::accumulateByteOffset(GetElementPtrInst *GEP,
                                                  bool &NeedsExtraction) {
   NeedsExtraction = false;
   int64_t AccumulativeByteOffset = 0;
   gep_type_iterator GTI = gep_type_begin(*GEP);
   for (unsigned I = 1, E = GEP->getNumOperands(); I != E; ++I, ++GTI) {
     if (GTI.isSequential()) {
+      // Constant offsets of scalable types are not really constant.
+      if (isa<ScalableVectorType>(GTI.getIndexedType()))
+        continue;
+
       // Tries to extract a constant offset from this GEP index.
       int64_t ConstantOffset =
           ConstantOffsetExtractor::Find(GEP->getOperand(I), GEP, DT);
       if (ConstantOffset != 0) {
         NeedsExtraction = true;
         // A GEP may have multiple indices.  We accumulate the extracted
         // constant offset to a byte offset, and later offset the remainder of
         // the original GEP with this byte offset.
bool SeparateConstOffsetFromGEP::splitGEP(GetElementPtrInst *GEP) {
   // Notice that we don't remove struct field indices here. If LowerGEP is
   // disabled, a structure index is not accumulated and we still use the old
   // one. If LowerGEP is enabled, a structure index is accumulated in the
   // constant offset. LowerToSingleIndexGEPs or lowerToArithmetics will later
   // handle the constant offset and won't need a new structure index.
   gep_type_iterator GTI = gep_type_begin(*GEP);
   for (unsigned I = 1, E = GEP->getNumOperands(); I != E; ++I, ++GTI) {
     if (GTI.isSequential()) {
+      // Constant offsets of scalable types are not really constant.
+      if (isa<ScalableVectorType>(GTI.getIndexedType()))
+        continue;
+
       // Splits this GEP index into a variadic part and a constant offset, and
       // uses the variadic part as the new index.
       Value *OldIdx = GEP->getOperand(I);
       User *UserChainTail;
       Value *NewIdx =
           ConstantOffsetExtractor::Extract(OldIdx, GEP, UserChainTail, DT);
       if (NewIdx != nullptr) {
         // Switches to the index with the constant offset removed.

llvm/test/Transforms/SeparateConstOffsetFromGEP/AArch64/scalable-vector-geps.ll

+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -S -passes=separate-const-offset-from-gep < %s | FileCheck %s
+
+target triple = "aarch64-linux-gnu"
+
+; Index is implicitly multiplied by vscale and so not really constant.
+define ptr @test1(ptr %base, i64 %idx) #0 {
+; CHECK-LABEL: @test1(
+; CHECK-NEXT:    [[IDX_NEXT:%.*]] = add nuw nsw i64 [[IDX:%.*]], 1
+; CHECK-NEXT:    [[GEP:%.*]] = getelementptr <vscale x 4 x float>, ptr [[BASE:%.*]], i64 [[IDX_NEXT]]
+; CHECK-NEXT:    ret ptr [[GEP]]
+;
+  %idx.next = add nuw nsw i64 %idx, 1
+  %gep = getelementptr <vscale x 4 x float>, ptr %base, i64 %idx.next
+  ret ptr %gep
+}
+
+; Whilst the first index is not constant, the calculation of the second index
+; does contain a constant that can be extracted.
+define ptr @test2(ptr %base, i64 %idx) {
+; CHECK-LABEL: @test2(
+; CHECK-NEXT:    [[TMP1:%.*]] = getelementptr <vscale x 4 x float>, ptr [[BASE:%.*]], i64 3, i64 [[IDX:%.*]]
+; CHECK-NEXT:    [[GEP2:%.*]] = getelementptr float, ptr [[TMP1]], i64 1
+; CHECK-NEXT:    ret ptr [[GEP2]]
+;
+  %idx.next = add nuw nsw i64 %idx, 1
+  %gep = getelementptr <vscale x 4 x float>, ptr %base, i64 3, i64 %idx.next
+  ret ptr %gep
+}
+
+attributes #0 = { "target-features"="+sve" }