[ValueTracking][SVE] Fix getOffsetFromIndex for scalable vector.

Summary:
Return None if GEP index type is scalable vector. Size of scalable vectors
are multiplied by a runtime constant.

Avoid transforming:
  %a = bitcast i8* %p to <vscale x 16 x i8>*
  %tmp0 = getelementptr <vscale x 16 x i8>, <vscale x 16 x i8>* %a, i64 0
  store <vscale x 16 x i8> zeroinitializer, <vscale x 16 x i8>* %tmp0
  %tmp1 = getelementptr <vscale x 16 x i8>, <vscale x 16 x i8>* %a, i64 1
  store <vscale x 16 x i8> zeroinitializer, <vscale x 16 x i8>* %tmp1

into:
  %a = bitcast i8* %p to <vscale x 16 x i8>*
  %tmp0 = getelementptr <vscale x 16 x i8>, <vscale x 16 x i8>* %a, i64 0
  %1 = bitcast <vscale x 16 x i8>* %tmp0 to i8*
  call void @llvm.memset.p0i8.i64(i8* align 16 %1, i8 0, i64 32, i1 false)

Reviewers: sdesmalen, efriedma, apazos, reames

Reviewed By: sdesmalen

Subscribers: tschuett, hiraditya, rkruppe, arphaman, psnobl, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D76464

1 files changed, 6 insertions, 4 deletions

diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 773f79c..3e62c45 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -6211,10 +6211,12 @@ getOffsetFromIndex(const GEPOperator *GEP, unsigned Idx, const DataLayout &DL) {
       continue;
     }
 
-    // Otherwise, we have a sequential type like an array or vector.  Multiply
-    // the index by the ElementSize.
-    uint64_t Size = DL.getTypeAllocSize(GTI.getIndexedType());
-    Offset += Size * OpC->getSExtValue();
+    // Otherwise, we have a sequential type like an array or fixed-length
+    // vector. Multiply the index by the ElementSize.
+    TypeSize Size = DL.getTypeAllocSize(GTI.getIndexedType());
+    if (Size.isScalable())
+      return None;
+    Offset += Size.getFixedSize() * OpC->getSExtValue();
   }
 
   return Offset;