[SLP]Fix PR78298: Assertion `GEP->getNumIndices() == 1 &&

!isa<Constant>(GEPIdx)' failed.

The non-constant index might be folded to constant during earlier stages
of vectorization. Need to consider this option and filter out out GEP
with the constant indices from the candidates list.

Author: alexey-bataev

llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp

@@ -16241,10 +16241,13 @@ bool SLPVectorizerPass::vectorizeGEPIndices(BasicBlock *BB, BoUpSLP &R) {
       SetVector<Value *> Candidates(GEPList.begin(), GEPList.end());
 
       // Some of the candidates may have already been vectorized after we
-      // initially collected them. If so, they are marked as deleted, so remove
-      // them from the set of candidates.
-      Candidates.remove_if(
-          [&R](Value *I) { return R.isDeleted(cast<Instruction>(I)); });
+      // initially collected them or their index is optimized to constant value.
+      // If so, they are marked as deleted, so remove them from the set of
+      // candidates.
+      Candidates.remove_if([&R](Value *I) {
+        return R.isDeleted(cast<Instruction>(I)) ||
+               isa<Constant>(cast<GetElementPtrInst>(I)->idx_begin()->get());
+      });
 
       // Remove from the set of candidates all pairs of getelementptrs with
       // constant differences. Such getelementptrs are likely not good

llvm/test/Transforms/SLPVectorizer/X86/gep-nonconst-idx-transformed-to-const.ll

@@ -0,0 +1,19 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 4
+; RUN: opt -passes=slp-vectorizer -mtriple=x86_64-unknown-linux-gnu -S < %s | FileCheck %s
+
+define void @foo(i64 %0) {
+; CHECK-LABEL: define void @foo(
+; CHECK-SAME: i64 [[TMP0:%.*]]) {
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[TMP1:%.*]] = insertelement <8 x i64> zeroinitializer, i64 0, i64 0
+; CHECK-NEXT:    [[TMP2:%.*]] = getelementptr i32, ptr addrspace(1) null, i64 0
+; CHECK-NEXT:    [[TMP3:%.*]] = getelementptr i32, ptr addrspace(1) null, i64 [[TMP0]]
+; CHECK-NEXT:    ret void
+;
+entry:
+  %1 = or i64 0, 0
+  %2 = insertelement <8 x i64> zeroinitializer, i64 %1, i64 0
+  %3 = getelementptr i32, ptr addrspace(1) null, i64 %1
+  %4 = getelementptr i32, ptr addrspace(1) null, i64 %0
+  ret void
+}