[SystemZ] Don't assert for i128 vectors in getInterleavedMemoryOpCost() (#78009)

This assert does not seem justified given that the LoopVectorizer can
form interleave groups containing i128 elements where the number of
elements per vector is indeed just one.

Author: JonPsson1

llvm/lib/Target/SystemZ/SystemZTargetTransformInfo.cpp

@@ -1236,7 +1236,6 @@ InstructionCost SystemZTTIImpl::getInterleavedMemoryOpCost(
     // dst vector for vperm (S.A.).
     unsigned NumSrcVecs = std::min(NumEltsPerVecReg, Factor);
     unsigned NumDstVecs = NumVectorMemOps;
-    assert (NumSrcVecs > 1 && "Expected at least two source vectors.");
     NumPermutes += (NumDstVecs * NumSrcVecs) - NumDstVecs;
   }
 

llvm/test/Transforms/LoopVectorize/SystemZ/mem-interleaving-costs-03.ll

@@ -0,0 +1,42 @@
+; REQUIRES: asserts
+; RUN: opt -mtriple=s390x-unknown-linux -mcpu=z16 -passes=loop-vectorize \
+; RUN:   -debug-only=loop-vectorize -force-vector-width=4 \
+; RUN:   -disable-output < %s 2>&1 | FileCheck %s
+;
+; Check cost function for <8 x i128> store interleave group.
+
+; CHECK: LV: Checking a loop in 'fun'
+; CHECK: LV: Found an estimated cost of 8 for VF 4 For instruction:   store i128 8721036757475490113
+
+define noundef i32 @fun(i32 %argc, ptr nocapture readnone %argv) {
+entry:
+  %l_4774.i = alloca [4 x [2 x i128]], align 8
+  call void @llvm.lifetime.start.p0(i64 128, ptr nonnull %l_4774.i)
+  br label %for.cond4.preheader.i
+
+for.cond4.preheader.i:                            ; preds = %for.cond4.preheader.i, %entry
+  %indvars.iv8.i = phi i64 [ 0, %entry ], [ %indvars.iv.next9.i, %for.cond4.preheader.i ]
+  %arrayidx10.i = getelementptr inbounds [4 x [2 x i128]], ptr %l_4774.i, i64 0, i64 %indvars.iv8.i, i64 0
+  store i128 8721036757475490113, ptr %arrayidx10.i, align 8
+  %arrayidx10.i.c = getelementptr inbounds [4 x [2 x i128]], ptr %l_4774.i, i64 0, i64 %indvars.iv8.i, i64 1
+  store i128 8721036757475490113, ptr %arrayidx10.i.c, align 8
+  %indvars.iv.next9.i = add nuw nsw i64 %indvars.iv8.i, 1
+  %exitcond.not.i = icmp eq i64 %indvars.iv.next9.i, 4
+  br i1 %exitcond.not.i, label %func_1.exit, label %for.cond4.preheader.i
+
+func_1.exit:                                      ; preds = %for.cond4.preheader.i
+  %arrayidx195.i = getelementptr inbounds [4 x [2 x i128]], ptr %l_4774.i, i64 0, i64 1
+  %0 = load i128, ptr %arrayidx195.i, align 8
+  %cmp200.i = icmp ne i128 %0, 0
+  %conv202.i = zext i1 %cmp200.i to i64
+  %call203.i = tail call i64 @safe_sub_func_int64_t_s_s(i64 noundef %conv202.i, i64 noundef 9139899272418802852)
+  call void @llvm.lifetime.end.p0(i64 128, ptr nonnull %l_4774.i)
+  br label %for.cond
+
+for.cond:                                         ; preds = %for.cond, %func_1.exit
+  br label %for.cond
+}
+
+declare void @llvm.lifetime.start.p0(i64, ptr nocapture)
+declare void @llvm.lifetime.end.p0(i64, ptr nocapture)
+declare dso_local i64 @safe_sub_func_int64_t_s_s(i64, i64)