[Matrix] Use TileInfo to create tiled loop nest for matrix multiply.

This patch uses the TileInfo introduced in D77550 to generate a loop
nest for tiled matrix multiplication, instead of generating the
unrolled code for the whole multiplication. This makes code-generation
more scalable for larger matrixes.

Initially loops are only used if both the number of rows and columns are
divisible by the tile size. Other cases will be added as follow-up.

Reviewers: anemet, Gerolf, hfinkel, andrew.w.kaylor, LuoYuanke, nicolasvasilache

Reviewed By: anemet

Differential Revision: https://reviews.llvm.org/D81308
diff --git a/llvm/test/Transforms/LowerMatrixIntrinsics/multiply-fused.ll b/llvm/test/Transforms/LowerMatrixIntrinsics/multiply-fused.ll
index 3ec7c42..7300a5f 100644
--- a/llvm/test/Transforms/LowerMatrixIntrinsics/multiply-fused.ll
+++ b/llvm/test/Transforms/LowerMatrixIntrinsics/multiply-fused.ll
@@ -1,10 +1,12 @@
-; RUN: opt -lower-matrix-intrinsics -fuse-matrix-tile-size=2 -matrix-allow-contract -force-fuse-matrix -instcombine -verify-dom-info %s -S | FileCheck %s
+; RUN: opt -lower-matrix-intrinsics -fuse-matrix-use-loops=false -fuse-matrix-tile-size=2 -matrix-allow-contract -force-fuse-matrix -instcombine -verify-dom-info %s -S | FileCheck %s
 
 ; REQUIRES: aarch64-registered-target
 
 target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "aarch64-apple-ios"
 
+; Test tiling without generating explicit loops.
+
 define void @multiply(<16 x double> * %A, <16 x double> * %B, <16 x double>* %C) {
 ; CHECK-LABEL: @multiply(
 ; CHECK-NEXT:  entry: