[SystemZ] Replicate the load with most uses in buildVector()

Iterate over all elements and count the number of uses among them for each
used load. Then make sure to REPLICATE the load which has the most uses in
order to minimize the number of needed element insertions.

Review: Ulrich Weigand
https://reviews.llvm.org/D54322

llvm-svn: 346637

1 files changed, 19 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/SystemZ/vec-move-20.ll b/llvm/test/CodeGen/SystemZ/vec-move-20.ll
new file mode 100644
index 00000000000..ebf1b7db520
--- /dev/null
+++ b/llvm/test/CodeGen/SystemZ/vec-move-20.ll
@@ -0,0 +1,19 @@
+; RUN: llc < %s -mtriple=s390x-linux-gnu -mcpu=z13 | FileCheck %s
+
+; Test a vector which is built with elements from two loads replicates the
+; load with most elements having its value.
+
+; CHECK:      vlef
+; CHECK-NOT:  vlvgf
+
+define void @update(i32* %src1, i32* %src2, <4 x i32>* %dst) {
+bb:
+  %tmp = load i32, i32* %src1
+  %tmp1 = load i32, i32* %src2
+  %tmp2 = insertelement <4 x i32> undef, i32 %tmp, i32 0
+  %tmp3 = insertelement <4 x i32> %tmp2, i32 %tmp1, i32 1
+  %tmp4 = insertelement <4 x i32> %tmp3, i32 %tmp1, i32 2
+  %tmp5 = insertelement <4 x i32> %tmp4, i32 %tmp1, i32 3
+  store <4 x i32> %tmp5, <4 x i32>* %dst
+  ret void
+}