From 97136c922ec4b492584cb91c1fc1cdcb40983ecf Mon Sep 17 00:00:00 2001
From: Bruno Cardoso Lopes <bruno.cardoso@gmail.com>
Date: Mon, 19 Sep 2011 23:36:50 +0000
Subject: [PATCH] Based on the small opt Zvi's patch was trying to achieve,
 eliminate 128-bit undef subvector insertion into a 256-bit vector

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@140097 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/X86/X86InstrSSE.td       | 15 +++++++++++++++
 test/CodeGen/X86/avx-vinsertf128.ll |  8 ++++++++
 2 files changed, 23 insertions(+)

diff --git a/lib/Target/X86/X86InstrSSE.td b/lib/Target/X86/X86InstrSSE.td
index bd43d0bcad3..fdf119e4767 100644
--- a/lib/Target/X86/X86InstrSSE.td
+++ b/lib/Target/X86/X86InstrSSE.td
@@ -157,6 +157,21 @@ def : Pat<(insert_subvector undef, (v8i16 VR128:$src), (i32 0)),
 def : Pat<(insert_subvector undef, (v16i8 VR128:$src), (i32 0)),
           (INSERT_SUBREG (v32i8 (IMPLICIT_DEF)), VR128:$src, sub_xmm)>;
 
+// Inserting a 128-bit undef vector into the high part of a 256-bit
+// vector should return the 256-bit vector itself.
+def : Pat<(insert_subvector (v8i32 VR256:$src), undef, (i32 4)),
+          (v8i32 VR256:$src)>;
+def : Pat<(insert_subvector (v8f32 VR256:$src), undef, (i32 4)),
+          (v8f32 VR256:$src)>;
+def : Pat<(insert_subvector (v4i64 VR256:$src), undef, (i32 4)),
+          (v4i64 VR256:$src)>;
+def : Pat<(insert_subvector (v4f64 VR256:$src), undef, (i32 4)),
+          (v4f64 VR256:$src)>;
+def : Pat<(insert_subvector (v16i16 VR256:$src), undef, (i32 4)),
+          (v16i16 VR256:$src)>;
+def : Pat<(insert_subvector (v32i8 VR256:$src), undef, (i32 4)),
+          (v32i8 VR256:$src)>;
+
 // Implicitly promote a 32-bit scalar to a vector.
 def : Pat<(v4f32 (scalar_to_vector FR32:$src)),
           (INSERT_SUBREG (v4f32 (IMPLICIT_DEF)), FR32:$src, sub_ss)>;
diff --git a/test/CodeGen/X86/avx-vinsertf128.ll b/test/CodeGen/X86/avx-vinsertf128.ll
index a6f258513a5..8813a7f6ab8 100644
--- a/test/CodeGen/X86/avx-vinsertf128.ll
+++ b/test/CodeGen/X86/avx-vinsertf128.ll
@@ -36,3 +36,11 @@ allocas:
   store <4 x i32> %blendAsInt.i503, <4 x i32>* undef, align 4
   ret void
 }
+
+; CHECK: _C
+; CHECK-NOT: vinsertf128 $1
+define <4 x i32> @C(<4 x i32> %v1) nounwind readonly {
+  %1 = shufflevector <4 x i32> %v1, <4 x i32> undef, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
+  %2 = shufflevector <8 x i32> %1, <8 x i32> undef, <4 x i32> <i32 0, i32 1, i32 2, i32 3>
+  ret <4 x i32> %2
+}