From 537a9f7685a8cd9d58fd7e448d89e513c1a45fb9 Mon Sep 17 00:00:00 2001
From: Lang Hames <lhames@gmail.com>
Date: Wed, 2 Nov 2011 22:52:45 +0000
Subject: [PATCH] Try to lower memset/memcpy/memmove to vector instructions on
 ARM where the alignment permits.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@143582 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/ARM/ARMISelLowering.cpp              | 28 +++++++++++++++++++++++++
 lib/Target/ARM/ARMISelLowering.h                |  7 ++++++-
 test/CodeGen/ARM/2011-10-26-memset-with-neon.ll | 20 ++++++++++++++++++
 3 files changed, 54 insertions(+), 1 deletion(-)
 create mode 100644 test/CodeGen/ARM/2011-10-26-memset-with-neon.ll

diff --git a/lib/Target/ARM/ARMISelLowering.cpp b/lib/Target/ARM/ARMISelLowering.cpp
index 31e522d4d70..222a399c28c 100644
--- a/lib/Target/ARM/ARMISelLowering.cpp
+++ b/lib/Target/ARM/ARMISelLowering.cpp
@@ -8127,6 +8127,34 @@ bool ARMTargetLowering::allowsUnalignedMemoryAccesses(EVT VT) const {
   }
 }
 
+static bool memOpAlign(unsigned DstAlign, unsigned SrcAlign,
+                       unsigned AlignCheck) {
+  return ((SrcAlign == 0 || SrcAlign % AlignCheck == 0) &&
+          (DstAlign == 0 || DstAlign % AlignCheck == 0));
+}
+
+EVT ARMTargetLowering::getOptimalMemOpType(uint64_t Size,
+                                           unsigned DstAlign, unsigned SrcAlign,
+                                           bool NonScalarIntSafe,
+                                           bool MemcpyStrSrc,
+                                           MachineFunction &MF) const {
+  const Function *F = MF.getFunction();
+
+  // See if we can use NEON instructions for this...
+  if (NonScalarIntSafe &&
+      !F->hasFnAttr(Attribute::NoImplicitFloat) &&
+      Subtarget->hasNEON()) {
+    if (memOpAlign(SrcAlign, DstAlign, 16) && Size >= 16) {
+      return MVT::v4i32;
+    } else if (memOpAlign(SrcAlign, DstAlign, 8) && Size >= 8) {
+      return MVT::v2i32;
+    }
+  }
+
+  // Let the target-independent logic figure it out.
+  return MVT::Other;
+}
+
 static bool isLegalT1AddressImmediate(int64_t V, EVT VT) {
   if (V < 0)
     return false;
diff --git a/lib/Target/ARM/ARMISelLowering.h b/lib/Target/ARM/ARMISelLowering.h
index 5da9b27fca6..43e43dd35bf 100644
--- a/lib/Target/ARM/ARMISelLowering.h
+++ b/lib/Target/ARM/ARMISelLowering.h
@@ -266,9 +266,14 @@ namespace llvm {
 
     /// allowsUnalignedMemoryAccesses - Returns true if the target allows
     /// unaligned memory accesses. of the specified type.
-    /// FIXME: Add getOptimalMemOpType to implement memcpy with NEON?
     virtual bool allowsUnalignedMemoryAccesses(EVT VT) const;
 
+    virtual EVT getOptimalMemOpType(uint64_t Size,
+                                    unsigned DstAlign, unsigned SrcAlign,
+                                    bool NonScalarIntSafe,
+                                    bool MemcpyStrSrc,
+                                    MachineFunction &MF) const;
+
     /// isLegalAddressingMode - Return true if the addressing mode represented
     /// by AM is legal for this target, for a load/store of the specified type.
     virtual bool isLegalAddressingMode(const AddrMode &AM, Type *Ty)const;
diff --git a/test/CodeGen/ARM/2011-10-26-memset-with-neon.ll b/test/CodeGen/ARM/2011-10-26-memset-with-neon.ll
new file mode 100644
index 00000000000..3c9216cde7b
--- /dev/null
+++ b/test/CodeGen/ARM/2011-10-26-memset-with-neon.ll
@@ -0,0 +1,20 @@
+; RUN: llc -march=arm -mcpu=cortex-a8 < %s | FileCheck %s
+
+; Should trigger a NEON store.
+; CHECK: vstr.64
+define void @f_0_12(i8* nocapture %c) nounwind optsize {
+entry:
+  call void @llvm.memset.p0i8.i64(i8* %c, i8 0, i64 12, i32 8, i1 false)
+  ret void
+}
+
+; Trigger multiple NEON stores.
+; CHECK:      vstmia
+; CHECK-NEXT: vstmia
+define void @f_0_40(i8* nocapture %c) nounwind optsize {
+entry:
+  call void @llvm.memset.p0i8.i64(i8* %c, i8 0, i64 40, i32 16, i1 false)
+  ret void
+}
+
+declare void @llvm.memset.p0i8.i64(i8* nocapture, i8, i64, i32, i1) nounwind
-- 
2.11.0