On Sandybridge loading unaligned 256bits using two XMM loads (vmovups and vinsertf128) is faster than using a single vmovups instruction.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@172868 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 53 insertions, 2 deletions

diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 2b6ff36..73a1d2e 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -16340,8 +16340,39 @@ static SDValue PerformLOADCombine(SDNode *N, SelectionDAG &DAG,
   EVT MemVT = Ld->getMemoryVT();
   DebugLoc dl = Ld->getDebugLoc();
   const TargetLowering &TLI = DAG.getTargetLoweringInfo();
+  unsigned RegSz = RegVT.getSizeInBits();
 
   ISD::LoadExtType Ext = Ld->getExtensionType();
+  unsigned Alignment = Ld->getAlignment();
+
+  // On Sandybridge unaligned 256bit loads are inefficient.
+  if (RegVT.is256BitVector() && !Subtarget->hasInt256() &&
+      !DCI.isBeforeLegalizeOps() && Alignment < 32 &&
+      Ext == ISD::NON_EXTLOAD) {
+    unsigned NumElems = RegVT.getVectorNumElements();
+    SDValue Ptr = Ld->getBasePtr();
+    SDValue Increment = DAG.getConstant(16, TLI.getPointerTy());
+
+    EVT HalfVT = EVT::getVectorVT(*DAG.getContext(), MemVT.getScalarType(),
+                                  NumElems/2);
+    SDValue Load1 = DAG.getLoad(HalfVT, dl, Ld->getChain(), Ptr,
+                                Ld->getPointerInfo(), Ld->isVolatile(),
+                                Ld->isNonTemporal(), Ld->isInvariant(),
+                                Alignment);
+    Ptr = DAG.getNode(ISD::ADD, dl, Ptr.getValueType(), Ptr, Increment);
+    SDValue Load2 = DAG.getLoad(HalfVT, dl, Ld->getChain(), Ptr,
+                                Ld->getPointerInfo(), Ld->isVolatile(),
+                                Ld->isNonTemporal(), Ld->isInvariant(),
+                                Alignment);
+    SDValue TF = DAG.getNode(ISD::TokenFactor, dl, MVT::Other,
+                             Load1.getValue(1),
+                             Load2.getValue(1));
+
+    SDValue NewVec = DAG.getUNDEF(RegVT);
+    NewVec = Insert128BitVector(NewVec, Load1, 0, DAG, dl);
+    NewVec = Insert128BitVector(NewVec, Load2, NumElems/2, DAG, dl);
+    return DCI.CombineTo(N, NewVec, TF, true);
+  }
 
   // If this is a vector EXT Load then attempt to optimize it using a
   // shuffle. If SSSE3 is not available we may emit an illegal shuffle but the
@@ -16356,7 +16387,6 @@ static SDValue PerformLOADCombine(SDNode *N, SelectionDAG &DAG,
     assert(MemVT.isVector() && "Must load a vector from memory");
 
     unsigned NumElems = RegVT.getVectorNumElements();
-    unsigned RegSz = RegVT.getSizeInBits();
     unsigned MemSz = MemVT.getSizeInBits();
     assert(RegSz > MemSz && "Register size must be greater than the mem size");
 
diff --git a/test/CodeGen/X86/sandybridge-loads.ll b/test/CodeGen/X86/sandybridge-loads.ll
new file mode 100644
index 0000000..d85c32e
--- /dev/null
+++ b/test/CodeGen/X86/sandybridge-loads.ll
@@ -0,0 +1,21 @@
+; RUN: llc -march=x86-64 -mtriple=x86_64-apple-darwin -mcpu=corei7-avx -o - < %s | FileCheck %s
+
+;CHECK: wideloads
+;CHECK: vmovaps
+;CHECK: vinsertf128
+;CHECK: vmovups
+;CHECK-NOT: vinsertf128
+;CHECK: ret
+
+define void @wideloads(<8 x float>* %a, <8 x float>* %b, <8 x float>* %c) nounwind uwtable noinline ssp {
+  %v0 = load <8 x float>* %a, align 16  ; <---- unaligned!
+  %v1 = load <8 x float>* %b, align 32  ; <---- aligned!
+  %m0 = fcmp olt <8 x float> %v1, %v0
+  %v2 = load <8 x float>* %c, align 16
+  %m1 = fcmp olt <8 x float> %v2, %v0
+  %mand = and <8 x i1> %m1, %m0
+  %r = zext <8 x i1> %mand to <8 x i32>
+  store <8 x i32> %r, <8 x i32>* undef, align 16
+  ret void
+}
+
diff --git a/test/CodeGen/X86/v8i1-masks.ll b/test/CodeGen/X86/v8i1-masks.ll
index abb4b39..ea231af 100644
--- a/test/CodeGen/X86/v8i1-masks.ll
+++ b/test/CodeGen/X86/v8i1-masks.ll
@@ -1,7 +1,7 @@
 ; RUN: llc -march=x86-64 -mtriple=x86_64-apple-darwin -mcpu=corei7-avx -o - < %s | FileCheck %s
 
 ;CHECK: and_masks
-;CHECK: vmovups
+;CHECK: vmovaps
 ;CHECK: vcmpltp
 ;CHECK: vcmpltp
 ;CHECK: vandps