This patch addresses the problem of poor code generation for the zext

v8i8 -> v8i32 on AVX machines. The codegen often scalarizes ANY_EXTEND nodes.
The DAGCombiner has two optimizations that can mitigate the problem. First,
if all of the operands of a BUILD_VECTOR node are extracted from an ZEXT/ANYEXT
nodes, then it is possible to create a new simplified BUILD_VECTOR which uses
UNDEFS/ZERO values to eliminate the scalar ZEXT/ANYEXT nodes.
Second, another dag combine optimization lowers BUILD_VECTOR into a shuffle
vector instruction.

In the case of zext v8i8->v8i32 on AVX, a value in an XMM register is to be
shuffled into a wide YMM register.

This patch modifes the second optimization and allows the creation of
shuffle vectors even when the newly generated vector and the original vector
from which we extract the values are of different types.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@150340 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index d029906fc31ab443cb3a4f1d30bc464e67c61b60..9fa5572e815f7c58bed97c8fd32a5cd749fbe56c 100644 (file)
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -7253,7 +7253,7 @@ SDValue DAGCombiner::visitBUILD_VECTOR(SDNode *N) {
   // same source type and all of the inputs must be any or zero extend.
   // Scalar sizes must be a power of two.
   EVT OutScalarTy = N->getValueType(0).getScalarType();
-  bool validTypes = SourceType != MVT::Other &&
+  bool ValidTypes = SourceType != MVT::Other &&
                  isPowerOf2_32(OutScalarTy.getSizeInBits()) &&
                  isPowerOf2_32(SourceType.getSizeInBits());
 
@@ -7263,7 +7263,8 @@ SDValue DAGCombiner::visitBUILD_VECTOR(SDNode *N) {
   // will be type-legalized to complex code sequences.
   // We perform this optimization only before the operation legalizer because we
   // may introduce illegal operations.
-  if (LegalTypes && !LegalOperations && validTypes) {
+  if ((Level == AfterLegalizeVectorOps || Level == AfterLegalizeTypes) &&
+      ValidTypes) {
     bool isLE = TLI.isLittleEndian();
     unsigned ElemRatio = OutScalarTy.getSizeInBits()/SourceType.getSizeInBits();
     assert(ElemRatio > 1 && "Invalid element size ratio");
@@ -7322,15 +7323,8 @@ SDValue DAGCombiner::visitBUILD_VECTOR(SDNode *N) {
       break;
     }
 
-    // If the input vector type disagrees with the result of the build_vector,
-    // we can't make a shuffle.
+    // We allow up to two distinct input vectors.
     SDValue ExtractedFromVec = N->getOperand(i).getOperand(0);
-    if (ExtractedFromVec.getValueType() != VT) {
-      VecIn1 = VecIn2 = SDValue(0, 0);
-      break;
-    }
-
-    // Otherwise, remember this.  We allow up to two distinct input vectors.
     if (ExtractedFromVec == VecIn1 || ExtractedFromVec == VecIn2)
       continue;
 
@@ -7345,7 +7339,7 @@ SDValue DAGCombiner::visitBUILD_VECTOR(SDNode *N) {
     }
   }
 
-  // If everything is good, we can make a shuffle operation.
+    // If everything is good, we can make a shuffle operation.
   if (VecIn1.getNode()) {
     SmallVector<int, 8> Mask;
     for (unsigned i = 0; i != NumInScalars; ++i) {
@@ -7371,14 +7365,35 @@ SDValue DAGCombiner::visitBUILD_VECTOR(SDNode *N) {
       Mask.push_back(Idx+NumInScalars);
     }
 
-    // Add count and size info.
-    if (!isTypeLegal(VT))
+    // We can't generate a shuffle node with mismatched input and output types.
+    // Attempt to transform a single input vector to the correct type.
+    if ((VT != VecIn1.getValueType())) {
+      // We don't support shuffeling between TWO values of different types.
+      if (VecIn2.getNode() != 0)
+        return SDValue();
+
+      // We only support widening of vectors which are half the size of the
+      // output registers. For example XMM->YMM widening on X86 with AVX.
+      if (VecIn1.getValueType().getSizeInBits()*2 != VT.getSizeInBits())
+        return SDValue();
+
+      // Widen the input vector by adding undef values.
+      VecIn1 = DAG.getNode(ISD::CONCAT_VECTORS, N->getDebugLoc(), VT,
+                           VecIn1, DAG.getUNDEF(VecIn1.getValueType()));
+    }
+
+    // If VecIn2 is unused then change it to undef.
+    VecIn2 = VecIn2.getNode() ? VecIn2 : DAG.getUNDEF(VT);
+
+    // Only type-legal BUILD_VECTOR nodes are converted to shuffle nodes.
+    if (!isTypeLegal(VT) || !isTypeLegal(VecIn1.getValueType()) ||
+        !isTypeLegal(VecIn2.getValueType()))
       return SDValue();
 
     // Return the new VECTOR_SHUFFLE node.
     SDValue Ops[2];
     Ops[0] = VecIn1;
-    Ops[1] = VecIn2.getNode() ? VecIn2 : DAG.getUNDEF(VT);
+    Ops[1] = VecIn2;
     return DAG.getVectorShuffle(VT, N->getDebugLoc(), Ops[0], Ops[1], &Mask[0]);
   }
 

diff --git a/test/CodeGen/CellSPU/rotate_ops.ll b/test/CodeGen/CellSPU/rotate_ops.ll
index 8b7af20b4a98332cfe0d3a11682cd5bfa20a6845..977093527609f8499a1c66ec45bdd29dddbb74b9 100644 (file)
--- a/test/CodeGen/CellSPU/rotate_ops.ll
+++ b/test/CodeGen/CellSPU/rotate_ops.ll
@@ -1,5 +1,5 @@
 ; RUN: llc < %s -march=cellspu -o %t1.s
-; RUN: grep rot          %t1.s | count 85
+; RUN: grep rot          %t1.s | count 86
 ; RUN: grep roth         %t1.s | count 8
 ; RUN: grep roti.*5      %t1.s | count 1
 ; RUN: grep roti.*27     %t1.s | count 1

diff --git a/test/CodeGen/X86/avx-zext.ll b/test/CodeGen/X86/avx-zext.ll
index 795a7b3dd45c2c35ccdf114e115092db8823db93..b630e9d1461258e5f19b6436eb278f2d9e496817 100755 (executable)
--- a/test/CodeGen/X86/avx-zext.ll
+++ b/test/CodeGen/X86/avx-zext.ll
@@ -3,6 +3,7 @@
 define <8 x i32> @zext_8i16_to_8i32(<8 x i16> %A) nounwind uwtable readnone ssp {
 ;CHECK: zext_8i16_to_8i32
 ;CHECK: vpunpckhwd
+;CHECK: ret
 
   %B = zext <8 x i16> %A to <8 x i32>
   ret <8 x i32>%B
@@ -11,7 +12,19 @@ define <8 x i32> @zext_8i16_to_8i32(<8 x i16> %A) nounwind uwtable readnone ssp
 define <4 x i64> @zext_4i32_to_4i64(<4 x i32> %A) nounwind uwtable readnone ssp {
 ;CHECK: zext_4i32_to_4i64
 ;CHECK: vpunpckhdq
+;CHECK: ret
 
   %B = zext <4 x i32> %A to <4 x i64>
   ret <4 x i64>%B
 }
+
+
+define <8 x i32> @zext_8i8_to_8i32(<8 x i8> %z) {
+;CHECK: zext_8i8_to_8i32
+;CHECK: vpunpckhwd
+;CHECK: vpunpcklwd
+;CHECK: vinsertf128
+;CHECK: ret
+  %t = zext <8 x i8> %z to <8 x i32>
+  ret <8 x i32> %t
+}