[PowerPC] Enable splat generation for BUILD_VECTOR with little endian

When enabling PPC64LE, I disabled some optimizations of BUILD_VECTOR
nodes for little endian because wrong results were produced.  I've
subsequently investigated and found this is due to a call to
BuildVectorSDNode::isConstantSplat that was always specifying
big-endian.  With this changed to correctly identify the target
endianness, the optimizations work as expected.

I found another case of a call to the same method with big-endian
hardcoded, in PPC::isAllNegativeZeroVector().  I discovered this was
an orphaned method with no callers, so I've just removed it.

The existing test/CodeGen/PowerPC/vec_constants.ll checks these
optimizations, so for testing I've just added a variant for little
endian.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@234011 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/PowerPC/PPCISelLowering.cpp

@@ -1287,22 +1287,6 @@ bool PPC::isSplatShuffleMask(ShuffleVectorSDNode *N, unsigned EltSize) {
   return true;
 }
 
-/// isAllNegativeZeroVector - Returns true if all elements of build_vector
-/// are -0.0.
-bool PPC::isAllNegativeZeroVector(SDNode *N) {
-  BuildVectorSDNode *BV = cast<BuildVectorSDNode>(N);
-
-  APInt APVal, APUndef;
-  unsigned BitSize;
-  bool HasAnyUndefs;
-
-  if (BV->isConstantSplat(APVal, APUndef, BitSize, HasAnyUndefs, 32, true))
-    if (ConstantFPSDNode *CFP = dyn_cast<ConstantFPSDNode>(N->getOperand(0)))
-      return CFP->getValueAPF().isNegZero();
-
-  return false;
-}
-
 /// getVSPLTImmediate - Return the appropriate VSPLT* immediate to splat the
 /// specified isSplatShuffleMask VECTOR_SHUFFLE mask.
 unsigned PPC::getVSPLTImmediate(SDNode *N, unsigned EltSize,
@@ -6609,7 +6593,8 @@ SDValue PPCTargetLowering::LowerBUILD_VECTOR(SDValue Op,
   unsigned SplatBitSize;
   bool HasAnyUndefs;
   if (! BVN->isConstantSplat(APSplatBits, APSplatUndef, SplatBitSize,
-                             HasAnyUndefs, 0, true) || SplatBitSize > 32)
+                             HasAnyUndefs, 0, !Subtarget.isLittleEndian()) ||
+      SplatBitSize > 32)
     return SDValue();
 
   unsigned SplatBits = APSplatBits.getZExtValue();
@@ -6676,22 +6661,6 @@ SDValue PPCTargetLowering::LowerBUILD_VECTOR(SDValue Op,
     return DAG.getNode(ISD::BITCAST, dl, Op.getValueType(), Res);
   }
 
-  // The remaining cases assume either big endian element order or
-  // a splat-size that equates to the element size of the vector
-  // to be built.  An example that doesn't work for little endian is
-  // {0, -1, 0, -1, 0, -1, 0, -1} which has a splat size of 32 bits
-  // and a vector element size of 16 bits.  The code below will
-  // produce the vector in big endian element order, which for little
-  // endian is {-1, 0, -1, 0, -1, 0, -1, 0}.
-
-  // For now, just avoid these optimizations in that case.
-  // FIXME: Develop correct optimizations for LE with mismatched
-  // splat and element sizes.
-
-  if (Subtarget.isLittleEndian() &&
-      SplatSize != Op.getValueType().getVectorElementType().getSizeInBits())
-    return SDValue();
-
   // Check to see if this is a wide variety of vsplti*, binop self cases.
   static const signed char SplatCsts[] = {
     -1, 1, -2, 2, -3, 3, -4, 4, -5, 5, -6, 6, -7, 7,

lib/Target/PowerPC/PPCISelLowering.h

@@ -368,10 +368,6 @@ namespace llvm {
     /// VSPLTB/VSPLTH/VSPLTW.
     bool isSplatShuffleMask(ShuffleVectorSDNode *N, unsigned EltSize);
 
-    /// isAllNegativeZeroVector - Returns true if all elements of build_vector
-    /// are -0.0.
-    bool isAllNegativeZeroVector(SDNode *N);
-
     /// getVSPLTImmediate - Return the appropriate VSPLT* immediate to splat the
     /// specified isSplatShuffleMask VECTOR_SHUFFLE mask.
     unsigned getVSPLTImmediate(SDNode *N, unsigned EltSize, SelectionDAG &DAG);

test/CodeGen/PowerPC/vec_constants.ll

@@ -1,7 +1,5 @@
-; RUN: llc -O0 -mcpu=pwr7 < %s | FileCheck %s
+; RUN: llc -O0 -mcpu=pwr7 -mtriple=powerpc64-unknown-linux-gnu < %s | FileCheck %s
-
+; RUN: llc -O0 -mcpu=pwr7 -mtriple=powerpc64le-unknown-linux-gnu < %s | FileCheck %s
-target datalayout = "E-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-f128:128:128-v128:128:128-n32:64"
-target triple = "powerpc64-unknown-linux-gnu"
 
 define void @test1(<4 x i32>* %P1, <4 x i32>* %P2, <4 x float>* %P3) nounwind {
 	%tmp = load <4 x i32>, <4 x i32>* %P1		; <<4 x i32>> [#uses=1]