SelectionDAG: Don't constant fold target-specific nodes.

FoldConstantArithmetic() only knows how to deal with a few target independent
ISD opcodes. Bail early if it sees a target-specific ISD node. These node do
funny things with operand types which may break the assumptions of the code
that follows, and there's no actual folding that can be done anyway. For example,
non-constant 256 bit vector shifts on X86 have a shift-amount operand that's a
128-bit v4i32 vector regardless of what the first operand type is and that breaks
the assumption that the operand types must match.

rdar://16530923

llvm-svn: 205937

llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp

@@ -2811,6 +2811,12 @@ SDValue SelectionDAG::getNode(unsigned Opcode, SDLoc DL,
 
 SDValue SelectionDAG::FoldConstantArithmetic(unsigned Opcode, EVT VT,
                                              SDNode *Cst1, SDNode *Cst2) {
+  // If the opcode is a target-specific ISD node, there's nothing we can
+  // do here and the operand rules may not line up with the below, so
+  // bail early.
+  if (Opcode >= ISD::BUILTIN_OP_END)
+    return SDValue();
+
   SmallVector<std::pair<ConstantSDNode *, ConstantSDNode *>, 4> Inputs;
   SmallVector<SDValue, 4> Outputs;
   EVT SVT = VT.getScalarType();

llvm/test/CodeGen/X86/avx2-vector-shifts.ll

@@ -52,6 +52,16 @@ entry:
 ; CHECK: vpaddd  %ymm0, %ymm0, %ymm0
 ; CHECK: ret
 
+define <8 x i32> @test_vpslld_var(i32 %shift) {
+  %amt = insertelement <8 x i32> undef, i32 %shift, i32 0
+  %tmp = shl <8 x i32> <i32 192, i32 193, i32 194, i32 195, i32 196, i32 197, i32 198, i32 199>, %amt
+  ret <8 x i32> %tmp
+}
+
+; CHECK-LABEL: test_vpslld_var:
+; CHECK: vpslld %xmm0, %ymm1, %ymm0
+; CHECK: ret
+
 define <8 x i32> @test_slld_3(<8 x i32> %InVec) {
 entry:
   %shl = shl <8 x i32> %InVec, <i32 31, i32 31, i32 31, i32 31, i32 31, i32 31, i32 31, i32 31>