[X86][SSE] Don't vectorize splat buildvector of binops (PR30780)

Don't combine buildvector(binop(),binop(),binop(),binop()) -> binop(buildvector(), buildvector()) if its a splat - keep the binop scalar and just splat the result to avoid large vector constants.

llvm-svn: 321607

1 files changed, 4 insertions, 0 deletions

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 33327ca6b79..19bff03f26a 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -7723,6 +7723,10 @@ static SDValue lowerBuildVectorToBitOp(BuildVectorSDNode *Op,
   case ISD::AND:
   case ISD::XOR:
   case ISD::OR:
+    // Don't do this if the buildvector is a splat - we'd replace one
+    // constant with an entire vector.
+    if (Op->getSplatValue())
+      return SDValue();
     if (!TLI.isOperationLegalOrPromote(Opcode, VT))
       return SDValue();
     break;