[DAGCombiner] Fix a wrong check in method SimplifyVBinOp.

This fixes a regression intruced by r199135.

Revision 199135 tried to simplify part of the logic in method
DAGCombiner::SimplifyVBinOp introducing calls to method BuildVectorSDNode::isConstant().

However, that revision wrongly changed the check performed by method
SimplifyVBinOp to identify dag nodes that can be folded.
Before revision 199135, that method only tried to simplify vector binary operations
if both operands were build_vector of Constant/ConstantFP/Undef only.

After revision 199135, method SimplifyVBinop tried to
simplify also vector binary operations with only one constant operand.

This fixes the problem restoring the old behavior of SimplifyVBinOp.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199328 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index b0e14266bc44bef1e8b9ed7200e5d7af7167979f..0530dbc12b244ed8e499d3e683dcaef0cbb6ee98 100644 (file)
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -10391,8 +10391,8 @@ SDValue DAGCombiner::SimplifyVBinOp(SDNode *N) {
   if (LHS.getOpcode() == ISD::BUILD_VECTOR &&
       RHS.getOpcode() == ISD::BUILD_VECTOR) {
     // Check if both vectors are constants. If not bail out.
-    if (!cast<BuildVectorSDNode>(LHS)->isConstant() &&
-        !cast<BuildVectorSDNode>(RHS)->isConstant())
+    if (!(cast<BuildVectorSDNode>(LHS)->isConstant() &&
+          cast<BuildVectorSDNode>(RHS)->isConstant()))
       return SDValue();
 
     SmallVector<SDValue, 8> Ops;

diff --git a/test/CodeGen/X86/vbinop-simplify-bug.ll b/test/CodeGen/X86/vbinop-simplify-bug.ll
new file mode 100644 (file)
index 0000000..81299ed
--- /dev/null
+++ b/test/CodeGen/X86/vbinop-simplify-bug.ll
@@ -0,0 +1,23 @@
+; RUN: llc %s -mtriple=x86_64-unknown-linux-gnu -mattr=sse2 -mcpu=corei7
+
+; Revision 199135 introduced a wrong check in method
+; DAGCombiner::SimplifyVBinOp in an attempt to refactor some code
+; using the new method 'BuildVectorSDNode::isConstant' when possible.
+; 
+; However the modified code in method SimplifyVBinOp now wrongly
+; checks that the operands of a vector bin-op are both constants.
+;
+; With that wrong change, this test started failing because of a
+; 'fatal error in the backend':
+;   Cannot select: 0x2e329d0: v4i32 = BUILD_VECTOR 0x2e2ea00, 0x2e2ea00, 0x2e2ea00, 0x2e2ea00
+;       0x2e2ea00: i32 = Constant<1> [ID=4]
+;       0x2e2ea00: i32 = Constant<1> [ID=4]
+;       0x2e2ea00: i32 = Constant<1> [ID=4]
+;       0x2e2ea00: i32 = Constant<1> [ID=4]
+
+define <8 x i32> @reduced_test_case() {
+  %Shuff = shufflevector <8 x i32> zeroinitializer, <8 x i32> zeroinitializer, <8 x i32> <i32 1, i32 3, i32 undef, i32 7, i32 9, i32 11, i32 13, i32 15>
+  %B23 = sub <8 x i32> %Shuff, <i32 -1, i32 -1, i32 -1, i32 -1, i32 -1, i32 -1, i32 -1, i32 -1>
+  ret <8 x i32> %B23
+}
+