[llvm] r345842 - [DAGCombiner] make sure we have a whole-number extract before trying to narrow a vector op (PR39511)

[Sanjay Patel via llvm-commits]

Author: spatel
Date: Thu Nov  1 08:41:12 2018
New Revision: 345842

URL: http://llvm.org/viewvc/llvm-project?rev=345842&view=rev
Log:
[DAGCombiner] make sure we have a whole-number extract before trying to narrow a vector op (PR39511)

The test causes a crash because we were trying to extract v4f32 to v3f32, and the
narrowing factor was then 4/3 = 1 producing a bogus narrow type.

This should fix:
https://bugs.llvm.org/show_bug.cgi?id=39511

Modified:
    llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
    llvm/trunk/test/CodeGen/X86/vector-narrow-binop.ll

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp?rev=345842&r1=345841&r2=345842&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp Thu Nov  1 08:41:12 2018
@@ -16708,10 +16708,14 @@ static SDValue narrowExtractedVectorBinO
   assert(ExtractIndex % NumElems == 0 &&
          "Extract index is not a multiple of the vector length.");
   EVT SrcVT = Extract->getOperand(0).getValueType();
+
+  // Bail out if this is not a proper multiple width extraction.
   unsigned NumSrcElems = SrcVT.getVectorNumElements();
-  unsigned NarrowingRatio = NumSrcElems / NumElems;
+  if (NumSrcElems % NumElems != 0)
+    return SDValue();
 
   // Bail out if the target does not support a narrower version of the binop.
+  unsigned NarrowingRatio = NumSrcElems / NumElems;
   unsigned BOpcode = BinOp.getOpcode();
   unsigned WideNumElts = WideBVT.getVectorNumElements();
   EVT NarrowBVT = EVT::getVectorVT(*DAG.getContext(), WideBVT.getScalarType(),

Modified: llvm/trunk/test/CodeGen/X86/vector-narrow-binop.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/vector-narrow-binop.ll?rev=345842&r1=345841&r2=345842&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/vector-narrow-binop.ll (original)
+++ llvm/trunk/test/CodeGen/X86/vector-narrow-binop.ll Thu Nov  1 08:41:12 2018
@@ -80,3 +80,21 @@ define <4 x i32> @do_not_use_256bit_op(<
   ret <4 x i32> %sub
 }
 
+; When extracting from a vector binop, the source width should be a multiple of the destination width.
+; https://bugs.llvm.org/show_bug.cgi?id=39511
+
+define <3 x float> @PR39511(<4 x float> %t0, <3 x float>* %b) {
+; SSE-LABEL: PR39511:
+; SSE:       # %bb.0:
+; SSE-NEXT:    addps {{.*}}(%rip), %xmm0
+; SSE-NEXT:    retq
+;
+; AVX-LABEL: PR39511:
+; AVX:       # %bb.0:
+; AVX-NEXT:    vaddps {{.*}}(%rip), %xmm0, %xmm0
+; AVX-NEXT:    retq
+  %add = fadd <4 x float> %t0, <float 1.0, float 2.0, float 3.0, float 4.0>
+  %ext = shufflevector <4 x float> %add, <4 x float> undef, <3 x i32> <i32 0, i32 1, i32 2>
+  ret <3 x float> %ext
+}
+