[DAGCombiner] Use the result value type in visitCONCAT_VECTORS

[thegameg]

Summary

This triggers an assert when combining concat_vectors of a bitcast of merge_values.

Assertion failed: (VT.isVector() && !Operand.getValueType().isVector() && (VT.getVectorElementType() == Operand.getValueType() || (VT.getVectorElementType().isInteger() && Operand.getValueType().isInteger() && VT.getVectorElementType().bitsLE(Operand.getValueType()))) && "Illegal SCALAR_TO_VECTOR node!"), function getNode, file ../lib/CodeGen/SelectionDAG/SelectionDAG.cpp, line 4172.

With asserts disabled, it fails to select:

fatal error: error in backend: Cannot select: 0x7ff19d000e90: i32 = any_extend 0x7ff19d000ae8
  0x7ff19d000ae8: f64,ch = CopyFromReg 0x7ff19d000c20:1, Register:f64 %1
    0x7ff19d000b50: f64 = Register %1
In function: d

[andreadb]

I only have one comment. Otherwise, this LGTM. Thanks.

Please add your test case to the already existing combine-concatvectors.ll.

test/CodeGen/X86/combine-concat-vectors.ll

1

You mean:

; RUN: llc -mtriple=x86_64-- < %s | FileCheck %s

That being said, there is already combine-concatvectors.ll. Your new test case should be added there.

lib/CodeGen/SelectionDAG/DAGCombiner.cpp

if (In->getOpcode() == ISD::BITCAST &&
       // If the bitcast type isn't legal, it might be a trunc of a legal type;
       // look through the trunc so we can still do the transform:
       //   concat_vectors(trunc(scalar), undef) -> scalar_to_vector(scalar)
       if (Scalar->getOpcode() == ISD::TRUNCATE &&
           !TLI.isTypeLegal(Scalar.getValueType()) &&
           TLI.isTypeLegal(Scalar->getOperand(0).getValueType()))
         Scalar = Scalar->getOperand(0);
 
-      EVT SclTy = Scalar->getValueType(0);
+      EVT SclTy = Scalar.getValueType();
 
       if (!SclTy.isFloatingPoint() && !SclTy.isInteger())
         return SDValue();
 
       // Bail out if the vector size is not a multiple of the scalar size.
       if (VT.getSizeInBits() % SclTy.getSizeInBits())
         return SDValue();
 

test/CodeGen/X86/combine-concat-vectors.ll

+; RUN: llc -mtriple=x86_64-- -o - | FileCheck %s
+; Check that this does not fail to combine concat_vectors of a value from
+; merge_values through a bitcast.
+define void @d() personality i8* undef {
+entry:
+  %call16 = invoke { i8, double } undef()
+          to label %bar unwind label %foo
+
+foo:                                              ; preds = %bar, %entry
+  %0 = landingpad { i8*, i32 }
+          cleanup
+  br label %bazr
+
+bar:                                              ; preds = %entry
+  %1 = extractvalue { i8, double } %call16, 1
+  %2 = bitcast double %1 to <2 x float>
+  invoke void undef()
+          to label %baz unwind label %foo
+
+baz:                                              ; preds = %bar
+  %3 = extractelement <2 x float> %2, i64 0
+  br label %bazr
+
+bazr:                                             ; preds = %baz, %foo
+  %exn.obj = extractvalue { i8*, i32 } undef, 0
+  unreachable
+}