[SLP] Remove seemingly bogus assert

[mkuper]

Summary

The assert seems bogus - it's perfectly legal for the vectorized subtrees to be equal even if the original scalar values aren't, if the original scalars happen to be equivalent.

I don't really see what we'd want to assert on here, so I'm nuking it. If you have alternative suggestions, let me know.

This fixes PR31599.

[ABataev]

LGTM

[mssimpso]

LGTM as well. I think this assert may have made sense before all the on-the-fly simplification was added (canReuseExtract, etc.).

lib/Transforms/Vectorize/SLPVectorizer.cpp

case Instruction::Xor: {
           RHSVL.push_back(cast<Instruction>(V)->getOperand(1));
         }
 
       setInsertPointAfterBundle(E->Scalars);
 
       Value *LHS = vectorizeTree(LHSVL);
       Value *RHS = vectorizeTree(RHSVL);
 
-      if (LHS == RHS && isa<Instruction>(LHS)) {
-        assert((VL0->getOperand(0) == VL0->getOperand(1)) && "Invalid order");
-      }
-
       if (Value *V = alreadyVectorized(E->Scalars))
         return V;
 
       BinaryOperator *BinOp = cast<BinaryOperator>(VL0);
       Value *V = Builder.CreateBinOp(BinOp->getOpcode(), LHS, RHS);
       E->VectorizedValue = V;
       propagateIRFlags(E->VectorizedValue, E->Scalars);
       ++NumVectorInstructions;

test/Transforms/SLPVectorizer/X86/pr31599.ll

+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -slp-vectorizer -S -mtriple=x86_64-unknown-linux-gnu < %s | FileCheck %s
+
+define <2 x float> @foo() {
+; CHECK-LABEL: @foo(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[SOURCE:%.*]] = insertelement <2 x float> undef, float undef, i32 0
+; CHECK-NEXT:    [[TMP0:%.*]] = fsub <2 x float> [[SOURCE]], [[SOURCE]]
+; CHECK-NEXT:    [[TMP1:%.*]] = extractelement <2 x float> [[TMP0]], i32 0
+; CHECK-NEXT:    [[RES1:%.*]] = insertelement <2 x float> undef, float [[TMP1]], i32 0
+; CHECK-NEXT:    [[TMP2:%.*]] = extractelement <2 x float> [[TMP0]], i32 1
+; CHECK-NEXT:    [[RES2:%.*]] = insertelement <2 x float> [[RES1]], float [[TMP2]], i32 1
+; CHECK-NEXT:    ret <2 x float> [[RES2]]
+;
+entry:
+  %source = insertelement <2 x float> undef, float undef, i32 0
+  %e0 = extractelement <2 x float> %source, i32 0
+  %e0.dup = extractelement <2 x float> %source, i32 0
+  %sub1 = fsub float %e0, %e0.dup
+  %e1 = extractelement <2 x float> %source, i32 1
+  %e1.dup = extractelement <2 x float> %source, i32 1
+  %sub2 = fsub float %e1, %e1.dup
+  %res1 = insertelement <2 x float> undef, float %sub1, i32 0
+  %res2 = insertelement <2 x float> %res1, float %sub2, i32 1
+  ret <2 x float> %res2
+}
+
+!llvm.ident = !{!0, !0}
+
+!0 = !{!"clang version 4.0.0 "}