[llvm-branch-commits] [llvm] [LV][REVEC] Initial support for re-vectorisation (PR #208213)

[Andrei Elovikov via llvm-branch-commits]

=?utf-8?q?Gaëtan?= Bossu <gaetan.bossu at arm.com>,
=?utf-8?q?Gaëtan?= Bossu <gaetan.bossu at arm.com>,
=?utf-8?q?Gaëtan?= Bossu <gaetan.bossu at arm.com>,
=?utf-8?q?Gaëtan?= Bossu <gaetan.bossu at arm.com>,
=?utf-8?q?Gaëtan?= Bossu <gaetan.bossu at arm.com>,
=?utf-8?q?Gaëtan?= Bossu <gaetan.bossu at arm.com>
Message-ID:
In-Reply-To: <llvm.org/llvm/llvm-project/pull/208213 at github.com>


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@@ -974,13 +991,19 @@ bool LoopVectorizationLegality::canVectorizeInstr(Instruction &I) {
            all_of(Inst.users(), IsaPred<ExtractValueInst>);
   };
 
+  auto CanWidenCast = [&](const Instruction &CastI) {
+    assert(isa<CastInst>(CastI));
+    assert(CanWidenInstructionTy(CastI) &&
+           "CanWidenInstructionTy was not checked beforehand.");
+    Type *FromTy = CastI.getOperand(0)->getType();
+    return VectorType::isValidElementType(FromTy) ||
+           (isa<FixedVectorType>(FromTy) && VectorizeVectorLoops);
+  };
+
   // Check that the instruction return type is vectorizable.
-  // We can't vectorize casts from vector type to scalar type.
-  // Also, we can't vectorize extractelement instructions.
-  if (!CanWidenInstructionTy(I) ||
-      (isa<CastInst>(I) &&
-       !VectorType::isValidElementType(I.getOperand(0)->getType())) ||
-      isa<ExtractElementInst>(I)) {
+  // Also, we cannot re-vectorize element or shuffle operations yet.
+  if (!CanWidenInstructionTy(I) || (isa<CastInst>(I) && !CanWidenCast(I)) ||
+      isa<ExtractElementInst, InsertElementInst, ShuffleVectorInst>(I)) {
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eas wrote:

Maybe it'll become clear later in the patch, but reading up until this point it's unclear why the `Intrinsic::vector_broadcast` change above was necessary if we bailout on any shuffle instruction here.

https://github.com/llvm/llvm-project/pull/208213