From f254f1d94e8d0070b2d006a3d1e7ee6eeae0aaa7 Mon Sep 17 00:00:00 2001
From: David Sherwood <david.sherwood@arm.com>
Date: Tue, 26 May 2020 16:07:46 +0100
Subject: [PATCH] [SVE] Remove getNumElements() warnings in
 InstCombiner::visitBitCast

Whilst trying to compile this test to assembly:

  CodeGen/aarch64-sve-intrinsics/acle_sve_reinterpret.c

I discovered some warnings were firing in InstCombiner::visitBitCast
due to calls to getNumElements() for scalable vector types. These
calls only really made sense for fixed width vectors so I have fixed
up the code appropriately.

Differential Revision: https://reviews.llvm.org/D80559
---
 .../lib/Transforms/InstCombine/InstCombineCasts.cpp |  4 ++--
 .../Transforms/InstCombine/AArch64/sve-bitcast.ll   | 13 +++++++++++++
 2 files changed, 15 insertions(+), 2 deletions(-)
 create mode 100644 llvm/test/Transforms/InstCombine/AArch64/sve-bitcast.ll

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
index 714d1ae8aaec..a2b75848ea02 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
@@ -2534,7 +2534,7 @@ Instruction *InstCombiner::visitBitCast(BitCastInst &CI) {
     }
   }
 
-  if (VectorType *DestVTy = dyn_cast<VectorType>(DestTy)) {
+  if (FixedVectorType *DestVTy = dyn_cast<FixedVectorType>(DestTy)) {
     // Beware: messing with this target-specific oddity may cause trouble.
     if (DestVTy->getNumElements() == 1 && SrcTy->isX86_MMXTy()) {
       Value *Elem = Builder.CreateBitCast(Src, DestVTy->getElementType());
@@ -2563,7 +2563,7 @@ Instruction *InstCombiner::visitBitCast(BitCastInst &CI) {
     }
   }
 
-  if (VectorType *SrcVTy = dyn_cast<VectorType>(SrcTy)) {
+  if (FixedVectorType *SrcVTy = dyn_cast<FixedVectorType>(SrcTy)) {
     if (SrcVTy->getNumElements() == 1) {
       // If our destination is not a vector, then make this a straight
       // scalar-scalar cast.
diff --git a/llvm/test/Transforms/InstCombine/AArch64/sve-bitcast.ll b/llvm/test/Transforms/InstCombine/AArch64/sve-bitcast.ll
new file mode 100644
index 000000000000..8049cad596b5
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/AArch64/sve-bitcast.ll
@@ -0,0 +1,13 @@
+; RUN: opt -instcombine -mtriple=aarch64-linux-gnu -mattr=+sve -S < %s | FileCheck %s
+
+; We shouldn't fold bitcast(insert <vscale x 1 x iX> .., iX %val, i32 0)
+; into bitcast(iX %val) for scalable vectors.
+define <vscale x 2 x i8> @bitcast_of_insert_i8_i16(i16 %val) #0 {
+; CHECK-LABEL: @bitcast_of_insert_i8_i16(
+; CHECK-NOT:   bitcast i16 %val to <vscale x 2 x i8>
+; CHECK:       bitcast <vscale x 1 x i16> %op2 to <vscale x 2 x i8>
+entry:
+  %op2 = insertelement <vscale x 1 x i16> undef, i16 %val, i32 0
+  %0 = bitcast <vscale x 1 x i16> %op2 to <vscale x 2 x i8>
+  ret <vscale x 2 x i8> %0
+}