[GlobalISel][AArch64] Legalize + select some llvm.ctlz.* intrinsics

Legalize/select llvm.ctlz.*

Add select-ctlz to show that we actually select them. Update arm64-clrsb.ll and
arm64-vclz.ll to show that we perform valid transformations in optimized builds,
and document where GISel can improve.

Differential Revision: https://reviews.llvm.org/D58155

llvm-svn: 354299

2 files changed, 5 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
index 38f0e221431..614a67f45fd 100644
--- a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
@@ -2099,6 +2099,7 @@ LegalizerHelper::fewerElementsVector(MachineInstr &MI, unsigned TypeIdx,
   case G_FSIN:
   case G_FSQRT:
   case G_BSWAP:
+  case G_CTLZ:
     return fewerElementsVectorBasic(MI, TypeIdx, NarrowTy);
   case G_SHL:
   case G_LSHR:
diff --git a/llvm/lib/Target/AArch64/AArch64LegalizerInfo.cpp b/llvm/lib/Target/AArch64/AArch64LegalizerInfo.cpp
index 3c57af84f03..94a66286368 100644
--- a/llvm/lib/Target/AArch64/AArch64LegalizerInfo.cpp
+++ b/llvm/lib/Target/AArch64/AArch64LegalizerInfo.cpp
@@ -457,6 +457,10 @@ AArch64LegalizerInfo::AArch64LegalizerInfo(const AArch64Subtarget &ST) {
       })
       .minScalarSameAs(1, 0);
 
+  getActionDefinitionsBuilder(G_CTLZ).legalForCartesianProduct(
+      {s32, s64, v8s8, v16s8, v4s16, v8s16, v2s32, v4s32})
+      .scalarize(1);
+
   computeTables();
   verify(*ST.getInstrInfo());
 }