[GlobalISel][AArch64] Add instruction selection support for @llvm.log2

This teaches GlobalISel to emit a RTLib call for @llvm.log2 when it encounters
it.

It updates the existing floating point tests to show that we don't fall back on
the intrinsic, and select the correct instructions. It also adds a legalizer
test for G_FLOG2.

https://reviews.llvm.org/D57357

llvm-svn: 352673

1 files changed, 7 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
index ee9163f5c74..91100d02af1 100644
--- a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
@@ -138,6 +138,10 @@ static RTLIB::Libcall getRTLibDesc(unsigned Opcode, unsigned Size) {
     assert((Size == 32 || Size == 64 || Size == 128) && "Unsupported size");
     return Size == 128 ? RTLIB::LOG_F128
                        : Size == 64 ? RTLIB::LOG_F64 : RTLIB::LOG_F32;
+  case TargetOpcode::G_FLOG2:
+    assert((Size == 32 || Size == 64 || Size == 128) && "Unsupported size");
+    return Size == 128 ? RTLIB::LOG2_F128
+                       : Size == 64 ? RTLIB::LOG2_F64 : RTLIB::LOG2_F32;
   }
   llvm_unreachable("Unknown libcall function");
 }
@@ -233,7 +237,8 @@ LegalizerHelper::libcall(MachineInstr &MI) {
   case TargetOpcode::G_FCOS:
   case TargetOpcode::G_FSIN:
   case TargetOpcode::G_FLOG10:
-  case TargetOpcode::G_FLOG: {
+  case TargetOpcode::G_FLOG:
+  case TargetOpcode::G_FLOG2: {
     if (Size > 64) {
       LLVM_DEBUG(dbgs() << "Size " << Size << " too large to legalize.\n");
       return UnableToLegalize;
@@ -1197,6 +1202,7 @@ LegalizerHelper::widenScalar(MachineInstr &MI, unsigned TypeIdx, LLT WideTy) {
   case TargetOpcode::G_FSIN:
   case TargetOpcode::G_FLOG10:
   case TargetOpcode::G_FLOG:
+  case TargetOpcode::G_FLOG2:
   case TargetOpcode::G_FSQRT:
     assert(TypeIdx == 0);
     Observer.changingInstr(MI);