2 files changed, 50 insertions, 0 deletions
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 79d916f5824..1e679ba3f0a 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -2465,6 +2465,12 @@ void SelectionDAG::computeKnownBits(SDValue Op, APInt &KnownZero,
     KnownOne = KnownOne.trunc(BitWidth);
     break;
   }
+  case ISD::BSWAP: {
+    computeKnownBits(Op.getOperand(0), KnownZero2, KnownOne2, Depth+1);
+    KnownZero = KnownZero2.byteSwap();
+    KnownOne = KnownOne2.byteSwap();
+    break;
+  }
   case ISD::SMIN:
   case ISD::SMAX:
   case ISD::UMIN:
diff --git a/llvm/test/CodeGen/AArch64/bswap-known-bits.ll b/llvm/test/CodeGen/AArch64/bswap-known-bits.ll
new file mode 100644
index 00000000000..e5de7953d1b
--- /dev/null
+++ b/llvm/test/CodeGen/AArch64/bswap-known-bits.ll
@@ -0,0 +1,44 @@
+; RUN: llc < %s -mtriple=aarch64-apple-darwin  | FileCheck %s
+
+declare i16 @llvm.bswap.i16(i16)
+declare i32 @llvm.bswap.i32(i32)
+
+; CHECK-LABEL: @test1
+; CHECK: orr w0, wzr, #0x1
+define i1 @test1(i16 %arg) {
+  %a = or i16 %arg, 511
+  %b = call i16 @llvm.bswap.i16(i16 %a)
+  %and = and i16 %b, 256
+  %res = icmp eq i16 %and, 256
+  ret i1 %res
+}
+
+; CHECK-LABEL: @test2
+; CHECK: orr w0, wzr, #0x1
+define i1 @test2(i16 %arg) {
+  %a = or i16 %arg, 1
+  %b = call i16 @llvm.bswap.i16(i16 %a)
+  %and = and i16 %b, 256
+  %res = icmp eq i16 %and, 256
+  ret i1 %res
+}
+
+; CHECK-LABEL: @test3
+; CHECK: orr w0, wzr, #0x1
+define i1 @test3(i16 %arg) {
+  %a = or i16 %arg, 256
+  %b = call i16 @llvm.bswap.i16(i16 %a)
+  %and = and i16 %b, 1
+  %res = icmp eq i16 %and, 1
+  ret i1 %res
+}
+
+; CHECK-LABEL: @test4
+; CHECK: orr w0, wzr, #0x1
+define i1 @test4(i32 %arg) {
+  %a = or i32 %arg, 2147483647  ; i32_MAX
+  %b = call i32 @llvm.bswap.i32(i32 %a)
+  %and = and i32 %b, 127
+  %res = icmp eq i32 %and, 127
+  ret i1 %res
+}