From 856ecbc0680beaff74891cac5917678acb080dc9 Mon Sep 17 00:00:00 2001
From: Tim Northover <tnorthover@apple.com>
Date: Mon, 14 Apr 2014 12:59:52 +0000
Subject: [PATCH] ARM64: remove buggy REV16 pattern.

The 32-bit pattern is still valid: 0123 -> 3210 -> 1032.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206172 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/ARM64/ARM64InstrInfo.td | 3 +--
 test/CodeGen/ARM64/rev.ll          | 5 ++++-
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/lib/Target/ARM64/ARM64InstrInfo.td b/lib/Target/ARM64/ARM64InstrInfo.td
index 2af217fe910..6a1154d4369 100644
--- a/lib/Target/ARM64/ARM64InstrInfo.td
+++ b/lib/Target/ARM64/ARM64InstrInfo.td
@@ -645,8 +645,7 @@ defm CLZ    : OneOperandData<0b100, "clz", ctlz>;
 defm RBIT   : OneOperandData<0b000, "rbit">;
 def  REV16Wr : OneWRegData<0b001, "rev16",
                                   UnOpFrag<(rotr (bswap node:$LHS), (i64 16))>>;
-def  REV16Xr : OneXRegData<0b001, "rev16",
-                                  UnOpFrag<(rotr (bswap node:$LHS), (i64 16))>>;
+def  REV16Xr : OneXRegData<0b001, "rev16", null_frag>;
 
 def : Pat<(cttz GPR32:$Rn),
           (CLZWr (RBITWr GPR32:$Rn))>;
diff --git a/test/CodeGen/ARM64/rev.ll b/test/CodeGen/ARM64/rev.ll
index 867d5b3c513..0006ea33175 100644
--- a/test/CodeGen/ARM64/rev.ll
+++ b/test/CodeGen/ARM64/rev.ll
@@ -36,10 +36,13 @@ entry:
   ret i32 %tmp14
 }
 
+; 64-bit REV16 is *not* a swap then a 16-bit rotation:
+;   01234567 ->(bswap) 76543210 ->(rotr) 10765432
+;   01234567 ->(rev16) 10325476
 define i64 @test_rev16_x(i64 %a) nounwind {
 entry:
 ; CHECK-LABEL: test_rev16_x:
-; CHECK: rev16 x0, x0
+; CHECK-NOT: rev16 x0, x0
   %0 = tail call i64 @llvm.bswap.i64(i64 %a)
   %1 = lshr i64 %0, 16
   %2 = shl i64 %0, 48
-- 
2.34.1