From 3808e8c85d0923c8adfb0645eed4fb0e595baaa8 Mon Sep 17 00:00:00 2001
From: James Molloy <james.molloy@arm.com>
Date: Fri, 13 Nov 2015 10:02:36 +0000
Subject: [PATCH] [SDAG] Fix expansion of BITREVERSE

Richard Trieu noted that UBSan detected an overflowing shift, and the obvious fix caused a crash.

What was happening was that the shiftee (1U) was indeed too small for the possible range of shifts it had to handle, but also we were using "VT.getSizeInBits()" to get the maximum type bitwidth, but we wanted "VT.getScalarSizeInBits()" to get the vector lane size instead of the entire vector size.

Use an APInt for the shift and VT.getScalarSizeInBits().

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@253023 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/SelectionDAG/LegalizeDAG.cpp |  8 +++---
 test/CodeGen/AArch64/bitreverse.ll       | 45 ++++++++++++++++++++++++++++++++
 2 files changed, 50 insertions(+), 3 deletions(-)

diff --git a/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp b/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
index 186697d3d02..e3a11cd27e1 100644
--- a/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
@@ -2780,7 +2780,7 @@ SDValue SelectionDAGLegalize::PromoteLegalFP_TO_INT(SDValue LegalOp,
 SDValue SelectionDAGLegalize::ExpandBITREVERSE(SDValue Op, SDLoc dl) {
   EVT VT = Op.getValueType();
   EVT SHVT = TLI.getShiftAmountTy(VT, DAG.getDataLayout());
-  unsigned Sz = VT.getSizeInBits();
+  unsigned Sz = VT.getScalarSizeInBits();
   
   SDValue Tmp, Tmp2;
   Tmp = DAG.getConstant(0, dl, VT);
@@ -2791,8 +2791,10 @@ SDValue SelectionDAGLegalize::ExpandBITREVERSE(SDValue Op, SDLoc dl) {
     else
       Tmp2 =
           DAG.getNode(ISD::SRL, dl, VT, Op, DAG.getConstant(I - J, dl, SHVT));
-    Tmp2 =
-        DAG.getNode(ISD::AND, dl, VT, Tmp2, DAG.getConstant(1U << J, dl, VT));
+    
+    APInt Shift(Sz, 1);
+    Shift = Shift.shl(J);
+    Tmp2 = DAG.getNode(ISD::AND, dl, VT, Tmp2, DAG.getConstant(Shift, dl, VT));
     Tmp = DAG.getNode(ISD::OR, dl, VT, Tmp, Tmp2);
   }
 
diff --git a/test/CodeGen/AArch64/bitreverse.ll b/test/CodeGen/AArch64/bitreverse.ll
index b780412f765..702581789bb 100644
--- a/test/CodeGen/AArch64/bitreverse.ll
+++ b/test/CodeGen/AArch64/bitreverse.ll
@@ -21,3 +21,48 @@ define i8 @g(i8 %a) {
   %b = call i8 @llvm.bitreverse.i8(i8 %a)
   ret i8 %b
 }
+
+declare <8 x i8> @llvm.bitreverse.v8i8(<8 x i8>) readnone
+
+define <8 x i8> @g_vec(<8 x i8> %a) {
+; Try and match as much of the sequence as precisely as possible.
+
+; CHECK-LABEL: g_vec:
+; CHECK-DAG: movi [[M1:v.*]], #0x80
+; CHECK-DAG: movi [[M2:v.*]], #0x40
+; CHECK-DAG: movi [[M3:v.*]], #0x20
+; CHECK-DAG: movi [[M4:v.*]], #0x10
+; CHECK-DAG: movi [[M5:v.*]], #0x8
+; CHECK-DAG: movi [[M6:v.*]], #0x4{{$}}
+; CHECK-DAG: movi [[M7:v.*]], #0x2{{$}}
+; CHECK-DAG: movi [[M8:v.*]], #0x1{{$}}
+; CHECK-DAG: shl  [[S1:v.*]], v0.8b, #7
+; CHECK-DAG: shl  [[S2:v.*]], v0.8b, #5
+; CHECK-DAG: shl  [[S3:v.*]], v0.8b, #3
+; CHECK-DAG: shl  [[S4:v.*]], v0.8b, #1
+; CHECK-DAG: ushr [[S5:v.*]], v0.8b, #1
+; CHECK-DAG: ushr [[S6:v.*]], v0.8b, #3
+; CHECK-DAG: ushr [[S7:v.*]], v0.8b, #5
+; CHECK-DAG: ushr [[S8:v.*]], v0.8b, #7
+; CHECK-DAG: and  [[A1:v.*]], [[S1]], [[M1]]
+; CHECK-DAG: and  [[A2:v.*]], [[S2]], [[M2]]
+; CHECK-DAG: and  [[A3:v.*]], [[S3]], [[M3]]
+; CHECK-DAG: and  [[A4:v.*]], [[S4]], [[M4]]
+; CHECK-DAG: and  [[A5:v.*]], [[S5]], [[M5]]
+; CHECK-DAG: and  [[A6:v.*]], [[S6]], [[M6]]
+; CHECK-DAG: and  [[A7:v.*]], [[S7]], [[M7]]
+; CHECK-DAG: and  [[A8:v.*]], [[S8]], [[M8]]
+
+; The rest can be ORRed together in any order; it's not worth the test
+; maintenance to match them precisely.
+; CHECK-DAG: orr
+; CHECK-DAG: orr
+; CHECK-DAG: orr
+; CHECK-DAG: orr
+; CHECK-DAG: orr
+; CHECK-DAG: orr
+; CHECK-DAG: orr
+; CHECK: ret
+  %b = call <8 x i8> @llvm.bitreverse.v8i8(<8 x i8> %a)
+  ret <8 x i8> %b
+}
-- 
2.11.0