When lowering vector shifts a check is performed to see if the value to shift by

is an immediate, in this check the value is negated and stored in and int64_t.
The value can be -2^63 yet the result cannot be stored in an int64_t and this
gives some undefined behaviour causing failures. The negation is only necessary
when the values is within a certain range and so it should not need to negate
-2^63, this patch introduces this and also a regression test.

Differential Revision: http://reviews.llvm.org/D11408



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@243100 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/AArch64/AArch64ISelLowering.cpp

@@ -6440,26 +6440,20 @@ static bool getVShiftImm(SDValue Op, unsigned ElementBits, int64_t &Cnt) {
 ///   0 <= Value <= ElementBits for a long left shift.
 static bool isVShiftLImm(SDValue Op, EVT VT, bool isLong, int64_t &Cnt) {
   assert(VT.isVector() && "vector shift count is not a vector type");
-  unsigned ElementBits = VT.getVectorElementType().getSizeInBits();
+  int64_t ElementBits = VT.getVectorElementType().getSizeInBits();
   if (!getVShiftImm(Op, ElementBits, Cnt))
     return false;
   return (Cnt >= 0 && (isLong ? Cnt - 1 : Cnt) < ElementBits);
 }
 
 /// isVShiftRImm - Check if this is a valid build_vector for the immediate
-/// operand of a vector shift right operation.  For a shift opcode, the value
+/// operand of a vector shift right operation. The value must be in the range:
-/// is positive, but for an intrinsic the value count must be negative. The
+///   1 <= Value <= ElementBits for a right shift; or
-/// absolute value must be in the range:
+static bool isVShiftRImm(SDValue Op, EVT VT, bool isNarrow, int64_t &Cnt) {
-///   1 <= |Value| <= ElementBits for a right shift; or
-///   1 <= |Value| <= ElementBits/2 for a narrow right shift.
-static bool isVShiftRImm(SDValue Op, EVT VT, bool isNarrow, bool isIntrinsic,
-                         int64_t &Cnt) {
   assert(VT.isVector() && "vector shift count is not a vector type");
-  unsigned ElementBits = VT.getVectorElementType().getSizeInBits();
+  int64_t ElementBits = VT.getVectorElementType().getSizeInBits();
   if (!getVShiftImm(Op, ElementBits, Cnt))
     return false;
-  if (isIntrinsic)
-    Cnt = -Cnt;
   return (Cnt >= 1 && Cnt <= (isNarrow ? ElementBits / 2 : ElementBits));
 }
 
@@ -6488,8 +6482,7 @@ SDValue AArch64TargetLowering::LowerVectorSRA_SRL_SHL(SDValue Op,
   case ISD::SRA:
   case ISD::SRL:
     // Right shift immediate
-    if (isVShiftRImm(Op.getOperand(1), VT, false, false, Cnt) &&
+    if (isVShiftRImm(Op.getOperand(1), VT, false, Cnt) && Cnt < EltSize) {
-        Cnt < EltSize) {
       unsigned Opc =
           (Op.getOpcode() == ISD::SRA) ? AArch64ISD::VASHR : AArch64ISD::VLSHR;
       return DAG.getNode(Opc, DL, VT, Op.getOperand(0),

lib/Target/ARM/ARMISelLowering.cpp

@@ -9691,7 +9691,7 @@ static bool getVShiftImm(SDValue Op, unsigned ElementBits, int64_t &Cnt) {
 ///   0 <= Value <= ElementBits for a long left shift.
 static bool isVShiftLImm(SDValue Op, EVT VT, bool isLong, int64_t &Cnt) {
   assert(VT.isVector() && "vector shift count is not a vector type");
-  unsigned ElementBits = VT.getVectorElementType().getSizeInBits();
+  int64_t ElementBits = VT.getVectorElementType().getSizeInBits();
   if (! getVShiftImm(Op, ElementBits, Cnt))
     return false;
   return (Cnt >= 0 && (isLong ? Cnt-1 : Cnt) < ElementBits);
@@ -9706,12 +9706,16 @@ static bool isVShiftLImm(SDValue Op, EVT VT, bool isLong, int64_t &Cnt) {
 static bool isVShiftRImm(SDValue Op, EVT VT, bool isNarrow, bool isIntrinsic,
                          int64_t &Cnt) {
   assert(VT.isVector() && "vector shift count is not a vector type");
-  unsigned ElementBits = VT.getVectorElementType().getSizeInBits();
+  int64_t ElementBits = VT.getVectorElementType().getSizeInBits();
   if (! getVShiftImm(Op, ElementBits, Cnt))
     return false;
-  if (isIntrinsic)
+  if (!isIntrinsic)
+    return (Cnt >= 1 && Cnt <= (isNarrow ? ElementBits/2 : ElementBits));
+  if (Cnt >= -(isNarrow ? ElementBits/2 : ElementBits) && Cnt <= -1) {
     Cnt = -Cnt;
-  return (Cnt >= 1 && Cnt <= (isNarrow ? ElementBits/2 : ElementBits));
+    return true;
+  }
+  return false;
 }
 
 /// PerformIntrinsicCombine - ARM-specific DAG combining for intrinsics.

test/CodeGen/ARM/neon_vshl_minint.ll

@@ -0,0 +1,13 @@
+; RUN: llc < %s -mtriple=arm-none-eabi -mcpu=cortex-a8 2>&1 | FileCheck %s
+; RUN: llc < %s -mtriple=thumb-none-eabi -mcpu=cortex-a8 2>&1 | FileCheck %s
+
+define <1 x i64> @vshl_minint() #0 {
+  entry:
+    ; CHECK-LABEL: vshl_minint
+    ; CHECK: vldr
+    ; CHECK: vshl.u64
+    %vshl.i = tail call <1 x i64> @llvm.arm.neon.vshiftu.v1i64(<1 x i64> undef, <1 x i64> <i64 -9223372036854775808>)
+    ret <1 x i64> %vshl.i
+}
+
+declare <1 x i64> @llvm.arm.neon.vshiftu.v1i64(<1 x i64>, <1 x i64>)