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[lanai] Custom lowering of SHL_PARTS

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Summary: Implement custom lowering of SHL_PARTS to enable lowering of left shift with larger than 32-bit shifts.

Reviewers: eliben, majnemer

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D27232

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@288541 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jacques Pienaar 2016-12-02 22:01:28 +00:00
parent fe88eab3e2
commit 8860d3c0df
3 changed files with 77 additions and 1 deletions
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53
lib/Target/Lanai/LanaiISelLowering.cpp
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@ -104,7 +104,7 @@ LanaiTargetLowering::LanaiTargetLowering(const TargetMachine &TM,
setOperationAction(ISD::ROTR, MVT::i32, Expand);
setOperationAction(ISD::ROTL, MVT::i32, Expand);
setOperationAction(ISD::SHL_PARTS, MVT::i32, Expand);
setOperationAction(ISD::SHL_PARTS, MVT::i32, Custom);
setOperationAction(ISD::SRL_PARTS, MVT::i32, Custom);
setOperationAction(ISD::SRA_PARTS, MVT::i32, Expand);
@ -179,6 +179,8 @@ SDValue LanaiTargetLowering::LowerOperation(SDValue Op,
return LowerSETCC(Op, DAG);
case ISD::SETCCE:
return LowerSETCCE(Op, DAG);
case ISD::SHL_PARTS:
return LowerSHL_PARTS(Op, DAG);
case ISD::SRL_PARTS:
return LowerSRL_PARTS(Op, DAG);
case ISD::VASTART:
@ -1233,6 +1235,55 @@ SDValue LanaiTargetLowering::LowerJumpTable(SDValue Op,
}
}
SDValue LanaiTargetLowering::LowerSHL_PARTS(SDValue Op,
SelectionDAG &DAG) const {
EVT VT = Op.getValueType();
unsigned VTBits = VT.getSizeInBits();
SDLoc dl(Op);
assert(Op.getNumOperands() == 3 && "Unexpected SHL!");
SDValue ShOpLo = Op.getOperand(0);
SDValue ShOpHi = Op.getOperand(1);
SDValue ShAmt = Op.getOperand(2);
// Performs the following for (ShOpLo + (ShOpHi << 32)) << ShAmt:
// LoBitsForHi = (ShAmt == 0) ? 0 : (ShOpLo >> (32-ShAmt))
// HiBitsForHi = ShOpHi << ShAmt
// Hi = (ShAmt >= 32) ? (ShOpLo << (ShAmt-32)) : (LoBitsForHi | HiBitsForHi)
// Lo = (ShAmt >= 32) ? 0 : (ShOpLo << ShAmt)
// return (Hi << 32) | Lo;
SDValue RevShAmt = DAG.getNode(ISD::SUB, dl, MVT::i32,
DAG.getConstant(VTBits, dl, MVT::i32), ShAmt);
SDValue LoBitsForHi = DAG.getNode(ISD::SRL, dl, VT, ShOpLo, RevShAmt);
// If ShAmt == 0, we just calculated "(SRL ShOpLo, 32)" which is "undef". We
// wanted 0, so CSEL it directly.
SDValue Zero = DAG.getConstant(0, dl, MVT::i32);
SDValue SetCC = DAG.getSetCC(dl, MVT::i32, ShAmt, Zero, ISD::SETEQ);
LoBitsForHi = DAG.getSelect(dl, MVT::i32, SetCC, Zero, LoBitsForHi);
SDValue ExtraShAmt = DAG.getNode(ISD::SUB, dl, MVT::i32, ShAmt,
DAG.getConstant(VTBits, dl, MVT::i32));
SDValue HiBitsForHi = DAG.getNode(ISD::SHL, dl, VT, ShOpHi, ShAmt);
SDValue HiForNormalShift =
DAG.getNode(ISD::OR, dl, VT, LoBitsForHi, HiBitsForHi);
SDValue HiForBigShift = DAG.getNode(ISD::SHL, dl, VT, ShOpLo, ExtraShAmt);
SetCC = DAG.getSetCC(dl, MVT::i32, ExtraShAmt, Zero, ISD::SETGE);
SDValue Hi =
DAG.getSelect(dl, MVT::i32, SetCC, HiForBigShift, HiForNormalShift);
// Lanai shifts of larger than register sizes are wrapped rather than
// clamped, so we can't just emit "lo << b" if b is too big.
SDValue LoForNormalShift = DAG.getNode(ISD::SHL, dl, VT, ShOpLo, ShAmt);
SDValue Lo = DAG.getSelect(
dl, MVT::i32, SetCC, DAG.getConstant(0, dl, MVT::i32), LoForNormalShift);
SDValue Ops[2] = {Lo, Hi};
return DAG.getMergeValues(Ops, dl);
}
SDValue LanaiTargetLowering::LowerSRL_PARTS(SDValue Op,
SelectionDAG &DAG) const {
MVT VT = Op.getSimpleValueType();

1
lib/Target/Lanai/LanaiISelLowering.h
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@ -88,6 +88,7 @@ public:
SDValue LowerSELECT_CC(SDValue Op, SelectionDAG &DAG) const;
SDValue LowerSETCC(SDValue Op, SelectionDAG &DAG) const;
SDValue LowerSETCCE(SDValue Op, SelectionDAG &DAG) const;
SDValue LowerSHL_PARTS(SDValue Op, SelectionDAG &DAG) const;
SDValue LowerSRL_PARTS(SDValue Op, SelectionDAG &DAG) const;
SDValue LowerVASTART(SDValue Op, SelectionDAG &DAG) const;

24
test/CodeGen/Lanai/lshift64.ll Normal file
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@ -0,0 +1,24 @@
; RUN: llc < %s -mtriple=lanai-unknown-unknown | FileCheck %s
; Test left-shift i64 lowering does not result in call being inserted.
; CHECK-LABEL: shift
; CHECKT: bt __ashldi3
; CHECK: or %r0, 0x0, %r[[T0:[0-9]+]]
; CHECK: mov 0x20, %r[[T1:[0-9]+]]
; CHECK: sub %r[[T1]], %r[[ShAmt:[0-9]+]], %r[[T1]]
; CHECK: sub %r0, %r[[T1]], %r[[T1]]
; CHECK: sh %r[[ShOpB:[0-9]+]], %r[[T1]], %r[[T1]]
; CHECK: sub.f %r[[ShAmt]], 0x0, %r0
; CHECK: sel.eq %r0, %r[[T1]], %r[[T1]]
; CHECK: sh %r[[ShOpA:[0-9]+]], %r[[ShAmt]], %r[[T2:[0-9]+]]
; CHECK: or %r[[T1]], %r[[T2]], %rv
; CHECK: sub.f %r[[ShAmt]], 0x20, %r[[T1]]
; CHECK: sh.pl %r[[ShOpB]], %r[[T1]], %rv
; CHECK: sh.mi %r[[ShOpB]], %r[[ShAmt]], %r[[T0]]
define i64 @shift(i64 inreg, i32 inreg) {
%3 = zext i32 %1 to i64
%4 = shl i64 %0, %3
ret i64 %4
}