[llvm-commits] Fixing Bug 13662: paired register for inline asm with 64-bit data on ARM

[Weiming Zhao]

Hi Jakob,

 

First, I’m really sorry for late repose. I was really busy on other parts of
LLVM in the past few weeks.

 

CopyFromReg can’t take a Untyped VT because
ScheduleDAGRRList.cpp::GetCostForDef() expects MachineOpCode for Untyped
node, while CopyFromReg is not a MachineOpCode:

 

static void GetCostForDef(
) {

  MVT VT = RegDefPos.GetValue();

 

  // Special handling for untyped values.  These values can only come from

  // the expansion of custom DAG-to-DAG patterns.

  if (VT == MVT::Untyped) {

    const SDNode *Node = RegDefPos.GetNode();

    unsigned Opcode = Node->getMachineOpcode(); à CopyFromReg is not a
MachineOpcode()

 

This is why I’m avoiding using CopyFromReg for Untyped.

 

Thanks,

Weiming

 

Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by
The Linux Foundation

 

From: Jakob Stoklund Olesen [mailto:stoklund at 2pi.dk] 
Sent: Thursday, January 03, 2013 12:58 PM
To: weimingz at codeaurora.org
Cc: llvm-commits at cs.uiuc.edu; 'James Grosbach'; Evan Cheng
Subject: Re: [llvm-commits] Fixing Bug 13662: paired register for inline asm
with 64-bit data on ARM

 

 

On Jan 3, 2013, at 12:03 PM, Weiming Zhao <weimingz at codeaurora.org> wrote:





Yes, I tried to use CopyToReg/CopyFromReg to enforce the order. The issue is
“Untyped” data type.

The REG_SEQUENCE and EXTRACT_SUBREG has to use “Untyped” data type. However,
CopyToReg/CopyFromReg doesn’t support such data type.

 

Why not?





 And I explicitly add a glue edge between the Extract_subreg and inline asm:

SDValue E0 = SDValue(CurDAG->getMachineNode(TargetOpcode::EXTRACT_SUBREG,

                           dl, MVT::i32, MVT::Glue, PairedReg,

                           CurDAG->getTargetConstant(ARM::gsub_0, MVT::i32),

                           Chain.getValue(1) è Guarantees that this node is
emitted after the linlineasm

                          ), 0);

 

In other words, this node has the same effect as CopyFromReg.

 

Your DAG may work, but your changes still allow bad DAGs to be emitted.
Plus, as I said, it's not necessary.

 

/jakob

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