[llvm-dev] What pattern string corresponds to CopyToReg? (original) (raw)

陳韋任 via llvm-dev llvm-dev at lists.llvm.org
Sun Nov 5 01:22:16 PDT 2017

Try match your instruction with (set REG16:$dst, i16imm:$src). Just give it a shot. :)

2017-11-05 12:56 GMT+08:00 Robert Baruch via llvm-dev < llvm-dev at lists.llvm.org>:

Well, that's the thing: I thought that was CopyToReg. I don't know what the name of the node is to load one value into a register, so I don't know how to construct such a pattern.

On Sat, Nov 4, 2017 at 9:23 PM Craig Topper <craig.topper at gmail.com> wrote:

Do you have a pattern for loading an i16 immediate into a 16-bit register?

~Craig On Sat, Nov 4, 2017 at 8:00 PM, Robert Baruch <robert.c.baruch at gmail.com> wrote:

Hmm, okay. Then what's the problem being reported here? I'm not sure what I'm supposed to do with "LLVM ERROR: Cannot select: t1: i16 = Constant<127>".BTW, the function is:

; ModuleID = 'return.c' sourcefilename = "return.c" target datalayout = "E-m:e-p:16:16:16-i1:16:16-i8: 16:16-i16:16:16-i32:16:16-i64:16:16-S16-n16" target triple = "tms9900" ; Function Attrs: noinline nounwind optnone define signext i16 @myfunc() #0 { entry: ret i16 127 } ------- debug output -------- Optimized legalized selection DAG: BB#0 'myfunc:entry' SelectionDAG has 5 nodes: t0: ch = EntryToken t3: ch,glue = CopyToReg t0, Register:i16 %R5, Constant:i16<127> t4: ch = TMS9900ISD::Ret t3, Register:i16 %R5, t3:1 ===== Instruction selection begins: BB#0 'entry' Selecting: t4: ch = TMS9900ISD::Ret t3, Register:i16 %R5, t3:1 ISEL: Starting pattern match on root node: t4: ch = TMS9900ISD::Ret t3, Register:i16 %R5, t3:1 Morphed node: t4: ch,glue = Retr Register:i16 %R5, t3 ISEL: Match complete! Selecting: t3: ch,glue = CopyToReg t0, Register:i16 %R5, Constant:i16<127> Selecting: t2: i16 = Register %R5 Selecting: t1: i16 = Constant<127> ISEL: Starting pattern match on root node: t1: i16 = Constant<127> Initial Opcode index to 0 Match failed at index 0 LLVM ERROR: Cannot select: t1: i16 = Constant<127> In function: myfunc

On Sat, Nov 4, 2017 at 7:22 PM Craig Topper <craig.topper at gmail.com> wrote: CopyToReg is not handle by patterns. It should be passed through isel unchanged. It’s part of a special list of ISD opcodes that don’t change in SelectioDAGISel::SelectCodeCommon It will then be turned into a TargetOpcode::COPY in InstrEmitter::EmitSpecialNode when the DAG is turned into MachineInstrs. On Sat, Nov 4, 2017 at 7:02 PM Robert Baruch via llvm-dev <_ _llvm-dev at lists.llvm.org> wrote: So there's a DAG that looks like this in the debug output:

Selecting: t3: ch,glue = CopyToReg t0, Register:i16 %R5, Constant:i16<127> In the instruction selection phase, what pattern would that match? I've constructed this so far: (??? REG16:$dst, i16imm:$src) but the problem is, I can't determine what to use as ???. There is an ISD::CopyToReg enum value, but I don't know how that translates to the string to use in the pattern. And more generally, how do I find out from a DAG diagram like the ones output by -view-isel-dags which node type corresponds to which pattern string? Thanks, --Rob

LLVM Developers mailing list llvm-dev at lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev -- ~Craig

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-- Wei-Ren Chen (陳韋任) Homepage: https://people.cs.nctu.edu.tw/~chenwj -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20171105/307bbf20/attachment.html>

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