(original) (raw)

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@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@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'

source\_filename = "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 @my\_func() #0 {

entry:

ret i16 127

}

------- debug output --------

Optimized legalized selection DAG: BB#0 'my\_func: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: my\_func

On Sat, Nov 4, 2017 at 7:22 PM Craig Topper <craig.topper@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@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@lists.llvm.org
http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev

--

\~Craig

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_
LLVM Developers mailing list
llvm-dev@lists.llvm.org
http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev