[llvm-dev] Work on DAG Isel for TableGen and compiler

[Thomas Lively via llvm-dev]

Yes, the CodeGenDAGPatterns is exactly right. Try applying the patch below
and rebuilding and you'll see what I mean about the error messages ;) That
being said, I'm sympathetic to Matt's point about shifting effort to
GlobalISel. Maybe it has similar problems you could work on? A nicer
development experience would certainly be a good carrot to get me excited
to switch over sooner.

--- a/llvm/lib/Target/WebAssembly/WebAssemblyInstrSIMD.td
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyInstrSIMD.td
@@ -413,7 +413,7 @@ defm SHUFFLE :
 def wasm_shuffle_t : SDTypeProfile<1, 18, []>;
 def wasm_shuffle : SDNode<"WebAssemblyISD::SHUFFLE", wasm_shuffle_t>;
 foreach vec_t = [v16i8, v8i16, v4i32, v2i64, v4f32, v2f64] in {
-def : Pat<(vec_t (wasm_shuffle (vec_t V128:$x), (vec_t V128:$y),
+def : Pat<(vec_t (wasm_shuffle V128:$x, (vec_t V128:$y),
             (i32 LaneIdx32:$m0), (i32 LaneIdx32:$m1),
             (i32 LaneIdx32:$m2), (i32 LaneIdx32:$m3),
             (i32 LaneIdx32:$m4), (i32 LaneIdx32:$m5),



On Wed, Nov 18, 2020 at 12:42 PM Paul C. Anagnostopoulos <paul at windfall.com>
wrote:

> Are you talking about the type checking done in CodeGenDAGPatterns.cpp? Is
> it easy to post an example?
>
> At 11/18/2020 01:55 PM, Thomas Lively wrote:
> >Hi Paul,
> >
> >I think this would be time well spent. At least in the WebAssembly
> backend, the vast majority of our ISel work is still done with DAG ISel. I
> know this is different from the performance work you have in mind, but one
> of my biggest pain points working on LLVM so far has been the poor error
> messages from the DAG ISel pattern type checker. If you could find time to
> improve those error messages, I would be extremely grateful.
> >
> >Thanks,
> >
> >Thomas
>
>
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