[WebAssembly] Fixed AsmPrinter not emitting .functype for intrinsics

[aardappel]

Summary

Intrinsics like memset were not emitted as .functype because
WebAssemblyAsmPrinter::emitExternalDecls explicitly skips symbols
that are isIntrinsic. Removing that check doesn't work, since the symbol
from the module refers to a 4-argument llvm.memset.p0i8.i32 rather
than the 3-argument memset symbol referenced in the call.
Our WebAssemblyMCLowerPrePass however does collect the
memset symbol, so the current solution is as simple as emitting
.functype for those.

Fixes: https://github.com/llvm/llvm-project/issues/53712

[aardappel]

This comment was removed by aardappel.

[sbc100]

llvm/test/MC/WebAssembly/extern-functype-intrinsic.ll

43

I think you can remove all the attributes here?

49

Maybe its enough to simply check for this line? Presumably a lot of the test is verified by the lack of failed verification?

[aardappel]

Reduced test, and added asm roundtrip test

[aardappel]

Further test reduction

llvm/lib/Target/WebAssembly/WebAssemblyAsmPrinter.cpp

void WebAssemblyAsmPrinter::emitExternalDecls(const Module &M) {
   signaturesEmitted = true;
 
   // Normally symbols for globals get discovered as the MI gets lowered,
   // but we need to know about them ahead of time. This will however,
   // only find symbols that have been used. Unused symbols from globals will
   // not be found here.
   MachineModuleInfoWasm &MMIW = MMI->getObjFileInfo<MachineModuleInfoWasm>();
   for (const auto &Name : MMIW.MachineSymbolsUsed) {
-    getOrCreateWasmSymbol(Name.getKey());
+    auto *WasmSym = cast<MCSymbolWasm>(getOrCreateWasmSymbol(Name.getKey()));
+    if (WasmSym->isFunction()) {
+      // TODO(wvo): is there any case where this overlaps with the call to
+      // emitFunctionType in the loop below?
+      getTargetStreamer()->emitFunctionType(WasmSym);
+    }
   }
 
   for (auto &It : OutContext.getSymbols()) {
     // Emit .globaltype, .tagtype, or .tabletype declarations for extern
     // declarations, i.e. those that have only been declared (but not defined)
     // in the current module
     auto Sym = cast<MCSymbolWasm>(It.getValue());
     if (!Sym->isDefined())

llvm/test/MC/WebAssembly/extern-functype-intrinsic.ll

+; RUN: llc %s -o - | FileCheck %s
+; RUN: llc %s -o - | llvm-mc -triple=wasm32-unknown-unknown | FileCheck %s
+
+; ModuleID = 'test.c'
+source_filename = "test.c"
+target datalayout = "e-m:e-p:32:32-p10:8:8-p20:8:8-i64:64-n32:64-S128-ni:1:10:20"
+target triple = "wasm32-unknown-wasi"
+
+; Function Attrs: nounwind
+define hidden i32 @d() local_unnamed_addr #0 {
+entry:
+  %0 = call i32 bitcast (i32 (...)* @g to i32 ()*)() #3
+  call void @llvm.memset.p0i8.i32(i8* nonnull align 4 inttoptr (i32 4 to i8*), i8 0, i32 %0, i1 false)                                        ; preds = %for.body.preheader, %entry
+  ret i32 undef
+}
+
+declare i32 @g(...) local_unnamed_addr #1
+
+; Function Attrs: argmemonly nofree nounwind willreturn writeonly
+declare void @llvm.memset.p0i8.i32(i8* nocapture writeonly, i8, i32, i1 immarg) #2
+
+attributes #0 = { nounwind "frame-pointer"="none" "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="generic" }
+attributes #1 = { "frame-pointer"="none" "no-prototype" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="generic" }
+attributes #2 = { argmemonly nofree nounwind willreturn writeonly }
+attributes #3 = { nounwind }
+
+; CHECK:         .functype       memset (i32, i32, i32) -> (i32)
+; CHECK:         .functype       g () -> (i32)
+; CHECK:         call    g
+; CHECK:         call    memset