[llvm] [WebAssemblyLowerEmscriptenEHSjLj] Avoid setting import_name where possible (PR #128564)

[Sam Clegg via llvm-commits]

https://github.com/sbc100 created https://github.com/llvm/llvm-project/pull/128564

Most of these symbols are just normal C symbols that get imported from wither libcompiler-rt or from emscripten's JS library code.  In most cases it should not be necessary to give them explicit import names.

The advantage of doing this is that we can wasm-ld can/will fail with a useful error message when these symbols are missing.  As opposed to today where it will simply import them and defer errors until later (when they are less specific).

>From e13b62548231dadec5608b4622b246be352b5ead Mon Sep 17 00:00:00 2001
From: Sam Clegg <sbc at chromium.org>
Date: Mon, 24 Feb 2025 11:47:41 -0800
Subject: [PATCH] [WebAssemblyLowerEmscriptenEHSjLj] Avoid setting import_name
 where possible

Most of these symbols are just normal C symbols that get imported from
wither libcompiler-rt or from emscripten's JS library code.  In most
cases it should not be necessary to give them explicit import names.

The advantage of doing this is that we can wasm-ld can/will fail with
a useful error message when these symbols are missing.  As opposed to
today where it will simply import them and defer errors until later
(when they are less specific).
---
 .../WebAssemblyLowerEmscriptenEHSjLj.cpp      | 29 +++++++++++--------
 1 file changed, 17 insertions(+), 12 deletions(-)

diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp
index c60cf69c30104..6eb61bd4b3159 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp
@@ -440,9 +440,14 @@ static std::string getSignature(FunctionType *FTy) {
   return Sig;
 }
 
+static Function *getFunction(FunctionType *Ty, const Twine &Name,
+                                       Module *M) {
+  return Function::Create(Ty, GlobalValue::ExternalLinkage, Name, M);
+}
+
 static Function *getEmscriptenFunction(FunctionType *Ty, const Twine &Name,
                                        Module *M) {
-  Function* F = Function::Create(Ty, GlobalValue::ExternalLinkage, Name, M);
+  Function* F = getFunction(Ty, Name, M);
   // Tell the linker that this function is expected to be imported from the
   // 'env' module.
   if (!F->hasFnAttribute("wasm-import-module")) {
@@ -927,11 +932,11 @@ bool WebAssemblyLowerEmscriptenEHSjLj::runOnModule(Module &M) {
   // exception handling and setjmp/longjmp handling
   ThrewGV = getGlobalVariable(M, getAddrIntType(&M), TM, "__THREW__");
   ThrewValueGV = getGlobalVariable(M, IRB.getInt32Ty(), TM, "__threwValue");
-  GetTempRet0F = getEmscriptenFunction(
-      FunctionType::get(IRB.getInt32Ty(), false), "getTempRet0", &M);
-  SetTempRet0F = getEmscriptenFunction(
-      FunctionType::get(IRB.getVoidTy(), IRB.getInt32Ty(), false),
-      "setTempRet0", &M);
+  GetTempRet0F = getFunction(FunctionType::get(IRB.getInt32Ty(), false),
+                             "getTempRet0", &M);
+  SetTempRet0F =
+      getFunction(FunctionType::get(IRB.getVoidTy(), IRB.getInt32Ty(), false),
+                  "setTempRet0", &M);
   GetTempRet0F->setDoesNotThrow();
   SetTempRet0F->setDoesNotThrow();
 
@@ -942,13 +947,13 @@ bool WebAssemblyLowerEmscriptenEHSjLj::runOnModule(Module &M) {
     // Register __resumeException function
     FunctionType *ResumeFTy =
         FunctionType::get(IRB.getVoidTy(), IRB.getPtrTy(), false);
-    ResumeF = getEmscriptenFunction(ResumeFTy, "__resumeException", &M);
+    ResumeF = getFunction(ResumeFTy, "__resumeException", &M);
     ResumeF->addFnAttr(Attribute::NoReturn);
 
     // Register llvm_eh_typeid_for function
     FunctionType *EHTypeIDTy =
         FunctionType::get(IRB.getInt32Ty(), IRB.getPtrTy(), false);
-    EHTypeIDF = getEmscriptenFunction(EHTypeIDTy, "llvm_eh_typeid_for", &M);
+    EHTypeIDF = getFunction(EHTypeIDTy, "llvm_eh_typeid_for", &M);
   }
 
   // Functions that contains calls to setjmp but don't have other longjmpable
@@ -988,14 +993,14 @@ bool WebAssemblyLowerEmscriptenEHSjLj::runOnModule(Module &M) {
       // Register emscripten_longjmp function
       FunctionType *FTy = FunctionType::get(
           IRB.getVoidTy(), {getAddrIntType(&M), IRB.getInt32Ty()}, false);
-      EmLongjmpF = getEmscriptenFunction(FTy, "emscripten_longjmp", &M);
+      EmLongjmpF = getFunction(FTy, "emscripten_longjmp", &M);
       EmLongjmpF->addFnAttr(Attribute::NoReturn);
     } else { // EnableWasmSjLj
       Type *Int8PtrTy = IRB.getPtrTy();
       // Register __wasm_longjmp function, which calls __builtin_wasm_longjmp.
       FunctionType *FTy = FunctionType::get(
           IRB.getVoidTy(), {Int8PtrTy, IRB.getInt32Ty()}, false);
-      WasmLongjmpF = getEmscriptenFunction(FTy, "__wasm_longjmp", &M);
+      WasmLongjmpF = getFunction(FTy, "__wasm_longjmp", &M);
       WasmLongjmpF->addFnAttr(Attribute::NoReturn);
     }
 
@@ -1009,11 +1014,11 @@ bool WebAssemblyLowerEmscriptenEHSjLj::runOnModule(Module &M) {
       FunctionType *FTy = FunctionType::get(
           IRB.getVoidTy(), {SetjmpFTy->getParamType(0), Int32Ty, Int32PtrTy},
           false);
-      WasmSetjmpF = getEmscriptenFunction(FTy, "__wasm_setjmp", &M);
+      WasmSetjmpF = getFunction(FTy, "__wasm_setjmp", &M);
 
       // Register __wasm_setjmp_test function
       FTy = FunctionType::get(Int32Ty, {Int32PtrTy, Int32PtrTy}, false);
-      WasmSetjmpTestF = getEmscriptenFunction(FTy, "__wasm_setjmp_test", &M);
+      WasmSetjmpTestF = getFunction(FTy, "__wasm_setjmp_test", &M);
 
       // wasm.catch() will be lowered down to wasm 'catch' instruction in
       // instruction selection.