From ed1cb75099f89e02b0e4a2d90f1cf31572c8a9dd Mon Sep 17 00:00:00 2001
From: Derek Schuff <dschuff@google.com>
Date: Fri, 8 Dec 2017 00:39:54 +0000
Subject: [PATCH] Revert "[WebAssemby] Support main functions with alternate
 signatures."

This reverts commit 959e37e669b0c3cfad4cb9f1f7c9261ce9f5e9ae.
That commit doesn't handle the case where main is declared rather than defined,
in particular the even-more special case where main is a prototypeless
declaration (which is of course the one actually used by musl currently).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@320121 91177308-0d34-0410-b5e6-96231b3b80d8
---
 .../WebAssembly/WebAssemblyFixFunctionBitcasts.cpp | 46 +---------------------
 test/CodeGen/WebAssembly/main.ll                   | 18 ---------
 2 files changed, 1 insertion(+), 63 deletions(-)
 delete mode 100644 test/CodeGen/WebAssembly/main.ll

diff --git a/lib/Target/WebAssembly/WebAssemblyFixFunctionBitcasts.cpp b/lib/Target/WebAssembly/WebAssemblyFixFunctionBitcasts.cpp
index 4888bf3a747..f1d2c00d163 100644
--- a/lib/Target/WebAssembly/WebAssemblyFixFunctionBitcasts.cpp
+++ b/lib/Target/WebAssembly/WebAssemblyFixFunctionBitcasts.cpp
@@ -142,41 +142,11 @@ static Function *CreateWrapper(Function *F, FunctionType *Ty) {
 }
 
 bool FixFunctionBitcasts::runOnModule(Module &M) {
-  Function *Main = nullptr;
-  CallInst *CallMain = nullptr;
   SmallVector<std::pair<Use *, Function *>, 0> Uses;
   SmallPtrSet<Constant *, 2> ConstantBCs;
 
   // Collect all the places that need wrappers.
-  for (Function &F : M) {
-    FindUses(&F, F, Uses, ConstantBCs);
-
-    // If we have a "main" function, and its type isn't
-    // "int main(int argc, char *argv[])", create an artificial call with it
-    // bitcasted to that type so that we generate a wrapper for it, so that
-    // the C runtime can call it.
-    if (F.getName() == "main") {
-      Main = &F;
-      LLVMContext &C = M.getContext();
-      Type *MainArgTys[] = {
-        PointerType::get(Type::getInt8PtrTy(C), 0),
-        Type::getInt32Ty(C)
-      };
-      FunctionType *MainTy = FunctionType::get(Type::getInt32Ty(C), MainArgTys,
-                                               /*isVarArg=*/false);
-      if (F.getFunctionType() != MainTy) {
-        Value *Args[] = {
-          UndefValue::get(MainArgTys[0]),
-          UndefValue::get(MainArgTys[1])
-        };
-        Value *Casted = ConstantExpr::getBitCast(Main,
-                                                 PointerType::get(MainTy, 0));
-        CallMain = CallInst::Create(Casted, Args, "call_main");
-        Use *UseMain = &CallMain->getOperandUse(2);
-        Uses.push_back(std::make_pair(UseMain, &F));
-      }
-    }
-  }
+  for (Function &F : M) FindUses(&F, F, Uses, ConstantBCs);
 
   DenseMap<std::pair<Function *, FunctionType *>, Function *> Wrappers;
 
@@ -211,19 +181,5 @@ bool FixFunctionBitcasts::runOnModule(Module &M) {
       U->set(Wrapper);
   }
 
-  // If we created a wrapper for main, rename the wrapper so that it's the
-  // one that gets called from startup.
-  if (CallMain) {
-    Main->setName("__original_main");
-    Function *MainWrapper =
-        cast<Function>(CallMain->getCalledValue()->stripPointerCasts());
-    MainWrapper->setName("main");
-    MainWrapper->setLinkage(Main->getLinkage());
-    MainWrapper->setVisibility(Main->getVisibility());
-    Main->setLinkage(Function::PrivateLinkage);
-    Main->setVisibility(Function::DefaultVisibility);
-    delete CallMain;
-  }
-
   return true;
 }
diff --git a/test/CodeGen/WebAssembly/main.ll b/test/CodeGen/WebAssembly/main.ll
deleted file mode 100644
index 314dde28307..00000000000
--- a/test/CodeGen/WebAssembly/main.ll
+++ /dev/null
@@ -1,18 +0,0 @@
-; RUN: llc < %s -asm-verbose=false | FileCheck %s
-
-; Test main functions with alternate signatures.
-
-target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128"
-target triple = "wasm32-unknown-unknown-wasm"
-
-define void @main() {
-  ret void
-}
-
-; CHECK-LABEL: .L__original_main:
-; CHECK-NEXT: end_function
-
-; CHECK-LABEL: main:
-; CHECK-NEXT: .param i32, i32
-; CHECK-NEXT: .result i32
-; CHECK:      call .L__original_main@FUNCTION
-- 
2.11.0