From: Sam Clegg <sbc@chromium.org>
Date: Mon, 4 Feb 2019 23:07:34 +0000 (+0000)
Subject: [WebAssembly] MC: Mark more function aliases as functions
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=dec46528529b6539b704dc15a4282b47196baa46;p=llvm

[WebAssembly] MC: Mark more function aliases as functions

Aliases of functions are now marked as function symbols even if
they are bitcast to some other other non-function type.
This is important for WebAssembly where object and function
symbols can't alias each other.

Fixes PR38866

Differential Revision: https://reviews.llvm.org/D57538

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@353109 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index be666add18b..619f706ec62 100644
--- a/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -1286,9 +1286,19 @@ void AsmPrinter::emitGlobalIndirectSymbol(Module &M,
   else
     assert(GIS.hasLocalLinkage() && "Invalid alias or ifunc linkage");
 
+  bool IsFunction = GIS.getType()->getPointerElementType()->isFunctionTy();
+
+  // Treat bitcasts of functions as functions also. This is important at least
+  // on WebAssembly where object and function addresses can't alias each other.
+  if (!IsFunction)
+    if (auto *CE = dyn_cast<ConstantExpr>(GIS.getIndirectSymbol()))
+      if (CE->getOpcode() == Instruction::BitCast)
+        IsFunction =
+          CE->getOperand(0)->getType()->getPointerElementType()->isFunctionTy();
+
   // Set the symbol type to function if the alias has a function type.
   // This affects codegen when the aliasee is not a function.
-  if (GIS.getType()->getPointerElementType()->isFunctionTy()) {
+  if (IsFunction) {
     OutStreamer->EmitSymbolAttribute(Name, MCSA_ELF_TypeFunction);
     if (isa<GlobalIFunc>(GIS))
       OutStreamer->EmitSymbolAttribute(Name, MCSA_ELF_TypeIndFunction);
diff --git a/test/MC/WebAssembly/function-alias.ll b/test/MC/WebAssembly/function-alias.ll
new file mode 100644
index 00000000000..d4ed06f2e4b
--- /dev/null
+++ b/test/MC/WebAssembly/function-alias.ll
@@ -0,0 +1,32 @@
+; RUN: llc -filetype=obj %s -o - | llvm-readobj -symbols | FileCheck %s
+
+target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128"
+target triple = "wasm32-unknown-unknown-wasm"
+
+@foo = alias i8, bitcast (i8* ()* @func to i8*)
+@bar = alias i8* (), i8* ()* @func
+
+define i8* @func() {
+  ret i8* @foo;
+}
+
+; CHECK:      Symbols [
+; CHECK-NEXT:   Symbol {
+; CHECK-NEXT:     Name: func
+; CHECK-NEXT:     Type: FUNCTION (0x0)
+; CHECK-NEXT:     Flags: 0x0
+; CHECK-NEXT:     ElementIndex: 0x0
+; CHECK-NEXT:   }
+; CHECK-NEXT:   Symbol {
+; CHECK-NEXT:     Name: foo
+; CHECK-NEXT:     Type: FUNCTION (0x0)
+; CHECK-NEXT:     Flags: 0x0
+; CHECK-NEXT:     ElementIndex: 0x0
+; CHECK-NEXT:   }
+; CHECK-NEXT:   Symbol {
+; CHECK-NEXT:     Name: bar
+; CHECK-NEXT:     Type: FUNCTION (0x0)
+; CHECK-NEXT:     Flags: 0x0
+; CHECK-NEXT:     ElementIndex: 0x0
+; CHECK-NEXT:   }
+; CHECK-NEXT: ]