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[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

llvm-svn: 353109
This commit is contained in:
Sam Clegg 2019-02-04 23:07:34 +00:00
parent 7c907bac6f
commit 313f9f54f5
2 changed files with 43 additions and 1 deletions
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12
llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
View File

@ -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);

32
llvm/test/MC/WebAssembly/function-alias.ll Normal file
View File

@ -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: ]