[PATCH] D15969: [WebAssembly] Don't create a needless .note.GNU-stack section

[Phabricator via llvm-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rL257962: [WebAssembly] Don't create a needless .note.GNU-stack section (authored by djg).

Changed prior to commit:
  http://reviews.llvm.org/D15969?vs=45027&id=45048#toc

Repository:
  rL LLVM

http://reviews.llvm.org/D15969

Files:
  llvm/trunk/include/llvm/MC/MCAsmInfoELF.h
  llvm/trunk/lib/MC/MCAsmInfoELF.cpp
  llvm/trunk/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCAsmInfo.cpp
  llvm/trunk/test/CodeGen/WebAssembly/non-executable-stack.ll

Index: llvm/trunk/include/llvm/MC/MCAsmInfoELF.h
===================================================================
--- llvm/trunk/include/llvm/MC/MCAsmInfoELF.h
+++ llvm/trunk/include/llvm/MC/MCAsmInfoELF.h
@@ -18,6 +18,10 @@
   MCSection *getNonexecutableStackSection(MCContext &Ctx) const final;
 
 protected:
+  /// Targets which have non-executable stacks by default can set this to false
+  /// to disable the special section which requests a non-executable stack.
+  bool UsesNonexecutableStackSection;
+
   MCAsmInfoELF();
 };
 }
Index: llvm/trunk/test/CodeGen/WebAssembly/non-executable-stack.ll
===================================================================
--- llvm/trunk/test/CodeGen/WebAssembly/non-executable-stack.ll
+++ llvm/trunk/test/CodeGen/WebAssembly/non-executable-stack.ll
@@ -0,0 +1,9 @@
+; RUN: llc < %s -asm-verbose=false | FileCheck %s
+
+; Test that we don't emit anything declaring a non-executable stack,
+; because wasm's stack is always non-executable.
+
+target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128"
+target triple = "wasm32-unknown-unknown"
+
+; CHECK-NOT: .note.GNU-stack
Index: llvm/trunk/lib/MC/MCAsmInfoELF.cpp
===================================================================
--- llvm/trunk/lib/MC/MCAsmInfoELF.cpp
+++ llvm/trunk/lib/MC/MCAsmInfoELF.cpp
@@ -21,12 +21,15 @@
 void MCAsmInfoELF::anchor() { }
 
 MCSection *MCAsmInfoELF::getNonexecutableStackSection(MCContext &Ctx) const {
+  if (!UsesNonexecutableStackSection)
+    return nullptr;
   return Ctx.getELFSection(".note.GNU-stack", ELF::SHT_PROGBITS, 0);
 }
 
 MCAsmInfoELF::MCAsmInfoELF() {
   HasIdentDirective = true;
   WeakRefDirective = "\t.weak\t";
   PrivateGlobalPrefix = ".L";
   PrivateLabelPrefix = ".L";
+  UsesNonexecutableStackSection = true;
 }
Index: llvm/trunk/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCAsmInfo.cpp
===================================================================
--- llvm/trunk/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCAsmInfo.cpp
+++ llvm/trunk/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCAsmInfo.cpp
@@ -48,4 +48,7 @@
   ExceptionsType = ExceptionHandling::None;
 
   // TODO: UseIntegratedAssembler?
+
+  // WebAssembly's stack is never executable.
+  UsesNonexecutableStackSection = false;
 }


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