[PATCH] D137360: [Linker] Remove nocallback attribute while linking

[Gulfem Savrun Yeniceri via Phabricator via llvm-commits]

gulfem updated this revision to Diff 483387.
gulfem added a comment.

Drop a nocallback attribute when it is on a call-site


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D137360/new/

https://reviews.llvm.org/D137360

Files:
  llvm/lib/Linker/LinkModules.cpp
  llvm/test/Linker/Inputs/drop-attribute.ll
  llvm/test/Linker/drop-attribute.ll


Index: llvm/test/Linker/drop-attribute.ll
===================================================================
--- /dev/null
+++ llvm/test/Linker/drop-attribute.ll
@@ -0,0 +1,45 @@
+; RUN: llvm-link %s %p/Inputs/drop-attribute.ll -S -o - | FileCheck %s
+
+; Test case that checks that nocallback attribute is dropped during linking.
+
+; CHECK: define i32 @main()
+; CHECK-NEXT: entry:
+; CHECK-NEXT: call void @test_nocallback_definition()
+; Test that checks that nocallback attribute on a call-site is dropped.
+; CHECK-NEXT: call void @test_nocallback_call_site(){{$}}
+; CHECK-NEXT: %0 = call float @llvm.sqrt.f32(float undef)
+; CHECK-NEXT: call void @test_nocallback_declaration_definition_not_linked_in()
+; CHECK-NEXT: call void @test_nocallback_declaration_definition_linked_in()
+define i32 @main() {
+entry:
+  call void @test_nocallback_definition()
+  call void @test_nocallback_call_site() nocallback
+  call float @llvm.sqrt.f32(float undef)
+  call void @test_nocallback_declaration_definition_not_linked_in()
+  call void @test_nocallback_declaration_definition_linked_in()
+  ret i32 0
+}
+
+; Test that checks that nocallback attribute on a definition is dropped.
+; CHECK: define void @test_nocallback_definition()
+define void @test_nocallback_definition() nocallback {
+  ret void
+}
+
+; Test that checks that nocallback attribute on a declaration when a definition is linked in is dropped.
+; CHECK: declare void @test_nocallback_call_site(){{$}}
+declare void @test_nocallback_call_site()
+
+; Test that checks that nocallback attribute on an intrinsic is NOT dropped.
+; CHECK: ; Function Attrs: nocallback nofree nosync nounwind speculatable willreturn
+; CHECK-NEXT: declare float @llvm.sqrt.f32(float) #0
+declare float @llvm.sqrt.f32(float) nocallback
+
+; Test that checks that nocallback attribute on a declaration when a definition is not linked in is dropped.
+; CHECK: declare void @test_nocallback_declaration_definition_not_linked_in(){{$}}
+declare void @test_nocallback_declaration_definition_not_linked_in() nocallback
+
+; Test that checks that nocallback attribute on a declaration when a definition is linked in is dropped.
+declare void @test_nocallback_declaration_definition_linked_in() nocallback
+
+; CHECK: define void @test_nocallback_declaration_definition_linked_in()
Index: llvm/test/Linker/Inputs/drop-attribute.ll
===================================================================
--- /dev/null
+++ llvm/test/Linker/Inputs/drop-attribute.ll
@@ -0,0 +1,4 @@
+define void @test_nocallback_declaration_definition_linked_in() {
+entry:
+  ret void
+}
Index: llvm/lib/Linker/LinkModules.cpp
===================================================================
--- llvm/lib/Linker/LinkModules.cpp
+++ llvm/lib/Linker/LinkModules.cpp
@@ -15,6 +15,8 @@
 #include "llvm/ADT/SetVector.h"
 #include "llvm/IR/Comdat.h"
 #include "llvm/IR/GlobalValue.h"
+#include "llvm/IR/Instruction.h"
+#include "llvm/IR/Instructions.h"
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/IR/Module.h"
 #include "llvm/Linker/Linker.h"
@@ -379,6 +381,24 @@
        GV.hasAvailableExternallyLinkage()))
     return false;
 
+  // Drop nocallback attribute while linking, because nocallback attribute
+  // indicates that the function is only allowed to jump back into caller's
+  // module only by a return or an exception. When modules are linked, this
+  // property cannot be guaranteed anymore. For example, the function with
+  // nocallback attribute might call an imported function. When it's caller
+  // module and important function's module are linked together, the function
+  // with nocallback attribute now jumps back into its caller's module.
+  if (auto *F = dyn_cast<Function>(&GV)) {
+    if (!F->isIntrinsic())
+      F->removeFnAttr(llvm::Attribute::NoCallback);
+
+    // Drop nocallback attribute when it is on a call-site.
+    for (BasicBlock &BB : *F)
+      for (Instruction &I : BB)
+        if (CallInst *CI = dyn_cast<CallInst>(&I))
+          CI->removeFnAttr(Attribute::NoCallback);
+  }
+
   if (GV.isDeclaration())
     return false;
 


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