[clang] [llvm] Revert "[Sema] Mark alias/ifunc targets used and consider mangled names" (PR #88919)

2024-04-16 Thread Fangrui Song via cfe-commits 

MaskRay wrote:

Thanks. 1c2afbae9af22b58190c10e3517242d01d89d612 is a codegen test of this 
involved llvm-libc pattern which would also catch the bug.

https://github.com/llvm/llvm-project/pull/88919
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[clang] [llvm] Revert "[Sema] Mark alias/ifunc targets used and consider mangled names" (PR #88919)

2024-04-16 Thread via cfe-commits 

llvmbot wrote:




@llvm/pr-subscribers-clang

Author: Mehdi Amini (joker-eph)


Changes

Reverts llvm/llvm-project#87130

Bot is broken with clang crash: 
https://lab.llvm.org/buildbot/#/builders/272/builds/14063/steps/6/logs/stdio



---
Full diff: https://github.com/llvm/llvm-project/pull/88919.diff


6 Files Affected:

- (modified) clang/lib/Sema/CMakeLists.txt (-1) 
- (modified) clang/lib/Sema/SemaDeclAttr.cpp (+11-33) 
- (modified) clang/test/AST/ast-dump-attr-json.cpp (-1) 
- (modified) clang/test/Sema/alias-unused-win.cpp (+1-1) 
- (modified) clang/test/Sema/alias-unused.cpp (+7-9) 
- (modified) utils/bazel/llvm-project-overlay/clang/BUILD.bazel (-1) 


``diff
diff --git a/clang/lib/Sema/CMakeLists.txt b/clang/lib/Sema/CMakeLists.txt
index a96439df664228..ab3b813a9ccd97 100644
--- a/clang/lib/Sema/CMakeLists.txt
+++ b/clang/lib/Sema/CMakeLists.txt
@@ -1,6 +1,5 @@
 set(LLVM_LINK_COMPONENTS
   Core
-  Demangle
   FrontendHLSL
   FrontendOpenMP
   MC
diff --git a/clang/lib/Sema/SemaDeclAttr.cpp b/clang/lib/Sema/SemaDeclAttr.cpp
index d26f130b5774ce..b7b1fbc625a150 100644
--- a/clang/lib/Sema/SemaDeclAttr.cpp
+++ b/clang/lib/Sema/SemaDeclAttr.cpp
@@ -45,7 +45,6 @@
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/STLForwardCompat.h"
 #include "llvm/ADT/StringExtras.h"
-#include "llvm/Demangle/Demangle.h"
 #include "llvm/IR/Assumptions.h"
 #include "llvm/MC/MCSectionMachO.h"
 #include "llvm/Support/Error.h"
@@ -1984,36 +1983,6 @@ static void handleWeakRefAttr(Sema , Decl *D, const 
ParsedAttr ) {
   D->addAttr(::new (S.Context) WeakRefAttr(S.Context, AL));
 }
 
-// Mark alias/ifunc target as used. Due to name mangling, we look up the
-// demangled name ignoring parameters (not supported by microsoftDemangle
-// https://github.com/llvm/llvm-project/issues/88825). This should handle the
-// majority of use cases while leaving namespace scope names unmarked.
-static void markUsedForAliasOrIfunc(Sema , Decl *D, const ParsedAttr ,
-StringRef Str) {
-  std::unique_ptr Demangled;
-  if (S.getASTContext().getCXXABIKind() != TargetCXXABI::Microsoft)
-Demangled.reset(llvm::itaniumDemangle(Str, /*ParseParams=*/false));
-  std::unique_ptr MC(S.Context.createMangleContext());
-  SmallString<256> Name;
-
-  const DeclarationNameInfo Target(
-  (Demangled ? Demangled.get() : Str), AL.getLoc());
-  LookupResult LR(S, Target, Sema::LookupOrdinaryName);
-  if (S.LookupName(LR, S.TUScope)) {
-for (NamedDecl *ND : LR) {
-  if (MC->shouldMangleDeclName(ND)) {
-llvm::raw_svector_ostream Out(Name);
-Name.clear();
-MC->mangleName(GlobalDecl(ND), Out);
-  } else {
-Name = ND->getIdentifier()->getName();
-  }
-  if (Name == Str)
-ND->markUsed(S.Context);
-}
-  }
-}
-
 static void handleIFuncAttr(Sema , Decl *D, const ParsedAttr ) {
   StringRef Str;
   if (!S.checkStringLiteralArgumentAttr(AL, 0, Str))
@@ -2026,7 +1995,6 @@ static void handleIFuncAttr(Sema , Decl *D, const 
ParsedAttr ) {
 return;
   }
 
-  markUsedForAliasOrIfunc(S, D, AL, Str);
   D->addAttr(::new (S.Context) IFuncAttr(S.Context, AL, Str));
 }
 
@@ -2061,7 +2029,17 @@ static void handleAliasAttr(Sema , Decl *D, const 
ParsedAttr ) {
 }
   }
 
-  markUsedForAliasOrIfunc(S, D, AL, Str);
+  // Mark target used to prevent unneeded-internal-declaration warnings.
+  if (!S.LangOpts.CPlusPlus) {
+// FIXME: demangle Str for C++, as the attribute refers to the mangled
+// linkage name, not the pre-mangled identifier.
+const DeclarationNameInfo target((Str), AL.getLoc());
+LookupResult LR(S, target, Sema::LookupOrdinaryName);
+if (S.LookupQualifiedName(LR, S.getCurLexicalContext()))
+  for (NamedDecl *ND : LR)
+ND->markUsed(S.Context);
+  }
+
   D->addAttr(::new (S.Context) AliasAttr(S.Context, AL, Str));
 }
 
diff --git a/clang/test/AST/ast-dump-attr-json.cpp 
b/clang/test/AST/ast-dump-attr-json.cpp
index 883e584bfedf07..051c2956abfdf7 100644
--- a/clang/test/AST/ast-dump-attr-json.cpp
+++ b/clang/test/AST/ast-dump-attr-json.cpp
@@ -46,7 +46,6 @@ __thread __attribute__ ((tls_model ("local-exec"))) int 
tls_model_var;
 // CHECK-NEXT:"tokLen": 11
 // CHECK-NEXT:   }
 // CHECK-NEXT:  },
-// CHECK-NEXT:  "isUsed": true,
 // CHECK-NEXT:  "name": "global_decl",
 // CHECK-NEXT:  "mangledName": "global_decl",
 // CHECK-NEXT:  "type": {
diff --git a/clang/test/Sema/alias-unused-win.cpp 
b/clang/test/Sema/alias-unused-win.cpp
index 97d57a3bbd1e31..47c96d41175179 100644
--- a/clang/test/Sema/alias-unused-win.cpp
+++ b/clang/test/Sema/alias-unused-win.cpp
@@ -7,7 +7,7 @@ extern "C" {
 static int f(void) { return 42; } // cxx-warning{{unused function 'f'}}
 int g(void) __attribute__((alias("f")));
 
-static int foo [] = { 42, 0xDEAD };
+static int foo [] = { 42, 0xDEAD }; // cxx-warning{{variable 'foo' is not 
needed and will not be emitted}}
 extern typeof(foo) bar __attribute__((unused, alias("foo")));
 
 static int

[clang] [llvm] Revert "[Sema] Mark alias/ifunc targets used and consider mangled names" (PR #88919)

2024-04-16 Thread Mehdi Amini via cfe-commits 

https://github.com/joker-eph closed 
https://github.com/llvm/llvm-project/pull/88919
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[clang] [llvm] Revert "[Sema] Mark alias/ifunc targets used and consider mangled names" (PR #88919)

2024-04-16 Thread Mehdi Amini via cfe-commits 

https://github.com/joker-eph created 
https://github.com/llvm/llvm-project/pull/88919

Reverts llvm/llvm-project#87130

Bot is broken with clang crash: 
https://lab.llvm.org/buildbot/#/builders/272/builds/14063/steps/6/logs/stdio



>From 271a8c2e5c8f57ab5d37f6056713dab530424470 Mon Sep 17 00:00:00 2001
From: Mehdi Amini 
Date: Tue, 16 Apr 2024 17:44:12 +0200
Subject: [PATCH] Revert "[Sema] Mark alias/ifunc targets used and consider
 mangled names"

This reverts commit 2ac562ab784c6bf04e6d3026c567d3552a735668.
---
 clang/lib/Sema/CMakeLists.txt |  1 -
 clang/lib/Sema/SemaDeclAttr.cpp   | 44 +--
 clang/test/AST/ast-dump-attr-json.cpp |  1 -
 clang/test/Sema/alias-unused-win.cpp  |  2 +-
 clang/test/Sema/alias-unused.cpp  | 16 +++
 .../llvm-project-overlay/clang/BUILD.bazel|  1 -
 6 files changed, 19 insertions(+), 46 deletions(-)

diff --git a/clang/lib/Sema/CMakeLists.txt b/clang/lib/Sema/CMakeLists.txt
index a96439df664228..ab3b813a9ccd97 100644
--- a/clang/lib/Sema/CMakeLists.txt
+++ b/clang/lib/Sema/CMakeLists.txt
@@ -1,6 +1,5 @@
 set(LLVM_LINK_COMPONENTS
   Core
-  Demangle
   FrontendHLSL
   FrontendOpenMP
   MC
diff --git a/clang/lib/Sema/SemaDeclAttr.cpp b/clang/lib/Sema/SemaDeclAttr.cpp
index d26f130b5774ce..b7b1fbc625a150 100644
--- a/clang/lib/Sema/SemaDeclAttr.cpp
+++ b/clang/lib/Sema/SemaDeclAttr.cpp
@@ -45,7 +45,6 @@
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/STLForwardCompat.h"
 #include "llvm/ADT/StringExtras.h"
-#include "llvm/Demangle/Demangle.h"
 #include "llvm/IR/Assumptions.h"
 #include "llvm/MC/MCSectionMachO.h"
 #include "llvm/Support/Error.h"
@@ -1984,36 +1983,6 @@ static void handleWeakRefAttr(Sema , Decl *D, const 
ParsedAttr ) {
   D->addAttr(::new (S.Context) WeakRefAttr(S.Context, AL));
 }
 
-// Mark alias/ifunc target as used. Due to name mangling, we look up the
-// demangled name ignoring parameters (not supported by microsoftDemangle
-// https://github.com/llvm/llvm-project/issues/88825). This should handle the
-// majority of use cases while leaving namespace scope names unmarked.
-static void markUsedForAliasOrIfunc(Sema , Decl *D, const ParsedAttr ,
-StringRef Str) {
-  std::unique_ptr Demangled;
-  if (S.getASTContext().getCXXABIKind() != TargetCXXABI::Microsoft)
-Demangled.reset(llvm::itaniumDemangle(Str, /*ParseParams=*/false));
-  std::unique_ptr MC(S.Context.createMangleContext());
-  SmallString<256> Name;
-
-  const DeclarationNameInfo Target(
-  (Demangled ? Demangled.get() : Str), AL.getLoc());
-  LookupResult LR(S, Target, Sema::LookupOrdinaryName);
-  if (S.LookupName(LR, S.TUScope)) {
-for (NamedDecl *ND : LR) {
-  if (MC->shouldMangleDeclName(ND)) {
-llvm::raw_svector_ostream Out(Name);
-Name.clear();
-MC->mangleName(GlobalDecl(ND), Out);
-  } else {
-Name = ND->getIdentifier()->getName();
-  }
-  if (Name == Str)
-ND->markUsed(S.Context);
-}
-  }
-}
-
 static void handleIFuncAttr(Sema , Decl *D, const ParsedAttr ) {
   StringRef Str;
   if (!S.checkStringLiteralArgumentAttr(AL, 0, Str))
@@ -2026,7 +1995,6 @@ static void handleIFuncAttr(Sema , Decl *D, const 
ParsedAttr ) {
 return;
   }
 
-  markUsedForAliasOrIfunc(S, D, AL, Str);
   D->addAttr(::new (S.Context) IFuncAttr(S.Context, AL, Str));
 }
 
@@ -2061,7 +2029,17 @@ static void handleAliasAttr(Sema , Decl *D, const 
ParsedAttr ) {
 }
   }
 
-  markUsedForAliasOrIfunc(S, D, AL, Str);
+  // Mark target used to prevent unneeded-internal-declaration warnings.
+  if (!S.LangOpts.CPlusPlus) {
+// FIXME: demangle Str for C++, as the attribute refers to the mangled
+// linkage name, not the pre-mangled identifier.
+const DeclarationNameInfo target((Str), AL.getLoc());
+LookupResult LR(S, target, Sema::LookupOrdinaryName);
+if (S.LookupQualifiedName(LR, S.getCurLexicalContext()))
+  for (NamedDecl *ND : LR)
+ND->markUsed(S.Context);
+  }
+
   D->addAttr(::new (S.Context) AliasAttr(S.Context, AL, Str));
 }
 
diff --git a/clang/test/AST/ast-dump-attr-json.cpp 
b/clang/test/AST/ast-dump-attr-json.cpp
index 883e584bfedf07..051c2956abfdf7 100644
--- a/clang/test/AST/ast-dump-attr-json.cpp
+++ b/clang/test/AST/ast-dump-attr-json.cpp
@@ -46,7 +46,6 @@ __thread __attribute__ ((tls_model ("local-exec"))) int 
tls_model_var;
 // CHECK-NEXT:"tokLen": 11
 // CHECK-NEXT:   }
 // CHECK-NEXT:  },
-// CHECK-NEXT:  "isUsed": true,
 // CHECK-NEXT:  "name": "global_decl",
 // CHECK-NEXT:  "mangledName": "global_decl",
 // CHECK-NEXT:  "type": {
diff --git a/clang/test/Sema/alias-unused-win.cpp 
b/clang/test/Sema/alias-unused-win.cpp
index 97d57a3bbd1e31..47c96d41175179 100644
--- a/clang/test/Sema/alias-unused-win.cpp
+++ b/clang/test/Sema/alias-unused-win.cpp
@@ -7,7 +7,7 @@ extern "C" {
 static int f(void) { return 42; } // cxx-warning{{unused function 'f'}}
 int g(void)