COFF: Allow the combined LTO object to define new symbols.

[pcc]

Summary

The LLVM code generator can sometimes synthesize symbols, such as SSE
constants, that are not visible via the LTOModule interface. Allow such
symbols so long as they have definitions.

[ruiu]

LGTM
2015/06/08 午後5:23 "Peter Collingbourne" <[e-mail]>:

Hi ruiu,

The LLVM code generator can sometimes synthesize symbols, such as SSE
constants, that are not visible via the LTOModule interface. Allow such
symbols so long as they have definitions.

http://reviews.llvm.org/D10331

Files:

COFF/SymbolTable.cpp
test/COFF/lto-new-symbol.ll

Index: COFF/SymbolTable.cpp

• COFF/SymbolTable.cpp

+++ COFF/SymbolTable.cpp
@@ -276,12 +276,18 @@

if (!Body->isExternal())
  continue;

• // Find an existing Symbol. We should not see any new symbols at

this point.

+ // Find an existing Symbol. We should not see any new undefined

symbols at

+ // this point.

StringRef Name = Body->getName();

• Symbol *Sym = Symtab[Name];

+ Symbol *&Sym = Symtab[Name];

Move this after "if".

if (!Sym) {

• llvm::errs() << "LTO: unexpected new symbol: " << Name << '\n';
• return make_error_code(LLDError::BrokenFile);

+ Sym = new (Alloc) Symbol(Body);
+ if (!isa<Defined>(Body)) {
+ llvm::errs() << "LTO: undefined symbol: " << Name << '\n';
+ return make_error_code(LLDError::BrokenFile);
+ }
+ Body->setBackref(Sym);
+ continue;

}
Body->setBackref(Sym);

Index: test/COFF/lto-new-symbol.ll

• /dev/null

+++ test/COFF/lto-new-symbol.ll
@@ -0,0 +1,16 @@
+; RUN: llvm-as -o %t.obj %s
+; RUN: lld -flavor link2 /out:%t.exe /entry:foo /subsystem:console %t.obj
+
+target datalayout = "e-m:w-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc-windows-msvc"
+
+define void @foo(<4 x i32>* %p, <4 x float>* %q, i1 %t) nounwind {
+entry:
+ br label %loop
+loop:
+ store <4 x i32><i32 1073741824, i32 1073741824, i32 1073741824, i32

1073741824>, <4 x i32>* %p

+ store <4 x float><float 2.0, float 2.0, float 2.0, float 2.0>, <4 x

float>* %q

+ br i1 %t, label %loop, label %ret
+ret:
+ ret void
+}

EMAIL PREFERENCES

http://reviews.llvm.org/settings/panel/emailpreferences/

[ruiu]

2015/06/08 午後5:23 "Peter Collingbourne" <[e-mail]>:

Hi ruiu,

The LLVM code generator can sometimes synthesize symbols, such as SSE
constants, that are not visible via the LTOModule interface. Allow such
symbols so long as they have definitions.

http://reviews.llvm.org/D10331

Files:

COFF/SymbolTable.cpp
test/COFF/lto-new-symbol.ll

Index: COFF/SymbolTable.cpp

• COFF/SymbolTable.cpp

+++ COFF/SymbolTable.cpp
@@ -276,12 +276,18 @@

if (!Body->isExternal())
  continue;

• // Find an existing Symbol. We should not see any new symbols at

this point.

+ // Find an existing Symbol. We should not see any new undefined

symbols at

+ // this point.

StringRef Name = Body->getName();

• Symbol *Sym = Symtab[Name];

+ Symbol *&Sym = Symtab[Name];

if (!Sym) {

• llvm::errs() << "LTO: unexpected new symbol: " << Name << '\n';
• return make_error_code(LLDError::BrokenFile);

+ Sym = new (Alloc) Symbol(Body);

I'm sorry, I was talking about this line.

+ if (!isa<Defined>(Body)) {
+ llvm::errs() << "LTO: undefined symbol: " << Name << '\n';
+ return make_error_code(LLDError::BrokenFile);
+ }
+ Body->setBackref(Sym);
+ continue;

}
Body->setBackref(Sym);

Index: test/COFF/lto-new-symbol.ll

• /dev/null

+++ test/COFF/lto-new-symbol.ll
@@ -0,0 +1,16 @@
+; RUN: llvm-as -o %t.obj %s
+; RUN: lld -flavor link2 /out:%t.exe /entry:foo /subsystem:console %t.obj
+
+target datalayout = "e-m:w-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc-windows-msvc"
+
+define void @foo(<4 x i32>* %p, <4 x float>* %q, i1 %t) nounwind {
+entry:
+ br label %loop
+loop:
+ store <4 x i32><i32 1073741824, i32 1073741824, i32 1073741824, i32

1073741824>, <4 x i32>* %p

+ store <4 x float><float 2.0, float 2.0, float 2.0, float 2.0>, <4 x

float>* %q

+ br i1 %t, label %loop, label %ret
+ret:
+ ret void
+}

EMAIL PREFERENCES

http://reviews.llvm.org/settings/panel/emailpreferences/

lld/trunk/COFF/SymbolTable.cpp

std::error_code SymbolTable::addCombinedLTOObject() {
   auto Obj = new ObjectFile(LTOObjectFile->getMemBufferRef());
   ObjectFiles.emplace_back(Obj);
   if (auto EC = Obj->parse())
     return EC;
   for (SymbolBody *Body : Obj->getSymbols()) {
     if (!Body->isExternal())
       continue;
 
-    // Find an existing Symbol. We should not see any new symbols at this point.
+    // Find an existing Symbol. We should not see any new undefined symbols at
+    // this point.
     StringRef Name = Body->getName();
-    Symbol *Sym = Symtab[Name];
+    Symbol *&Sym = Symtab[Name];
     if (!Sym) {
-      llvm::errs() << "LTO: unexpected new symbol: " << Name << '\n';
+      if (!isa<Defined>(Body)) {
+        llvm::errs() << "LTO: undefined symbol: " << Name << '\n';
         return make_error_code(LLDError::BrokenFile);
       }
+      Sym = new (Alloc) Symbol(Body);
+      Body->setBackref(Sym);
+      continue;
+    }
     Body->setBackref(Sym);
 
     if (isa<DefinedBitcode>(Sym->Body)) {
       // The symbol should now be defined.
       if (!isa<Defined>(Body)) {
         llvm::errs() << "LTO: undefined symbol: " << Name << '\n';
         return make_error_code(LLDError::BrokenFile);
       }

lld/trunk/test/COFF/lto-new-symbol.ll

+; RUN: llvm-as -o %t.obj %s
+; RUN: lld -flavor link2 /out:%t.exe /entry:foo /subsystem:console %t.obj
+
+target datalayout = "e-m:w-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc-windows-msvc"
+
+define void @foo(<4 x i32>* %p, <4 x float>* %q, i1 %t) nounwind {
+entry:
+  br label %loop
+loop:
+  store <4 x i32><i32 1073741824, i32 1073741824, i32 1073741824, i32 1073741824>, <4 x i32>* %p
+  store <4 x float><float 2.0, float 2.0, float 2.0, float 2.0>, <4 x float>* %q
+  br i1 %t, label %loop, label %ret
+ret:
+  ret void
+}