[llvm] e6112a5 - [AsmPrinter] Emit .weak directive for weak linkage on COFF for symbols without a comdat
Martin Storsjö via llvm-commits
llvm-commits at lists.llvm.org
Sat Mar 28 09:50:00 PDT 2020
Author: Martin Storsjö
Date: 2020-03-28T18:48:58+02:00
New Revision: e6112a56dde6db13ea29721077cb9d294d01b54d
URL: https://github.com/llvm/llvm-project/commit/e6112a56dde6db13ea29721077cb9d294d01b54d
DIFF: https://github.com/llvm/llvm-project/commit/e6112a56dde6db13ea29721077cb9d294d01b54d.diff
LOG: [AsmPrinter] Emit .weak directive for weak linkage on COFF for symbols without a comdat
MC already knows how to emulate the .weak directive (with its ELF
semantics; i.e., an undefined weak symbol resolves to 0, and a defined
weak symbol has lower link precedence than a strong symbol of the same
name) using COFF weak externals. Plumb this through the ASM printer too,
so that definitions marked with __attribute__((weak)) at the language
level (which gets translated to weak linkage at the IR level) have the
corresponding .weak directive emitted. Note that declarations marked
with __attribute__((weak)) at the language level (which translates to
extern_weak at the IR level) already have .weak directives emitted.
Weak*/linkonce* symbols without an associated comdat (in particular, ones
generated with __attribute__((weak)) in C/C++) were earlier emitted as
normal unique globals, as the comdat is required to provide the linkonce
semantics. This change makes sure they are emitted as .weak instead,
allowing other symbols to override them.
Rename the existing coff-weak.ll test to coff-linkonce.ll. I'm not
quite sure what that test covers, since the behavior being tested in it
(the emission of a one_only section) is just a result of passing
-function-sections to llc; the linkonce_odr makes no difference.
Add a new coff-weak.ll which tests the new directive emission.
Based on an previous patch by Shoaib Meenai.
Differential Revision: https://reviews.llvm.org/D44543
Added:
llvm/test/CodeGen/X86/coff-linkonce.ll
Modified:
llvm/include/llvm/MC/MCAsmInfo.h
llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
llvm/lib/MC/MCAsmInfoCOFF.cpp
llvm/test/CodeGen/X86/coff-weak.ll
llvm/test/CodeGen/X86/dllexport-x86_64.ll
llvm/test/CodeGen/X86/dllexport.ll
Removed:
################################################################################
diff --git a/llvm/include/llvm/MC/MCAsmInfo.h b/llvm/include/llvm/MC/MCAsmInfo.h
index b4f7c350739a..18f1637deb50 100644
--- a/llvm/include/llvm/MC/MCAsmInfo.h
+++ b/llvm/include/llvm/MC/MCAsmInfo.h
@@ -322,9 +322,10 @@ class MCAsmInfo {
/// symbol that can be hidden (unexported). Defaults to false.
bool HasWeakDefCanBeHiddenDirective = false;
- /// True if we have a .linkonce directive. This is used on cygwin/mingw.
+ /// True if we should mark symbols as global instead of weak, for
+ /// weak*/linkonce*, if the symbol has a comdat.
/// Defaults to false.
- bool HasLinkOnceDirective = false;
+ bool AvoidWeakIfComdat = false;
/// True if we have a .lglobl directive, which is used to emit the information
/// of a static symbol into the symbol table. Defaults to false.
@@ -590,7 +591,7 @@ class MCAsmInfo {
return HasWeakDefCanBeHiddenDirective;
}
- bool hasLinkOnceDirective() const { return HasLinkOnceDirective; }
+ bool avoidWeakIfComdat() const { return AvoidWeakIfComdat; }
bool hasDotLGloblDirective() const { return HasDotLGloblDirective; }
diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index a75f16b796d0..6d96205c615f 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -414,7 +414,7 @@ void AsmPrinter::emitLinkage(const GlobalValue *GV, MCSymbol *GVSym) const {
OutStreamer->emitSymbolAttribute(GVSym, MCSA_WeakDefinition);
else
OutStreamer->emitSymbolAttribute(GVSym, MCSA_WeakDefAutoPrivate);
- } else if (MAI->hasLinkOnceDirective()) {
+ } else if (MAI->avoidWeakIfComdat() && GV->hasComdat()) {
// .globl _foo
OutStreamer->emitSymbolAttribute(GVSym, MCSA_Global);
//NOTE: linkonce is handled by the section the symbol was assigned to.
diff --git a/llvm/lib/MC/MCAsmInfoCOFF.cpp b/llvm/lib/MC/MCAsmInfoCOFF.cpp
index 9f19d163f57b..d9971028649c 100644
--- a/llvm/lib/MC/MCAsmInfoCOFF.cpp
+++ b/llvm/lib/MC/MCAsmInfoCOFF.cpp
@@ -26,7 +26,7 @@ MCAsmInfoCOFF::MCAsmInfoCOFF() {
HasDotTypeDotSizeDirective = false;
HasSingleParameterDotFile = true;
WeakRefDirective = "\t.weak\t";
- HasLinkOnceDirective = true;
+ AvoidWeakIfComdat = true;
// Doesn't support visibility:
HiddenVisibilityAttr = HiddenDeclarationVisibilityAttr = MCSA_Invalid;
diff --git a/llvm/test/CodeGen/X86/coff-linkonce.ll b/llvm/test/CodeGen/X86/coff-linkonce.ll
new file mode 100644
index 000000000000..369750147f29
--- /dev/null
+++ b/llvm/test/CodeGen/X86/coff-linkonce.ll
@@ -0,0 +1,9 @@
+; RUN: llc -function-sections -o - %s | FileCheck %s
+
+target datalayout = "e-m:w-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc-windows-msvc"
+
+; CHECK: .section{{.*}}one_only
+define linkonce_odr void @foo() {
+ ret void
+}
diff --git a/llvm/test/CodeGen/X86/coff-weak.ll b/llvm/test/CodeGen/X86/coff-weak.ll
index 369750147f29..485e8f6a3847 100644
--- a/llvm/test/CodeGen/X86/coff-weak.ll
+++ b/llvm/test/CodeGen/X86/coff-weak.ll
@@ -1,9 +1,50 @@
-; RUN: llc -function-sections -o - %s | FileCheck %s
+; RUN: llc -mtriple=i686-windows-msvc -o - %s | FileCheck -check-prefix=X86 %s
+; RUN: llc -mtriple=x86_64-windows-msvc -o - %s | FileCheck -check-prefix=X64 %s
-target datalayout = "e-m:w-i64:64-f80:128-n8:16:32:64-S128"
-target triple = "x86_64-pc-windows-msvc"
+; X86: .weak _foo
+; X64: .weak foo
+define weak void @foo() {
+ ret void
+}
+
+; X86: .weak _bar
+; X64: .weak bar
+define weak_odr void @bar() {
+ ret void
+}
+
+; X86-NOT: .weak _bar_comdat
+; X64-NOT: .weak bar_comdat
+$bar_comdat = comdat any
+
+define weak_odr void @bar_comdat() comdat {
+ ret void
+}
+
+; X86: .weak _baz
+; X64: .weak baz
+define linkonce void @baz() {
+ ret void
+}
+
+; X86-NOT: .weak _baz_comdat
+; X64-NOT: .weak baz_comdat
+$baz_comdat = comdat any
+
+define linkonce void @baz_comdat() comdat {
+ ret void
+}
+
+; X86: .weak _quux
+; X64: .weak quux
+define linkonce_odr void @quux() {
+ ret void
+}
+
+; X86-NOT: .weak _quux_comdat
+; X64-NOT: .weak quux_comdat
+$quux_comdat = comdat any
-; CHECK: .section{{.*}}one_only
-define linkonce_odr void @foo() {
+define linkonce_odr void @quux_comdat() comdat {
ret void
}
diff --git a/llvm/test/CodeGen/X86/dllexport-x86_64.ll b/llvm/test/CodeGen/X86/dllexport-x86_64.ll
index a2825bc0458a..9f427f60e623 100644
--- a/llvm/test/CodeGen/X86/dllexport-x86_64.ll
+++ b/llvm/test/CodeGen/X86/dllexport-x86_64.ll
@@ -20,16 +20,20 @@ define dllexport void @f2() unnamed_addr {
}
; CHECK: .globl lnk1
-define linkonce_odr dllexport void @lnk1() {
+$lnk1 = comdat any
+
+define linkonce_odr dllexport void @lnk1() comdat {
ret void
}
; CHECK: .globl lnk2
-define linkonce_odr dllexport void @lnk2() alwaysinline {
+$lnk2 = comdat any
+
+define linkonce_odr dllexport void @lnk2() alwaysinline comdat {
ret void
}
-; CHECK: .globl weak1
+; CHECK: .weak weak1
define weak_odr dllexport void @weak1() {
ret void
}
@@ -46,14 +50,14 @@ define weak_odr dllexport void @weak1() {
; CHECK: .comm Var3
@Var3 = common dllexport global i32 0, align 4
-; CHECK: .globl WeakVar1
+; CHECK: .weak WeakVar1
@WeakVar1 = weak_odr dllexport global i32 1, align 4
-; CHECK: .globl WeakVar2
+; CHECK: .weak WeakVar2
@WeakVar2 = weak_odr dllexport unnamed_addr constant i32 1
; CHECK: .bss
-; CHECK: .globl WeakVar3
+; CHECK: .weak WeakVar3
@WeakVar3 = weak_odr dllexport global i32 0, align 4
diff --git a/llvm/test/CodeGen/X86/dllexport.ll b/llvm/test/CodeGen/X86/dllexport.ll
index 999733949ab2..f08395a8d3be 100644
--- a/llvm/test/CodeGen/X86/dllexport.ll
+++ b/llvm/test/CodeGen/X86/dllexport.ll
@@ -45,16 +45,20 @@ define dllexport x86_thiscallcc void @thisfun() nounwind {
}
; CHECK: .globl _lnk1
-define linkonce_odr dllexport void @lnk1() {
+$lnk1 = comdat any
+
+define linkonce_odr dllexport void @lnk1() comdat {
ret void
}
; CHECK: .globl _lnk2
-define linkonce_odr dllexport void @lnk2() alwaysinline {
+$lnk2 = comdat any
+
+define linkonce_odr dllexport void @lnk2() alwaysinline comdat {
ret void
}
-; CHECK: .globl _weak1
+; CHECK: .weak _weak1
define weak_odr dllexport void @weak1() {
ret void
}
@@ -71,10 +75,10 @@ define weak_odr dllexport void @weak1() {
; CHECK: .comm _Var3
@Var3 = common dllexport global i32 0, align 4
-; CHECK: .globl _WeakVar1
+; CHECK: .weak _WeakVar1
@WeakVar1 = weak_odr dllexport global i32 1, align 4
-; CHECK: .globl _WeakVar2
+; CHECK: .weak _WeakVar2
@WeakVar2 = weak_odr dllexport unnamed_addr constant i32 1
More information about the llvm-commits
mailing list