Linker: Add flag to override linkage rules
Add a flag to lib/Linker (and `llvm-link`) to override linkage rules.
When set, the functions in the source module *always* replace those in
the destination module.
The `llvm-link` option is `-override=abc.ll`. All the "regular" modules
are loaded and linked first, followed by the `-override` modules. This
is useful for debugging workflows where some subset of the module (e.g.,
a single function) is extracted into a separate file where it's
optimized differently, before being merged back in.
Patch by Luqman Aden!
llvm-svn: 235473
diff --git a/llvm/include/llvm/Linker/Linker.h b/llvm/include/llvm/Linker/Linker.h
index 5ca815c..c43b90e 100644
--- a/llvm/include/llvm/Linker/Linker.h
+++ b/llvm/include/llvm/Linker/Linker.h
@@ -68,8 +68,10 @@
void deleteModule();
/// \brief Link \p Src into the composite. The source is destroyed.
+ /// Passing OverrideSymbols as true will have symbols from Src
+ /// shadow those in the Dest.
/// Returns true on error.
- bool linkInModule(Module *Src);
+ bool linkInModule(Module *Src, bool OverrideSymbols = false);
/// \brief Set the composite to the passed-in module.
void setModule(Module *Dst);
diff --git a/llvm/lib/Linker/LinkModules.cpp b/llvm/lib/Linker/LinkModules.cpp
index 1e0c5e9..65a02a7 100644
--- a/llvm/lib/Linker/LinkModules.cpp
+++ b/llvm/lib/Linker/LinkModules.cpp
@@ -424,12 +424,17 @@
DiagnosticHandlerFunction DiagnosticHandler;
+ /// For symbol clashes, prefer those from Src.
+ bool OverrideFromSrc;
+
public:
ModuleLinker(Module *dstM, Linker::IdentifiedStructTypeSet &Set, Module *srcM,
- DiagnosticHandlerFunction DiagnosticHandler)
+ DiagnosticHandlerFunction DiagnosticHandler,
+ bool OverrideFromSrc)
: DstM(dstM), SrcM(srcM), TypeMap(Set),
ValMaterializer(TypeMap, DstM, LazilyLinkGlobalValues),
- DiagnosticHandler(DiagnosticHandler) {}
+ DiagnosticHandler(DiagnosticHandler), OverrideFromSrc(OverrideFromSrc) {
+ }
bool run();
@@ -725,6 +730,12 @@
bool ModuleLinker::shouldLinkFromSource(bool &LinkFromSrc,
const GlobalValue &Dest,
const GlobalValue &Src) {
+ // Should we unconditionally use the Src?
+ if (OverrideFromSrc) {
+ LinkFromSrc = true;
+ return false;
+ }
+
// We always have to add Src if it has appending linkage.
if (Src.hasAppendingLinkage()) {
LinkFromSrc = true;
@@ -1071,8 +1082,9 @@
} else {
// If the GV is to be lazily linked, don't create it just yet.
// The ValueMaterializerTy will deal with creating it if it's used.
- if (!DGV && (SGV->hasLocalLinkage() || SGV->hasLinkOnceLinkage() ||
- SGV->hasAvailableExternallyLinkage())) {
+ if (!DGV && !OverrideFromSrc &&
+ (SGV->hasLocalLinkage() || SGV->hasLinkOnceLinkage() ||
+ SGV->hasAvailableExternallyLinkage())) {
DoNotLinkFromSource.insert(SGV);
return false;
}
@@ -1738,9 +1750,9 @@
Composite = nullptr;
}
-bool Linker::linkInModule(Module *Src) {
+bool Linker::linkInModule(Module *Src, bool OverrideSymbols) {
ModuleLinker TheLinker(Composite, IdentifiedStructTypes, Src,
- DiagnosticHandler);
+ DiagnosticHandler, OverrideSymbols);
bool RetCode = TheLinker.run();
Composite->dropTriviallyDeadConstantArrays();
return RetCode;
diff --git a/llvm/test/Linker/Inputs/override-different-linkage.ll b/llvm/test/Linker/Inputs/override-different-linkage.ll
new file mode 100644
index 0000000..bc15140
--- /dev/null
+++ b/llvm/test/Linker/Inputs/override-different-linkage.ll
@@ -0,0 +1,4 @@
+define linkonce i32 @foo(i32 %i) {
+entry:
+ ret i32 4
+}
diff --git a/llvm/test/Linker/Inputs/override-with-internal-linkage-2.ll b/llvm/test/Linker/Inputs/override-with-internal-linkage-2.ll
new file mode 100644
index 0000000..2f54a15
--- /dev/null
+++ b/llvm/test/Linker/Inputs/override-with-internal-linkage-2.ll
@@ -0,0 +1,4 @@
+define internal i32 @foo(i32 %i) {
+entry:
+ ret i32 4
+}
diff --git a/llvm/test/Linker/Inputs/override-with-internal-linkage.ll b/llvm/test/Linker/Inputs/override-with-internal-linkage.ll
new file mode 100644
index 0000000..6e06fa5
--- /dev/null
+++ b/llvm/test/Linker/Inputs/override-with-internal-linkage.ll
@@ -0,0 +1,4 @@
+define i32 @foo(i32 %i) {
+entry:
+ ret i32 4
+}
diff --git a/llvm/test/Linker/Inputs/override.ll b/llvm/test/Linker/Inputs/override.ll
new file mode 100644
index 0000000..6e06fa5
--- /dev/null
+++ b/llvm/test/Linker/Inputs/override.ll
@@ -0,0 +1,4 @@
+define i32 @foo(i32 %i) {
+entry:
+ ret i32 4
+}
diff --git a/llvm/test/Linker/override-different-linkage.ll b/llvm/test/Linker/override-different-linkage.ll
new file mode 100644
index 0000000..19961f2
--- /dev/null
+++ b/llvm/test/Linker/override-different-linkage.ll
@@ -0,0 +1,19 @@
+; RUN: llvm-link %s -override %S/Inputs/override-different-linkage.ll -S | FileCheck %s
+; RUN: llvm-link -override %S/Inputs/override-different-linkage.ll %s -S | FileCheck %s
+
+
+; CHECK-LABEL: define linkonce i32 @foo
+; CHECK-NEXT: entry:
+; CHECK-NEXT: ret i32 4
+define weak i32 @foo(i32 %i) {
+entry:
+ %add = add nsw i32 %i, %i
+ ret i32 %add
+}
+
+; Function Attrs: nounwind ssp uwtable
+define i32 @main(i32 %argc, i8** %argv) {
+entry:
+ %a = call i32 @foo(i32 2)
+ ret i32 %a
+}
diff --git a/llvm/test/Linker/override-with-internal-linkage-2.ll b/llvm/test/Linker/override-with-internal-linkage-2.ll
new file mode 100644
index 0000000..2de52a9
--- /dev/null
+++ b/llvm/test/Linker/override-with-internal-linkage-2.ll
@@ -0,0 +1,23 @@
+; RUN: llvm-link %s -override %S/Inputs/override-with-internal-linkage-2.ll -S | FileCheck %s
+; RUN: llvm-link -override %S/Inputs/override-with-internal-linkage-2.ll %s -S | FileCheck %s
+
+; CHECK-LABEL: define i32 @foo
+; CHECK-NEXT: entry:
+; CHECK-NEXT: %add = add nsw i32 %i, %i
+; CHECK-NEXT: ret i32 %add
+define i32 @foo(i32 %i) {
+entry:
+ %add = add nsw i32 %i, %i
+ ret i32 %add
+}
+
+; CHECK-LABEL: define internal i32 @foo1
+; CHECK-NEXT: entry:
+; CHECK-NEXT: ret i32 4
+
+; Function Attrs: nounwind ssp uwtable
+define i32 @main(i32 %argc, i8** %argv) {
+entry:
+ %a = call i32 @foo(i32 2)
+ ret i32 %a
+}
diff --git a/llvm/test/Linker/override-with-internal-linkage.ll b/llvm/test/Linker/override-with-internal-linkage.ll
new file mode 100644
index 0000000..f1163d3
--- /dev/null
+++ b/llvm/test/Linker/override-with-internal-linkage.ll
@@ -0,0 +1,23 @@
+; RUN: llvm-link %s -override %S/Inputs/override-with-internal-linkage.ll -S | FileCheck %s
+; RUN: llvm-link -override %S/Inputs/override-with-internal-linkage.ll %s -S | FileCheck %s
+
+; CHECK-LABEL: define internal i32 @foo2
+; CHECK-NEXT: entry:
+; CHECK-NEXT: %add = add nsw i32 %i, %i
+; CHECK-NEXT: ret i32 %add
+
+; CHECK-LABEL: define i32 @foo
+; CHECK-NEXT: entry:
+; CHECK-NEXT: ret i32 4
+define internal i32 @foo(i32 %i) {
+entry:
+ %add = add nsw i32 %i, %i
+ ret i32 %add
+}
+
+; Function Attrs: nounwind ssp uwtable
+define i32 @main(i32 %argc, i8** %argv) {
+entry:
+ %a = call i32 @foo(i32 2)
+ ret i32 %a
+}
diff --git a/llvm/test/Linker/override.ll b/llvm/test/Linker/override.ll
new file mode 100644
index 0000000..015cb4c
--- /dev/null
+++ b/llvm/test/Linker/override.ll
@@ -0,0 +1,19 @@
+; RUN: llvm-link %s -override %S/Inputs/override.ll -S | FileCheck %s
+; RUN: llvm-link -override %S/Inputs/override.ll %s -S | FileCheck %s
+
+
+; CHECK-LABEL: define i32 @foo
+; CHECK-NEXT: entry:
+; CHECK-NEXT: ret i32 4
+define i32 @foo(i32 %i) {
+entry:
+ %add = add nsw i32 %i, %i
+ ret i32 %add
+}
+
+; Function Attrs: nounwind ssp uwtable
+define i32 @main(i32 %argc, i8** %argv) {
+entry:
+ %a = call i32 @foo(i32 2)
+ ret i32 %a
+}
diff --git a/llvm/tools/llvm-link/llvm-link.cpp b/llvm/tools/llvm-link/llvm-link.cpp
index 9f287e4..369f347 100644
--- a/llvm/tools/llvm-link/llvm-link.cpp
+++ b/llvm/tools/llvm-link/llvm-link.cpp
@@ -38,6 +38,11 @@
InputFilenames(cl::Positional, cl::OneOrMore,
cl::desc("<input bitcode files>"));
+static cl::list<std::string> OverridingInputs(
+ "override", cl::ZeroOrMore, cl::value_desc("filename"),
+ cl::desc(
+ "input bitcode file which can override previously defined symbol(s)"));
+
static cl::opt<std::string>
OutputFilename("o", cl::desc("Override output filename"), cl::init("-"),
cl::value_desc("filename"));
@@ -108,7 +113,8 @@
}
static bool linkFiles(const char *argv0, LLVMContext &Context, Linker &L,
- const cl::list<std::string> &Files) {
+ const cl::list<std::string> &Files,
+ bool OverrideDuplicateSymbols) {
for (const auto &File : Files) {
std::unique_ptr<Module> M = loadFile(argv0, File, Context);
if (!M.get()) {
@@ -124,7 +130,7 @@
if (Verbose)
errs() << "Linking in '" << File << "'\n";
- if (L.linkInModule(M.get()))
+ if (L.linkInModule(M.get(), OverrideDuplicateSymbols))
return false;
}
@@ -143,7 +149,12 @@
auto Composite = make_unique<Module>("llvm-link", Context);
Linker L(Composite.get(), diagnosticHandler);
- if (!linkFiles(argv[0], Context, L, InputFilenames))
+ // First add all the regular input files
+ if (!linkFiles(argv[0], Context, L, InputFilenames, false))
+ return 1;
+
+ // Next the -override ones.
+ if (!linkFiles(argv[0], Context, L, OverridingInputs, true))
return 1;
if (DumpAsm) errs() << "Here's the assembly:\n" << *Composite;