[MC, COFF] Support link /incremental conditionally

Today, we always take into account the possibility that object files
produced by MC may be consumed by an incremental linker.  This results
in us initialing fields which vary with time (TimeDateStamp) which harms
hermetic builds (e.g. verifying a self-host went well) and produces
sub-optimal code because we cannot assume anything about the relative
position of functions within a section (call sites can get redirected
through incremental linker thunks).

Let's provide an MCTargetOption which controls this behavior so that we
can disable this functionality if we know a-priori that the build will
not rely on /incremental.

llvm-svn: 256203

2 files changed, 4 insertions, 2 deletions

diff --git a/llvm/lib/Target/X86/MCTargetDesc/X86MCTargetDesc.h b/llvm/lib/Target/X86/MCTargetDesc/X86MCTargetDesc.h
index 6221baba179..f8e4e70e53f 100644
--- a/llvm/lib/Target/X86/MCTargetDesc/X86MCTargetDesc.h
+++ b/llvm/lib/Target/X86/MCTargetDesc/X86MCTargetDesc.h
@@ -79,7 +79,7 @@ MCAsmBackend *createX86_64AsmBackend(const Target &T, const MCRegisterInfo &MRI,
 /// Takes ownership of \p AB and \p CE.
 MCStreamer *createX86WinCOFFStreamer(MCContext &C, MCAsmBackend &AB,
                                      raw_pwrite_stream &OS, MCCodeEmitter *CE,
-                                     bool RelaxAll);
+                                     bool RelaxAll, bool IncrementalLinkerCompatible);
 
 /// Construct an X86 Mach-O object writer.
 MCObjectWriter *createX86MachObjectWriter(raw_pwrite_stream &OS, bool Is64Bit,
diff --git a/llvm/lib/Target/X86/MCTargetDesc/X86WinCOFFStreamer.cpp b/llvm/lib/Target/X86/MCTargetDesc/X86WinCOFFStreamer.cpp
index 92f42b68ae5..d04511873b4 100644
--- a/llvm/lib/Target/X86/MCTargetDesc/X86WinCOFFStreamer.cpp
+++ b/llvm/lib/Target/X86/MCTargetDesc/X86WinCOFFStreamer.cpp
@@ -50,9 +50,11 @@ void X86WinCOFFStreamer::FinishImpl() {
 
 MCStreamer *llvm::createX86WinCOFFStreamer(MCContext &C, MCAsmBackend &AB,
                                            raw_pwrite_stream &OS,
-                                           MCCodeEmitter *CE, bool RelaxAll) {
+                                           MCCodeEmitter *CE, bool RelaxAll,
+                                           bool IncrementalLinkerCompatible) {
   X86WinCOFFStreamer *S = new X86WinCOFFStreamer(C, AB, CE, OS);
   S->getAssembler().setRelaxAll(RelaxAll);
+  S->getAssembler().setIncrementalLinkerCompatible(IncrementalLinkerCompatible);
   return S;
 }