[patch] Adjust behavior of FDE cross-section relocs for targets that don't support abs-differences.

Modern versions of OSX/Darwin's ld (ld64 > 97.17) have an optimisation present that allows the back end to omit relocations (and replace them with an absolute difference) for FDE some text section refs.

This patch allows a backend to opt-in to this behaviour by setting "DwarfFDESymbolsUseAbsDiff".  At present, this is only enabled for modern x86 OSX ports.

test changes by David Fang.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198744 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 7 insertions, 0 deletions

diff --git a/include/llvm/MC/MCAsmInfo.h b/include/llvm/MC/MCAsmInfo.h
index a46c300bf2..0d1052be6d 100644
--- a/include/llvm/MC/MCAsmInfo.h
+++ b/include/llvm/MC/MCAsmInfo.h
@@ -292,6 +292,10 @@ namespace llvm {
     /// uses relocations for references to other .debug_* sections.
     bool DwarfUsesRelocationsAcrossSections;
 
+    /// DwarfFDESymbolsUseAbsDiff - true if DWARF FDE symbol reference
+    /// relocations should be replaced by an absolute difference.
+    bool DwarfFDESymbolsUseAbsDiff;
+
     /// DwarfRegNumForCFI - True if dwarf register numbers are printed
     /// instead of symbolic register names in .cfi_* directives.
     bool DwarfRegNumForCFI;  // Defaults to false;
@@ -513,6 +517,9 @@ namespace llvm {
     bool doesDwarfUseRelocationsAcrossSections() const {
       return DwarfUsesRelocationsAcrossSections;
     }
+    bool doDwarfFDESymbolsUseAbsDiff() const {
+      return DwarfFDESymbolsUseAbsDiff;
+    }
     bool useDwarfRegNumForCFI() const {
       return DwarfRegNumForCFI;
     }