[MC] Allow backends to decide relaxation for unresolved fixups.

Differential Revision: http://reviews.llvm.org/D8217

llvm-svn: 238659

Author: Colin LeMahieu

llvm/include/llvm/MC/MCAsmBackend.h

@@ -97,6 +97,12 @@ class MCAsmBackend {
 
   /// Target specific predicate for whether a given fixup requires the
   /// associated instruction to be relaxed.
+  virtual bool fixupNeedsRelaxationAdvanced(const MCFixup &Fixup, bool Resolved,
+                                            uint64_t Value,
+                                            const MCRelaxableFragment *DF,
+                                            const MCAsmLayout &Layout) const;
+
+  /// Simple predicate for targets where !Resolved implies requiring relaxation
   virtual bool fixupNeedsRelaxation(const MCFixup &Fixup, uint64_t Value,
                                     const MCRelaxableFragment *DF,
                                     const MCAsmLayout &Layout) const = 0;

llvm/lib/MC/MCAsmBackend.cpp

@@ -16,27 +16,33 @@ MCAsmBackend::MCAsmBackend() : HasDataInCodeSupport(false) {}
 
 MCAsmBackend::~MCAsmBackend() {}
 
-const MCFixupKindInfo &
-MCAsmBackend::getFixupKindInfo(MCFixupKind Kind) const {
+const MCFixupKindInfo &MCAsmBackend::getFixupKindInfo(MCFixupKind Kind) const {
   static const MCFixupKindInfo Builtins[] = {
-    { "FK_Data_1",  0,  8, 0 },
-    { "FK_Data_2",  0, 16, 0 },
-    { "FK_Data_4",  0, 32, 0 },
-    { "FK_Data_8",  0, 64, 0 },
-    { "FK_PCRel_1", 0,  8, MCFixupKindInfo::FKF_IsPCRel },
-    { "FK_PCRel_2", 0, 16, MCFixupKindInfo::FKF_IsPCRel },
-    { "FK_PCRel_4", 0, 32, MCFixupKindInfo::FKF_IsPCRel },
-    { "FK_PCRel_8", 0, 64, MCFixupKindInfo::FKF_IsPCRel },
-    { "FK_GPRel_1", 0,  8, 0 },
-    { "FK_GPRel_2", 0, 16, 0 },
-    { "FK_GPRel_4", 0, 32, 0 },
-    { "FK_GPRel_8", 0, 64, 0 },
-    { "FK_SecRel_1", 0,  8, 0 },
-    { "FK_SecRel_2", 0, 16, 0 },
-    { "FK_SecRel_4", 0, 32, 0 },
-    { "FK_SecRel_8", 0, 64, 0 }
-  };
+      {"FK_Data_1", 0, 8, 0},
+      {"FK_Data_2", 0, 16, 0},
+      {"FK_Data_4", 0, 32, 0},
+      {"FK_Data_8", 0, 64, 0},
+      {"FK_PCRel_1", 0, 8, MCFixupKindInfo::FKF_IsPCRel},
+      {"FK_PCRel_2", 0, 16, MCFixupKindInfo::FKF_IsPCRel},
+      {"FK_PCRel_4", 0, 32, MCFixupKindInfo::FKF_IsPCRel},
+      {"FK_PCRel_8", 0, 64, MCFixupKindInfo::FKF_IsPCRel},
+      {"FK_GPRel_1", 0, 8, 0},
+      {"FK_GPRel_2", 0, 16, 0},
+      {"FK_GPRel_4", 0, 32, 0},
+      {"FK_GPRel_8", 0, 64, 0},
+      {"FK_SecRel_1", 0, 8, 0},
+      {"FK_SecRel_2", 0, 16, 0},
+      {"FK_SecRel_4", 0, 32, 0},
+      {"FK_SecRel_8", 0, 64, 0}};
 
   assert((size_t)Kind <= array_lengthof(Builtins) && "Unknown fixup kind");
   return Builtins[Kind];
 }
+
+bool MCAsmBackend::fixupNeedsRelaxationAdvanced(
+    const MCFixup &Fixup, bool Resolved, uint64_t Value,
+    const MCRelaxableFragment *DF, const MCAsmLayout &Layout) const {
+  if (!Resolved)
+    return true;
+  return fixupNeedsRelaxation(Fixup, Value, DF, Layout);
+}

llvm/lib/MC/MCAssembler.cpp

@@ -895,13 +895,11 @@ void MCAssembler::Finish() {
 bool MCAssembler::fixupNeedsRelaxation(const MCFixup &Fixup,
                                        const MCRelaxableFragment *DF,
                                        const MCAsmLayout &Layout) const {
-  // If we cannot resolve the fixup value, it requires relaxation.
   MCValue Target;
   uint64_t Value;
-  if (!evaluateFixup(Layout, Fixup, DF, Target, Value))
-    return true;
-
-  return getBackend().fixupNeedsRelaxation(Fixup, Value, DF, Layout);
+  bool Resolved = evaluateFixup(Layout, Fixup, DF, Target, Value);
+  return getBackend().fixupNeedsRelaxationAdvanced(Fixup, Resolved, Value, DF,
+                                                   Layout);
 }
 
 bool MCAssembler::fragmentNeedsRelaxation(const MCRelaxableFragment *F,