From d9ffd4cb92c95806b05df2d9f9e2be5c27cfe7fd Mon Sep 17 00:00:00 2001
From: Dale Johannesen <dalej@apple.com>
Date: Wed, 26 Mar 2008 23:31:39 +0000
Subject: [PATCH] Fix a bug in Darwin EH:  FDE->CIE pointer must be
 relocatable.  Describe why .set is needed better.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@48848 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/llvm/Target/TargetAsmInfo.h | 11 +++++++++--
 lib/CodeGen/DwarfWriter.cpp         | 22 +++++++++-------------
 2 files changed, 18 insertions(+), 15 deletions(-)

diff --git a/include/llvm/Target/TargetAsmInfo.h b/include/llvm/Target/TargetAsmInfo.h
index 2f54696945d..7fd88b2eae9 100644
--- a/include/llvm/Target/TargetAsmInfo.h
+++ b/include/llvm/Target/TargetAsmInfo.h
@@ -65,8 +65,15 @@ namespace llvm {
     /// section on this target.  Null if this target doesn't support zerofill.
     const char *ZeroFillDirective;        // Default is null.
     
-    /// NeedsSet - True if target asm can't compute addresses on data
-    /// directives.
+    /// NeedsSet - True if target asm treats expressions in data directives
+    /// as linktime-relocatable.  For assembly-time computation, we need to
+    /// use a .set.  Thus:
+    /// .set w, x-y
+    /// .long w
+    /// is computed at assembly time, while
+    /// .long x-y
+    /// is relocated if the relative locations of x and y change at linktime.
+    /// We want both these things in different places.
     bool NeedsSet;                        // Defaults to false.
     
     /// MaxInstLength - This is the maximum possible length of an instruction,
diff --git a/lib/CodeGen/DwarfWriter.cpp b/lib/CodeGen/DwarfWriter.cpp
index dd7ba9cb888..e72ff07a9d7 100644
--- a/lib/CodeGen/DwarfWriter.cpp
+++ b/lib/CodeGen/DwarfWriter.cpp
@@ -925,19 +925,20 @@ public:
 
   void EmitSectionOffset(const char* Label, const char* Section,
                          unsigned LabelNumber, unsigned SectionNumber,
-                         bool IsSmall = false, bool isEH = false) {
+                         bool IsSmall = false, bool isEH = false,
+                         bool useSet = true) {
     bool printAbsolute = false;
-    if (TAI->needsSet()) {
+    if (isEH)
+      printAbsolute = TAI->isAbsoluteEHSectionOffsets();
+    else
+      printAbsolute = TAI->isAbsoluteDebugSectionOffsets();
+
+    if (TAI->needsSet() && useSet) {
       O << "\t.set\t";
       PrintLabelName("set", SetCounter, Flavor);
       O << ",";
       PrintLabelName(Label, LabelNumber);
 
-      if (isEH)
-        printAbsolute = TAI->isAbsoluteEHSectionOffsets();
-      else
-        printAbsolute = TAI->isAbsoluteDebugSectionOffsets();
-      
       if (!printAbsolute) {
         O << "-";
         PrintLabelName(Section, SectionNumber);
@@ -953,11 +954,6 @@ public:
         
       PrintLabelName(Label, LabelNumber);
 
-      if (isEH)
-        printAbsolute = TAI->isAbsoluteEHSectionOffsets();
-      else
-        printAbsolute = TAI->isAbsoluteDebugSectionOffsets();
-
       if (!printAbsolute) {
         O << "-";
         PrintLabelName(Section, SectionNumber);
@@ -2919,7 +2915,7 @@ private:
 
       EmitSectionOffset("eh_frame_begin", "eh_frame_common",
                         EHFrameInfo.Number, EHFrameInfo.PersonalityIndex,
-                        true, true);
+                        true, true, false);
       Asm->EOL("FDE CIE offset");
 
       EmitReference("eh_func_begin", EHFrameInfo.Number, true);