From e43ce1a958aa0c2da41961f77a4dbd7ff97487e0 Mon Sep 17 00:00:00 2001
From: Hsiangkai Wang <hsiangkai@gmail.com>
Date: Thu, 18 Jul 2019 14:47:34 +0000
Subject: [DebugInfo] Generate fixups as emitting DWARF .debug_frame/.eh_frame.

It is necessary to generate fixups in .debug_frame or .eh_frame as
relaxation is enabled due to the address delta may be changed after
relaxation.

There is an opcode with 6-bits data in debug frame encoding. So, we
also need 6-bits fixup types.

Differential Revision: https://reviews.llvm.org/D58335

llvm-svn: 366442
---
 llvm/lib/MC/MCDwarf.cpp | 40 ++++++++++++++++++++++++++++++++++------
 1 file changed, 34 insertions(+), 6 deletions(-)

(limited to 'llvm/lib/MC/MCDwarf.cpp')

diff --git a/llvm/lib/MC/MCDwarf.cpp b/llvm/lib/MC/MCDwarf.cpp
index aae6fdf9093..8456b3421bc 100644
--- a/llvm/lib/MC/MCDwarf.cpp
+++ b/llvm/lib/MC/MCDwarf.cpp
@@ -1897,26 +1897,54 @@ void MCDwarfFrameEmitter::EmitAdvanceLoc(MCObjectStreamer &Streamer,
 }
 
 void MCDwarfFrameEmitter::EncodeAdvanceLoc(MCContext &Context,
-                                           uint64_t AddrDelta,
-                                           raw_ostream &OS) {
+                                           uint64_t AddrDelta, raw_ostream &OS,
+                                           uint32_t *Offset, uint32_t *Size) {
   // Scale the address delta by the minimum instruction length.
   AddrDelta = ScaleAddrDelta(Context, AddrDelta);
 
+  bool WithFixups = false;
+  if (Offset && Size)
+    WithFixups = true;
+
   support::endianness E =
       Context.getAsmInfo()->isLittleEndian() ? support::little : support::big;
   if (AddrDelta == 0) {
+    if (WithFixups) {
+      *Offset = 0;
+      *Size = 0;
+    }
   } else if (isUIntN(6, AddrDelta)) {
     uint8_t Opcode = dwarf::DW_CFA_advance_loc | AddrDelta;
-    OS << Opcode;
+    if (WithFixups) {
+      *Offset = OS.tell();
+      *Size = 6;
+      OS << uint8_t(dwarf::DW_CFA_advance_loc);
+    } else
+      OS << Opcode;
   } else if (isUInt<8>(AddrDelta)) {
     OS << uint8_t(dwarf::DW_CFA_advance_loc1);
-    OS << uint8_t(AddrDelta);
+    if (WithFixups) {
+      *Offset = OS.tell();
+      *Size = 8;
+      OS.write_zeros(1);
+    } else
+      OS << uint8_t(AddrDelta);
   } else if (isUInt<16>(AddrDelta)) {
     OS << uint8_t(dwarf::DW_CFA_advance_loc2);
-    support::endian::write<uint16_t>(OS, AddrDelta, E);
+    if (WithFixups) {
+      *Offset = OS.tell();
+      *Size = 16;
+      OS.write_zeros(2);
+    } else
+      support::endian::write<uint16_t>(OS, AddrDelta, E);
   } else {
     assert(isUInt<32>(AddrDelta));
     OS << uint8_t(dwarf::DW_CFA_advance_loc4);
-    support::endian::write<uint32_t>(OS, AddrDelta, E);
+    if (WithFixups) {
+      *Offset = OS.tell();
+      *Size = 32;
+      OS.write_zeros(4);
+    } else
+      support::endian::write<uint32_t>(OS, AddrDelta, E);
   }
 }
-- 
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