[PATCH] D12610: [dsymutil] Ensure PC offsets with within specified bit width

[Vedant Kumar via llvm-commits]

vsk created this revision.
vsk added a reviewer: friss.
vsk added a subscriber: llvm-commits.

Fixes a bug where dsymutil did not truncate negative PC offsets to the specified width. E.g: if "Low + LocPcOffset" is negative and AddressSize is 4, the bits 32..63 are high, which causes EmitIntValue to assertion-fail.

http://reviews.llvm.org/D12610

Files:
  include/llvm/Support/MathExtras.h
  tools/dsymutil/DwarfLinker.cpp

Index: tools/dsymutil/DwarfLinker.cpp
===================================================================
--- tools/dsymutil/DwarfLinker.cpp
+++ tools/dsymutil/DwarfLinker.cpp
@@ -34,6 +34,7 @@
 #include "llvm/Object/MachO.h"
 #include "llvm/Support/Dwarf.h"
 #include "llvm/Support/LEB128.h"
+#include "llvm/Support/MathExtras.h"
 #include "llvm/Support/TargetRegistry.h"
 #include "llvm/Target/TargetMachine.h"
 #include "llvm/Target/TargetOptions.h"
@@ -838,8 +839,10 @@
         Asm->OutStreamer->EmitIntValue(0, AddressSize);
         break;
       }
-      Asm->OutStreamer->EmitIntValue(Low + LocPcOffset, AddressSize);
-      Asm->OutStreamer->EmitIntValue(High + LocPcOffset, AddressSize);
+      Asm->OutStreamer->EmitIntValue(
+          llvm::Lo_Bits(Low + LocPcOffset, 8 * AddressSize), AddressSize);
+      Asm->OutStreamer->EmitIntValue(
+          llvm::Lo_Bits(High + LocPcOffset, 8 * AddressSize), AddressSize);
       uint64_t Length = Data.getU16(&Offset);
       Asm->OutStreamer->EmitIntValue(Length, 2);
       // Just copy the bytes over.
Index: include/llvm/Support/MathExtras.h
===================================================================
--- include/llvm/Support/MathExtras.h
+++ include/llvm/Support/MathExtras.h
@@ -252,6 +252,12 @@
   return static_cast<uint32_t>(Value);
 }
 
+/// Lo_Bits - This function returns the low \p Bits bits of Value.
+inline uint64_t Lo_Bits(uint64_t Value, unsigned Bits) {
+  assert(Bits <= 64);
+  return Value & (~0ULL >> (64 - Bits));
+}
+
 /// Make_64 - This functions makes a 64-bit integer from a high / low pair of
 ///           32-bit integers.
 inline uint64_t Make_64(uint32_t High, uint32_t Low) {


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