Revert "[PPC64] Add split - stack support."

This reverts commit https://reviews.llvm.org/rL344544, which causes failures on
a undefined behaviour sanitizer bot -->
lld/ELF/Arch/PPC64.cpp:849:35: runtime error: left shift of negative value -1

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@344551 91177308-0d34-0410-b5e6-96231b3b80d8

Author: Sean Fertile

ELF/Arch/PPC64.cpp

@@ -120,9 +120,6 @@ class PPC64 final : public TargetInfo {
   void relaxTlsGdToLe(uint8_t *Loc, RelType Type, uint64_t Val) const override;
   void relaxTlsLdToLe(uint8_t *Loc, RelType Type, uint64_t Val) const override;
   void relaxTlsIeToLe(uint8_t *Loc, RelType Type, uint64_t Val) const override;
-
-  bool adjustPrologueForCrossSplitStack(uint8_t *Loc, uint8_t *End,
-                                        uint8_t StOther) const override;
 };
 } // namespace
 
@@ -216,8 +213,6 @@ PPC64::PPC64() {
 
   TlsGotRel = R_PPC64_TPREL64;
 
-  NeedsMoreStackNonSplit = false;
-
   // We need 64K pages (at least under glibc/Linux, the loader won't
   // set different permissions on a finer granularity than that).
   DefaultMaxPageSize = 65536;
@@ -766,115 +761,7 @@ void PPC64::relaxTlsGdToIe(uint8_t *Loc, RelType Type, uint64_t Val) const {
   }
 }
 
-// The prologue for a split-stack function is expected to look roughly
-// like this:
-//    .Lglobal_entry_point:
-//      # TOC pointer initalization.
-//      ...
-//    .Llocal_entry_point:
-//      # load the __private_ss member of the threads tcbhead.
-//      ld r0,-0x7000-64(r13)
-//      # subtract the functions stack size from the stack pointer.
-//      addis r12, r1, ha(-stack-frame size)
-//      addi  r12, r12, l(-stack-frame size)
-//      # compare needed to actual and branch to allocate_more_stack if more
-//      # space is needed, otherwise fallthrough to 'normal' function body.
-//      cmpld cr7,r12,r0
-//      blt- .Lallocate_more_stack
-//
-// -) The allocate_more_stack block might be placed after the split-stack
-//    prologue and the `blt-` replaced with a `bge+ .Lnormal_func_body`
-//    instead.
-// -) If either the addis or addi is not needed due to the stack size being
-//    smaller then 32K or a multiple of 64K they will be replaced with a nop,
-//    but there will always be 2 instructions the linker can overwrite for the
-//    adjusted stack size.
-//
-// The linkers job here is to increase the stack size used in the addis/addi
-// pair by split-stack-size-adjust.
-// addis r12, r1, ha(-stack-frame size - split-stack-adjust-size)
-// addi  r12, r12, l(-stack-frame size - split-stack-adjust-size)
-bool PPC64::adjustPrologueForCrossSplitStack(uint8_t *Loc, uint8_t *End,
-                                             uint8_t StOther) const {
-  // If the caller has a global entry point adjust the buffer past it. The start
-  // of the split-stack prologue will be at the local entry point.
-  Loc += getPPC64GlobalEntryToLocalEntryOffset(StOther);
-
-  // At the very least we expect to see a load of some split-stack data from the
-  // tcb, and 2 instructions that calculate the ending stack address this
-  // function will require. If there is not enough room for at least 3
-  // instructions it can't be a split-stack prologue.
-  if (Loc + 12 >= End)
-    return false;
-
-  // First instruction must be `ld r0, -0x7000-64(r13)`
-  if (read32(Loc) != 0xe80d8fc0)
-    return false;
-
-  int16_t HiImm = 0;
-  int16_t LoImm = 0;
-  // First instruction can be either an addis if the frame size is larger then
-  // 32K, or an addi if the size is less then 32K.
-  int32_t FirstInstr = read32(Loc + 4);
-  if (getPrimaryOpCode(FirstInstr) == 15) {
-    HiImm = FirstInstr & 0xFFFF;
-  } else if (getPrimaryOpCode(FirstInstr) == 14) {
-    LoImm = FirstInstr & 0xFFFF;
-  } else {
-    return false;
-  }
-
-  // Second instruction is either an addi or a nop. If the first instruction was
-  // an addi then LoImm is set and the second instruction must be a nop.
-  uint32_t SecondInstr = read32(Loc + 8);
-  if (!LoImm && getPrimaryOpCode(SecondInstr) == 14) {
-    LoImm = SecondInstr & 0xFFFF;
-  } else if (SecondInstr != 0x60000000) {
-    return false;
-  }
-
-  // The register operands of the first instruction should be the stack-pointer
-  // (r1) as the input (RA) and r12 as the output (RT). If the second
-  // instruction is not a nop, then it should use r12 as both input and output.
-  auto CheckRegOperands =
-      [](uint32_t Instr, uint8_t ExpectedRT, uint8_t ExpectedRA) {
-        return ((Instr & 0x3E00000) >> 21 == ExpectedRT) &&
-               ((Instr & 0x1F0000) >> 16  == ExpectedRA);
-      };
-  if (!CheckRegOperands(FirstInstr, 12, 1))
-    return false;
-  if (SecondInstr != 0x60000000 && !CheckRegOperands(SecondInstr, 12, 12))
-    return false;
-
-  int32_t StackFrameSize = (HiImm << 16) + LoImm;
-  // Check that the adjusted size doesn't overflow what we can represent with 2
-  // instructions.
-  if (StackFrameSize < -2147483648 + Config->SplitStackAdjustSize) {
-    error(getErrorLocation(Loc) + "split-stack prologue adjustment overflows");
-    return false;
-  }
-
-  int32_t AdjustedStackFrameSize =
-      StackFrameSize - Config->SplitStackAdjustSize;
-
-  LoImm = AdjustedStackFrameSize & 0xFFFF;
-  HiImm = (AdjustedStackFrameSize + 0x8000) >> 16;
-  if (HiImm) {
-    write32(Loc + 4, 0x3D810000 | (uint16_t)HiImm);
-    // If the low immediate is zero the second instruction will be a nop.
-    SecondInstr =
-        LoImm ? 0x398C0000 | (uint16_t)LoImm : 0x60000000;
-    write32(Loc + 8, SecondInstr);
-  } else {
-    // addi r12, r1, imm
-    write32(Loc + 4, (0x39810000) | (uint16_t)LoImm);
-    write32(Loc + 8, 0x60000000);
-  }
-
-  return true;
-}
-
 TargetInfo *elf::getPPC64TargetInfo() {
   static PPC64 Target;
   return &Target;
-  }
+}

ELF/Arch/X86_64.cpp

@@ -43,8 +43,8 @@ template <class ELFT> class X86_64 : public TargetInfo {
   void relaxTlsGdToLe(uint8_t *Loc, RelType Type, uint64_t Val) const override;
   void relaxTlsIeToLe(uint8_t *Loc, RelType Type, uint64_t Val) const override;
   void relaxTlsLdToLe(uint8_t *Loc, RelType Type, uint64_t Val) const override;
-  bool adjustPrologueForCrossSplitStack(uint8_t *Loc, uint8_t *End,
-                                        uint8_t StOther) const override;
+  bool adjustPrologueForCrossSplitStack(uint8_t *Loc,
+                                        uint8_t *End) const override;
 
 private:
   void relaxGotNoPic(uint8_t *Loc, uint64_t Val, uint8_t Op,
@@ -482,8 +482,7 @@ namespace {
 // B) Or a load of a stack pointer offset with an lea to r10 or r11.
 template <>
 bool X86_64<ELF64LE>::adjustPrologueForCrossSplitStack(uint8_t *Loc,
-                                                       uint8_t *End,
-                                                       uint8_t StOther) const {
+                                                       uint8_t *End) const {
   if (Loc + 8 >= End)
     return false;
 
@@ -510,8 +509,7 @@ bool X86_64<ELF64LE>::adjustPrologueForCrossSplitStack(uint8_t *Loc,
 
 template <>
 bool X86_64<ELF32LE>::adjustPrologueForCrossSplitStack(uint8_t *Loc,
-                                                       uint8_t *End,
-                                                       uint8_t StOther) const {
+                                                       uint8_t *End) const {
   llvm_unreachable("Target doesn't support split stacks.");
 }
 

ELF/Config.h

@@ -217,7 +217,6 @@ struct Configuration {
   unsigned LTOO;
   unsigned Optimize;
   unsigned ThinLTOJobs;
-  int32_t SplitStackAdjustSize;
 
   // The following config options do not directly correspond to any
   // particualr command line options.

ELF/Driver.cpp

@@ -829,7 +829,6 @@ void LinkerDriver::readConfigs(opt::InputArgList &Args) {
   Config->SingleRoRx = Args.hasArg(OPT_no_rosegment);
   Config->SoName = Args.getLastArgValue(OPT_soname);
   Config->SortSection = getSortSection(Args);
-  Config->SplitStackAdjustSize = args::getInteger(Args, OPT_split_stack_adjust_size, 16384);
   Config->Strip = getStrip(Args);
   Config->Sysroot = Args.getLastArgValue(OPT_sysroot);
   Config->Target1Rel = Args.hasFlag(OPT_target1_rel, OPT_target1_abs, false);
@@ -902,9 +901,6 @@ void LinkerDriver::readConfigs(opt::InputArgList &Args) {
   if (Config->ThinLTOJobs == 0)
     error("--thinlto-jobs: number of threads must be > 0");
 
-  if (Config->SplitStackAdjustSize < 0)
-    error("--split-stack-adjust-size: size must be >= 0");
-
   // Parse ELF{32,64}{LE,BE} and CPU type.
   if (auto *Arg = Args.getLastArg(OPT_m)) {
     StringRef S = Arg->getValue();

ELF/InputSection.cpp

@@ -1009,17 +1009,15 @@ void InputSectionBase::adjustSplitStackFunctionPrologues(uint8_t *Buf,
     if (Defined *F = getEnclosingFunction<ELFT>(Rel.Offset)) {
       Prologues.insert(F);
       if (Target->adjustPrologueForCrossSplitStack(Buf + getOffset(F->Value),
-                                                   End, F->StOther))
+                                                   End))
         continue;
       if (!getFile<ELFT>()->SomeNoSplitStack)
         error(lld::toString(this) + ": " + F->getName() +
               " (with -fsplit-stack) calls " + Rel.Sym->getName() +
               " (without -fsplit-stack), but couldn't adjust its prologue");
     }
   }
-
-  if (Target->NeedsMoreStackNonSplit)
-    switchMorestackCallsToMorestackNonSplit(Prologues, MorestackCalls);
+  switchMorestackCallsToMorestackNonSplit(Prologues, MorestackCalls);
 }
 
 template <class ELFT> void InputSection::writeTo(uint8_t *Buf) {

ELF/Options.td

@@ -42,12 +42,6 @@ defm compress_debug_sections:
 
 defm defsym: Eq<"defsym", "Define a symbol alias">, MetaVarName<"<symbol>=<value>">;
 
-defm split_stack_adjust_size
-    : Eq<"split-stack-adjust-size",
-         "Specify adjustment to stack size when a split-stack function calls a "
-         "non-split-stack function">,
-      MetaVarName<"<value>">;
-
 defm library_path:
   Eq<"library-path", "Add a directory to the library search path">, MetaVarName<"<dir>">;
 

ELF/Target.cpp

@@ -132,11 +132,12 @@ bool TargetInfo::needsThunk(RelExpr Expr, RelType Type, const InputFile *File,
   return false;
 }
 
-bool TargetInfo::adjustPrologueForCrossSplitStack(uint8_t *Loc, uint8_t *End,
-                                                  uint8_t StOther) const {
+bool TargetInfo::adjustPrologueForCrossSplitStack(uint8_t *Loc,
+                                                  uint8_t *End) const {
   llvm_unreachable("Target doesn't support split stacks.");
 }
 
+
 bool TargetInfo::inBranchRange(RelType Type, uint64_t Src, uint64_t Dst) const {
   return true;
 }

ELF/Target.h

@@ -69,10 +69,8 @@ class TargetInfo {
   // The function with a prologue starting at Loc was compiled with
   // -fsplit-stack and it calls a function compiled without. Adjust the prologue
   // to do the right thing. See https://gcc.gnu.org/wiki/SplitStacks.
-  // The symbols st_other flags are needed on PowerPC64 for determining the
-  // offset to the split-stack prologue.
-  virtual bool adjustPrologueForCrossSplitStack(uint8_t *Loc, uint8_t *End,
-                                                uint8_t StOther) const;
+  virtual bool adjustPrologueForCrossSplitStack(uint8_t *Loc,
+                                                uint8_t *End) const;
 
   // Return true if we can reach Dst from Src with Relocation RelocType
   virtual bool inBranchRange(RelType Type, uint64_t Src,
@@ -132,11 +130,6 @@ class TargetInfo {
   // executable OutputSections.
   uint32_t TrapInstr = 0;
 
-  // If a target needs to rewrite calls to __morestack to instead call
-  // __morestack_non_split when a split-stack enabled caller calls a
-  // non-split-stack callee this will return true. Otherwise returns false.
-  bool NeedsMoreStackNonSplit = true;
-
   virtual RelExpr adjustRelaxExpr(RelType Type, const uint8_t *Data,
                                   RelExpr Expr) const;
   virtual void relaxGot(uint8_t *Loc, uint64_t Val) const;