[llvm] r249522 - [X86] Emit .cfi_escape GNU_ARGS_SIZE when adjusting the stack before calls
Frédéric Riss via llvm-commits
llvm-commits at lists.llvm.org
Wed Oct 7 14:09:58 PDT 2015
Hi Michael,
I just spent quite some time debugging an issue that should be fixed by that patch, unfortunately there are 2 issues with it:
- You can end up generating an args size directive right after the prologue, which means the assert in that function of DwarfDebug.cpp will sometimes fire:
static DebugLoc findPrologueEndLoc(const MachineFunction *MF) {
// First known non-DBG_VALUE and non-frame setup location marks
// the beginning of the function body.
for (const auto &MBB : *MF)
for (const auto &MI : MBB)
if (!MI.isDebugValue() && !MI.getFlag(MachineInstr::FrameSetup) &&
MI.getDebugLoc()) {
// Did the target forget to set the FrameSetup flag for CFI insns?
assert(!MI.isCFIInstruction() &&
"First non-frame-setup instruction is a CFI instruction.");
return MI.getDebugLoc();
}
return DebugLoc();
}
- Darwin uses compact_unwind, and a dynamic SP during the function can’t really be described by that (because if you look at the code, we currently emit one compact unwind entry per function. Not sure if the runtime depends on that or if we could emit multiple ones). So the exception handling is still totally broken on Darwin.
At least as a short-term thing, what’s the right place to just disable the push optimizations on Darwin (or maybe any platform that uses compact_unwind) when the function needs an EH description?
Fred
> On Oct 7, 2015, at 12:01 AM, Michael Kuperstein via llvm-commits <llvm-commits at lists.llvm.org> wrote:
>
> Author: mkuper
> Date: Wed Oct 7 02:01:31 2015
> New Revision: 249522
>
> URL: http://llvm.org/viewvc/llvm-project?rev=249522&view=rev
> Log:
> [X86] Emit .cfi_escape GNU_ARGS_SIZE when adjusting the stack before calls
>
> When outgoing function arguments are passed using push instructions, and EH
> is enabled, we may need to indicate to the stack unwinder that the stack
> pointer was adjusted before the call.
>
> This should fix the exception handling issues in PR24792.
>
> Differential Revision: http://reviews.llvm.org/D13132
>
> Added:
> llvm/trunk/test/CodeGen/X86/push-cfi-obj.ll
> llvm/trunk/test/CodeGen/X86/push-cfi.ll
> Modified:
> llvm/trunk/include/llvm/MC/MCDwarf.h
> llvm/trunk/include/llvm/MC/MCStreamer.h
> llvm/trunk/lib/CodeGen/AsmPrinter/AsmPrinterDwarf.cpp
> llvm/trunk/lib/MC/MCAsmStreamer.cpp
> llvm/trunk/lib/MC/MCDwarf.cpp
> llvm/trunk/lib/MC/MCStreamer.cpp
> llvm/trunk/lib/Target/X86/X86FrameLowering.cpp
>
> Modified: llvm/trunk/include/llvm/MC/MCDwarf.h
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/MC/MCDwarf.h?rev=249522&r1=249521&r2=249522&view=diff
> ==============================================================================
> --- llvm/trunk/include/llvm/MC/MCDwarf.h (original)
> +++ llvm/trunk/include/llvm/MC/MCDwarf.h Wed Oct 7 02:01:31 2015
> @@ -340,7 +340,8 @@ public:
> OpRestore,
> OpUndefined,
> OpRegister,
> - OpWindowSave
> + OpWindowSave,
> + OpGnuArgsSize
> };
>
> private:
> @@ -454,6 +455,11 @@ public:
> return MCCFIInstruction(OpEscape, L, 0, 0, Vals);
> }
>
> + /// \brief A special wrapper for .cfi_escape that indicates GNU_ARGS_SIZE
> + static MCCFIInstruction createGnuArgsSize(MCSymbol *L, int Size) {
> + return MCCFIInstruction(OpGnuArgsSize, L, 0, Size, "");
> + }
> +
> OpType getOperation() const { return Operation; }
> MCSymbol *getLabel() const { return Label; }
>
> @@ -473,7 +479,7 @@ public:
> int getOffset() const {
> assert(Operation == OpDefCfa || Operation == OpOffset ||
> Operation == OpRelOffset || Operation == OpDefCfaOffset ||
> - Operation == OpAdjustCfaOffset);
> + Operation == OpAdjustCfaOffset || Operation == OpGnuArgsSize);
> return Offset;
> }
>
>
> Modified: llvm/trunk/include/llvm/MC/MCStreamer.h
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/MC/MCStreamer.h?rev=249522&r1=249521&r2=249522&view=diff
> ==============================================================================
> --- llvm/trunk/include/llvm/MC/MCStreamer.h (original)
> +++ llvm/trunk/include/llvm/MC/MCStreamer.h Wed Oct 7 02:01:31 2015
> @@ -661,6 +661,7 @@ public:
> virtual void EmitCFIRelOffset(int64_t Register, int64_t Offset);
> virtual void EmitCFIAdjustCfaOffset(int64_t Adjustment);
> virtual void EmitCFIEscape(StringRef Values);
> + virtual void EmitCFIGnuArgsSize(int64_t Size);
> virtual void EmitCFISignalFrame();
> virtual void EmitCFIUndefined(int64_t Register);
> virtual void EmitCFIRegister(int64_t Register1, int64_t Register2);
>
> Modified: llvm/trunk/lib/CodeGen/AsmPrinter/AsmPrinterDwarf.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/AsmPrinterDwarf.cpp?rev=249522&r1=249521&r2=249522&view=diff
> ==============================================================================
> --- llvm/trunk/lib/CodeGen/AsmPrinter/AsmPrinterDwarf.cpp (original)
> +++ llvm/trunk/lib/CodeGen/AsmPrinter/AsmPrinterDwarf.cpp Wed Oct 7 02:01:31 2015
> @@ -246,6 +246,12 @@ void AsmPrinter::emitCFIInstruction(cons
> case MCCFIInstruction::OpSameValue:
> OutStreamer->EmitCFISameValue(Inst.getRegister());
> break;
> + case MCCFIInstruction::OpGnuArgsSize:
> + OutStreamer->EmitCFIGnuArgsSize(Inst.getOffset());
> + break;
> + case MCCFIInstruction::OpEscape:
> + OutStreamer->EmitCFIEscape(Inst.getValues());
> + break;
> }
> }
>
>
> Modified: llvm/trunk/lib/MC/MCAsmStreamer.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/MC/MCAsmStreamer.cpp?rev=249522&r1=249521&r2=249522&view=diff
> ==============================================================================
> --- llvm/trunk/lib/MC/MCAsmStreamer.cpp (original)
> +++ llvm/trunk/lib/MC/MCAsmStreamer.cpp Wed Oct 7 02:01:31 2015
> @@ -29,6 +29,7 @@
> #include "llvm/Support/ErrorHandling.h"
> #include "llvm/Support/Format.h"
> #include "llvm/Support/FormattedStream.h"
> +#include "llvm/Support/LEB128.h"
> #include "llvm/Support/MathExtras.h"
> #include "llvm/Support/Path.h"
> #include <cctype>
> @@ -210,6 +211,8 @@ public:
> void EmitCFISameValue(int64_t Register) override;
> void EmitCFIRelOffset(int64_t Register, int64_t Offset) override;
> void EmitCFIAdjustCfaOffset(int64_t Adjustment) override;
> + void EmitCFIEscape(StringRef Values) override;
> + void EmitCFIGnuArgsSize(int64_t Size) override;
> void EmitCFISignalFrame() override;
> void EmitCFIUndefined(int64_t Register) override;
> void EmitCFIRegister(int64_t Register1, int64_t Register2) override;
> @@ -1010,6 +1013,32 @@ void MCAsmStreamer::EmitCFIDefCfaOffset(
> EmitEOL();
> }
>
> +static void PrintCFIEscape(llvm::formatted_raw_ostream &OS, StringRef Values) {
> + OS << "\t.cfi_escape ";
> + if (!Values.empty()) {
> + size_t e = Values.size() - 1;
> + for (size_t i = 0; i < e; ++i)
> + OS << format("0x%02x", uint8_t(Values[i])) << ", ";
> + OS << format("0x%02x", uint8_t(Values[e]));
> + }
> +}
> +
> +void MCAsmStreamer::EmitCFIEscape(StringRef Values) {
> + MCStreamer::EmitCFIEscape(Values);
> + PrintCFIEscape(OS, Values);
> + EmitEOL();
> +}
> +
> +void MCAsmStreamer::EmitCFIGnuArgsSize(int64_t Size) {
> + MCStreamer::EmitCFIGnuArgsSize(Size);
> +
> + uint8_t Buffer[16] = { dwarf::DW_CFA_GNU_args_size };
> + unsigned Len = encodeULEB128(Size, Buffer + 1) + 1;
> +
> + PrintCFIEscape(OS, StringRef((const char *)&Buffer[0], Len));
> + EmitEOL();
> +}
> +
> void MCAsmStreamer::EmitCFIDefCfaRegister(int64_t Register) {
> MCStreamer::EmitCFIDefCfaRegister(Register);
> OS << "\t.cfi_def_cfa_register ";
>
> Modified: llvm/trunk/lib/MC/MCDwarf.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/MC/MCDwarf.cpp?rev=249522&r1=249521&r2=249522&view=diff
> ==============================================================================
> --- llvm/trunk/lib/MC/MCDwarf.cpp (original)
> +++ llvm/trunk/lib/MC/MCDwarf.cpp Wed Oct 7 02:01:31 2015
> @@ -1147,6 +1147,11 @@ void FrameEmitterImpl::EmitCFIInstructio
> Streamer.EmitIntValue(dwarf::DW_CFA_restore | Reg, 1);
> return;
> }
> + case MCCFIInstruction::OpGnuArgsSize: {
> + Streamer.EmitIntValue(dwarf::DW_CFA_GNU_args_size, 1);
> + Streamer.EmitULEB128IntValue(Instr.getOffset());
> + return;
> + }
> case MCCFIInstruction::OpEscape:
> Streamer.EmitBytes(Instr.getValues());
> return;
>
> Modified: llvm/trunk/lib/MC/MCStreamer.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/MC/MCStreamer.cpp?rev=249522&r1=249521&r2=249522&view=diff
> ==============================================================================
> --- llvm/trunk/lib/MC/MCStreamer.cpp (original)
> +++ llvm/trunk/lib/MC/MCStreamer.cpp Wed Oct 7 02:01:31 2015
> @@ -359,6 +359,14 @@ void MCStreamer::EmitCFIEscape(StringRef
> CurFrame->Instructions.push_back(Instruction);
> }
>
> +void MCStreamer::EmitCFIGnuArgsSize(int64_t Size) {
> + MCSymbol *Label = EmitCFICommon();
> + MCCFIInstruction Instruction =
> + MCCFIInstruction::createGnuArgsSize(Label, Size);
> + MCDwarfFrameInfo *CurFrame = getCurrentDwarfFrameInfo();
> + CurFrame->Instructions.push_back(Instruction);
> +}
> +
> void MCStreamer::EmitCFISignalFrame() {
> EnsureValidDwarfFrame();
> MCDwarfFrameInfo *CurFrame = getCurrentDwarfFrameInfo();
>
> Modified: llvm/trunk/lib/Target/X86/X86FrameLowering.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86FrameLowering.cpp?rev=249522&r1=249521&r2=249522&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Target/X86/X86FrameLowering.cpp (original)
> +++ llvm/trunk/lib/Target/X86/X86FrameLowering.cpp Wed Oct 7 02:01:31 2015
> @@ -2073,8 +2073,6 @@ eliminateCallFramePseudoInstr(MachineFun
> // If the stack pointer can be changed after prologue, turn the
> // adjcallstackup instruction into a 'sub ESP, <amt>' and the
> // adjcallstackdown instruction into 'add ESP, <amt>'
> - if (Amount == 0)
> - return;
>
> // We need to keep the stack aligned properly. To do this, we round the
> // amount of space needed for the outgoing arguments up to the next
> @@ -2082,6 +2080,25 @@ eliminateCallFramePseudoInstr(MachineFun
> unsigned StackAlign = getStackAlignment();
> Amount = RoundUpToAlignment(Amount, StackAlign);
>
> + // If we have any exception handlers in this function, and we adjust
> + // the SP before calls, we may need to indicate this to the unwinder,
> + // using GNU_ARGS_SIZE. Note that this may be necessary
> + // even when Amount == 0, because the preceding function may have
> + // set a non-0 GNU_ARGS_SIZE.
> + // TODO: We don't need to reset this between subsequent functions,
> + // if it didn't change.
> + bool HasDwarfEHHandlers =
> + !MF.getTarget().getMCAsmInfo()->usesWindowsCFI() &&
> + !MF.getMMI().getLandingPads().empty();
> +
> + if (HasDwarfEHHandlers && !isDestroy &&
> + MF.getInfo<X86MachineFunctionInfo>()->getHasPushSequences())
> + BuildCFI(MBB, I, DL,
> + MCCFIInstruction::createGnuArgsSize(nullptr, Amount));
> +
> + if (Amount == 0)
> + return;
> +
> // Factor out the amount that gets handled inside the sequence
> // (Pushes of argument for frame setup, callee pops for frame destroy)
> Amount -= InternalAmt;
>
> Added: llvm/trunk/test/CodeGen/X86/push-cfi-obj.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/push-cfi-obj.ll?rev=249522&view=auto
> ==============================================================================
> --- llvm/trunk/test/CodeGen/X86/push-cfi-obj.ll (added)
> +++ llvm/trunk/test/CodeGen/X86/push-cfi-obj.ll Wed Oct 7 02:01:31 2015
> @@ -0,0 +1,38 @@
> +; RUN: llc < %s -mtriple=i686-pc-linux -filetype=obj | llvm-readobj -s -sr -sd | FileCheck %s
> +
> +; CHECK: Index: 8
> +; CHECK-NEXT: Name: .eh_frame (41)
> +; CHECK-NEXT: Type: SHT_PROGBITS (0x1)
> +; CHECK-NEXT: Flags [ (0x2)
> +; CHECK-NEXT: SHF_ALLOC (0x2)
> +; CHECK-NEXT: ]
> +; CHECK-NEXT: Address: 0x0
> +; CHECK-NEXT: Offset: 0x64
> +; CHECK-NEXT: Size: 60
> +; CHECK-NEXT: Link: 0
> +; CHECK-NEXT: Info: 0
> +; CHECK-NEXT: AddressAlignment: 4
> +; CHECK-NEXT: EntrySize: 0
> +; CHECK-NEXT: Relocations [
> +; CHECK-NEXT: ]
> +; CHECK-NEXT: SectionData (
> +; CHECK-NEXT: 0000: 1C000000 00000000 017A504C 5200017C |.........zPLR..||
> +; CHECK-NEXT: 0010: 08070000 00000000 1B0C0404 88010000 |................|
> +; CHECK-NEXT: 0020: 18000000 24000000 00000000 19000000 |....$...........|
> +; CHECK-NEXT: 0030: 04000000 00430E10 2E100000 |.....C......|
> +; CHECK-NEXT: )
> +
> +declare i32 @__gxx_personality_v0(...)
> +declare void @good(i32 %a, i32 %b, i32 %c, i32 %d)
> +
> +define void @test() optsize personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*) {
> +entry:
> + invoke void @good(i32 1, i32 2, i32 3, i32 4)
> + to label %continue unwind label %cleanup
> +continue:
> + ret void
> +cleanup:
> + landingpad { i8*, i32 }
> + cleanup
> + ret void
> +}
>
> Added: llvm/trunk/test/CodeGen/X86/push-cfi.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/push-cfi.ll?rev=249522&view=auto
> ==============================================================================
> --- llvm/trunk/test/CodeGen/X86/push-cfi.ll (added)
> +++ llvm/trunk/test/CodeGen/X86/push-cfi.ll Wed Oct 7 02:01:31 2015
> @@ -0,0 +1,143 @@
> +; RUN: llc < %s -mtriple=i686-pc-linux | FileCheck %s
> +
> +declare i32 @__gxx_personality_v0(...)
> +declare void @good(i32 %a, i32 %b, i32 %c, i32 %d)
> +declare void @large(i32 %a, i32 %b, i32 %c, i32 %d, i32 %e, i32 %f)
> +declare void @empty()
> +
> +; We use an invoke, and expect a .cfi_escape GNU_ARGS_SIZE with size 16
> +; before the invocation
> +; CHECK-LABEL: test1:
> +; CHECK: .cfi_escape 0x2e, 0x10
> +; CHECK-NEXT: pushl $4
> +; CHECK-NEXT: pushl $3
> +; CHECK-NEXT: pushl $2
> +; CHECK-NEXT: pushl $1
> +; CHECK-NEXT: call
> +; CHECK-NEXT: addl $16, %esp
> +define void @test1() optsize personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*) {
> +entry:
> + invoke void @good(i32 1, i32 2, i32 3, i32 4)
> + to label %continue unwind label %cleanup
> +continue:
> + ret void
> +cleanup:
> + landingpad { i8*, i32 }
> + cleanup
> + ret void
> +}
> +
> +; If the function has no handlers, we don't need to generate GNU_ARGS_SIZE,
> +; even if it has an unwind table.
> +; CHECK-LABEL: test2:
> +; CHECK-NOT: .cfi_escape
> +; CHECK: pushl $4
> +; CHECK-NEXT: pushl $3
> +; CHECK-NEXT: pushl $2
> +; CHECK-NEXT: pushl $1
> +; CHECK-NEXT: call
> +; CHECK-NEXT: addl $16, %esp
> +define void @test2() optsize personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*) {
> +entry:
> + call void @good(i32 1, i32 2, i32 3, i32 4)
> + ret void
> +}
> +
> +; If we did not end up using any pushes, no need for GNU_ARGS_SIZE anywhere
> +; CHECK-LABEL: test3:
> +; CHECK-NOT: .cfi_escape
> +; CHECK-NOT: pushl
> +; CHECK: retl
> +define void @test3() optsize personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*) {
> +entry:
> + invoke void @empty()
> + to label %continue unwind label %cleanup
> +continue:
> + ret void
> +cleanup:
> + landingpad { i8*, i32 }
> + cleanup
> + ret void
> +}
> +
> +; Different sized stacks need different GNU_ARGS_SIZEs
> +; CHECK-LABEL: test4:
> +; CHECK: .cfi_escape 0x2e, 0x10
> +; CHECK-NEXT: pushl $4
> +; CHECK-NEXT: pushl $3
> +; CHECK-NEXT: pushl $2
> +; CHECK-NEXT: pushl $1
> +; CHECK-NEXT: call
> +; CHECK-NEXT: addl $16, %esp
> +; CHECK: .cfi_escape 0x2e, 0x20
> +; CHECK-NEXT: subl $8, %esp
> +; CHECK-NEXT: pushl $11
> +; CHECK-NEXT: pushl $10
> +; CHECK-NEXT: pushl $9
> +; CHECK-NEXT: pushl $8
> +; CHECK-NEXT: pushl $7
> +; CHECK-NEXT: pushl $6
> +; CHECK-NEXT: calll large
> +; CHECK-NEXT: addl $32, %esp
> +define void @test4() optsize personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*) {
> +entry:
> + invoke void @good(i32 1, i32 2, i32 3, i32 4)
> + to label %continue1 unwind label %cleanup
> +continue1:
> + invoke void @large(i32 6, i32 7, i32 8, i32 9, i32 10, i32 11)
> + to label %continue2 unwind label %cleanup
> +continue2:
> + ret void
> +cleanup:
> + landingpad { i8*, i32 }
> + cleanup
> + ret void
> +}
> +
> +; If we did use pushes, we need to reset GNU_ARGS_SIZE before a call
> +; without parameters
> +; CHECK-LABEL: test5:
> +; CHECK: .cfi_escape 0x2e, 0x10
> +; CHECK-NEXT: pushl $4
> +; CHECK-NEXT: pushl $3
> +; CHECK-NEXT: pushl $2
> +; CHECK-NEXT: pushl $1
> +; CHECK-NEXT: call
> +; CHECK-NEXT: addl $16, %esp
> +; CHECK: .cfi_escape 0x2e, 0x00
> +; CHECK-NEXT: call
> +define void @test5() optsize personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*) {
> +entry:
> + invoke void @good(i32 1, i32 2, i32 3, i32 4)
> + to label %continue1 unwind label %cleanup
> +continue1:
> + invoke void @empty()
> + to label %continue2 unwind label %cleanup
> +continue2:
> + ret void
> +cleanup:
> + landingpad { i8*, i32 }
> + cleanup
> + ret void
> +}
> +
> +; This is actually inefficient - we don't need to repeat the .cfi_escape twice.
> +; CHECK-LABEL: test6:
> +; CHECK: .cfi_escape 0x2e, 0x10
> +; CHECK: call
> +; CHECK: .cfi_escape 0x2e, 0x10
> +; CHECK: call
> +define void @test6() optsize personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*) {
> +entry:
> + invoke void @good(i32 1, i32 2, i32 3, i32 4)
> + to label %continue1 unwind label %cleanup
> +continue1:
> + invoke void @good(i32 5, i32 6, i32 7, i32 8)
> + to label %continue2 unwind label %cleanup
> +continue2:
> + ret void
> +cleanup:
> + landingpad { i8*, i32 }
> + cleanup
> + ret void
> +}
>
>
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