[XRay] ARM 32-bit no-Thumb support in LLVM
This is a port of XRay to ARM 32-bit, without Thumb support yet. The XRay instrumentation support is moving up to AsmPrinter.
This is one of 3 commits to different repositories of XRay ARM port. The other 2 are:
https://reviews.llvm.org/D23932 (Clang test)
https://reviews.llvm.org/D23933 (compiler-rt)
Differential Revision: https://reviews.llvm.org/D23931
llvm-svn: 281878
diff --git a/llvm/lib/Target/ARM/ARMAsmPrinter.cpp b/llvm/lib/Target/ARM/ARMAsmPrinter.cpp
index 0ffa5b6..80e2f0a 100644
--- a/llvm/lib/Target/ARM/ARMAsmPrinter.cpp
+++ b/llvm/lib/Target/ARM/ARMAsmPrinter.cpp
@@ -164,6 +164,9 @@
// Emit the rest of the function body.
EmitFunctionBody();
+ // Emit the XRay table for this function.
+ EmitXRayTable();
+
// If we need V4T thumb mode Register Indirect Jump pads, emit them.
// These are created per function, rather than per TU, since it's
// relatively easy to exceed the thumb branch range within a TU.
@@ -2019,6 +2022,12 @@
.addReg(0));
return;
}
+ case ARM::PATCHABLE_FUNCTION_ENTER:
+ LowerPATCHABLE_FUNCTION_ENTER(*MI);
+ return;
+ case ARM::PATCHABLE_FUNCTION_EXIT:
+ LowerPATCHABLE_FUNCTION_EXIT(*MI);
+ return;
}
MCInst TmpInst;
diff --git a/llvm/lib/Target/ARM/ARMAsmPrinter.h b/llvm/lib/Target/ARM/ARMAsmPrinter.h
index 30abdbc..0db0a0f 100644
--- a/llvm/lib/Target/ARM/ARMAsmPrinter.h
+++ b/llvm/lib/Target/ARM/ARMAsmPrinter.h
@@ -101,7 +101,19 @@
// lowerOperand - Convert a MachineOperand into the equivalent MCOperand.
bool lowerOperand(const MachineOperand &MO, MCOperand &MCOp);
+ //===------------------------------------------------------------------===//
+ // XRay implementation
+ //===------------------------------------------------------------------===//
+public:
+ // XRay-specific lowering for ARM.
+ void LowerPATCHABLE_FUNCTION_ENTER(const MachineInstr &MI);
+ void LowerPATCHABLE_FUNCTION_EXIT(const MachineInstr &MI);
+ // Helper function that emits the XRay sleds we've collected for a particular
+ // function.
+ void EmitXRayTable();
+
private:
+ void EmitSled(const MachineInstr &MI, SledKind Kind);
// Helpers for EmitStartOfAsmFile() and EmitEndOfAsmFile()
void emitAttributes();
diff --git a/llvm/lib/Target/ARM/ARMBaseInstrInfo.h b/llvm/lib/Target/ARM/ARMBaseInstrInfo.h
index a42ed0c..b01d5c8 100644
--- a/llvm/lib/Target/ARM/ARMBaseInstrInfo.h
+++ b/llvm/lib/Target/ARM/ARMBaseInstrInfo.h
@@ -100,6 +100,10 @@
// Return whether the target has an explicit NOP encoding.
bool hasNOP() const;
+ virtual void getNoopForElfTarget(MCInst &NopInst) const {
+ getNoopForMachoTarget(NopInst);
+ }
+
// Return the non-pre/post incrementing version of 'Opc'. Return 0
// if there is not such an opcode.
virtual unsigned getUnindexedOpcode(unsigned Opc) const =0;
diff --git a/llvm/lib/Target/ARM/ARMMCInstLower.cpp b/llvm/lib/Target/ARM/ARMMCInstLower.cpp
index 7429acd..19c9151 100644
--- a/llvm/lib/Target/ARM/ARMMCInstLower.cpp
+++ b/llvm/lib/Target/ARM/ARMMCInstLower.cpp
@@ -21,6 +21,11 @@
#include "llvm/IR/Mangler.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCInst.h"
+#include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCSymbolELF.h"
+#include "llvm/MC/MCSectionELF.h"
+#include "llvm/MC/MCInstBuilder.h"
+#include "llvm/MC/MCStreamer.h"
using namespace llvm;
@@ -150,3 +155,92 @@
}
}
}
+
+void ARMAsmPrinter::EmitSled(const MachineInstr &MI, SledKind Kind)
+{
+ if (MI.getParent()->getParent()->getInfo<ARMFunctionInfo>()
+ ->isThumbFunction())
+ {
+ MI.emitError("An attempt to perform XRay instrumentation for a"
+ " Thumb function (not supported). Detected when emitting a sled.");
+ return;
+ }
+ static const int8_t NoopsInSledCount = 6;
+ // We want to emit the following pattern:
+ //
+ // .Lxray_sled_N:
+ // ALIGN
+ // B #20
+ // ; 6 NOP instructions (24 bytes)
+ // .tmpN
+ //
+ // We need the 24 bytes (6 instructions) because at runtime, we'd be patching
+ // over the full 28 bytes (7 instructions) with the following pattern:
+ //
+ // PUSH{ r0, lr }
+ // MOVW r0, #<lower 16 bits of function ID>
+ // MOVT r0, #<higher 16 bits of function ID>
+ // MOVW ip, #<lower 16 bits of address of __xray_FunctionEntry/Exit>
+ // MOVT ip, #<higher 16 bits of address of __xray_FunctionEntry/Exit>
+ // BLX ip
+ // POP{ r0, lr }
+ //
+ OutStreamer->EmitCodeAlignment(4);
+ auto CurSled = OutContext.createTempSymbol("xray_sled_", true);
+ OutStreamer->EmitLabel(CurSled);
+ auto Target = OutContext.createTempSymbol();
+
+ // Emit "B #20" instruction, which jumps over the next 24 bytes (because
+ // register pc is 8 bytes ahead of the jump instruction by the moment CPU
+ // is executing it).
+ // By analogy to ARMAsmPrinter::emitPseudoExpansionLowering() |case ARM::B|.
+ // It is not clear why |addReg(0)| is needed (the last operand).
+ EmitToStreamer(*OutStreamer, MCInstBuilder(ARM::Bcc).addImm(20)
+ .addImm(ARMCC::AL).addReg(0));
+
+ MCInst Noop;
+ Subtarget->getInstrInfo()->getNoopForElfTarget(Noop);
+ for (int8_t I = 0; I < NoopsInSledCount; I++)
+ {
+ OutStreamer->EmitInstruction(Noop, getSubtargetInfo());
+ }
+
+ OutStreamer->EmitLabel(Target);
+ recordSled(CurSled, MI, Kind);
+}
+
+void ARMAsmPrinter::LowerPATCHABLE_FUNCTION_ENTER(const MachineInstr &MI)
+{
+ EmitSled(MI, SledKind::FUNCTION_ENTER);
+}
+
+void ARMAsmPrinter::LowerPATCHABLE_FUNCTION_EXIT(const MachineInstr &MI)
+{
+ EmitSled(MI, SledKind::FUNCTION_EXIT);
+}
+
+void ARMAsmPrinter::EmitXRayTable()
+{
+ if (Sleds.empty())
+ return;
+ if (Subtarget->isTargetELF()) {
+ auto *Section = OutContext.getELFSection(
+ "xray_instr_map", ELF::SHT_PROGBITS,
+ ELF::SHF_ALLOC | ELF::SHF_GROUP | ELF::SHF_MERGE, 0,
+ CurrentFnSym->getName());
+ auto PrevSection = OutStreamer->getCurrentSectionOnly();
+ OutStreamer->SwitchSection(Section);
+ for (const auto &Sled : Sleds) {
+ OutStreamer->EmitSymbolValue(Sled.Sled, 4);
+ OutStreamer->EmitSymbolValue(CurrentFnSym, 4);
+ auto Kind = static_cast<uint8_t>(Sled.Kind);
+ OutStreamer->EmitBytes(
+ StringRef(reinterpret_cast<const char *>(&Kind), 1));
+ OutStreamer->EmitBytes(
+ StringRef(reinterpret_cast<const char *>(&Sled.AlwaysInstrument), 1));
+ OutStreamer->EmitZeros(6);
+ }
+ OutStreamer->SwitchSection(PrevSection);
+ }
+ Sleds.clear();
+}
diff --git a/llvm/lib/Target/ARM/ARMSubtarget.cpp b/llvm/lib/Target/ARM/ARMSubtarget.cpp
index 469d340..a90b495 100644
--- a/llvm/lib/Target/ARM/ARMSubtarget.cpp
+++ b/llvm/lib/Target/ARM/ARMSubtarget.cpp
@@ -101,6 +101,11 @@
: (ARMBaseInstrInfo *)new Thumb2InstrInfo(*this)),
TLInfo(TM, *this) {}
+bool ARMSubtarget::isXRaySupported() const {
+ // We don't currently suppport Thumb, but Windows requires Thumb.
+ return hasV6Ops() && hasARMOps() && !isTargetWindows();
+}
+
void ARMSubtarget::initializeEnvironment() {
// MCAsmInfo isn't always present (e.g. in opt) so we can't initialize this
// directly from it, but we can try to make sure they're consistent when both
diff --git a/llvm/lib/Target/ARM/ARMSubtarget.h b/llvm/lib/Target/ARM/ARMSubtarget.h
index 2c14eb0..6d528b8 100644
--- a/llvm/lib/Target/ARM/ARMSubtarget.h
+++ b/llvm/lib/Target/ARM/ARMSubtarget.h
@@ -540,6 +540,8 @@
}
bool isTargetAndroid() const { return TargetTriple.isAndroid(); }
+ virtual bool isXRaySupported() const override;
+
bool isAPCS_ABI() const;
bool isAAPCS_ABI() const;
bool isAAPCS16_ABI() const;
diff --git a/llvm/lib/Target/X86/X86AsmPrinter.h b/llvm/lib/Target/X86/X86AsmPrinter.h
index dcb7b5a..50acb39 100644
--- a/llvm/lib/Target/X86/X86AsmPrinter.h
+++ b/llvm/lib/Target/X86/X86AsmPrinter.h
@@ -71,27 +71,6 @@
StackMapShadowTracker SMShadowTracker;
- // This describes the kind of sled we're storing in the XRay table.
- enum class SledKind : uint8_t {
- FUNCTION_ENTER = 0,
- FUNCTION_EXIT = 1,
- TAIL_CALL = 2,
- };
-
- // The table will contain these structs that point to the sled, the function
- // containing the sled, and what kind of sled (and whether they should always
- // be instrumented).
- struct XRayFunctionEntry {
- const MCSymbol *Sled;
- const MCSymbol *Function;
- SledKind Kind;
- bool AlwaysInstrument;
- const class Function *Fn;
- };
-
- // All the sleds to be emitted.
- std::vector<XRayFunctionEntry> Sleds;
-
// All instructions emitted by the X86AsmPrinter should use this helper
// method.
//
@@ -117,8 +96,6 @@
// function.
void EmitXRayTable();
- // Helper function to record a given XRay sled.
- void recordSled(MCSymbol *Sled, const MachineInstr &MI, SledKind Kind);
public:
explicit X86AsmPrinter(TargetMachine &TM,
std::unique_ptr<MCStreamer> Streamer)
diff --git a/llvm/lib/Target/X86/X86MCInstLower.cpp b/llvm/lib/Target/X86/X86MCInstLower.cpp
index 52c0551..7dfe9f2 100644
--- a/llvm/lib/Target/X86/X86MCInstLower.cpp
+++ b/llvm/lib/Target/X86/X86MCInstLower.cpp
@@ -1020,16 +1020,6 @@
getSubtargetInfo());
}
-void X86AsmPrinter::recordSled(MCSymbol *Sled, const MachineInstr &MI,
- SledKind Kind) {
- auto Fn = MI.getParent()->getParent()->getFunction();
- auto Attr = Fn->getFnAttribute("function-instrument");
- bool AlwaysInstrument =
- Attr.isStringAttribute() && Attr.getValueAsString() == "xray-always";
- Sleds.emplace_back(
- XRayFunctionEntry{Sled, CurrentFnSym, Kind, AlwaysInstrument, Fn});
-}
-
void X86AsmPrinter::LowerPATCHABLE_FUNCTION_ENTER(const MachineInstr &MI,
X86MCInstLower &MCIL) {
// We want to emit the following pattern:
diff --git a/llvm/lib/Target/X86/X86Subtarget.h b/llvm/lib/Target/X86/X86Subtarget.h
index c1f862d..a5cd83d 100644
--- a/llvm/lib/Target/X86/X86Subtarget.h
+++ b/llvm/lib/Target/X86/X86Subtarget.h
@@ -460,6 +460,8 @@
bool hasPKU() const { return HasPKU; }
bool hasMPX() const { return HasMPX; }
+ virtual bool isXRaySupported() const override { return is64Bit(); }
+
bool isAtom() const { return X86ProcFamily == IntelAtom; }
bool isSLM() const { return X86ProcFamily == IntelSLM; }
bool useSoftFloat() const { return UseSoftFloat; }