1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
|
//===-- XRayInstrumentation.cpp - Adds XRay instrumentation to functions. -===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements a MachineFunctionPass that inserts the appropriate
// XRay instrumentation instructions. We look for XRay-specific attributes
// on the function to determine whether we should insert the replacement
// operations.
//
//===---------------------------------------------------------------------===//
#include "llvm/CodeGen/Analysis.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/Support/TargetRegistry.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetSubtargetInfo.h"
using namespace llvm;
namespace {
struct XRayInstrumentation : public MachineFunctionPass {
static char ID;
XRayInstrumentation() : MachineFunctionPass(ID) {
initializeXRayInstrumentationPass(*PassRegistry::getPassRegistry());
}
bool runOnMachineFunction(MachineFunction &MF) override;
};
}
bool XRayInstrumentation::runOnMachineFunction(MachineFunction &MF) {
auto &F = *MF.getFunction();
auto InstrAttr = F.getFnAttribute("function-instrument");
bool AlwaysInstrument = !InstrAttr.hasAttribute(Attribute::None) &&
InstrAttr.isStringAttribute() &&
InstrAttr.getValueAsString() == "xray-always";
Attribute Attr = F.getFnAttribute("xray-instruction-threshold");
unsigned XRayThreshold = 0;
if (!AlwaysInstrument) {
if (Attr.hasAttribute(Attribute::None) || !Attr.isStringAttribute())
return false; // XRay threshold attribute not found.
if (Attr.getValueAsString().getAsInteger(10, XRayThreshold))
return false; // Invalid value for threshold.
if (F.size() < XRayThreshold)
return false; // Function is too small.
}
// FIXME: Do the loop triviality analysis here or in an earlier pass.
// First, insert an PATCHABLE_FUNCTION_ENTER as the first instruction of the
// MachineFunction.
auto &FirstMBB = *MF.begin();
auto &FirstMI = *FirstMBB.begin();
auto *TII = MF.getSubtarget().getInstrInfo();
BuildMI(FirstMBB, FirstMI, FirstMI.getDebugLoc(),
TII->get(TargetOpcode::PATCHABLE_FUNCTION_ENTER));
// Then we look for *all* terminators and returns, then replace those with
// PATCHABLE_RET instructions.
SmallVector<MachineInstr *, 4> Terminators;
for (auto &MBB : MF) {
for (auto &T : MBB.terminators()) {
// FIXME: Handle tail calls here too?
if (T.isReturn() && T.getOpcode() == TII->getReturnOpcode()) {
// Replace return instructions with:
// PATCHABLE_RET <Opcode>, <Operand>...
auto MIB = BuildMI(MBB, T, T.getDebugLoc(),
TII->get(TargetOpcode::PATCHABLE_RET))
.addImm(T.getOpcode());
for (auto &MO : T.operands())
MIB.addOperand(MO);
Terminators.push_back(&T);
break;
}
}
}
for (auto &I : Terminators)
I->eraseFromParent();
return true;
}
char XRayInstrumentation::ID = 0;
char &llvm::XRayInstrumentationID = XRayInstrumentation::ID;
INITIALIZE_PASS(XRayInstrumentation, "xray-instrumentation", "Insert XRay ops",
false, false)
|
