blob: af313a6b001d751405f0e727ff2db65816ad382f (
plain) (
blame)
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
|
//===-- ElimAvailExtern.cpp - DCE unreachable internal functions
//----------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This transform is designed to eliminate available external global
// definitions from the program, turning them into declarations.
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/IPO.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/Module.h"
#include "llvm/Transforms/Utils/GlobalStatus.h"
#include "llvm/Pass.h"
using namespace llvm;
#define DEBUG_TYPE "elim-avail-extern"
STATISTIC(NumFunctions, "Number of functions removed");
STATISTIC(NumVariables, "Number of global variables removed");
namespace {
struct EliminateAvailableExternally : public ModulePass {
static char ID; // Pass identification, replacement for typeid
EliminateAvailableExternally() : ModulePass(ID) {
initializeEliminateAvailableExternallyPass(
*PassRegistry::getPassRegistry());
}
// run - Do the EliminateAvailableExternally pass on the specified module,
// optionally updating the specified callgraph to reflect the changes.
//
bool runOnModule(Module &M) override;
};
}
char EliminateAvailableExternally::ID = 0;
INITIALIZE_PASS(EliminateAvailableExternally, "elim-avail-extern",
"Eliminate Available Externally Globals", false, false)
ModulePass *llvm::createEliminateAvailableExternallyPass() {
return new EliminateAvailableExternally();
}
bool EliminateAvailableExternally::runOnModule(Module &M) {
bool Changed = false;
// Drop initializers of available externally global variables.
for (GlobalVariable &GV : M.globals()) {
if (!GV.hasAvailableExternallyLinkage())
continue;
if (GV.hasInitializer()) {
Constant *Init = GV.getInitializer();
GV.setInitializer(nullptr);
if (isSafeToDestroyConstant(Init))
Init->destroyConstant();
}
GV.removeDeadConstantUsers();
GV.setLinkage(GlobalValue::ExternalLinkage);
NumVariables++;
Changed = true;
}
// Drop the bodies of available externally functions.
for (Function &F : M) {
if (!F.hasAvailableExternallyLinkage())
continue;
if (!F.isDeclaration())
// This will set the linkage to external
F.deleteBody();
F.removeDeadConstantUsers();
NumFunctions++;
Changed = true;
}
return Changed;
}
|
