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
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
|
//===- AsmExpr.cpp - Assembly file expressions ----------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "AsmExpr.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/MC/MCValue.h"
using namespace llvm;
AsmExpr::~AsmExpr() {
}
bool AsmExpr::EvaluateAsAbsolute(MCContext &Ctx, int64_t &Res) const {
MCValue Value;
if (!EvaluateAsRelocatable(Ctx, Value) || !Value.isAbsolute())
return false;
Res = Value.getConstant();
return true;
}
static bool EvaluateSymbolicAdd(const MCValue &LHS, MCSymbol *RHS_A,
MCSymbol *RHS_B, int64_t RHS_Cst,
MCValue &Res) {
// We can't add or subtract two symbols.
if ((LHS.getSymA() && RHS_A) ||
(LHS.getSymB() && RHS_B))
return false;
MCSymbol *A = LHS.getSymA() ? LHS.getSymA() : RHS_A;
MCSymbol *B = LHS.getSymB() ? LHS.getSymB() : RHS_B;
if (B) {
// If we have a negated symbol, then we must have also have a non-negated
// symbol in order to encode the expression. We can do this check later to
// permit expressions which eventually fold to a representable form -- such
// as (a + (0 - b)) -- if necessary.
if (!A)
return false;
}
Res = MCValue::get(A, B, LHS.getConstant() + RHS_Cst);
return true;
}
bool AsmExpr::EvaluateAsRelocatable(MCContext &Ctx, MCValue &Res) const {
switch (getKind()) {
default:
assert(0 && "Invalid assembly expression kind!");
case Constant:
Res = MCValue::get(cast<AsmConstantExpr>(this)->getValue());
return true;
case SymbolRef: {
MCSymbol *Sym = cast<AsmSymbolRefExpr>(this)->getSymbol();
if (const MCValue *Value = Ctx.GetSymbolValue(Sym))
Res = *Value;
else
Res = MCValue::get(Sym, 0, 0);
return true;
}
case Unary: {
const AsmUnaryExpr *AUE = cast<AsmUnaryExpr>(this);
MCValue Value;
if (!AUE->getSubExpr()->EvaluateAsRelocatable(Ctx, Value))
return false;
switch (AUE->getOpcode()) {
case AsmUnaryExpr::LNot:
if (!Value.isAbsolute())
return false;
Res = MCValue::get(!Value.getConstant());
break;
case AsmUnaryExpr::Minus:
/// -(a - b + const) ==> (b - a - const)
if (Value.getSymA() && !Value.getSymA())
return false;
Res = MCValue::get(Value.getSymB(), Value.getSymA(),
-Value.getConstant());
break;
case AsmUnaryExpr::Not:
if (!Value.isAbsolute())
return false;
Res = MCValue::get(~Value.getConstant());
break;
case AsmUnaryExpr::Plus:
Res = Value;
break;
}
return true;
}
case Binary: {
const AsmBinaryExpr *ABE = cast<AsmBinaryExpr>(this);
MCValue LHSValue, RHSValue;
if (!ABE->getLHS()->EvaluateAsRelocatable(Ctx, LHSValue) ||
!ABE->getRHS()->EvaluateAsRelocatable(Ctx, RHSValue))
return false;
// We only support a few operations on non-constant expressions, handle
// those first.
if (!LHSValue.isAbsolute() || !RHSValue.isAbsolute()) {
switch (ABE->getOpcode()) {
default:
return false;
case AsmBinaryExpr::Sub:
// Negate RHS and add.
return EvaluateSymbolicAdd(LHSValue,
RHSValue.getSymB(), RHSValue.getSymA(),
-RHSValue.getConstant(),
Res);
case AsmBinaryExpr::Add:
return EvaluateSymbolicAdd(LHSValue,
RHSValue.getSymA(), RHSValue.getSymB(),
RHSValue.getConstant(),
Res);
}
}
// FIXME: We need target hooks for the evaluation. It may be limited in
// width, and gas defines the result of comparisons differently from Apple
// as (the result is sign extended).
int64_t LHS = LHSValue.getConstant(), RHS = RHSValue.getConstant();
int64_t Result = 0;
switch (ABE->getOpcode()) {
case AsmBinaryExpr::Add: Result = LHS + RHS; break;
case AsmBinaryExpr::And: Result = LHS & RHS; break;
case AsmBinaryExpr::Div: Result = LHS / RHS; break;
case AsmBinaryExpr::EQ: Result = LHS == RHS; break;
case AsmBinaryExpr::GT: Result = LHS > RHS; break;
case AsmBinaryExpr::GTE: Result = LHS >= RHS; break;
case AsmBinaryExpr::LAnd: Result = LHS && RHS; break;
case AsmBinaryExpr::LOr: Result = LHS || RHS; break;
case AsmBinaryExpr::LT: Result = LHS < RHS; break;
case AsmBinaryExpr::LTE: Result = LHS <= RHS; break;
case AsmBinaryExpr::Mod: Result = LHS % RHS; break;
case AsmBinaryExpr::Mul: Result = LHS * RHS; break;
case AsmBinaryExpr::NE: Result = LHS != RHS; break;
case AsmBinaryExpr::Or: Result = LHS | RHS; break;
case AsmBinaryExpr::Shl: Result = LHS << RHS; break;
case AsmBinaryExpr::Shr: Result = LHS >> RHS; break;
case AsmBinaryExpr::Sub: Result = LHS - RHS; break;
case AsmBinaryExpr::Xor: Result = LHS ^ RHS; break;
}
Res = MCValue::get(Result);
return true;
}
}
}
|
