1/*****************************************************************************/
2/* */
3/* shiftexpr.c */
4/* */
5/* Parse the << and >> operators */
6/* */
7/* */
8/* */
9/* (C) 2004-2006 Ullrich von Bassewitz */
10/* Roemerstrasse 52 */
11/* D-70794 Filderstadt */
12/* EMail: uz@cc65.org */
13/* */
14/* */
15/* This software is provided 'as-is', without any expressed or implied */
16/* warranty. In no event will the authors be held liable for any damages */
17/* arising from the use of this software. */
18/* */
19/* Permission is granted to anyone to use this software for any purpose, */
20/* including commercial applications, and to alter it and redistribute it */
21/* freely, subject to the following restrictions: */
22/* */
23/* 1. The origin of this software must not be misrepresented; you must not */
24/* claim that you wrote the original software. If you use this software */
25/* in a product, an acknowledgment in the product documentation would be */
26/* appreciated but is not required. */
27/* 2. Altered source versions must be plainly marked as such, and must not */
28/* be misrepresented as being the original software. */
29/* 3. This notice may not be removed or altered from any source */
30/* distribution. */
31/* */
32/*****************************************************************************/
33
34
35
36/* cc65 */
37#include "asmcode.h"
38#include "codegen.h"
39#include "datatype.h"
40#include "error.h"
41#include "expr.h"
42#include "exprdesc.h"
43#include "loadexpr.h"
44#include "scanner.h"
45#include "shiftexpr.h"
46
47
48
49/*****************************************************************************/
50/* Data */
51/*****************************************************************************/
52
53
54
55/*****************************************************************************/
56/* Code */
57/*****************************************************************************/
58
59
60
61void ShiftExpr (struct ExprDesc* Expr)
62/* Parse the << and >> operators. */
63{
64 ExprDesc Expr2;
65 CodeMark Mark1;
66 CodeMark Mark2;
67 token_t Tok; /* The operator token */
68 Type* EffType; /* Effective lhs type */
69 Type* ResultType; /* Type of the result */
70 unsigned ExprBits; /* Bits of the lhs operand */
71 unsigned GenFlags; /* Generator flags */
72 unsigned ltype;
73 int rconst; /* Operand is a constant */
74
75
76 /* Evaluate the lhs */
77 ExprWithCheck (hie8, Expr);
78
79 while (CurTok.Tok == TOK_SHL || CurTok.Tok == TOK_SHR) {
80
81 /* All operators that call this function expect an int on the lhs */
82 if (!IsClassInt (Expr->Type)) {
83 Error ("Integer expression expected");
84 ED_MakeConstAbsInt (Expr, 1);
85 }
86
87 /* Remember the operator token, then skip it */
88 Tok = CurTok.Tok;
89 NextToken ();
90
91 /* Get the type of the result */
92 ResultType = EffType = IntPromotion (Expr->Type);
93
94 /* Prepare the code generator flags */
95 GenFlags = TypeOf (ResultType);
96
97 /* Calculate the number of bits the lhs operand has */
98 ExprBits = SizeOf (ResultType) * 8;
99
100 /* Get the lhs on stack */
101 GetCodePos (&Mark1);
102 ltype = TypeOf (Expr->Type);
103 if (ED_IsConstAbs (Expr)) {
104 /* Constant value */
105 GetCodePos (&Mark2);
106 g_push (ltype | CF_CONST, Expr->IVal);
107 } else {
108 /* Value not constant */
109 LoadExpr (CF_NONE, Expr);
110 GetCodePos (&Mark2);
111 g_push (ltype, 0);
112 }
113
114 /* Get the right hand side */
115 ExprWithCheck (hie8, &Expr2);
116
117 /* Check the type of the rhs */
118 if (!IsClassInt (Expr2.Type)) {
119 Error ("Integer expression expected");
120 ED_MakeConstAbsInt (&Expr2, 1);
121 }
122
123 /* Check for a constant right side expression */
124 rconst = ED_IsConstAbs (&Expr2);
125 if (!rconst) {
126
127 /* Not constant, load into the primary */
128 LoadExpr (CF_NONE, &Expr2);
129
130 } else {
131
132 /* The rhs is a constant numeric value. */
133 GenFlags |= CF_CONST;
134
135 /* Remove the code that pushes the rhs onto the stack. */
136 RemoveCode (&Mark2);
137
138 /* If the shift count is greater or equal than the bit count of
139 ** the operand, the behaviour is undefined according to the
140 ** standard.
141 */
142 if (Expr2.IVal < 0 || Expr2.IVal >= (long) ExprBits) {
143
144 Warning ("Shift count too large for operand type");
145 Expr2.IVal &= ExprBits - 1;
146
147 }
148
149 /* If the shift count is zero, nothing happens */
150 if (Expr2.IVal == 0) {
151
152 /* Result is already in Expr, remove the generated code */
153 RemoveCode (&Mark1);
154
155 /* Done */
156 goto Next;
157 }
158
159 /* If the left hand side is a constant, the result is constant */
160 if (ED_IsConstAbs (Expr)) {
161
162 /* Evaluate the result */
163 switch (Tok) {
164 case TOK_SHL: Expr->IVal <<= Expr2.IVal; break;
165 case TOK_SHR: Expr->IVal >>= Expr2.IVal; break;
166 default: /* Shutup gcc */ break;
167 }
168
169 /* Both operands are constant, remove the generated code */
170 RemoveCode (&Mark1);
171
172 /* Done */
173 goto Next;
174 }
175
176 /* If we're shifting an integer or unsigned to the right, the
177 ** lhs has a const address, and the shift count is larger than 8,
178 ** we can load just the high byte as a char with the correct
179 ** signedness, and reduce the shift count by 8. If the remaining
180 ** shift count is zero, we're done.
181 */
182 if (Tok == TOK_SHR &&
183 IsTypeInt (Expr->Type) &&
184 ED_IsLVal (Expr) &&
185 (ED_IsLocConst (Expr) || ED_IsLocStack (Expr)) &&
186 Expr2.IVal >= 8) {
187
188 Type* OldType;
189
190 /* Increase the address by one and decrease the shift count */
191 ++Expr->IVal;
192 Expr2.IVal -= 8;
193
194 /* Replace the type of the expression temporarily by the
195 ** corresponding char type.
196 */
197 OldType = Expr->Type;
198 if (IsSignUnsigned (Expr->Type)) {
199 Expr->Type = type_uchar;
200 } else {
201 Expr->Type = type_schar;
202 }
203
204 /* Remove the generated load code */
205 RemoveCode (&Mark1);
206
207 /* Generate again code for the load, this time with the new type */
208 LoadExpr (CF_NONE, Expr);
209
210 /* Reset the type */
211 Expr->Type = OldType;
212
213 /* If the shift count is now zero, we're done */
214 if (Expr2.IVal == 0) {
215 /* Be sure to mark the value as in the primary */
216 goto MakeRVal;
217 }
218 }
219
220 }
221
222 /* Generate code */
223 switch (Tok) {
224 case TOK_SHL: g_asl (GenFlags, Expr2.IVal); break;
225 case TOK_SHR: g_asr (GenFlags, Expr2.IVal); break;
226 default: break;
227 }
228
229MakeRVal:
230 /* We have a rvalue in the primary now */
231 ED_MakeRValExpr (Expr);
232
233Next:
234 /* Set the type of the result */
235 Expr->Type = ResultType;
236 }
237}
238