system.cc (5268:5bfc53fe60e7) system.cc (5543:3af77710f397)
1/*
2 * Copyright (c) 2002-2005 The Regents of The University of Michigan
3 * Copyright (c) 2007 MIPS Technologies, Inc.
4 * All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions are
8 * met: redistributions of source code must retain the above copyright

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129 * Mips binaries may have multiple global offset table (GOT)
130 * sections. A function that uses the GOT starts with a
131 * two-instruction prolog which sets the global pointer (gp == r29) to
132 * the appropriate GOT section. The proper gp value is calculated
133 * based on the function address, which must be passed by the caller
134 * in the procedure value register (pv aka t12 == r27). This sequence
135 * looks like the following:
136 *
1/*
2 * Copyright (c) 2002-2005 The Regents of The University of Michigan
3 * Copyright (c) 2007 MIPS Technologies, Inc.
4 * All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions are
8 * met: redistributions of source code must retain the above copyright

--- 120 unchanged lines hidden (view full) ---

129 * Mips binaries may have multiple global offset table (GOT)
130 * sections. A function that uses the GOT starts with a
131 * two-instruction prolog which sets the global pointer (gp == r29) to
132 * the appropriate GOT section. The proper gp value is calculated
133 * based on the function address, which must be passed by the caller
134 * in the procedure value register (pv aka t12 == r27). This sequence
135 * looks like the following:
136 *
137 * opcode Ra Rb offset
138 * ldah gp,X(pv) 09 29 27 X
139 * lda gp,Y(gp) 08 29 29 Y
137 * opcode Ra Rb offset
138 * ldah gp,X(pv) 09 29 27 X
139 * lda gp,Y(gp) 08 29 29 Y
140 *
141 * for some constant offsets X and Y. The catch is that the linker
142 * (or maybe even the compiler, I'm not sure) may recognize that the
143 * caller and callee are using the same GOT section, making this
144 * prolog redundant, and modify the call target to skip these
145 * instructions. If we check for execution of the first instruction
146 * of a function (the one the symbol points to) to detect when to skip
147 * it, we'll miss all these modified calls. It might work to

--- 75 unchanged lines hidden --- 		140 *
141 * for some constant offsets X and Y. The catch is that the linker
142 * (or maybe even the compiler, I'm not sure) may recognize that the
143 * caller and callee are using the same GOT section, making this
144 * prolog redundant, and modify the call target to skip these
145 * instructions. If we check for execution of the first instruction
146 * of a function (the one the symbol points to) to detect when to skip
147 * it, we'll miss all these modified calls. It might work to

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