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Don't issue a ldrd when the register holding the address is also a de… #1658

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Don't issue a ldrd when the register holding the address is also a de… #1658

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31 changes: 20 additions & 11 deletions Source/JavaScriptCore/assembler/MacroAssemblerARMv7.h
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Original file line number Diff line number Diff line change
Expand Up @@ -940,23 +940,32 @@ class MacroAssemblerARMv7 : public AbstractMacroAssembler<Assembler> {
loadPair32(Address(scratch), dest1, dest2);
} else {
ASSERT(dest1 != dest2); // If it is the same, ldp becomes illegal instruction.
int32_t absOffset = address.u.offset;
if (absOffset < 0)
absOffset = -absOffset;
if (!(absOffset & ~0x3fc)) {
if ((dest1 == addressTempRegister) || (dest2 == addressTempRegister))
invalidateCachedAddressTempRegister();
if ((dest1 == dataTempRegister) || (dest2 == dataTempRegister))
cachedDataTempRegister().invalidate();
m_assembler.ldrd(dest1, dest2, address.base, address.u.offset, /* index: */ true, /* wback: */ false);
} else if (address.base == dest1) {
// Check if dest1 or dest2 aliases the base register to avoid UNPREDICTABLE ldrd behavior
if (address.base == dest1) {
// Load high word first to avoid clobbering base register
ArmAddress highAddress(address.base, address.u.offset + 4);
load32(highAddress, dest2);
load32(address, dest1);
} else {
} else if (address.base == dest2) {
// Load low word first to avoid clobbering base register
load32(address, dest1);
ArmAddress highAddress(address.base, address.u.offset + 4);
load32(highAddress, dest2);
} else {
int32_t absOffset = address.u.offset;
if (absOffset < 0)
absOffset = -absOffset;
if (!(absOffset & ~0x3fc)) {
if ((dest1 == addressTempRegister) || (dest2 == addressTempRegister))
invalidateCachedAddressTempRegister();
if ((dest1 == dataTempRegister) || (dest2 == dataTempRegister))
cachedDataTempRegister().invalidate();
m_assembler.ldrd(dest1, dest2, address.base, address.u.offset, /* index: */ true, /* wback: */ false);
} else {
load32(address, dest1);
ArmAddress highAddress(address.base, address.u.offset + 4);
load32(highAddress, dest2);
}
}
}
}
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