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Split double MoveOperands that conflict with floats.

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wolfbeast 2018-02-05 16:36:15 +01:00 • committed by Roy Tam
commit 27bb9f94c3
3 changed files with 203 additions and 1 deletions
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99
js/src/jit/MoveResolver.cpp
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@ -106,12 +106,111 @@ MoveResolver::findCycledMove(PendingMoveIterator* iter, PendingMoveIterator end,
return nullptr;
}
#ifdef JS_CODEGEN_ARM
static inline bool
MoveIsDouble(const MoveOperand& move)
{
if (!move.isFloatReg())
return false;
return move.floatReg().isDouble();
}
#endif
#ifdef JS_CODEGEN_ARM
static inline bool
MoveIsSingle(const MoveOperand& move)
{
if (!move.isFloatReg())
return false;
return move.floatReg().isSingle();
}
#endif
#ifdef JS_CODEGEN_ARM
bool
MoveResolver::isDoubleAliasedAsSingle(const MoveOperand& move)
{
if (!MoveIsDouble(move))
return false;
for (auto iter = pending_.begin(); iter != pending_.end(); ++iter) {
PendingMove* other = *iter;
if (other->from().aliases(move) && MoveIsSingle(other->from()))
return true;
if (other->to().aliases(move) && MoveIsSingle(other->to()))
return true;
}
return false;
}
#endif
#ifdef JS_CODEGEN_ARM
static MoveOperand
SplitIntoLowerHalf(const MoveOperand& move)
{
if (MoveIsDouble(move)) {
FloatRegister lowerSingle = move.floatReg().asSingle();
return MoveOperand(lowerSingle);
}
MOZ_ASSERT(move.isMemoryOrEffectiveAddress());
return move;
}
#endif
#ifdef JS_CODEGEN_ARM
static MoveOperand
SplitIntoUpperHalf(const MoveOperand& move)
{
if (MoveIsDouble(move)) {
FloatRegister lowerSingle = move.floatReg().asSingle();
FloatRegister upperSingle = VFPRegister(lowerSingle.code() + 1, VFPRegister::Single);
return MoveOperand(upperSingle);
}
MOZ_ASSERT(move.isMemoryOrEffectiveAddress());
return MoveOperand(move.base(), move.disp() + sizeof(float));
}
#endif
bool
MoveResolver::resolve()
{
resetState();
orderedMoves_.clear();
#ifdef JS_CODEGEN_ARM
// Some of ARM's double registers alias two of its single registers,
// but the algorithm below assumes that every register can participate
// in at most one cycle. To satisfy the algorithm, any double registers
// that may conflict are split into their single-register halves.
//
// This logic is only applicable because ARM only uses registers d0-d15,
// all of which alias s0-s31. Double registers d16-d31 are unused.
// Therefore there is never a double move that cannot be split.
// If this changes in the future, the algorithm will have to be fixed.
for (auto iter = pending_.begin(); iter != pending_.end(); ++iter) {
PendingMove* pm = *iter;
if (isDoubleAliasedAsSingle(pm->from()) || isDoubleAliasedAsSingle(pm->to())) {
PendingMove* lower = movePool_.allocate();
if (!lower)
return false;
// Insert the new node before the current position to not affect iteration.
MoveOperand fromLower = SplitIntoLowerHalf(pm->from());
MoveOperand toLower = SplitIntoLowerHalf(pm->to());
new (lower) PendingMove(fromLower, toLower, MoveOp::FLOAT32);
pending_.insertBefore(pm, lower);
// Overwrite pm in place for the upper move. Iteration proceeds as normal.
MoveOperand fromUpper = SplitIntoUpperHalf(pm->from());
MoveOperand toUpper = SplitIntoUpperHalf(pm->to());
pm->overwrite(fromUpper, toUpper, MoveOp::FLOAT32);
}
}
#endif
InlineList<PendingMove> stack;
// This is a depth-first-search without recursion, which tries to find