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authorwolfbeast <mcwerewolf@gmail.com>2018-02-05 16:36:15 +0100
committerwolfbeast <mcwerewolf@gmail.com>2018-02-05 16:36:15 +0100
commit6f0f1f85ebf218aef8839e17442dbaf15460be4f (patch)
tree92ef251a0b090d2d1ede09c6cf47b3e4a43ce3c8 /js/src/jit
parenta54e46aeb5497ec0c54ec453e6e0b22b2b54792b (diff)
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Split double MoveOperands that conflict with floats.
Diffstat (limited to 'js/src/jit')
-rw-r--r--js/src/jit/MoveResolver.cpp99
-rw-r--r--js/src/jit/MoveResolver.h11
2 files changed, 110 insertions, 0 deletions
diff --git a/js/src/jit/MoveResolver.cpp b/js/src/jit/MoveResolver.cpp
index 5fd6c7bd5..383b45073 100644
--- a/js/src/jit/MoveResolver.cpp
+++ b/js/src/jit/MoveResolver.cpp
@@ -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
diff --git a/js/src/jit/MoveResolver.h b/js/src/jit/MoveResolver.h
index fad2ba9e3..db045cfcf 100644
--- a/js/src/jit/MoveResolver.h
+++ b/js/src/jit/MoveResolver.h
@@ -252,6 +252,13 @@ class MoveOp
bool aliases(const MoveOp& other) const {
return aliases(other.from()) || aliases(other.to());
}
+#ifdef JS_CODEGEN_ARM
+ void overwrite(MoveOperand& from, MoveOperand& to, Type type) {
+ from_ = from;
+ to_ = to;
+ type_ = type;
+ }
+#endif
};
class MoveResolver
@@ -299,6 +306,10 @@ class MoveResolver
// Internal reset function. Does not clear lists.
void resetState();
+#ifdef JS_CODEGEN_ARM
+ bool isDoubleAliasedAsSingle(const MoveOperand& move);
+#endif
+
public:
MoveResolver();