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[mono][interp] Improve precision of native offset estimation #103956

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Jun 26, 2024
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[mono][interp] Improve precision of native offset estimation #103956

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2 changes: 1 addition & 1 deletion src/mono/mono/mini/interp/transform-opt.c
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Original file line number Diff line number Diff line change
Expand Up @@ -3387,7 +3387,7 @@ can_propagate_var_def (TransformData *td, int var, InterpLivenessPosition cur_li
static void
interp_super_instructions (TransformData *td)
{
interp_compute_native_offset_estimates (td);
interp_compute_native_offset_estimates (td, FALSE);

// Add some actual super instructions
for (int bb_dfs_index = 0; bb_dfs_index < td->bblocks_count_eh; bb_dfs_index++) {
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24 changes: 22 additions & 2 deletions src/mono/mono/mini/interp/transform.c
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Expand Up @@ -8791,12 +8791,18 @@ interp_foreach_ins_var (TransformData *td, InterpInst *ins, gpointer data, void
}

int
interp_compute_native_offset_estimates (TransformData *td)
interp_compute_native_offset_estimates (TransformData *td, gboolean final_code)
{
InterpBasicBlock *bb;
int noe = 0;

for (bb = td->entry_bb; bb != NULL; bb = bb->next_bb) {
InterpInst *ins;
// FIXME This doesn't currently hold because of bblock reordering potentially
// inserting additional instructions after the estimate is computed.
//
// if (bb->native_offset_estimate)
// g_assert (bb->native_offset_estimate >= noe);
bb->native_offset_estimate = noe;
if (!td->optimized && bb->patchpoint_bb)
noe += 2;
Expand All @@ -8815,6 +8821,20 @@ interp_compute_native_offset_estimates (TransformData *td)
if (MINT_IS_EMIT_NOP (opcode))
continue;
noe += interp_get_ins_length (ins);

if (!final_code && td->optimized &&
(ins->flags & INTERP_INST_FLAG_CALL) &&
ins->info.call_info &&
ins->info.call_info->call_args) {
// When code is optimized, for a call, the offset allocator
// might end up inserting additional moves for the arguments
int *call_args = ins->info.call_info->call_args;
while (*call_args != -1) {
noe += 4; // mono_interp_oplen [MINT_MOV_VT];
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Is it always a single MINT_MOV_VT per argument?

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It is either a scalar mov (size 3) or a vt move (which also has size embedded so it is size 4). We are being conservative here since it is not worth checking the signature.

call_args++;
}
}

if (!td->optimized)
interp_foreach_ins_var (td, ins, NULL, alloc_unopt_global_local);
}
Expand Down Expand Up @@ -9255,7 +9275,7 @@ generate_compacted_code (InterpMethod *rtm, TransformData *td)

// This iteration could be avoided at the cost of less precise size result, following
// super instruction pass
size = interp_compute_native_offset_estimates (td);
size = interp_compute_native_offset_estimates (td, TRUE);

// Generate the compacted stream of instructions
td->new_code = ip = (guint16*)imethod_alloc0 (td, size * sizeof (guint16));
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2 changes: 1 addition & 1 deletion src/mono/mono/mini/interp/transform.h
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Expand Up @@ -522,7 +522,7 @@ void
interp_link_bblocks (TransformData *td, InterpBasicBlock *from, InterpBasicBlock *to);

int
interp_compute_native_offset_estimates (TransformData *td);
interp_compute_native_offset_estimates (TransformData *td, gboolean final_code);

void
interp_optimize_code (TransformData *td);
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