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| author | Richard Biener <rguenther@suse.de> | 2020-02-14 08:32:53 +0100 |
|---|---|---|
| committer | Tom de Vries <tdevries@suse.de> | 2020-02-14 08:32:53 +0100 |
| commit | 258bf0ee3748d4354e13daf00f02266cafa96389 (patch) | |
| tree | a6f6a7933d4d14869687dcf606e1f66fc1c23d97 /gdb/dwarf2 | |
| parent | d4059b1d6cb65296134ca9f3497249e84acb622e (diff) | |
| download | gdb-258bf0ee3748d4354e13daf00f02266cafa96389.zip gdb-258bf0ee3748d4354e13daf00f02266cafa96389.tar.gz gdb-258bf0ee3748d4354e13daf00f02266cafa96389.tar.bz2 | |
[gdb] Speedup lnp_state_machine::handle_special_opcode
I see for some program at gdb startup:
...
Samples: 102K of event 'cycles:pu', Event count (approx.): 91710925103
Overhead Command Shared Object Symbol
15.21% gdb gdb [.]
lnp_state_machine::handle_special
...
where the divisions are the places we stall. The following
micro-optimizes things but it smells like m_line_header->line_range
is constant, likewise probably m_line_header->maximum_ops_per_instruction
so eventually the divisions could be avoided completely with some
lookup table.
Well. Micro-optimizing with this patch improves things
(don't expect [load] CSE over the gdbarch_adjust_dwarf2_line call).
Build and reg-tested on x86_64-linux.
gdb/ChangeLog:
2020-02-14 Richard Biener <rguenther@suse.de>
* dwarf2/read.c (lnp_state_machine::handle_special_opcode): Apply CSE
on expression with division operators.
Diffstat (limited to 'gdb/dwarf2')
| -rw-r--r-- | gdb/dwarf2/read.c | 10 |
1 files changed, 5 insertions, 5 deletions
diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c index 7edbd9d..e74383e 100644 --- a/gdb/dwarf2/read.c +++ b/gdb/dwarf2/read.c @@ -19812,16 +19812,16 @@ void lnp_state_machine::handle_special_opcode (unsigned char op_code) { unsigned char adj_opcode = op_code - m_line_header->opcode_base; - CORE_ADDR addr_adj = (((m_op_index - + (adj_opcode / m_line_header->line_range)) + unsigned char adj_opcode_d = adj_opcode / m_line_header->line_range; + unsigned char adj_opcode_r = adj_opcode % m_line_header->line_range; + CORE_ADDR addr_adj = (((m_op_index + adj_opcode_d) / m_line_header->maximum_ops_per_instruction) * m_line_header->minimum_instruction_length); m_address += gdbarch_adjust_dwarf2_line (m_gdbarch, addr_adj, true); - m_op_index = ((m_op_index + (adj_opcode / m_line_header->line_range)) + m_op_index = ((m_op_index + adj_opcode_d) % m_line_header->maximum_ops_per_instruction); - int line_delta = (m_line_header->line_base - + (adj_opcode % m_line_header->line_range)); + int line_delta = m_line_header->line_base + adj_opcode_r; advance_line (line_delta); record_line (false); m_discriminator = 0; |