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dwarf: optimize dwarf parsing for speed

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This code is run when printing a stack trace in a debug executable, so
it has to be fast even without compiler optimizations.

Adding a `@panic` to the top of `main` and running an x86_64 backend
compiled compiler goes from `1m32.773s` to `0m3.232s`.
This commit is contained in:
Jacob Young 2024-02-18 10:14:39 +01:00
parent 57b2b3df52
commit 247e4ac3cc
3 changed files with 699 additions and 723 deletions
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1360
lib/std/dwarf.zig
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File diff suppressed because it is too large Load diff

18
lib/std/dwarf/expressions.zig
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@ -12,8 +12,8 @@ const native_endian = builtin.cpu.arch.endian();
/// Callers should specify all the fields relevant to their context. If a field is required
/// by the expression and it isn't in the context, error.IncompleteExpressionContext is returned.
pub const ExpressionContext = struct {
/// This expression is from a DWARF64 section
is_64: bool = false,
/// The dwarf format of the section this expression is in
format: dwarf.Format = .@"32",
/// If specified, any addresses will pass through this function before being acccessed
isValidMemory: ?*const fn (address: usize) bool = null,
@ -190,10 +190,10 @@ pub fn StackMachine(comptime options: ExpressionOptions) type {
const reader = stream.reader();
return switch (opcode) {
OP.addr => generic(try reader.readInt(addr_type, options.endian)),
OP.call_ref => if (context.is_64)
generic(try reader.readInt(u64, options.endian))
else
generic(try reader.readInt(u32, options.endian)),
OP.call_ref => switch (context.format) {
.@"32" => generic(try reader.readInt(u32, options.endian)),
.@"64" => generic(try reader.readInt(u64, options.endian)),
},
OP.const1u,
OP.pick,
=> generic(try reader.readByte()),
@ -366,15 +366,15 @@ pub fn StackMachine(comptime options: ExpressionOptions) type {
_ = offset;
switch (context.compile_unit.?.frame_base.?.*) {
.ExprLoc => {
.exprloc => {
// TODO: Run this expression in a nested stack machine
return error.UnimplementedOpcode;
},
.LocListOffset => {
.loclistx => {
// TODO: Read value from .debug_loclists
return error.UnimplementedOpcode;
},
.SecOffset => {
.sec_offset => {
// TODO: Read value from .debug_loclists
return error.UnimplementedOpcode;
},

8
lib/std/io/fixed_buffer_stream.zig
View file

@ -62,11 +62,7 @@ pub fn FixedBufferStream(comptime Buffer: type) type {
if (bytes.len == 0) return 0;
if (self.pos >= self.buffer.len) return error.NoSpaceLeft;
const n = if (self.pos + bytes.len <= self.buffer.len)
bytes.len
else
self.buffer.len - self.pos;
const n = @min(self.buffer.len - self.pos, bytes.len);
@memcpy(self.buffer[self.pos..][0..n], bytes[0..n]);
self.pos += n;
@ -76,7 +72,7 @@ pub fn FixedBufferStream(comptime Buffer: type) type {
}
pub fn seekTo(self: *Self, pos: u64) SeekError!void {
self.pos = if (std.math.cast(usize, pos)) |x| @min(self.buffer.len, x) else self.buffer.len;
self.pos = @min(std.math.lossyCast(usize, pos), self.buffer.len);
}
pub fn seekBy(self: *Self, amt: i64) SeekError!void {