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Sema: optimize comptime @memset by setting all elements at once

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Previously, @memset at comptime performed N pointer stores. This is less
efficient than just storing a whole array of values at once. The
difference can be quite drastic when reinterpreting memory - a test case
which is 40s on master branch now takes under a second on a debug
compiler build.

Resolves: #17214
This commit is contained in:
mlugg 2023-09-21 21:06:32 +01:00 committed by Andrew Kelley
parent 272a57eeed
commit e011c31ee8
1 changed files with 24 additions and 30 deletions
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54
src/Sema.zig
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@ -24406,10 +24406,12 @@ fn zirMemset(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileError!void
});
};
const runtime_src = if (try sema.resolveDefinedValue(block, dest_src, dest_ptr)) |ptr_val| rs: {
const elem = try sema.coerce(block, dest_elem_ty, uncoerced_elem, value_src);
const runtime_src = rs: {
const ptr_val = try sema.resolveDefinedValue(block, dest_src, dest_ptr) orelse break :rs dest_src;
const len_air_ref = try sema.fieldVal(block, src, dest_ptr, try ip.getOrPutString(gpa, "len"), dest_src);
const len_val = (try sema.resolveDefinedValue(block, dest_src, len_air_ref)) orelse
break :rs dest_src;
const len_val = (try sema.resolveDefinedValue(block, dest_src, len_air_ref)) orelse break :rs dest_src;
const len_u64 = (try len_val.getUnsignedIntAdvanced(mod, sema)).?;
const len = try sema.usizeCast(block, dest_src, len_u64);
if (len == 0) {
@ -24418,33 +24420,25 @@ fn zirMemset(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileError!void
}
if (!ptr_val.isComptimeMutablePtr(mod)) break :rs dest_src;
if (try sema.resolveMaybeUndefVal(uncoerced_elem)) |_| {
for (0..len) |i| {
const elem_index = try mod.intRef(Type.usize, i);
const elem_ptr = try sema.elemPtrOneLayerOnly(
block,
src,
dest_ptr,
elem_index,
src,
true, // init
false, // oob_safety
);
try sema.storePtr2(
block,
src,
elem_ptr,
dest_src,
uncoerced_elem,
value_src,
.store,
);
}
return;
} else break :rs value_src;
} else dest_src;
const elem = try sema.coerce(block, dest_elem_ty, uncoerced_elem, value_src);
const elem_val = try sema.resolveMaybeUndefVal(elem) orelse break :rs value_src;
const array_ty = try mod.arrayType(.{
.child = dest_elem_ty.toIntern(),
.len = len_u64,
});
const array_val = (try mod.intern(.{ .aggregate = .{
.ty = array_ty.toIntern(),
.storage = .{ .repeated_elem = elem_val.toIntern() },
} })).toValue();
const array_ptr_ty = ty: {
var info = dest_ptr_ty.ptrInfo(mod);
info.flags.size = .One;
info.child = array_ty.toIntern();
break :ty try mod.ptrType(info);
};
const raw_ptr_val = if (dest_ptr_ty.isSlice(mod)) ptr_val.slicePtr(mod) else ptr_val;
const array_ptr_val = try mod.getCoerced(raw_ptr_val, array_ptr_ty);
return sema.storePtrVal(block, src, array_ptr_val, array_val, array_ty);
};
try sema.requireRuntimeBlock(block, src, runtime_src);
_ = try block.addInst(.{