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ZJIT: Constant-fold LoadField/GuardBitEquals from known-frozen object

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Resolves https://github.com/Shopify/ruby/issues/915

When we have `LoadField` with a `Shape` return type, we can fold it similar to the object case.
`GuardBitEquals` can be removed when the argument is `Const` and the values are equal.

The behaviors for loading instances variables from frozen/dynamic objects are already covered in existing tests so no new tests were added.
This commit is contained in:
Jeff Zhang 2026-01-13 20:06:01 -05:00 committed by GitHub
parent 4f8478f50c
commit 65a4845780
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GPG Key ID: B5690EEEBB952194
Notes: git 2026-01-14 01:06:29 +00:00 
Merged: https://github.com/ruby/ruby/pull/15863

Merged-By: tekknolagi <donotemailthisaddress@bernsteinbear.com>
2 changed files with 45 additions and 39 deletions
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24
zjit/src/hir.rs
View File

@ -3798,6 +3798,30 @@ impl Function {
_ => insn_id,
}
}
Insn::LoadField { recv, offset, return_type, .. } if return_type.is_subtype(types::CShape) &&
u32::try_from(offset).is_ok() => {
let offset = (offset as u32).to_usize();
let recv_type = self.type_of(recv);
match recv_type.ruby_object() {
Some(recv_obj) if recv_obj.is_frozen() => {
let recv_ptr = recv_obj.as_ptr() as *const u32;
let val = unsafe { recv_ptr.byte_add(offset).read() };
self.new_insn(Insn::Const { val: Const::CShape(ShapeId(val)) })
}
_ => insn_id,
}
}
Insn::GuardBitEquals { val, expected, .. } => {
match self.find(val) {
// TODO: Refactor this into a more general method like
// has_value(Const) that can check on the value specialization
// of the Type instead
Insn::Const { val: const_val } if const_val == expected => {
continue;
}
_ => insn_id
}
}
Insn::AnyToString { str, .. } if self.is_a(str, types::String) => {
self.make_equal_to(insn_id, str);
// Don't bother re-inferring the type of str; we already know it.

60
zjit/src/hir/opt_tests.rs
View File

@ -9927,11 +9927,9 @@ mod hir_opt_tests {
v20:HeapObject[VALUE(0x1008)] = Const Value(VALUE(0x1008))
PatchPoint MethodRedefined(TestFrozen@0x1010, a@0x1018, cme:0x1020)
PatchPoint NoSingletonClass(TestFrozen@0x1010)
v25:CShape = LoadField v20, :_shape_id@0x1048
v26:CShape[0x1049] = GuardBitEquals v25, CShape(0x1049)
v28:Fixnum[1] = Const Value(1)
v29:Fixnum[1] = Const Value(1)
CheckInterrupts
Return v28
Return v29
");
}
@ -9969,11 +9967,9 @@ mod hir_opt_tests {
v20:HeapObject[VALUE(0x1008)] = Const Value(VALUE(0x1008))
PatchPoint MethodRedefined(TestMultiIvars@0x1010, b@0x1018, cme:0x1020)
PatchPoint NoSingletonClass(TestMultiIvars@0x1010)
v25:CShape = LoadField v20, :_shape_id@0x1048
v26:CShape[0x1049] = GuardBitEquals v25, CShape(0x1049)
v28:Fixnum[20] = Const Value(20)
v29:Fixnum[20] = Const Value(20)
CheckInterrupts
Return v28
Return v29
");
}
@ -10009,11 +10005,9 @@ mod hir_opt_tests {
v20:HeapObject[VALUE(0x1008)] = Const Value(VALUE(0x1008))
PatchPoint MethodRedefined(TestFrozenStr@0x1010, name@0x1018, cme:0x1020)
PatchPoint NoSingletonClass(TestFrozenStr@0x1010)
v25:CShape = LoadField v20, :_shape_id@0x1048
v26:CShape[0x1049] = GuardBitEquals v25, CShape(0x1049)
v28:StringExact[VALUE(0x1050)] = Const Value(VALUE(0x1050))
v29:StringExact[VALUE(0x1048)] = Const Value(VALUE(0x1048))
CheckInterrupts
Return v28
Return v29
");
}
@ -10049,11 +10043,9 @@ mod hir_opt_tests {
v20:HeapObject[VALUE(0x1008)] = Const Value(VALUE(0x1008))
PatchPoint MethodRedefined(TestFrozenNil@0x1010, value@0x1018, cme:0x1020)
PatchPoint NoSingletonClass(TestFrozenNil@0x1010)
v25:CShape = LoadField v20, :_shape_id@0x1048
v26:CShape[0x1049] = GuardBitEquals v25, CShape(0x1049)
v28:NilClass = Const Value(nil)
v29:NilClass = Const Value(nil)
CheckInterrupts
Return v28
Return v29
");
}
@ -10129,11 +10121,9 @@ mod hir_opt_tests {
v20:HeapObject[VALUE(0x1008)] = Const Value(VALUE(0x1008))
PatchPoint MethodRedefined(TestAttrReader@0x1010, value@0x1018, cme:0x1020)
PatchPoint NoSingletonClass(TestAttrReader@0x1010)
v25:CShape = LoadField v20, :_shape_id@0x1048
v26:CShape[0x1049] = GuardBitEquals v25, CShape(0x1049)
v28:Fixnum[42] = Const Value(42)
v29:Fixnum[42] = Const Value(42)
CheckInterrupts
Return v28
Return v29
");
}
@ -10169,11 +10159,9 @@ mod hir_opt_tests {
v20:HeapObject[VALUE(0x1008)] = Const Value(VALUE(0x1008))
PatchPoint MethodRedefined(TestFrozenSym@0x1010, sym@0x1018, cme:0x1020)
PatchPoint NoSingletonClass(TestFrozenSym@0x1010)
v25:CShape = LoadField v20, :_shape_id@0x1048
v26:CShape[0x1049] = GuardBitEquals v25, CShape(0x1049)
v28:StaticSymbol[:hello] = Const Value(VALUE(0x1050))
v29:StaticSymbol[:hello] = Const Value(VALUE(0x1048))
CheckInterrupts
Return v28
Return v29
");
}
@ -10209,11 +10197,9 @@ mod hir_opt_tests {
v20:HeapObject[VALUE(0x1008)] = Const Value(VALUE(0x1008))
PatchPoint MethodRedefined(TestFrozenBool@0x1010, flag@0x1018, cme:0x1020)
PatchPoint NoSingletonClass(TestFrozenBool@0x1010)
v25:CShape = LoadField v20, :_shape_id@0x1048
v26:CShape[0x1049] = GuardBitEquals v25, CShape(0x1049)
v28:TrueClass = Const Value(true)
v29:TrueClass = Const Value(true)
CheckInterrupts
Return v28
Return v29
");
}
@ -10288,22 +10274,18 @@ mod hir_opt_tests {
v28:HeapObject[VALUE(0x1008)] = Const Value(VALUE(0x1008))
PatchPoint MethodRedefined(TestNestedAccess@0x1010, x@0x1018, cme:0x1020)
PatchPoint NoSingletonClass(TestNestedAccess@0x1010)
v39:CShape = LoadField v28, :_shape_id@0x1048
v40:CShape[0x1049] = GuardBitEquals v39, CShape(0x1049)
v52:Fixnum[100] = Const Value(100)
v53:Fixnum[100] = Const Value(100)
PatchPoint SingleRactorMode
PatchPoint StableConstantNames(0x1050, NESTED_FROZEN)
PatchPoint StableConstantNames(0x1048, NESTED_FROZEN)
v34:HeapObject[VALUE(0x1008)] = Const Value(VALUE(0x1008))
PatchPoint MethodRedefined(TestNestedAccess@0x1010, y@0x1058, cme:0x1060)
PatchPoint MethodRedefined(TestNestedAccess@0x1010, y@0x1050, cme:0x1058)
PatchPoint NoSingletonClass(TestNestedAccess@0x1010)
v43:CShape = LoadField v34, :_shape_id@0x1048
v44:CShape[0x1049] = GuardBitEquals v43, CShape(0x1049)
v53:Fixnum[200] = Const Value(200)
PatchPoint MethodRedefined(Integer@0x1088, +@0x1090, cme:0x1098)
v54:Fixnum[300] = Const Value(300)
v55:Fixnum[200] = Const Value(200)
PatchPoint MethodRedefined(Integer@0x1080, +@0x1088, cme:0x1090)
v56:Fixnum[300] = Const Value(300)
IncrCounter inline_cfunc_optimized_send_count
CheckInterrupts
Return v54
Return v56
");
}