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perf(compiler): optimize vector arithmetic and numeric loop type inference #2237

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94a330d
perf(compiler): optimize constant folding for vectors and loop variables
ActualMasterOogway Feb 8, 2026
26cd015
test(compiler): align compiler tests with loop variable type inference
ActualMasterOogway Feb 8, 2026
9d873fe
test(codegen): align IR lowering tests with vector optimizations
ActualMasterOogway Feb 8, 2026
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6 changes: 3 additions & 3 deletions Compiler/src/Compiler.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1862,8 +1862,8 @@ struct Compiler
}
else if (options.optimizationLevel >= 2 && (expr->op == AstExprBinary::Add || expr->op == AstExprBinary::Mul))
{
// Optimization: replace k*r with r*k when r is known to be a number (otherwise metamethods may be called)
if (LuauBytecodeType* ty = exprTypes.find(expr); ty && *ty == LBC_TYPE_NUMBER)
// Optimization: replace k*r with r*k when r is known to be a number or vector (otherwise metamethods may be called)
if (LuauBytecodeType* ty = exprTypes.find(expr); ty && (*ty == LBC_TYPE_NUMBER || *ty == LBC_TYPE_VECTOR))
{
int32_t lc = getConstantNumber(expr->left);

Expand All @@ -1873,7 +1873,7 @@ struct Compiler

bytecode.emitABC(getBinaryOpArith(expr->op, /* k= */ true), target, rr, uint8_t(lc));

hintTemporaryExprRegType(expr->right, rr, LBC_TYPE_NUMBER, /* instLength */ 1);
hintTemporaryExprRegType(expr->right, rr, *ty, /* instLength */ 1);
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@vegorov-rbx vegorov-rbx Feb 10, 2026

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Suggested change
hintTemporaryExprRegType(expr->right, rr, *ty, /* instLength */ 1);
hintTemporaryExprRegType(expr->right, rr, LBC_TYPE_NUMBER, /* instLength */ 1);

Hint system is used to provide hints on types that are not the expected operands of an instruction.
By saying that 'vector' is expected for an add/mul, hint will not be generated and this will cause jit performance to regress on a wrong type speculation.
For example in this case:

local function foo(t: {a: vector})
    return 2 * t.a
end

With this change, the fast-path is generated for number*number, causing a fallback to be taken at runtime.

Since this was a regression not caught by existing tests, this example should be added as a regression test to IrLowering.test.cpp

return;
}
}
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13 changes: 13 additions & 0 deletions Compiler/src/Types.cpp
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Expand Up @@ -448,6 +448,19 @@ struct TypeMapVisitor : AstVisitor
return false;
}

bool visit(AstStatFor* node) override
{
resolvedLocals[node->var] = &builtinTypes.numberType;

node->from->visit(this);
node->to->visit(this);
if (node->step)
node->step->visit(this);
node->body->visit(this);

return false;
}

bool visit(AstExprIndexExpr* node) override
{
node->expr->visit(this);
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4 changes: 2 additions & 2 deletions tests/Compiler.test.cpp
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Expand Up @@ -3846,7 +3846,7 @@ R0: vector [argument]
R1: mat3 [argument]
R2: userdata [argument]
U0: number
R6: any from 1 to 9
R6: number from 1 to 9
R3: vector from 0 to 30
MUL R3 R0 R0
LOADN R6 1
Expand Down Expand Up @@ -4756,7 +4756,7 @@ TEST_CASE("JumpTrampoline")
CHECK_EQ("\n" + head, R"(
local 0: reg 3, start pc 8 line 3, end pc 54545 line 20002
local 1: reg 0, start pc 2 line 2, end pc 54549 line 20004
R3: any from 2 to 54546
R3: number from 2 to 54546
R0: number from 1 to 54550
LOADN R0 0
LOADN R3 1
Expand Down
42 changes: 21 additions & 21 deletions tests/IrLowering.test.cpp
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Expand Up @@ -496,17 +496,17 @@ end
%22 = FLOAT_TO_VEC 4
%23 = DIV_VEC %20, %22
%32 = ADD_VEC %15, %23
%43 = FLOAT_TO_VEC 0.5
%44 = LOAD_TVALUE R2, 0i, tvector
%45 = MUL_VEC %43, %44
%54 = ADD_VEC %32, %45
%60 = FLOAT_TO_VEC 40
%61 = LOAD_TVALUE R3, 0i, tvector
%62 = DIV_VEC %60, %61
%71 = ADD_VEC %54, %62
%72 = TAG_VECTOR %71
STORE_TVALUE R4, %72
INTERRUPT 8u
%37 = LOAD_TVALUE R2, 0i, tvector
%39 = FLOAT_TO_VEC 0.5
%40 = MUL_VEC %37, %39
%49 = ADD_VEC %32, %40
%55 = FLOAT_TO_VEC 40
%56 = LOAD_TVALUE R3, 0i, tvector
%57 = DIV_VEC %55, %56
%66 = ADD_VEC %49, %57
%67 = TAG_VECTOR %66
STORE_TVALUE R4, %67
INTERRUPT 7u
RETURN R4, 1i
)"
);
Expand Down Expand Up @@ -6995,16 +6995,16 @@ end
STORE_POINTER R2, %7
STORE_TAG R2, ttable
CHECK_GC
%19 = FLOAT_TO_VEC 2
%20 = LOAD_TVALUE R0, 0i, tvector
%21 = MUL_VEC %19, %20
%29 = LOAD_TVALUE R1, 0i, tvector
%30 = ADD_VEC %21, %29
%31 = TAG_VECTOR %30
STORE_TVALUE R3, %31
STORE_TVALUE R4, %31
SETLIST 8u, R2, R3, 2i, 1u, 2u
INTERRUPT 10u
%13 = LOAD_TVALUE R0, 0i, tvector
%15 = FLOAT_TO_VEC 2
%16 = MUL_VEC %13, %15
%24 = LOAD_TVALUE R1, 0i, tvector
%25 = ADD_VEC %16, %24
%26 = TAG_VECTOR %25
STORE_TVALUE R3, %26
STORE_TVALUE R4, %26
SETLIST 6u, R2, R3, 2i, 1u, 2u
INTERRUPT 8u
RETURN R2, 1i
)"
);
Expand Down