|
| 1 | +""" |
| 2 | + AliasTracker |
| 3 | +
|
| 4 | +Tracks alias sets for each SSA value during fixed-point analysis. |
| 5 | +""" |
| 6 | +mutable struct AliasTracker |
| 7 | + dirty::Bool |
| 8 | + aliases::Dict{Any, AliasSet} # SSAValue/Argument/SlotNumber -> AliasSet |
| 9 | +end |
| 10 | + |
| 11 | +AliasTracker() = AliasTracker(false, Dict{Any, AliasSet}()) |
| 12 | + |
| 13 | +function Base.getindex(tracker::AliasTracker, key) |
| 14 | + return get(tracker.aliases, key, ALIAS_UNIVERSE) |
| 15 | +end |
| 16 | + |
| 17 | +function Base.setindex!(tracker::AliasTracker, value::AliasSet, key) |
| 18 | + current = get(tracker.aliases, key, nothing) |
| 19 | + if current !== value |
| 20 | + tracker.dirty = true |
| 21 | + tracker.aliases[key] = value |
| 22 | + end |
| 23 | + return |
| 24 | +end |
| 25 | + |
| 26 | +""" |
| 27 | + alias_analysis_pass!(sci::StructuredIRCode) -> Dict{Any, AliasSet} |
| 28 | +
|
| 29 | +Perform fixed-point alias analysis on structured IR. |
| 30 | +Returns mapping from SSA values to alias sets. |
| 31 | +""" |
| 32 | +function alias_analysis_pass!(sci::StructuredIRCode) |
| 33 | + tracker = AliasTracker() |
| 34 | + |
| 35 | + # Initialize: each argument gets its own alias set |
| 36 | + for (idx, argtype) in enumerate(sci.argtypes) |
| 37 | + argtype_unwrapped = CC.widenconst(argtype) |
| 38 | + if contains_pointers(argtype_unwrapped) |
| 39 | + arg_ref = Argument(idx) |
| 40 | + tracker[arg_ref] = Set{Any}([arg_ref]) |
| 41 | + end |
| 42 | + end |
| 43 | + |
| 44 | + # Fixed-point iteration |
| 45 | + iteration = 0 |
| 46 | + max_iterations = 100 |
| 47 | + |
| 48 | + tracker.dirty = true |
| 49 | + while tracker.dirty && iteration < max_iterations |
| 50 | + tracker.dirty = false |
| 51 | + iteration += 1 |
| 52 | + |
| 53 | + analyze_block!(tracker, sci.entry) |
| 54 | + end |
| 55 | + |
| 56 | + @debug "Alias analysis converged in $iteration iterations" |
| 57 | + |
| 58 | + return tracker.aliases |
| 59 | +end |
| 60 | + |
| 61 | +""" |
| 62 | + propagate!(tracker::AliasTracker, from, to) |
| 63 | +
|
| 64 | +Propagate alias set from `from` to `to`. |
| 65 | +Uses direct assignment when `to` is uninitialized, union otherwise. |
| 66 | +""" |
| 67 | +function propagate!(tracker::AliasTracker, from, to) |
| 68 | + from_aliases = tracker[from] |
| 69 | + |
| 70 | + if from_aliases === ALIAS_UNIVERSE |
| 71 | + # Propagating UNIVERSE is always conservative |
| 72 | + tracker[to] = ALIAS_UNIVERSE |
| 73 | + return |
| 74 | + end |
| 75 | + |
| 76 | + if haskey(tracker.aliases, to) |
| 77 | + # Target already has an alias set union with it |
| 78 | + to_aliases = tracker.aliases[to] |
| 79 | + new_aliases = union(from_aliases, to_aliases) |
| 80 | + if new_aliases != to_aliases |
| 81 | + tracker[to] = new_aliases |
| 82 | + end |
| 83 | + else |
| 84 | + # Target not yet analyzed assign directly |
| 85 | + tracker[to] = from_aliases |
| 86 | + end |
| 87 | + return |
| 88 | +end |
| 89 | + |
| 90 | +""" |
| 91 | + analyze_block!(tracker::AliasTracker, block) |
| 92 | +
|
| 93 | +Analyze all statements in a block, recursing into nested control flow. |
| 94 | +""" |
| 95 | +function analyze_block!(tracker::AliasTracker, block) |
| 96 | + for (ssa_idx, entry) in block.body |
| 97 | + if entry.stmt isa ControlFlowOp |
| 98 | + analyze_control_flow!(tracker, entry.stmt) |
| 99 | + else |
| 100 | + analyze_statement!(tracker, SSAValue(ssa_idx), entry.stmt) |
| 101 | + end |
| 102 | + end |
| 103 | + return |
| 104 | +end |
| 105 | + |
| 106 | +# Recurse into nested control flow regions |
| 107 | +function analyze_control_flow!(tracker::AliasTracker, op::IfOp) |
| 108 | + analyze_block!(tracker, op.then_region) |
| 109 | + return analyze_block!(tracker, op.else_region) |
| 110 | +end |
| 111 | + |
| 112 | +function analyze_control_flow!(tracker::AliasTracker, op::ForOp) |
| 113 | + return analyze_block!(tracker, op.body) |
| 114 | +end |
| 115 | + |
| 116 | +function analyze_control_flow!(tracker::AliasTracker, op::WhileOp) |
| 117 | + analyze_block!(tracker, op.before) |
| 118 | + return analyze_block!(tracker, op.after) |
| 119 | +end |
| 120 | + |
| 121 | +function analyze_control_flow!(tracker::AliasTracker, op::LoopOp) |
| 122 | + return analyze_block!(tracker, op.body) |
| 123 | +end |
| 124 | + |
| 125 | +# Fallback for unknown control flow ops |
| 126 | +function analyze_control_flow!(::AliasTracker, ::ControlFlowOp) |
| 127 | + return |
| 128 | +end |
| 129 | + |
| 130 | +""" |
| 131 | + analyze_statement!(tracker::AliasTracker, ssa::SSAValue, stmt) |
| 132 | +
|
| 133 | +Analyze a single statement and propagate aliases. |
| 134 | +Handles both `:call` and `:invoke` expression forms. |
| 135 | +""" |
| 136 | +function analyze_statement!(tracker::AliasTracker, ssa::SSAValue, stmt) |
| 137 | + if stmt isa Expr && (stmt.head === :call || stmt.head === :invoke) |
| 138 | + # Normalize :call and :invoke into (func, operands) |
| 139 | + # :call -> args = [func, operands...] |
| 140 | + # :invoke -> args = [MethodInstance, func, operands...] |
| 141 | + if stmt.head === :call |
| 142 | + func = stmt.args[1] |
| 143 | + operands = @view stmt.args[2:end] |
| 144 | + else # :invoke |
| 145 | + func = stmt.args[2] |
| 146 | + operands = @view stmt.args[3:end] |
| 147 | + end |
| 148 | + |
| 149 | + # Resolve func to its runtime value for intrinsic matching. |
| 150 | + # In :invoke, func may already be the function object (not a GlobalRef). |
| 151 | + resolved_func = if func isa GlobalRef |
| 152 | + try |
| 153 | + getfield(func.mod, func.name) |
| 154 | + catch |
| 155 | + nothing |
| 156 | + end |
| 157 | + else |
| 158 | + func # Direct function value (common in :invoke) |
| 159 | + end |
| 160 | + |
| 161 | + # getfield: propagate from parent |
| 162 | + if func === GlobalRef(Core, :getfield) && length(operands) >= 1 |
| 163 | + field = length(operands) >= 2 ? operands[2] : nothing |
| 164 | + |
| 165 | + # For TileArray.ptr field access, propagate pointer alias |
| 166 | + if field isa QuoteNode && field.value === :ptr |
| 167 | + propagate!(tracker, operands[1], ssa) |
| 168 | + else |
| 169 | + # Conservatively mark as UNIVERSE for non-pointer fields |
| 170 | + tracker[ssa] = ALIAS_UNIVERSE |
| 171 | + end |
| 172 | + |
| 173 | + # Pointer arithmetic: propagate from pointer operand |
| 174 | + elseif func === GlobalRef(Base, :+) || func === GlobalRef(Base, :-) |
| 175 | + for arg in operands |
| 176 | + # Find the pointer argument and propagate |
| 177 | + arg_aliases = tracker[arg] |
| 178 | + if arg_aliases !== ALIAS_UNIVERSE && arg_aliases isa Set |
| 179 | + propagate!(tracker, arg, ssa) |
| 180 | + break |
| 181 | + end |
| 182 | + end |
| 183 | + |
| 184 | + # View construction: propagate alias from first operand |
| 185 | + elseif is_view_constructor(resolved_func) |
| 186 | + if length(operands) >= 1 |
| 187 | + propagate!(tracker, operands[1], ssa) |
| 188 | + end |
| 189 | + |
| 190 | + # Default: unknown operation -> UNIVERSE |
| 191 | + else |
| 192 | + tracker[ssa] = ALIAS_UNIVERSE |
| 193 | + end |
| 194 | + |
| 195 | + elseif stmt isa ReturnNode |
| 196 | + # No alias propagation needed |
| 197 | + |
| 198 | + else |
| 199 | + # Unknown statement type -> conservative |
| 200 | + tracker[ssa] = ALIAS_UNIVERSE |
| 201 | + end |
| 202 | + return |
| 203 | +end |
| 204 | + |
| 205 | +# Helper functions |
| 206 | +contains_pointers(T) = T <: Ptr || T <: TileArray || (T <: Tile && eltype(T) <: Ptr) |
| 207 | + |
| 208 | +""" |
| 209 | + is_view_constructor(func) -> Bool |
| 210 | +
|
| 211 | +Check if a resolved function is a tensor/partition view constructor. |
| 212 | +These propagate alias identity from their first operand. |
| 213 | +""" |
| 214 | +function is_view_constructor(func) |
| 215 | + return func === Intrinsics.make_tensor_view || |
| 216 | + func === Intrinsics.make_partition_view |
| 217 | +end |
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