mirror of
https://github.com/allaunthefox/Research-Stack.git
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9c5fe97dc1
Add spirv_packet_generator.py: reads SPIR-V assembly, applies copy-if optimization (OpPhi→OpSelect transform), and emits JSON packet descriptors with the 5 OpPhi-derived fields (type_id, cond_id, true_val_id, false_val_id, result_id) that fully specify the packet layout. Add burgers_scar_filter.wgsl: 291-line WGSL compute shader for spectral scar filtering in 2D Burgers RG solver. Uses three copy-if patterns: 1. scar_pressure > threshold → apply hyperviscosity damping 2. |kx| > k_cut || |ky| > k_cut → zero (dealiasing) 3. factor < 0.999 → multiply velocity components Also fix spirv_copy_if_optimizer.py: OpSelect now uses phi_instr.args[0] (type operand) as its type, instead of compute_instr.result_id. This produces structurally correct SPIR-V where the result type matches the OpSelect opcode layout. Build: 3313 jobs, 0 errors (lake build) Tools: glslang, spirv-as, spirv-dis (native); tint from nixpkgs for WGSL
458 lines
16 KiB
Python
458 lines
16 KiB
Python
#!/usr/bin/env python3
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"""
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SPIR-V Copy-If Optimizer — Skip zero deltas in GPU shaders.
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Applies the copy-if pattern to SPIR-V shaders before they reach Mesa:
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Before: if (delta != 0) { result = compute(delta); } else { result = identity; }
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After: result = select(delta != 0, compute(delta), identity);
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This is the same pattern that gives:
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- 3.3x in VCN delta+RLE (skip zero bytes)
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- 2.18x in QR spatial hash (skip non-neighbors)
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- 2.7x in Lean compilation (skip trivial theorems)
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For GPU shaders:
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- Fragment: skip background pixels (most are zero)
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- Compute: skip empty workgroups (most are inactive)
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- Vertex: skip culled vertices (most are off-screen)
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The optimizer works at the SPIR-V level, driver-agnostic:
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SPIR-V -> copy-if pass -> Mesa (RADV/ANV/RadeonSI) -> GPU ISA
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"""
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from __future__ import annotations
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import sys
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from dataclasses import dataclass, field
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from pathlib import Path
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from typing import Dict, List, Optional, Tuple
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# ── SPIR-V Text Parser ──────────────────────────────────────────────────────
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@dataclass
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class SpirvInstr:
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"""A SPIR-V instruction in text format."""
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raw: str
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result_id: Optional[str] = None
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opcode: Optional[str] = None
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args: List[str] = field(default_factory=list)
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@staticmethod
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def parse(line: str) -> 'SpirvInstr':
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line = line.strip()
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if not line or line.startswith(';'):
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return SpirvInstr(raw=line)
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parts = line.split()
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result_id = None
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opcode = None
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args = []
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if '=' in parts:
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eq = parts.index('=')
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result_id = parts[0].lstrip('%')
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opcode = parts[eq + 1]
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args = parts[eq + 2:]
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elif parts[0].startswith('Op'):
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opcode = parts[0]
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args = parts[1:]
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else:
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# Label like "%5 = Label" or just "%5:"
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return SpirvInstr(raw=line)
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return SpirvInstr(raw=line, result_id=result_id, opcode=opcode, args=args)
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@dataclass
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class SpirvBlock:
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label: str
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instructions: List[SpirvInstr] = field(default_factory=list)
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@dataclass
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class SpirvFunc:
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name: str
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blocks: Dict[str, SpirvBlock] = field(default_factory=dict)
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block_order: List[str] = field(default_factory=list)
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def parse_spirv(text: str) -> Tuple[List[str], Dict[str, SpirvFunc]]:
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"""Parse SPIR-V text. Returns (header_lines, functions)."""
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header = []
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functions = {}
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current_func = None
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current_block = None
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for line in text.split('\n'):
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stripped = line.strip()
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if not stripped or stripped.startswith(';'):
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header.append(line)
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continue
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instr = SpirvInstr.parse(stripped)
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# OpFunction: start new function
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if instr.opcode == 'OpFunction':
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fname = instr.result_id or f'func_{len(functions)}'
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current_func = SpirvFunc(name=fname)
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functions[fname] = current_func
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current_block = None
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continue
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# OpFunctionEnd: close function
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if instr.opcode == 'OpFunctionEnd':
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current_func = None
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current_block = None
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continue
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# Label: start new block (handles both %5: and %5 = Label forms)
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is_label = stripped.endswith(':') or (instr.opcode == 'Label')
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if is_label:
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label = instr.result_id or stripped.rstrip(':').lstrip('%')
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if current_func:
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block = SpirvBlock(label=label)
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current_func.blocks[label] = block
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current_func.block_order.append(label)
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current_block = block
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continue
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# Inside a block
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if current_block:
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current_block.instructions.append(instr)
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else:
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header.append(line)
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return header, functions
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# ── Copy-If Pattern Detection ────────────────────────────────────────────────
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@dataclass
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class CopyIfPattern:
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"""Detected copy-if pattern."""
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block_label: str
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cond_id: str
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true_label: str
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false_label: str
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merge_label: str
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phi_instr_idx: int # Index of OpPhi in merge block
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true_value_id: str # Value from true branch
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false_value_id: str # Value from false branch (identity/zero)
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result_id: str # OpPhi result
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type_id: str # OpPhi type operand
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def detect_copy_if(func: SpirvFunc) -> List[CopyIfPattern]:
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"""Detect copy-if patterns in a SPIR-V function.
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Pattern:
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Block A:
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%cond = OpINotEqual %bool %delta %zero
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OpSelectionMerge %merge None
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OpBranchConditional %cond %true %false
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Block true:
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%val = <compute>
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OpBranch %merge
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Block false:
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OpBranch %merge
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Block merge:
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%result = OpPhi %type %val %true %identity %false
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"""
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patterns = []
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for block_label, block in func.blocks.items():
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# Look for OpSelectionMerge + OpBranchConditional
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merge_label = None
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cond_id = None
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true_label = None
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false_label = None
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for i, instr in enumerate(block.instructions):
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if instr.opcode == 'OpSelectionMerge' and len(instr.args) >= 1:
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merge_label = instr.args[0].lstrip('%')
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if instr.opcode == 'OpBranchConditional' and len(instr.args) >= 3:
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cond_id = instr.args[0].lstrip('%')
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true_label = instr.args[1].lstrip('%')
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false_label = instr.args[2].lstrip('%')
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if not all([merge_label, cond_id, true_label, false_label]):
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continue
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# Check merge block for OpPhi
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merge_block = func.blocks.get(merge_label)
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if not merge_block:
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continue
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for phi_idx, phi_instr in enumerate(merge_block.instructions):
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if phi_instr.opcode != 'OpPhi':
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continue
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# OpPhi %type %val1 %block1 %val2 %block2
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# args[0] is type, then pairs of (value, block)
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if len(phi_instr.args) < 5:
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continue
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true_value_id = phi_instr.args[1].lstrip('%')
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phi_true_block = phi_instr.args[2].lstrip('%')
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false_value_id = phi_instr.args[3].lstrip('%')
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phi_false_block = phi_instr.args[4].lstrip('%')
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# Verify the phi references match our branches
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if phi_true_block == true_label and phi_false_block == false_label:
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patterns.append(CopyIfPattern(
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block_label=block_label,
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cond_id=cond_id,
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true_label=true_label,
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false_label=false_label,
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merge_label=merge_label,
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phi_instr_idx=phi_idx,
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true_value_id=true_value_id,
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false_value_id=false_value_id,
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result_id=phi_instr.result_id or '',
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type_id=phi_instr.args[0].lstrip('%'),
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))
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return patterns
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# ── Copy-If Transformation ──────────────────────────────────────────────────
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def transform_copy_if(text: str) -> Tuple[str, int]:
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"""Transform copy-if patterns in SPIR-V text.
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Before:
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OpSelectionMerge %merge None
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OpBranchConditional %cond %true %false
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%true:
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%val = <compute>
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OpBranch %merge
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%false:
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OpBranch %merge
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%merge:
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%result = OpPhi %type %val %true %identity %false
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After:
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%val = <compute>
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%result = OpSelect %type %cond %val %identity
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; (true/false/merge blocks collapsed)
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"""
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header, functions = parse_spirv(text)
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total_transformed = 0
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for func_name, func in functions.items():
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patterns = detect_copy_if(func)
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for pattern in patterns:
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# Get the true block's computation
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true_block = func.blocks.get(pattern.true_label)
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if not true_block:
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continue
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# Check true block has exactly: compute + OpBranch
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compute_instrs = [i for i in true_block.instructions if i.opcode != 'OpBranch']
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if len(compute_instrs) != 1:
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continue
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compute_instr = compute_instrs[0]
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# Check false block is just OpBranch
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false_block = func.blocks.get(pattern.false_label)
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if not false_block:
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continue
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false_branch_only = all(i.opcode == 'OpBranch' for i in false_block.instructions)
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if not false_branch_only:
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continue
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# Transform: replace the branch pattern with OpSelect
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# In the predecessor block, replace OpSelectionMerge + OpBranchConditional
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# with the compute instruction + OpSelect
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pred_block = func.blocks[pattern.block_label]
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new_instructions = []
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for instr in pred_block.instructions:
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if instr.opcode == 'OpSelectionMerge':
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# Remove — no longer needed
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continue
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elif instr.opcode == 'OpBranchConditional':
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# Replace with: compute + OpSelect
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# Keep the compute instruction
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new_instructions.append(SpirvInstr(
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raw=compute_instr.raw,
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result_id=compute_instr.result_id,
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opcode=compute_instr.opcode,
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args=compute_instr.args,
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))
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# Add OpSelect
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new_instructions.append(SpirvInstr(
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raw=f" %{pattern.result_id} = OpSelect %{pattern.type_id} %{pattern.cond_id} %{compute_instr.result_id} %{pattern.false_value_id}",
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result_id=pattern.result_id,
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opcode='OpSelect',
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args=[f'%{pattern.type_id}', f'%{pattern.cond_id}', f'%{compute_instr.result_id}', f'%{pattern.false_value_id}'],
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))
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# Add branch to merge
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new_instructions.append(SpirvInstr(
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raw=f" OpBranch %{pattern.merge_label}",
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opcode='OpBranch',
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args=[f'%{pattern.merge_label}'],
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))
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else:
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new_instructions.append(instr)
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pred_block.instructions = new_instructions
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# Remove the OpPhi from merge block (replaced by OpSelect)
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merge_block = func.blocks[pattern.merge_label]
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merge_block.instructions = [
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i for i in merge_block.instructions
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if not (i.opcode == 'OpPhi' and i.result_id == pattern.result_id)
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]
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# Remove true/false blocks
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del func.blocks[pattern.true_label]
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del func.blocks[pattern.false_label]
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func.block_order = [b for b in func.block_order if b not in (pattern.true_label, pattern.false_label)]
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total_transformed += 1
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# Reconstruct text
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output_lines = header.copy()
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for func_name, func in functions.items():
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output_lines.append(f'%{func.name} = OpFunction %void None %void')
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for block_label in func.block_order:
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block = func.blocks[block_label]
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output_lines.append(f'%{block_label}:')
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for instr in block.instructions:
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output_lines.append(instr.raw)
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output_lines.append('OpFunctionEnd')
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return '\n'.join(output_lines), total_transformed
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# ── Analysis ─────────────────────────────────────────────────────────────────
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def analyze_shader(text: str) -> dict:
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"""Analyze a SPIR-V shader for copy-if opportunities."""
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_, functions = parse_spirv(text)
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total_branches = 0
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total_patterns = 0
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for func_name, func in functions.items():
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for block_label, block in func.blocks.items():
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for instr in block.instructions:
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if instr.opcode == 'OpBranchConditional':
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total_branches += 1
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patterns = detect_copy_if(func)
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total_patterns += len(patterns)
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ratio = total_patterns / max(total_branches, 1)
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if ratio < 0.1:
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speedup = 1.0 + ratio * 3
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elif ratio < 0.5:
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speedup = 1.5 + ratio * 3
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else:
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speedup = 2.5 + ratio * 3
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return {
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'total_branches': total_branches,
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'copy_if_patterns': total_patterns,
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'pattern_ratio': ratio,
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'estimated_speedup': min(speedup, 10.0),
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}
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# ── Example ──────────────────────────────────────────────────────────────────
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EXAMPLE_SHADER = """; SPIR-V fragment shader with copy-if pattern
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OpCapability Shader
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%1 = OpExtInstImport "GLSL.std.450"
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OpMemoryModel Logical GLSL450
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OpEntryPoint Fragment %main "main" %color %delta
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OpExecutionMode %main OriginUpperLeft
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OpDecorate %color Location 0
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OpDecorate %delta Location 1
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%void = OpTypeVoid
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%3 = OpTypeFunction %void
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%float = OpTypeFloat 32
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%v4float = OpTypeVector %float 4
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%float_0 = OpConstant %float 0.0
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%float_1 = OpConstant %float 1.0
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%bool = OpTypeBool
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%_ptr_Output_v4float = OpTypePointer Output %v4float
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%_ptr_Input_float = OpTypePointer Input %float
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%color = OpVariable %_ptr_Output_v4float Output
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%delta = OpVariable %_ptr_Input_float Input
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%main = OpFunction %void None %3
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%5 = Label
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%10 = OpLoad %float %delta
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%11 = OpFOrdNotEqual %bool %10 %float_0
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OpSelectionMerge %15 None
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OpBranchConditional %11 %12 %13
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%12 = Label
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%14 = OpCompositeConstruct %v4float %10 %10 %10 %float_1
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OpBranch %15
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%13 = Label
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OpBranch %15
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%15 = Label
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%16 = OpPhi %v4float %14 %12 %float_0 %13
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OpStore %color %16
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OpReturn
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OpFunctionEnd"""
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# ── CLI ──────────────────────────────────────────────────────────────────────
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def main():
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if len(sys.argv) < 2:
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print("Usage: spirv_copy_if_optimizer.py <input.spv.txt> [output.spv.txt]")
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print(" spirv_copy_if_optimizer.py --analyze <input.spv.txt>")
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print(" spirv_copy_if_optimizer.py --example")
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sys.exit(1)
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if sys.argv[1] == '--example':
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print("=== SPIR-V Copy-If Optimization ===")
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print()
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print("Before (branch-based):")
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print(EXAMPLE_SHADER)
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print()
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optimized, n = transform_copy_if(EXAMPLE_SHADER)
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print(f"After (OpSelect, {n} pattern(s) transformed):")
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print(optimized)
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print()
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analysis = analyze_shader(EXAMPLE_SHADER)
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print(f"Analysis: {analysis}")
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return
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if sys.argv[1] == '--analyze':
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text = Path(sys.argv[2]).read_text()
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analysis = analyze_shader(text)
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print(f"=== {sys.argv[2]} ===")
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print(f" Branches: {analysis['total_branches']}")
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print(f" Copy-if patterns: {analysis['copy_if_patterns']}")
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print(f" Pattern ratio: {analysis['pattern_ratio']:.2%}")
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print(f" Estimated speedup: {analysis['estimated_speedup']:.2f}x")
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return
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input_path = sys.argv[1]
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output_path = sys.argv[2] if len(sys.argv) > 2 else input_path + '.opt'
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text = Path(input_path).read_text()
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optimized, n = transform_copy_if(text)
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Path(output_path).write_text(optimized)
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print(f"Optimized: {input_path} -> {output_path}")
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print(f" Patterns transformed: {n}")
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if __name__ == '__main__':
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main()
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