diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 4a5a0e290..55127b75e 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -47,17 +47,15 @@ jobs:
           Remove-Item '.\tools.zip'
           Remove-Item -LiteralPath 'tools2' -Force -Recurse
 
-      - name: Re-generate assembly
-        run: python -m mkwutil.gen_asm
+      - uses: actions/cache@v2
+        with:
+          path: asm/dol
+          key: asm-dol
 
-      # https://stackoverflow.com/a/56389437
-      - name: Verify assembly still the same
-        run: |
-          $ChangedFiles = $(git status --porcelain | Measure-Object | Select-Object -expand Count)
-          if ($ChangedFiles -gt 0) {
-            git status --porcelain
-            throw "Found $ChangedFiles changed files! Did you run gen_asm?"
-          }
+      - uses: actions/cache@v2
+        with:
+          path: asm/rel
+          key: asm-rel
 
       - name: Build mkw
         shell: bash
diff --git a/.gitignore b/.gitignore
index 2949f224e..1b03f4115 100644
--- a/.gitignore
+++ b/.gitignore
@@ -30,6 +30,10 @@
 /pack/dol.lcf
 /pack/rel.lcf
 
+# Auto-generated assembly
+/asm/dol/
+/asm/rel/
+
 # Executables
 *.exe
 *.dll
@@ -58,9 +62,6 @@ tmp
 *.map
 out.html
 
-# Compiler tools bundle
-tools.7z
-
 # Editors
 .vscode/
 *.bndb
diff --git a/README.md b/README.md
index 875871c4d..654d15119 100644
--- a/README.md
+++ b/README.md
@@ -85,7 +85,6 @@ The dead-stripping feature can be re-enabled by:
   - [pack/dol_slices.csv](./pack/dol_slices.csv)
   - [pack/rel_slices.csv](./pack/rel_slices.csv)
 - Entries must be sorted in the spreadsheet (current limitation).
-- After modifying slices, run `python3 -m mkwutil.gen_asm`.
 - Add your new build target to `mkwutil/sources.py`.
 - Run `build.py`.
 
diff --git a/build.py b/build.py
index d5b7d1bda..a91a94981 100644
--- a/build.py
+++ b/build.py
@@ -3,6 +3,7 @@
 """
 
 
+import argparse
 from itertools import chain
 import os
 import os.path
@@ -26,9 +27,17 @@
 from mkwutil.verify_main_dol import verify_dol
 from mkwutil.verify_staticr_rel import verify_rel
 from mkwutil.progress.percent_decompiled import percent_decompiled
-
+from mkwutil.gen_asm import gen_asm
 from mkwutil.project import load_dol_slices
 
+
+parser = argparse.ArgumentParser(description="Build main.dol and StaticR.rel.")
+parser.add_argument("--regen_asm", action="store_true", help="Regenerate all ASM")
+args = parser.parse_args()
+# Start by running gen_asm.
+gen_asm(args.regen_asm)
+
+
 colorama.init()
 print_mutex = Lock()
 
diff --git a/mkwutil/gen_asm.py b/mkwutil/gen_asm.py
index bdbdbf9e9..dff2674e8 100644
--- a/mkwutil/gen_asm.py
+++ b/mkwutil/gen_asm.py
@@ -454,52 +454,47 @@ def __gen_asm(self, section: Section, _slice: Slice):
             gen = AsmGenerator(data, _slice, SymbolsList(), asm_file)
             gen.dump_section()
 
-def main():
-    parser = argparse.ArgumentParser(
-        description="Generate ASM blobs and linker object lists."
-    )
-    parser.add_argument("--asm_dir", type=Path, default="./asm", help="Path to ASM dir")
-    parser.add_argument(
-        "--pack_dir", type=Path, default="./pack", help="Path to link instructions dir"
-    )
-    parser.add_argument(
-        "--binary_dir",
-        type=Path,
-        default="./artifacts/orig/pal",
-        help="Binary containing main.dol and StaticR.rel",
-    )
-    parser.add_argument("--regen_asm", action="store_true", help="Regenerate all ASM")
-    args = parser.parse_args()
-    args.asm_dir.mkdir(exist_ok=True)
 
-    symbols = read_symbol_map(args.pack_dir / "symbols.txt")
+def gen_asm(regen_asm=False):
+    asm_dir = Path("./asm")
+    pack_dir = Path("./pack")
+    binary_dir = Path("./artifacts/orig/pal")
 
-    dol = read_dol(args.binary_dir / "main.dol")
-    dol_slices = read_enabled_slices(dol, args.pack_dir / "dol_slices.csv")
+    asm_dir.mkdir(exist_ok=True)
+
+    symbols = read_symbol_map(pack_dir / "symbols.txt")
+
+    dol = read_dol(binary_dir / "main.dol")
+    dol_slices = read_enabled_slices(dol, pack_dir / "dol_slices.csv")
 
     # Disassemble DOL sections.
-    dol_asm_dir = args.asm_dir / "dol"
+    dol_asm_dir = asm_dir / "dol"
     dol_asm_dir.mkdir(exist_ok=True)
     dol_gen = DOLSrcGenerator(
-        dol_slices, dol, symbols, dol_asm_dir, args.pack_dir, args.regen_asm
+        dol_slices, dol, symbols, dol_asm_dir, pack_dir, regen_asm
     )
     dol_gen.run()
 
-    rel = read_rel(args.binary_dir / "StaticR.rel")
+    rel = read_rel(binary_dir / "StaticR.rel")
     # Dump StaticR.rel segments.
-    rel_bin_dir = args.binary_dir / "rel"
+    rel_bin_dir = binary_dir / "rel"
     dump_staticr(rel, rel_bin_dir)
     # Map out slices in REL.
     rel_slices = load_rel_slices(sections=REL_SECTIONS)
     rel_slices.filter(SliceTable.ONLY_ENABLED)
     # Disassemble REL sections.
-    rel_asm_dir = args.asm_dir / "rel"
+    rel_asm_dir = asm_dir / "rel"
     rel_asm_dir.mkdir(exist_ok=True)
     rel_gen = RELSrcGenerator(
-        rel_slices, rel, rel_asm_dir, rel_bin_dir, args.pack_dir, args.regen_asm
+        rel_slices, rel, rel_asm_dir, rel_bin_dir, pack_dir, regen_asm
     )
     rel_gen.run()
 
 
 if __name__ == "__main__":
-    main()
+    parser = argparse.ArgumentParser(
+        description="Generate ASM blobs and linker object lists."
+    )
+    parser.add_argument("--regen_asm", action="store_true", help="Regenerate all ASM")
+    args = parser.parse_args()
+    gen_asm(args.regen_asm)