main.star: triple sharding amount for misc-compile builders

It completes in under 30 minutes as is. Go with a tentative target
of 10 minutes for now (via golang/go#17104), we can revisit it later.

In comparison, the previous build system currently uses effectively
the equivalent of 33 shards (that each handle one port), so even 12
shards is only about a third of that.

For golang/go#61698.
For golang/go#17104.

Change-Id: Ie641e0574127fcb72b081219f540fb5e7a9cf020
Reviewed-on: https://go-review.googlesource.com/c/build/+/515735
TryBot-Bypass: Dmitri Shuralyov <[email protected]>
Reviewed-by: Dmitri Shuralyov <[email protected]>
Auto-Submit: Dmitri Shuralyov <[email protected]>
Reviewed-by: Michael Knyszek <[email protected]>

Author: dmitshur

generated/cr-buildbucket.cfg

@@ -1052,7 +1052,7 @@ buckets {
         '      "golang/ci/x_vulndb-go1.20-linux-amd64-misccompile",'
         '      "golang/ci/x_website-go1.20-linux-amd64-misccompile"'
         '    ],'
-        '    "num_test_shards": 1,'
+        '    "num_test_shards": 12,'
         '    "test_builder": "golang/ci/go1.20-linux-amd64-misccompile-test_only"'
         '  },'
         '  "env": {},'
@@ -3259,7 +3259,7 @@ buckets {
         '      "golang/ci/x_vulndb-go1.21-linux-amd64-misccompile",'
         '      "golang/ci/x_website-go1.21-linux-amd64-misccompile"'
         '    ],'
-        '    "num_test_shards": 4,'
+        '    "num_test_shards": 12,'
         '    "test_builder": "golang/ci/go1.21-linux-amd64-misccompile-test_only"'
         '  },'
         '  "env": {},'
@@ -5471,7 +5471,7 @@ buckets {
         '      "golang/ci/x_vulndb-gotip-linux-amd64-misccompile",'
         '      "golang/ci/x_website-gotip-linux-amd64-misccompile"'
         '    ],'
-        '    "num_test_shards": 4,'
+        '    "num_test_shards": 12,'
         '    "test_builder": "golang/ci/gotip-linux-amd64-misccompile-test_only"'
         '  },'
         '  "env": {},'
@@ -48430,7 +48430,7 @@ buckets {
         '  "coord_mode": {'
         '    "build_builder": "golang/try/go1.20-internal-linux-amd64-misccompile-build_go",'
         '    "builders_to_trigger_after_toolchain_build": [],'
-        '    "num_test_shards": 1,'
+        '    "num_test_shards": 12,'
         '    "test_builder": "golang/try/go1.20-internal-linux-amd64-misccompile-test_only"'
         '  },'
         '  "env": {},'
@@ -50129,7 +50129,7 @@ buckets {
         '  "coord_mode": {'
         '    "build_builder": "golang/try/go1.20-linux-amd64-misccompile-build_go",'
         '    "builders_to_trigger_after_toolchain_build": [],'
-        '    "num_test_shards": 1,'
+        '    "num_test_shards": 12,'
         '    "test_builder": "golang/try/go1.20-linux-amd64-misccompile-test_only"'
         '  },'
         '  "env": {},'
@@ -52064,7 +52064,7 @@ buckets {
         '  "coord_mode": {'
         '    "build_builder": "golang/try/go1.21-internal-linux-amd64-misccompile-build_go",'
         '    "builders_to_trigger_after_toolchain_build": [],'
-        '    "num_test_shards": 4,'
+        '    "num_test_shards": 12,'
         '    "test_builder": "golang/try/go1.21-internal-linux-amd64-misccompile-test_only"'
         '  },'
         '  "env": {},'
@@ -53763,7 +53763,7 @@ buckets {
         '  "coord_mode": {'
         '    "build_builder": "golang/try/go1.21-linux-amd64-misccompile-build_go",'
         '    "builders_to_trigger_after_toolchain_build": [],'
-        '    "num_test_shards": 4,'
+        '    "num_test_shards": 12,'
         '    "test_builder": "golang/try/go1.21-linux-amd64-misccompile-test_only"'
         '  },'
         '  "env": {},'
@@ -55703,7 +55703,7 @@ buckets {
         '  "coord_mode": {'
         '    "build_builder": "golang/try/gotip-internal-linux-amd64-misccompile-build_go",'
         '    "builders_to_trigger_after_toolchain_build": [],'
-        '    "num_test_shards": 4,'
+        '    "num_test_shards": 12,'
         '    "test_builder": "golang/try/gotip-internal-linux-amd64-misccompile-test_only"'
         '  },'
         '  "env": {},'
@@ -57408,7 +57408,7 @@ buckets {
         '  "coord_mode": {'
         '    "build_builder": "golang/try/gotip-linux-amd64-misccompile-build_go",'
         '    "builders_to_trigger_after_toolchain_build": [],'
-        '    "num_test_shards": 4,'
+        '    "num_test_shards": 12,'
         '    "test_builder": "golang/try/gotip-linux-amd64-misccompile-test_only"'
         '  },'
         '  "env": {},'

main.star

@@ -424,13 +424,13 @@ def define_builder(bucket, project, go_branch_short, builder_type, gerrit_host =
 
     # Emit the builder definitions.
     if project == "go":
-        define_go_builder(name, bucket, go_branch_short, builder_type, base_props, base_dims, emit_builder)
+        define_go_builder(name, bucket, go_branch_short, builder_type, run_mods, base_props, base_dims, emit_builder)
     else:
         define_subrepo_builder(name, base_props, base_dims, emit_builder)
 
     return bucket + "/" + name
 
-def define_go_builder(name, bucket, go_branch_short, builder_type, base_props, base_dims, emit_builder):
+def define_go_builder(name, bucket, go_branch_short, builder_type, run_mods, base_props, base_dims, emit_builder):
     # Create 3 builders: the main entrypoint/coordinator builder,
     # a builder just to run make.bash, and a builder to run tests.
     #
@@ -446,12 +446,13 @@ def define_go_builder(name, bucket, go_branch_short, builder_type, base_props, b
     test_name = name + "-test_only"
 
     # Determine if we should be sharding tests, and how many shards.
-    #
-    # TODO(mknyszek): Remove the exception for the go1.20 branch once it
-    # is no longer supported.
     test_shards = 1
     if not is_capacity_constrained(builder_type) and go_branch_short != "go1.20":
+        # TODO(mknyszek): Remove the exception for the go1.20 branch once it
+        # is no longer supported.
         test_shards = 4
+    if "misccompile" in run_mods:
+        test_shards = 12
 
     # The main repo builder also triggers subrepo builders of the same builder type.
     #