[features] Add feature for Oz minsize opt level

When enabling LTO, Oz is required to have a smaller firmware size. This PR adds the "minsize" feature, which will be enabled along with LTO on some ROM_EXT targets through bazel transition. In our tests with ROM_EXT on the master branch, * Os + LTO ~ +2,904 bytes * Oz - LTO ~ -1,260 bytes * Oz + LTO ~ -1,640 bytes Change-Id: I141284b331b9760fb25f690bba4c10b02057f13f Signed-off-by: Yi-Hsuan Deng <[email protected]>
lowRISC · Dec 13, 2024 · a63989d · a63989d
1 parent 8551be6
commit a63989d
Showing 1 changed file with 20 additions and 0 deletions.
diff --git a/features/common/BUILD.bazel b/features/common/BUILD.bazel
@@ -203,6 +203,25 @@ feature(
     ],
 )
 
+feature(
+    name = "minsize",
+    enabled = False,
+    flag_sets = [
+        flag_set(
+            actions = C_ALL_COMPILE_ACTIONS + CPP_ALL_COMPILE_ACTIONS + LD_ALL_ACTIONS,
+            flag_groups = [
+                flag_group(
+                    flags = [
+                        "-Oz",
+                        # Inline slightly more which is actually smaller.
+                        "-mllvm", "--inline-threshold=10",
+                    ],
+                ),
+            ],
+        ),
+    ],
+)
+
 feature(
     name = "symbol_garbage_collection",
     enabled = True,
@@ -345,6 +364,7 @@ feature_set(
         ":exceptions",
         ":use_lld",
         ":lto",
+        ":minsize",
         ":symbol_garbage_collection",
         ":dbg",
         ":fastbuild",