From cb82c790d50dd87f301df67b710161906dafb0c2 Mon Sep 17 00:00:00 2001
From: Isaac Torres <isaac@isaactorz.dev>
Date: Wed, 8 Nov 2023 11:26:06 -0800
Subject: [PATCH] third_party: make mkl a constraint [DIP-196] (#103)

We need to model mkl version of the build as a proper platform with a
toolchain -
See: https://bazel.build/extending/platforms for more details.

Not having this in place is what caused our multi-arch builds to be
built against
vanilla x86 without mkl
---
 cc/repositories.bzl                         |  1 +
 cc/toolchains/llvm/x86_64-linux/BUILD.bazel | 16 ++++++++++++++++
 platforms/BUILD.bazel                       |  9 +++++++++
 third_party/BUILD.bazel                     |  8 ++++++++
 third_party/eigen.BUILD                     |  2 ++
 5 files changed, 36 insertions(+)

diff --git a/cc/repositories.bzl b/cc/repositories.bzl
index ac39c79..4608083 100644
--- a/cc/repositories.bzl
+++ b/cc/repositories.bzl
@@ -102,6 +102,7 @@ def register_swift_cc_toolchains():
     native.register_toolchains("@rules_swiftnav//cc/toolchains/llvm/x86_64-darwin:cc-toolchain-x86_64-darwin")
     native.register_toolchains("@rules_swiftnav//cc/toolchains/llvm/aarch64-linux:cc-toolchain-aarch64-linux")
     native.register_toolchains("@rules_swiftnav//cc/toolchains/llvm/x86_64-linux:cc-toolchain-x86_64-linux")
+    native.register_toolchains("@rules_swiftnav//cc/toolchains/llvm/x86_64-linux:cc-toolchain-intel-mkl")
     native.register_toolchains("@rules_swiftnav//cc/toolchains/llvm/x86_64-aarch64-linux:cc-toolchain-aarch64-bullseye-graviton2")
     native.register_toolchains("@rules_swiftnav//cc/toolchains/llvm/x86_64-aarch64-linux:cc-toolchain-aarch64-bullseye-graviton3")
 
diff --git a/cc/toolchains/llvm/x86_64-linux/BUILD.bazel b/cc/toolchains/llvm/x86_64-linux/BUILD.bazel
index 408e9cd..552aa5f 100644
--- a/cc/toolchains/llvm/x86_64-linux/BUILD.bazel
+++ b/cc/toolchains/llvm/x86_64-linux/BUILD.bazel
@@ -177,3 +177,19 @@ toolchain(
     toolchain = ":cc-clang-x86_64-linux",
     toolchain_type = "@bazel_tools//tools/cpp:toolchain_type",
 )
+
+toolchain(
+    name = "cc-toolchain-intel-mkl",
+    exec_compatible_with = [
+        "@platforms//cpu:x86_64",
+        "@platforms//os:linux",
+    ],
+    target_compatible_with = [
+        "@platforms//cpu:x86_64",
+        "@platforms//os:linux",
+        "//third_party:intel_mkl",
+    ],
+    target_settings = None,
+    toolchain = ":cc-clang-x86_64-linux",
+    toolchain_type = "@bazel_tools//tools/cpp:toolchain_type",
+)
diff --git a/platforms/BUILD.bazel b/platforms/BUILD.bazel
index 615eb98..85df801 100644
--- a/platforms/BUILD.bazel
+++ b/platforms/BUILD.bazel
@@ -100,6 +100,15 @@ platform(
     visibility = ["//visibility:public"],
 )
 
+platform(
+    name = "intel_mkl",
+    constraint_values = [
+        "@platforms//os:linux",
+        "//third_party:intel_mkl",
+        "@platforms//cpu:x86_64",
+    ],
+)
+
 platform(
     name = "x86_64_linux_musl",
     constraint_values = [
diff --git a/third_party/BUILD.bazel b/third_party/BUILD.bazel
index 8385a89..97b02b4 100644
--- a/third_party/BUILD.bazel
+++ b/third_party/BUILD.bazel
@@ -10,6 +10,14 @@
 
 load("@bazel_skylib//rules:common_settings.bzl", "bool_flag")
 
+constraint_setting(name = "intel")
+
+constraint_value(
+    name = "intel_mkl",
+    constraint_setting = ":intel",
+    visibility = ["//visibility:public"],
+)
+
 bool_flag(
     name = "enable_mkl",
     build_setting_default = False,
diff --git a/third_party/eigen.BUILD b/third_party/eigen.BUILD
index 7f99b88..c68f0b1 100644
--- a/third_party/eigen.BUILD
+++ b/third_party/eigen.BUILD
@@ -18,11 +18,13 @@ cc_library(
     defines = [
         "EIGEN_NO_DEBUG",
     ] + select({
+        "@rules_swiftnav//third_party:intel_mkl": ["EIGEN_USE_MKL_ALL"],
         "@rules_swiftnav//third_party:_enable_mkl": ["EIGEN_USE_MKL_ALL"],
         "//conditions:default": [],
     }),
     includes = ["."],
     deps = select({
+        "@rules_swiftnav//third_party:intel_mkl": ["@mkl"],
         "@rules_swiftnav//third_party:_enable_mkl": ["@mkl"],
         "//conditions:default": [],
     }),