PGO and LTO in clang-cl

build/autoconf/clang-cl-pgo.m4

@@ -0,0 +1,30 @@
+dnl This Source Code Form is subject to the terms of the Mozilla Public
+dnl License, v. 2.0. If a copy of the MPL was not distributed with this
+dnl file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+AC_DEFUN([MOZ_CLANG_CL_PGO], [
+if test -n "$CLANG_CL"; then
+    dnl Override the MSVC/GCC flags: clang-cl uses LLVM instrumentation.
+    PROFILE_GEN_CFLAGS="-clang:-fprofile-instr-generate"
+    PROFILE_USE_CFLAGS='-clang:-fprofile-instr-use="$(DEPTH)/merged.profdata"'
+    PROFILE_GEN_LDFLAGS=
+    PROFILE_USE_LDFLAGS=
+
+    if test -n "$MOZ_PGO"; then
+        AC_PATH_PROG(LLVM_PROFDATA, llvm-profdata.exe)
+        if test -z "$LLVM_PROFDATA"; then
+            AC_MSG_ERROR([clang-cl PGO requires llvm-profdata from the compiler's LLVM installation on PATH])
+        fi
+        dnl The training harness uses native Windows Python, not an MSYS shell.
+        LLVM_PROFDATA="$(cd "$(dirname "$LLVM_PROFDATA")" && pwd -W)/$(basename "$LLVM_PROFDATA")"
+        dnl clang-cl emits a default-library directive for its profile runtime.
+        dnl We invoke the linker directly, so supply the runtime search path.
+        clang_resource_dir=`$CC -print-resource-dir | tr '\\' '/'`
+        if test ! -d "$clang_resource_dir/lib/windows"; then
+            AC_MSG_ERROR([clang-cl PGO requires the Windows compiler-rt profile runtime])
+        fi
+        PROFILE_GEN_LDFLAGS="-LIBPATH:\"$clang_resource_dir/lib/windows\""
+    fi
+fi
+AC_SUBST(LLVM_PROFDATA)
+])