build : use pkg-config for OpenBLAS (#1778)

* make : use pkg-config for finding CFLAGS & LDFLAGS needed by OpenBLAS

That way building on *nix like environments (including MSYS2 on Windows)
with WHISPER_OPENBLAS=1 works out of the box.

Fix handling of WHISPER_OPENBLAS, so that empty value or 0 won't be
misinterpreted by make as enabled.  Mind that it's not intended to
detect CMake false constants (OFF NO FALSE N).  make is not CMake.

By default OpenBLAS with 64-bit interface is used, but that can be
changed with `WHISPER_OPENBLAS_INTERFACE64=0` if 32-bit one is desired.

If OpenBLAS headers and library are respectively in include/ and lib/
subdirectories of given path, then you can specify it, e.g.
`OPENBLAS_PATH=/usr/local/openblas`, and this will take precedence over
any pkg-config file.

If there is no pkg-config file (.pc) for OpenBLAS and OPENBLAS_PATH is
empty, then headers are assumed to be in /usr/include/openblas and
library as assumed to be called 'openblas64' (or 'openblas' if
`WHISPER_OPENBLAS_INTERFACE64=0`).  If different headers location should
be used, then it can be done, e.g.
`WHISPER_BLAS_CFLAGS=-I/usr/local/include/openblas`.
If different library should be used, it can be specified, e.g.
`WHISPER_BLAS_LIB=openblasp64` (pthreads version as seen on Fedora), or
you can provide LDFLAGS needed to link with OpenBLAS directly:
`WHISPER_BLAS_LDFLAGS="-L/usr/local/lib/openblas -lopenblas64"`.

Current solution is flexible enough to handle most cases out there
without needlessly hardcoding possible OpenBLAS installation details.

* cmake : fix how pkg-config is used for finding include dirs and libraries needed by OpenBLAS

That way building on *nix like environments (including MSYS2 on Windows)
with -DWHISPER_OPENBLAS=ON should work out of the box as long as you
have CMake 3.25 or newer.

Make OPENBLAS_PATH environment variable supported not only on Windows.
It sets OpenBLAS include dir to ${OPENBLAS_PATH}/include and library to
${WHISPER_BLAS_LIB} (name without prefixes and suffixes) in
${OPENBLAS_PATH}/lib and avoids further package finding.

By default OpenBLAS with 64-bit interface is used (equivalent to setting
`-DWHISPER_BLAS_LIB=openblas64`), but that can be changed with
`-DWHISPER_OPENBLAS_INTERFACE64=OFF` (equivalent to setting
`-DWHISPER_BLAS_LIB=openblas`) if 32-bit one is desired.

Turn on BLA_STATIC for FindBLAS only when WHISPER_STATIC is enabled.
BLA_STATIC may not work as expected for pkg-config based operation.

Get rid of supporting BLAS_HOME environment variable.  If OPENBLAS_PATH
is insufficient in your case, there is no pkg-config file to rely on,
then you can manually specify include dir, e.g.
`-DBLAS_INCLUDE_DIRS=/usr/local/include/openblas`, and library, e.g.
`-DBLAS_LIBRARIES=/usr/local/lib/libopenblas.so`.

* make / cmake : use OpenBLAS with 32-bit interface by default.

OpenBLAS w/o INTERFACE64=1 vel USE_64BITINT=1 seems to be more common.

* cmake : hardcode "lib" prefix for OpenBLAS lib filename (even on Windows)

* cmake : hardcode OpenBLAS library name when building in MSVC (Windows)

Most *nix like environments (including MSYS2 on Windows) have OpenBLAS
packages that allow coexistence of OpenBLAS builds with 32-bit and
64-bit interface (w/o and w/ OPENBLAS_USE64BITINT defined) and they
differ by not having or having "64" suffix in their library filenames.
That's not the case for OpenBLAS prebuilt libraries for Windows.

CMakeLists.txt

@@ -74,6 +74,7 @@ else()
     option(WHISPER_BLAS                  "whisper: use BLAS libraries"                        OFF)
     option(WHISPER_BLAS_VENDOR           "whisper: BLAS library vendor"                       Generic)
     option(WHISPER_OPENBLAS              "whisper: prefer OpenBLAS"                           OFF)
+    option(WHISPER_OPENBLAS_INTERFACE64  "whisper: use OpenBLAS w/ 64-bit interface"          OFF)
     option(WHISPER_CUDA                  "whisper: support for CUDA"                          OFF)
     option(WHISPER_CUBLAS                "whisper: support for CUDA (deprecated)"             OFF)
     option(WHISPER_HIPBLAS               "whisper: support for hipBLAS"                       OFF)
@@ -207,30 +208,82 @@ endif()
 if (WHISPER_OPENBLAS)
     set(WHISPER_BLAS_VENDOR "OpenBLAS")
     set(WHISPER_BLAS ON)
+    # BLA_PKGCONFIG_BLAS is supported since CMake 3.25.
+    # FindBLAS.cmake pkg-config logic seems incomplete, because when
+    # BLA_SIZEOF_INTEGER is 8, then it should search for blas64 instead of blas.
+    # blas.pc/blas64.pc are not always provided, so let's be more specific
+    # and go with openblas.pc/openblas64.pc if WHISPER_OPENBLAS is on.
+    if (WHISPER_OPENBLAS_INTERFACE64)
+        set(WHISPER_BLAS_LIB "openblas64")
+    else ()
+        set(WHISPER_BLAS_LIB "openblas")
+    endif ()
+    set(BLA_PKGCONFIG_BLAS ${WHISPER_BLAS_LIB})
+    # OpenBLAS prebuilt libraries for Windows do not have "64" suffix in filename.
+    # (But .pc file has "64" suffix in filename for USE_64BITINT=1 Windows build.)
+    if (MSVC)
+        set(WHISPER_BLAS_LIB "openblas")
+    endif ()
 endif()
 
 if (WHISPER_BLAS)
-    if (WIN32)
+    if (NOT "$ENV{OPENBLAS_PATH}" STREQUAL "")
-        if(DEFINED ENV{OPENBLAS_PATH})
+        if (WHISPER_STATIC)
-            set(BLAS_LIBRARIES $ENV{OPENBLAS_PATH}/lib/libopenblas.dll.a)
+            set(WHISPER_BLAS_LIB_PREFIX ${CMAKE_STATIC_LIBRARY_PREFIX})
-            message(STATUS "Libraries ${BLAS_LIBRARIES}")
+            set(WHISPER_BLAS_LIB_SUFFIX ${CMAKE_STATIC_LIBRARY_SUFFIX})
-            set(WHISPER_EXTRA_FLAGS ${WHISPER_EXTRA_FLAGS} -DGGML_USE_OPENBLAS)
-            include_directories($ENV{OPENBLAS_PATH}/include)
-            set(WHISPER_EXTRA_LIBS ${WHISPER_EXTRA_LIBS} ${BLAS_LIBRARIES})
         else ()
-            message(FATAL_ERROR "BLAS library was not found. Environment variable OPENBLAS_PATH not defined.")
+            if (CMAKE_IMPORT_LIBRARY_SUFFIX)
+                set(WHISPER_BLAS_LIB_PREFIX ${CMAKE_IMPORT_LIBRARY_PREFIX})
+                set(WHISPER_BLAS_LIB_SUFFIX ${CMAKE_IMPORT_LIBRARY_SUFFIX})
+            else ()
+                set(WHISPER_BLAS_LIB_PREFIX ${CMAKE_SHARED_LIBRARY_PREFIX})
+                set(WHISPER_BLAS_LIB_SUFFIX ${CMAKE_SHARED_LIBRARY_SUFFIX})
+            endif ()
         endif ()
+        # OpenBLAS prebuilt libraries hardcode "lib" prefix in filename even on Windows
+        if (WHISPER_OPENBLAS)
+            set(WHISPER_BLAS_LIB_PREFIX "lib")
+        endif ()
+        message(STATUS "BLAS compatible library path provided")
+        set(BLAS_LIBRARIES "$ENV{OPENBLAS_PATH}/lib/${WHISPER_BLAS_LIB_PREFIX}${WHISPER_BLAS_LIB}${WHISPER_BLAS_LIB_SUFFIX}")
+        message(STATUS "Libraries ${BLAS_LIBRARIES}")
+        set(BLAS_INCLUDE_DIRS "$ENV{OPENBLAS_PATH}/include")
+        message(STATUS "Include dirs ${BLAS_INCLUDE_DIRS}")
+        if (NOT EXISTS "${BLAS_LIBRARIES}")
+            message(FATAL_ERROR "BLAS library was not found. Environment variable OPENBLAS_PATH misdefined.")
+        endif ()
+        set(WHISPER_EXTRA_FLAGS ${WHISPER_EXTRA_FLAGS} -DGGML_USE_OPENBLAS)
+        include_directories(${BLAS_INCLUDE_DIRS})
+        set(WHISPER_EXTRA_LIBS ${WHISPER_EXTRA_LIBS} ${BLAS_LIBRARIES})
     else ()
-        set(BLA_STATIC 1)
+        if (WHISPER_STATIC)
+            # FindBLAS.cmake pkg-config logic seems incomplete, because when
+            # BLA_STATIC is on, then it should use pkg_check_modules_static
+            # instead of pkg_check_modules.
+            # Some manual variable overriding may be necessary if you don't
+            # achieve desired results.
+            set(BLA_STATIC 1)
+        endif ()
         set(BLA_VENDOR ${WHISPER_BLAS_VENDOR})
-        set(BLA_SIZEOF_INTEGER 8)
+        if (WHISPER_OPENBLAS_INTERFACE64)
+            set(BLA_SIZEOF_INTEGER 8)
+        else ()
+            set(BLA_SIZEOF_INTEGER 4)
+        endif()
         set(BLA_PREFER_PKGCONFIG 1)
         find_package(BLAS)
 
         if(BLAS_FOUND)
             message(STATUS "BLAS compatible library found")
             message(STATUS "Libraries ${BLAS_LIBRARIES}")
-            find_path(BLAS_INCLUDE_DIRS cblas.h /usr/include/openblas /usr/local/include/openblas $ENV{BLAS_HOME}/include)
+            if (NOT DEFINED BLAS_INCLUDE_DIRS)
+                if (PKGC_BLAS_FOUND)
+                    set(BLAS_INCLUDE_DIRS "${PKGC_BLAS_INCLUDE_DIRS}")
+                else ()
+                    find_path(BLAS_INCLUDE_DIRS cblas.h /usr/include/openblas)
+                endif()
+            endif()
+            message(STATUS "Include dirs ${BLAS_INCLUDE_DIRS}")
             set(WHISPER_EXTRA_FLAGS ${WHISPER_EXTRA_FLAGS} -DGGML_USE_OPENBLAS)
             include_directories(${BLAS_INCLUDE_DIRS})
             set(WHISPER_EXTRA_LIBS ${WHISPER_EXTRA_LIBS} ${BLAS_LIBRARIES})

Makefile

@@ -210,9 +210,28 @@ ifndef WHISPER_NO_METAL
 	endif
 endif
 
-ifdef WHISPER_OPENBLAS
+ifneq ($(filter-out 0,$(WHISPER_OPENBLAS)),) # OpenBLAS
-	CFLAGS  += -DGGML_USE_OPENBLAS -I/usr/local/include/openblas -I/usr/include/openblas
+	WHISPER_OPENBLAS_INTERFACE64 ?= 0 # use 32-bit interface by default
-	LDFLAGS += -lopenblas
+	ifneq ($(filter-out 0,$(WHISPER_OPENBLAS_INTERFACE64)),)
+		WHISPER_BLAS_LIB := openblas64
+	else
+		WHISPER_BLAS_LIB := openblas
+	endif
+	ifneq ($(OPENBLAS_PATH),)
+		WHISPER_BLAS_CFLAGS  := -I$(OPENBLAS_PATH)/include
+		WHISPER_BLAS_LDFLAGS := -L$(OPENBLAS_PATH)/lib -l$(WHISPER_BLAS_LIB)
+	else
+		WHISPER_BLAS_LIB_PC_EXISTS := $(shell pkg-config --exists $(WHISPER_BLAS_LIB) && echo 1)
+		ifneq ($(filter-out 0,$(WHISPER_BLAS_LIB_PC_EXISTS)),)
+			WHISPER_BLAS_CFLAGS  := $(shell pkg-config --cflags $(WHISPER_BLAS_LIB))
+			WHISPER_BLAS_LDFLAGS := $(shell pkg-config --libs   $(WHISPER_BLAS_LIB))
+		else
+			WHISPER_BLAS_CFLAGS  := -I/usr/include/openblas
+			WHISPER_BLAS_LDFLAGS := -l$(WHISPER_BLAS_LIB)
+		endif
+	endif
+	CFLAGS  += $(WHISPER_BLAS_CFLAGS) -DGGML_USE_OPENBLAS
+	LDFLAGS += $(WHISPER_BLAS_LDFLAGS)
 endif
 
 ifdef WHISPER_CUBLAS