[build] Support building Kaldi to WASM with OpenBLAS (#4954)

* Support OpenBLAS with WASM

* Update README

* Force g_num_threads = 0 in WASM

Author: msqr1

README.md

@@ -86,6 +86,6 @@ cmake --build /home/gerhard/workspace/kaldi/build/Release
 ### Web Assembly
 
 - Kaldi supports cross compiling for Web Assembly for in-browser execution
-  using [emscripten](https://emscripten.org/) and CLAPACK.
-- See [this post](https://gitlab.inria.fr/kaldi.web/kaldi-wasm/-/wikis/build_details.md)
+  using [emscripten](https://emscripten.org) and OpenBLAS
+- See [this repo](https://github.com/msqr1/kaldi-wasm2)
   for a step-by-step description of the build process.

src/configure

@@ -894,6 +894,12 @@ if is_set $HOST; then
     fi
   else
     TARGET_ARCH="$HOST"
+    if ! $static_fst || ! $static_math || $dynamic_kaldi; then
+      echo "WARNING: Dynamic libraries are not currently supported when compiling to WASM. Overriding --static, --static-math, and --static-fst."
+    fi
+    dynamic_kaldi=false
+    static_math=true
+    static_fst=true
   fi
 
   HOST_CXX="$HOST-c++"
@@ -1360,14 +1366,6 @@ or try another math library, e.g. --mathlib=OPENBLAS (Kaldi may be slower)."
 ** You can also use other matrix algebra libraries. For information, see:
 **   http://kaldi-asr.org/doc/matrixwrap.html"
     fi
-    if [ -f $OPENBLASROOT/lib/libopenblas.so ]; then
-      OPENBLASLIBDIR=$OPENBLASROOT/lib
-    elif [ -f $OPENBLASROOT/lib64/libopenblas.so ]; then
-      # in REDHAT/CentOS package installs, the library is located here
-      OPENBLASLIBDIR=$OPENBLASROOT/lib64
-    else
-      failure "Expected to find the file $OPENBLASROOT/lib/libopenblas.so"
-    fi
     if [ -f $OPENBLASROOT/include/cblas.h ] ; then
       OPENBLASINCDIR=$OPENBLASROOT/include
     elif [ -f $OPENBLASROOT/include/openblas/cblas.h ] ; then
@@ -1381,18 +1379,35 @@ or try another math library, e.g. --mathlib=OPENBLAS (Kaldi may be slower)."
       echo "** if it is a package-based install)."
       OPENBLASINCDIR="/usr/include"
     fi
-    echo "Your math library seems to be OpenBLAS from $OPENBLASROOT.  Configuring appropriately."
-    # TODO(kkm): Probably, OpenBLAS required libgfortran.so.3 at some point, but
-    # no longer does. *My* linker does not complain about a missing library, but
-    # is it safe to keep the reference if no longer required? Try to figure out
-    # how long ago the dependency was dropped.
     if $static_math; then
+      if [ -f $OPENBLASROOT/lib/libopenblas.a ]; then
+        OPENBLASLIBDIR=$OPENBLASROOT/lib
+      else
+        failure "Expected to find the file $OPENBLASROOT/lib/libopenblas.a"
+      fi
       echo "Configuring static OpenBlas since --static-math=yes"
-      OPENBLASLIBS="-L$OPENBLASLIBDIR -l:libopenblas.a -lgfortran"
+      OPENBLASLIBS="-L$OPENBLASLIBDIR -l:libopenblas.a"
+      # No Fortran for OpenBLAS
+      if [[ "$HOST" != WASM ]]; then
+        OPENBLASLIBS+="-lgfortran"
+      fi
     else
+      if [ -f $OPENBLASROOT/lib/libopenblas.so ]; then
+        OPENBLASLIBDIR=$OPENBLASROOT/lib
+      elif [ -f $OPENBLASROOT/lib64/libopenblas.so ]; then
+        # in REDHAT/CentOS package installs, the library is located here
+        OPENBLASLIBDIR=$OPENBLASROOT/lib64
+      else
+        failure "Expected to find the file $OPENBLASROOT/lib/libopenblas.so"
+      fi
       echo "Configuring dynamically loaded OpenBlas since --static-math=no (the default)"
       OPENBLASLIBS="-L$OPENBLASLIBDIR -lopenblas -lgfortran -Wl,-rpath=$OPENBLASLIBDIR"
     fi
+    echo "Your math library seems to be OpenBLAS from $OPENBLASROOT.  Configuring appropriately."
+    # TODO(kkm): Probably, OpenBLAS required libgfortran.so.3 at some point, but
+    # no longer does. *My* linker does not complain about a missing library, but
+    # is it safe to keep the reference if no longer required? Try to figure out
+    # how long ago the dependency was dropped.
     echo "OPENBLASINC = $OPENBLASINCDIR" >> kaldi.mk
     echo "OPENBLASLIBS = $OPENBLASLIBS" >> kaldi.mk
     echo >> kaldi.mk

src/makefiles/linux_clapack.mk

@@ -44,10 +44,11 @@ ifeq ($(findstring clang,$(COMPILER)),clang)
 CXXFLAGS += -Wno-mismatched-tags
 endif
 
-LDFLAGS = $(EXTRA_LDFLAGS) $(OPENFSTLDFLAGS) -rdynamic
+LDFLAGS = $(EXTRA_LDFLAGS) $(OPENFSTLDFLAGS)
 LDLIBS = $(EXTRA_LDLIBS) $(OPENFSTLIBS) $(CLAPACKLIBS) -lm -ldl
 
 ifneq ($(ARCH), WASM)
+    LDFLAGS += -rdynamic
     CXXFLAGS += -pthread
     LDLIBS += -lpthread
 endif

src/makefiles/linux_openblas.mk

@@ -25,7 +25,7 @@ CXXFLAGS = -std=$(CXXLANGVERSION) -I.. -isystem $(OPENFSTINC) -O1 $(EXTRA_CXXFLA
            -DOPENFST_VER=$(OPENFSTVER) \
            -DKALDI_DOUBLEPRECISION=$(DOUBLE_PRECISION) \
            -DHAVE_EXECINFO_H=1 -DHAVE_CXXABI_H -DHAVE_OPENBLAS -I$(OPENBLASINC) \
-           -msse -msse2 -pthread \
+           -msse -msse2 \
            -g
 
 ifeq ($(KALDI_FLAVOR), dynamic)
@@ -46,5 +46,13 @@ ifeq ($(findstring clang,$(COMPILER)),clang)
 CXXFLAGS += -Wno-mismatched-tags
 endif
 
-LDFLAGS = $(EXTRA_LDFLAGS) $(OPENFSTLDFLAGS) -rdynamic
-LDLIBS = $(EXTRA_LDLIBS) $(OPENFSTLIBS) $(OPENBLASLIBS) -lm -lpthread -ldl
+LDFLAGS = $(EXTRA_LDFLAGS) $(OPENFSTLDFLAGS)
+LDLIBS = $(EXTRA_LDLIBS) $(OPENFSTLIBS) $(OPENBLASLIBS) -lm -ldl
+
+ifneq ($(ARCH), WASM)
+  CXXFLAGS += -pthread
+  LDLIBS += -lpthread
+  LDFLAGS += -rdynamic
+else 
+  CXXFLAGS += -DKALDI_WASM
+endif

src/util/kaldi-thread.cc

@@ -22,8 +22,14 @@
 #include "util/kaldi-thread.h"
 
 namespace kaldi {
-int32 g_num_threads = 8;  // Initialize this global variable.
 
+int32 g_num_threads = 
+#ifdef KALDI_WASM
+0 // Everything will run on the main thread for WASM
+#else 
+8  // Initialize this global variable.
+#endif
+;
 MultiThreadable::~MultiThreadable() {
   // default implementation does nothing
 }