diff --git a/CMakeLists.txt b/CMakeLists.txt
index a91f2559..94cb34fd 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -76,6 +76,8 @@ ELSEIF (LOWERCASE_CMAKE_SYSTEM_PROCESSOR MATCHES "(x86_64|amd64)")
     SET(WTF_CPU_X86_64 1)
 ELSEIF (LOWERCASE_CMAKE_SYSTEM_PROCESSOR MATCHES "(i[3-6]86|x86)")
     SET(WTF_CPU_X86 1)
+ELSEIF (LOWERCASE_CMAKE_SYSTEM_PROCESSOR MATCHES "^riscv64")
+    SET(WTF_CPU_RISCV64 1)
 ELSE ()
     MESSAGE(FATAL_ERROR "Unknown CPU '${CMAKE_SYSTEM_PROCESSOR}'")
 ENDIF ()
diff --git a/Source/JavaScriptCore/CMakeLists.txt b/Source/JavaScriptCore/CMakeLists.txt
index 0a7a8bd3..14fbcdbf 100644
--- a/Source/JavaScriptCore/CMakeLists.txt
+++ b/Source/JavaScriptCore/CMakeLists.txt
@@ -471,6 +471,7 @@ IF (WTF_CPU_ARM)
 ELSEIF (WTF_CPU_MIPS)
 ELSEIF (WTF_CPU_X86)
 ELSEIF (WTF_CPU_X86_64)
+ELSEIF (WTF_CPU_RISCV64)
 ELSE ()
     MESSAGE(FATAL_ERROR "Unknown CPU")
 ENDIF ()
diff --git a/Source/JavaScriptCore/JavaScriptCore.pri b/Source/JavaScriptCore/JavaScriptCore.pri
index e5f4362c..f175d09e 100644
--- a/Source/JavaScriptCore/JavaScriptCore.pri
+++ b/Source/JavaScriptCore/JavaScriptCore.pri
@@ -37,6 +37,14 @@ macx: INCLUDEPATH += $$JAVASCRIPTCORE_GENERATED_SOURCES_DIR/$$activeBuildConfig(
 
 win32-*: LIBS += -lwinmm
 
+# Hack around RISCV64 fail wrt JSValue.h
+# SValue.h unconditionally casts pointer to int32_t.
+# add -fpermissive locally as a workaround
+equals(QT_ARCH, riscv64) {
+    message("JavaScriptCore riscv64 hack: -fpermissive")
+    QMAKE_CXXFLAGS += -fpermissive
+}
+
 wince* {
     INCLUDEPATH += $$QT.core.sources/../3rdparty/ce-compat
     INCLUDEPATH += $$SOURCE_DIR/os-win32
diff --git a/Source/WTF/wtf/Platform.h b/Source/WTF/wtf/Platform.h
index 56c6f256..639063bb 100644
--- a/Source/WTF/wtf/Platform.h
+++ b/Source/WTF/wtf/Platform.h
@@ -164,6 +164,11 @@
 #define WTF_CPU_BIG_ENDIAN 1
 #endif
 
+/* CPU(RISCV64) - RISCV64 */
+#if defined(__riscv) && defined(__riscv_xlen) && __riscv_xlen == 64
+#define WTF_CPU_RISCV64 1
+#endif
+
 /* CPU(X86) - i386 / x86 32-bit */
 #if   defined(__i386__) \
     || defined(i386)     \
@@ -906,7 +911,8 @@
     || CPU(S390X) \
     || CPU(AARCH64) \
     || CPU(MIPS64) \
-    || CPU(PPC64)
+    || CPU(PPC64) \
+    || CPU(RISCV64)
 #define WTF_USE_JSVALUE64 1
 #else
 #define WTF_USE_JSVALUE32_64 1
@@ -932,7 +938,8 @@
     && (CPU(X86) || CPU(X86_64) || CPU(ARM) || CPU(MIPS)) \
     && (OS(DARWIN) || !COMPILER(GCC) || GCC_VERSION_AT_LEAST(4, 1, 0)) \
     && !OS(WINCE) \
-    && !OS(QNX)
+    && !OS(QNX) \
+    && !CPU(RISCV64)
 #define ENABLE_JIT 1
 #endif
 
diff --git a/Source/WTF/wtf/dtoa/utils.h b/Source/WTF/wtf/dtoa/utils.h
index bc17f043..91493297 100644
--- a/Source/WTF/wtf/dtoa/utils.h
+++ b/Source/WTF/wtf/dtoa/utils.h
@@ -49,7 +49,7 @@
 defined(__ARMEL__) || \
 defined(_MIPS_ARCH_MIPS32R2)
 #define DOUBLE_CONVERSION_CORRECT_DOUBLE_OPERATIONS 1
-#elif CPU(MIPS) || CPU(PPC) || CPU(PPC64) || OS(WINCE) || CPU(SH4) || CPU(S390) || CPU(S390X) || CPU(IA64) || CPU(SPARC) || CPU(ALPHA) || CPU(MIPS64) || CPU(AARCH64) || CPU(HPPA)
+#elif CPU(MIPS) || CPU(PPC) || CPU(PPC64) || OS(WINCE) || CPU(SH4) || CPU(S390) || CPU(S390X) || CPU(IA64) || CPU(SPARC) || CPU(ALPHA) || CPU(MIPS64) || CPU(AARCH64) || CPU(HPPA) || CPU(RISCV64)
 #define DOUBLE_CONVERSION_CORRECT_DOUBLE_OPERATIONS 1
 #elif defined(_M_IX86) || defined(__i386__)
 #if defined(_WIN32)