diff --git a/builtins.cpp b/builtins.cpp
index d6eefde5..da66ed5f 100644
--- a/builtins.cpp
+++ b/builtins.cpp
@@ -497,6 +497,8 @@ lSetInternalFunctions(llvm::Module *module) {
         "__prefetch_read_uniform_nt",
         "__rcp_uniform_float",
         "__rcp_varying_float",
+        "__rcp_uniform_double",
+        "__rcp_varying_double",
         "__rdrand_i16",
         "__rdrand_i32",
         "__rdrand_i64",
@@ -534,6 +536,8 @@ lSetInternalFunctions(llvm::Module *module) {
         "__round_varying_float",
         "__rsqrt_uniform_float",
         "__rsqrt_varying_float",
+        "__rsqrt_uniform_double",
+        "__rsqrt_varying_double",
         "__set_system_isa",
         "__sext_uniform_bool",
         "__sext_varying_bool",
diff --git a/builtins/target-avx-x2.ll b/builtins/target-avx-x2.ll
index f8fd5cd5..802f726b 100644
--- a/builtins/target-avx-x2.ll
+++ b/builtins/target-avx-x2.ll
@@ -687,3 +687,10 @@ define <16 x double> @__max_varying_double(<16 x double>, <16 x double>) nounwin
   binary4to16(ret, double, @llvm.x86.avx.max.pd.256, %0, %1)
   ret <16 x double> %ret
 }
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; reciprocals in double precision, if supported
+
+rsqrt_double()
+rcp_double()
+
diff --git a/builtins/target-avx.ll b/builtins/target-avx.ll
index e98a3843..2abed8fe 100644
--- a/builtins/target-avx.ll
+++ b/builtins/target-avx.ll
@@ -559,3 +559,9 @@ gen_scatter(float)
 gen_scatter(i64)
 gen_scatter(double)
 
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; reciprocals in double precision, if supported
+
+rsqrt_double()
+rcp_double()
+
diff --git a/builtins/target-generic-1.ll b/builtins/target-generic-1.ll
index c43a12a7..40d7ae8c 100644
--- a/builtins/target-generic-1.ll
+++ b/builtins/target-generic-1.ll
@@ -992,3 +992,9 @@ declare <WIDTH x i16> @__float_to_half_varying(<WIDTH x float> %v) nounwind read
 
 define_avgs()
 
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; reciprocals in double precision, if supported
+
+rsqrt_double()
+rcp_double()
+
diff --git a/builtins/target-generic-common.ll b/builtins/target-generic-common.ll
index 2b2b21c9..4f87ad26 100644
--- a/builtins/target-generic-common.ll
+++ b/builtins/target-generic-common.ll
@@ -191,9 +191,13 @@ declare <WIDTH x double> @__max_varying_double(<WIDTH x double>,
 
 declare float @__rsqrt_uniform_float(float) nounwind readnone 
 declare float @__rcp_uniform_float(float) nounwind readnone 
+declare double @__rsqrt_uniform_double(double) nounwind readnone 
+declare double @__rcp_uniform_double(double) nounwind readnone 
 declare float @__sqrt_uniform_float(float) nounwind readnone 
 declare <WIDTH x float> @__rcp_varying_float(<WIDTH x float>) nounwind readnone 
 declare <WIDTH x float> @__rsqrt_varying_float(<WIDTH x float>) nounwind readnone 
+declare <WIDTH x double> @__rcp_varying_double(<WIDTH x double>) nounwind readnone 
+declare <WIDTH x double> @__rsqrt_varying_double(<WIDTH x double>) nounwind readnone 
 declare <WIDTH x float> @__sqrt_varying_float(<WIDTH x float>) nounwind readnone 
 
 declare double @__sqrt_uniform_double(double) nounwind readnone
diff --git a/builtins/target-neon-16.ll b/builtins/target-neon-16.ll
index a0575927..0f144b66 100644
--- a/builtins/target-neon-16.ll
+++ b/builtins/target-neon-16.ll
@@ -515,3 +515,9 @@ define <8 x i16> @__avg_down_int16(<8 x i16>, <8 x i16>) nounwind readnone {
   %r = call <8 x i16> @llvm.arm.neon.vhadds.v8i16(<8 x i16> %0, <8 x i16> %1)
   ret <8 x i16> %r
 }
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; reciprocals in double precision, if supported
+
+rsqrt_double()
+rcp_double()
diff --git a/builtins/target-neon-32.ll b/builtins/target-neon-32.ll
index 30b062c9..d30efff2 100644
--- a/builtins/target-neon-32.ll
+++ b/builtins/target-neon-32.ll
@@ -485,3 +485,9 @@ define <4 x i16> @__avg_down_int16(<4 x i16>, <4 x i16>) nounwind readnone {
   %r = call <4 x i16> @llvm.arm.neon.vhadds.v4i16(<4 x i16> %0, <4 x i16> %1)
   ret <4 x i16> %r
 }
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; reciprocals in double precision, if supported
+
+rsqrt_double()
+rcp_double()
diff --git a/builtins/target-neon-8.ll b/builtins/target-neon-8.ll
index 2accfe53..4b6dfa3a 100644
--- a/builtins/target-neon-8.ll
+++ b/builtins/target-neon-8.ll
@@ -581,3 +581,9 @@ define <16 x i16> @__avg_down_int16(<16 x i16>, <16 x i16>) nounwind readnone {
   v8tov16(i16, %r0, %r1, %r)
   ret <16 x i16> %r
 }
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; reciprocals in double precision, if supported
+
+rsqrt_double()
+rcp_double()
diff --git a/builtins/target-sse2-x2.ll b/builtins/target-sse2-x2.ll
index 77bf1a9d..41b4be09 100644
--- a/builtins/target-sse2-x2.ll
+++ b/builtins/target-sse2-x2.ll
@@ -652,3 +652,9 @@ define <8 x double> @__max_varying_double(<8 x double>, <8 x double>) nounwind r
   binary2to8(ret, double, @llvm.x86.sse2.max.pd, %0, %1)
   ret <8 x double> %ret
 }
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; reciprocals in double precision, if supported
+
+rsqrt_double()
+rcp_double()
diff --git a/builtins/target-sse2.ll b/builtins/target-sse2.ll
index e42d4990..ac091cdb 100644
--- a/builtins/target-sse2.ll
+++ b/builtins/target-sse2.ll
@@ -587,3 +587,9 @@ gen_scatter(i32)
 gen_scatter(float)
 gen_scatter(i64)
 gen_scatter(double)
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; reciprocals in double precision, if supported
+
+rsqrt_double()
+rcp_double()
diff --git a/builtins/target-sse4-16.ll b/builtins/target-sse4-16.ll
index 72b81ff0..55c94ce6 100644
--- a/builtins/target-sse4-16.ll
+++ b/builtins/target-sse4-16.ll
@@ -488,3 +488,10 @@ define <8 x i16> @__avg_up_uint16(<8 x i16>, <8 x i16>) {
 define_avg_up_int8()
 define_avg_up_int16()
 define_down_avgs()
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; reciprocals in double precision, if supported
+
+rsqrt_double()
+rcp_double()
+
diff --git a/builtins/target-sse4-8.ll b/builtins/target-sse4-8.ll
index 69b355e3..4d81df92 100644
--- a/builtins/target-sse4-8.ll
+++ b/builtins/target-sse4-8.ll
@@ -490,3 +490,10 @@ define <16 x i16> @__avg_up_uint16(<16 x i16>, <16 x i16>) nounwind readnone {
 define_avg_up_int8()
 define_avg_up_int16()
 define_down_avgs()
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; reciprocals in double precision, if supported
+
+rsqrt_double()
+rcp_double()
+
diff --git a/builtins/target-sse4-x2.ll b/builtins/target-sse4-x2.ll
index 842db53f..09088dc3 100644
--- a/builtins/target-sse4-x2.ll
+++ b/builtins/target-sse4-x2.ll
@@ -592,3 +592,9 @@ define <8 x double> @__max_varying_double(<8 x double>, <8 x double>) nounwind r
 
 define_avgs()
 
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; reciprocals in double precision, if supported
+
+rsqrt_double()
+rcp_double()
+
diff --git a/builtins/target-sse4.ll b/builtins/target-sse4.ll
index 16177b47..747a6a58 100644
--- a/builtins/target-sse4.ll
+++ b/builtins/target-sse4.ll
@@ -515,3 +515,9 @@ gen_scatter(double)
 
 define_avgs()
 
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; reciprocals in double precision, if supported
+
+rsqrt_double()
+rcp_double()
+
diff --git a/builtins/util.m4 b/builtins/util.m4
index f9ae7cd1..a8340adb 100644
--- a/builtins/util.m4
+++ b/builtins/util.m4
@@ -4531,3 +4531,37 @@ define(`define_avgs', `
 define_up_avgs()
 define_down_avgs()
 ')
+
+define(`rsqrt_double', `
+define double @__rsqrt_uniform_double(double) nounwind alwaysinline readnone
+{
+  %flt = fptrunc double %0 to float
+  %res = call float @__rsqrt_uniform_float(float %flt)
+  %dres = fpext float %res to double
+  ret double %dres
+}
+define <WIDTH x double> @__rsqrt_varying_double(<WIDTH x double>) nounwind alwaysinline readnone
+{
+  %flt = fptrunc <WIDTH x double> %0 to <WIDTH x float>
+  %res = call <WIDTH x float> @__rsqrt_varying_float(<WIDTH x float> %flt)
+  %dres = fpext <WIDTH x float> %res to <WIDTH x double>
+  ret <WIDTH x double> %dres
+}
+')
+
+define(`rcp_double', `
+define double @__rcp_uniform_double(double) nounwind alwaysinline readnone
+{
+  %flt = fptrunc double %0 to float
+  %res = call float @__rcp_uniform_float(float %flt)
+  %dres = fpext float %res to double
+  ret double %dres
+}
+define <WIDTH x double> @__rcp_varying_double(<WIDTH x double>) nounwind alwaysinline readnone
+{
+  %flt = fptrunc <WIDTH x double> %0 to <WIDTH x float>
+  %res = call <WIDTH x float> @__rcp_varying_float(<WIDTH x float> %flt)
+  %dres = fpext <WIDTH x float> %res to <WIDTH x double>
+  ret <WIDTH x double> %dres
+}
+')
diff --git a/stdlib.ispc b/stdlib.ispc
index 3b17283d..de2221b2 100644
--- a/stdlib.ispc
+++ b/stdlib.ispc
@@ -3517,6 +3517,15 @@ static inline uniform double sqrt(uniform double v) {
     return __sqrt_uniform_double(v);
 }
 
+__declspec(safe)
+static inline double rsqrt(double v) {
+    return __rsqrt_varying_double(v);
+}
+
+__declspec(safe)
+static inline uniform double rsqrt(uniform double v) {
+    return __rsqrt_uniform_double(v);
+}
 __declspec(safe)
 static inline double ldexp(double x, int n) {
     unsigned int64 ex = 0x7ff0000000000000;