diff --git a/gcc/d/dmd/MERGE b/gcc/d/dmd/MERGE
index a878cb9f42e..f933cf1c992 100644
--- a/gcc/d/dmd/MERGE
+++ b/gcc/d/dmd/MERGE
@@ -1,4 +1,4 @@
-09db0c41ee922502fa0966bde24c1cb9b15ad436
+f8a1a515346b16ebbd9da56a908540cbef1ee582
 
 The first line of this file holds the git revision number of the last
 merge done from the dlang/dmd repository.
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 1f412a0ef1d..d6529ea7d1f 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2020-04-27  Iain Buclaw  <ibuclaw@gdcproject.org>
+
+	PR d/89418
+	* lib/gdc-utils.exp (gdc-convert-test): Add dg-skip-if for compilable
+	tests that depend on the phobos standard library.
+
 2020-04-27  Iain Buclaw  <ibuclaw@gdcproject.org>
 
 	PR d/94777
diff --git a/gcc/testsuite/gdc.test/compilable/ctfe_math.d b/gcc/testsuite/gdc.test/compilable/ctfe_math.d
index 78de869d090..334b75ac941 100644
--- a/gcc/testsuite/gdc.test/compilable/ctfe_math.d
+++ b/gcc/testsuite/gdc.test/compilable/ctfe_math.d
@@ -1,3 +1,4 @@
+// COMPILABLE_MATH_TEST
 // Test CTFE builtins for std.math functions.
 
 import std.math;
diff --git a/gcc/testsuite/gdc.test/compilable/test5227.d b/gcc/testsuite/gdc.test/compilable/test5227.d
index c270b79245b..63ca752f4fb 100644
--- a/gcc/testsuite/gdc.test/compilable/test5227.d
+++ b/gcc/testsuite/gdc.test/compilable/test5227.d
@@ -1,4 +1,5 @@
 /*
+COMPILABLE_MATH_TEST
 REQUIRED_ARGS:
 PERMUTE_ARGS:
 TEST_OUTPUT:
diff --git a/gcc/testsuite/lib/gdc-utils.exp b/gcc/testsuite/lib/gdc-utils.exp
index 87d1105a9db..5c17346dbf5 100644
--- a/gcc/testsuite/lib/gdc-utils.exp
+++ b/gcc/testsuite/lib/gdc-utils.exp
@@ -302,6 +302,12 @@ proc gdc-convert-test { base test } {
 	    # It will need skipping if phobos is not available on the target.
 	    regsub -- {RUNNABLE_PHOBOS_TEST.*$} $copy_line "" out_line
 	    set needs_phobos 1
+
+	} elseif [regexp -- {COMPILABLE_MATH_TEST} $copy_line match sources] {
+	    # COMPILABLE_MATH_TEST annotates tests that import the std.math
+	    # module.  Which will need skipping if not available on the target.
+	    regsub -- {RUNNABLE_PHOBOS_TEST.*$} $copy_line "" out_line
+	    set needs_phobos 1
 	}
 
 	puts $fdout $out_line
@@ -358,6 +364,9 @@ proc gdc-convert-test { base test } {
 		# Cleanup extra generated files.
 		puts $fdout "// { dg-final { file delete $genfile } }"
 	    }
+	    if $needs_phobos {
+		puts $fdout "// { dg-skip-if \"imports phobos\" { ! d_runtime_has_std_library } }"
+	    }
 	}
 
 	fail_compilation {
diff --git a/libphobos/libdruntime/MERGE b/libphobos/libdruntime/MERGE
index 8b461f76ad0..e3763485adf 100644
--- a/libphobos/libdruntime/MERGE
+++ b/libphobos/libdruntime/MERGE
@@ -1,4 +1,4 @@
-e68a5ae36790fa9dc5bab6155bc450eb6bf8c12c
+2b5c0b2766949e788e4929c5fb0e2ba698ff79a3
 
 The first line of this file holds the git revision number of the last
 merge done from the dlang/druntime repository.
diff --git a/libphobos/libdruntime/core/internal/convert.d b/libphobos/libdruntime/core/internal/convert.d
index 3d2cb59a64a..0f540f83d42 100644
--- a/libphobos/libdruntime/core/internal/convert.d
+++ b/libphobos/libdruntime/core/internal/convert.d
@@ -73,8 +73,8 @@ const(ubyte)[] toUbyte(T)(const ref T val) if (is(Unqual!T == float) || is(Unqua
             // Parse DoubleDoubles as a pair of doubles.
             // The layout of the type is:
             //
-            //   [1|  7  |       56      ][   8    |       56       ]
-            //   [S| Exp | Fraction (hi) ][ Unused | Fraction (low) ]
+            //   [1|    11    |       52      ][1|    11    |       52       ]
+            //   [S| Exponent | Fraction (hi) ][S| Exponent | Fraction (low) ]
             //
             // We can get the least significant bits by subtracting the IEEE
             // double precision portion from the real value.