From NetBSD http://cvsweb.netbsd.org/bsdweb.cgi/pkgsrc/lang/openjdk7/hacks.mk
Work around incorrect constant folding of subnormals in javac when the FPU
does not handle subnormal arithmetic, like on ARM in flush-to-zero mode.
These workarounds avoid underflow conditions during the bootstrap so the JDK
can correctly build itself.  Compiling or running programs other than OpenJDK
itself on such hardware may still cause unexpected behaviour.

--- jdk/src/share/classes/java/lang/Double.java.orig	2014-03-04 02:57:59 UTC
+++ jdk/src/share/classes/java/lang/Double.java
@@ -86,7 +86,7 @@ public final class Double extends Number
      *
      * @since 1.6
      */
-    public static final double MIN_NORMAL = 0x1.0p-1022; // 2.2250738585072014E-308
+    public static final double MIN_NORMAL = Double.longBitsToDouble(0x10000000000000L); // 2.2250738585072014E-308
 
     /**
      * A constant holding the smallest positive nonzero value of type
@@ -95,7 +95,7 @@ public final class Double extends Number
      * {@code 0x0.0000000000001P-1022} and also equal to
      * {@code Double.longBitsToDouble(0x1L)}.
      */
-    public static final double MIN_VALUE = 0x0.0000000000001P-1022; // 4.9e-324
+    public static final double MIN_VALUE = Double.longBitsToDouble(0x1L); // 4.9e-324
 
     /**
      * Maximum exponent a finite {@code double} variable may have.
--- jdk/src/share/classes/java/lang/Float.java.orig	2014-03-04 02:57:59 UTC
+++ jdk/src/share/classes/java/lang/Float.java
@@ -85,7 +85,7 @@ public final class Float extends Number 
      *
      * @since 1.6
      */
-    public static final float MIN_NORMAL = 0x1.0p-126f; // 1.17549435E-38f
+    public static final float MIN_NORMAL = Float.intBitsToFloat(0x800000); // 1.17549435E-38f
 
     /**
      * A constant holding the smallest positive nonzero value of type
@@ -93,7 +93,7 @@ public final class Float extends Number 
      * hexadecimal floating-point literal {@code 0x0.000002P-126f}
      * and also equal to {@code Float.intBitsToFloat(0x1)}.
      */
-    public static final float MIN_VALUE = 0x0.000002P-126f; // 1.4e-45f
+    public static final float MIN_VALUE = Float.intBitsToFloat(0x1); // 1.4e-45f
 
     /**
      * Maximum exponent a finite {@code float} variable may have.  It
--- jdk/src/share/classes/sun/misc/DoubleConsts.java.orig	2014-03-04 02:58:49 UTC
+++ jdk/src/share/classes/sun/misc/DoubleConsts.java
@@ -52,7 +52,7 @@ public class DoubleConsts {
      *
      * @since 1.5
      */
-    public static final double  MIN_NORMAL      = 2.2250738585072014E-308;
+    public static final double  MIN_NORMAL      = Double.longBitsToDouble(0x10000000000000L);
 
 
     /**
--- jdk/src/share/classes/sun/misc/FloatConsts.java.orig	2014-03-04 02:58:49 UTC
+++ jdk/src/share/classes/sun/misc/FloatConsts.java
@@ -49,7 +49,7 @@ public class FloatConsts {
      * <code>float</code>, 2<sup>-126</sup>.  It is equal to the value
      * returned by <code>Float.intBitsToFloat(0x00800000)</code>.
      */
-    public static final float   MIN_NORMAL      = 1.17549435E-38f;
+    public static final float   MIN_NORMAL      = Float.intBitsToFloat(0x800000);
 
     /**
      * The number of logical bits in the significand of a
--- langtools/src/share/classes/com/sun/tools/javac/jvm/Items.java.orig	2014-03-04 02:51:48 UTC
+++ langtools/src/share/classes/com/sun/tools/javac/jvm/Items.java
@@ -623,12 +623,12 @@ public class Items {
             /** Return true iff float number is positive 0.
              */
             private boolean isPosZero(float x) {
-                return x == 0.0f && 1.0f / x > 0.0f;
+                return Float.floatToIntBits(x) == 0x0;
             }
             /** Return true iff double number is positive 0.
              */
             private boolean isPosZero(double x) {
-                return x == 0.0d && 1.0d / x > 0.0d;
+                return Double.doubleToLongBits(x) == 0x0L;
             }
 
         CondItem mkCond() {
--- langtools/src/share/classes/com/sun/tools/javac/parser/JavacParser.java.orig	2015-09-29 16:38:49 UTC
+++ langtools/src/share/classes/com/sun/tools/javac/parser/JavacParser.java
@@ -703,7 +703,7 @@ public class JavacParser implements Pars
                 // error already reported in scanner
                 n = Float.NaN;
             }
-            if (n.floatValue() == 0.0f && !isZero(proper))
+            if (n.floatValue() == 0.0f && !isZero(proper) && Float.floatToIntBits(n) != 0x1)
                 error(token.pos, "fp.number.too.small");
             else if (n.floatValue() == Float.POSITIVE_INFINITY)
                 error(token.pos, "fp.number.too.large");
@@ -722,7 +722,7 @@ public class JavacParser implements Pars
                 // error already reported in scanner
                 n = Double.NaN;
             }
-            if (n.doubleValue() == 0.0d && !isZero(proper))
+            if (n.doubleValue() == 0.0d && !isZero(proper) && Double.doubleToLongBits(n) != 0x1L)
                 error(token.pos, "fp.number.too.small");
             else if (n.doubleValue() == Double.POSITIVE_INFINITY)
                 error(token.pos, "fp.number.too.large");