[Ada] Fix floating-point exponentiation with Integer'First exponent

gcc/ada/

	* urealp.adb (Scale): Change first paramter to Uint and adjust.
	(Equivalent_Decimal_Exponent): Pass U.Den directly to Scale.
	* libgnat/s-exponr.adb (Negative): Rename to...
	(Safe_Negative): ...this and change its lower bound.
	(Exponr): Adjust to above renaming and deal with Integer'First.

1 files changed, 6 insertions, 3 deletions

diff --git a/gcc/ada/libgnat/s-exponr.adb b/gcc/ada/libgnat/s-exponr.adb
index ece53b5..ad7f401 100644
--- a/gcc/ada/libgnat/s-exponr.adb
+++ b/gcc/ada/libgnat/s-exponr.adb
@@ -57,8 +57,8 @@ function System.Exponr (Left : Num; Right : Integer) return Num is
    subtype Double_T is Double_Real.Double_T;
    --  The double floating-point type
 
-   subtype Negative is Integer range Integer'First .. -1;
-   --  The range of negative exponents
+   subtype Safe_Negative is Integer range Integer'First + 1 .. -1;
+   --  The range of safe negative exponents
 
    function Expon (Left : Num; Right : Natural) return Num;
    --  Routine used if Right is greater than 4
@@ -113,9 +113,12 @@ begin
             return Num'Machine (Sqr * Sqr);
          end;
 
-      when Negative =>
+      when Safe_Negative =>
          return Num'Machine (1.0 / Exponr (Left, -Right));
 
+      when Integer'First =>
+         return Num'Machine (1.0 / (Exponr (Left, Integer'Last) * Left));
+
       when others =>
          return Num'Machine (Expon (Left, Right));
    end case;