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Re: [PATCH][4.3] Deprecate -ftrapv


On Sat, 1 Mar 2008, Richard Guenther wrote:

> I missed once point noticed by Joseph also, that the libgcc implementation
> uses signed types in the implementation of the trapping arithmetics.
> Where we of course optimize away the overflow check, so the libgcc
> routines will never trap.  (if it does work in some cases then this
> would be a missed optimization, so sooner or later it is going to
> break more)

This is of course trivial to fix.  OK to commit the following patch?  
Bootstrapped with no regressions on i686-pc-linux-gnu.

2008-03-02  Joseph Myers  <joseph@codesourcery.com>

	* libgcc2.c (__addvSI3, __addvsi3, __addvDI3, __subvSI3,
	__subvsi3, __subvDI3, __negvSI2, __negvsi2, __negvDI2, __absvSI2,
	__absvsi2, __absvDI2): Use unsigned arithmetic.

Index: libgcc2.c
===================================================================
--- libgcc2.c	(revision 132803)
+++ libgcc2.c	(working copy)
@@ -84,7 +84,7 @@
 Wtype
 __addvSI3 (Wtype a, Wtype b)
 {
-  const Wtype w = a + b;
+  const Wtype w = (UWtype) a + (UWtype) b;
 
   if (b >= 0 ? w < a : w > a)
     abort ();
@@ -95,7 +95,7 @@
 SItype
 __addvsi3 (SItype a, SItype b)
 {
-  const SItype w = a + b;
+  const SItype w = (USItype) a + (USItype) b;
 
   if (b >= 0 ? w < a : w > a)
     abort ();
@@ -109,7 +109,7 @@
 DWtype
 __addvDI3 (DWtype a, DWtype b)
 {
-  const DWtype w = a + b;
+  const DWtype w = (UDWtype) a + (UDWtype) b;
 
   if (b >= 0 ? w < a : w > a)
     abort ();
@@ -122,7 +122,7 @@
 Wtype
 __subvSI3 (Wtype a, Wtype b)
 {
-  const Wtype w = a - b;
+  const Wtype w = (UWtype) a - (UWtype) b;
 
   if (b >= 0 ? w > a : w < a)
     abort ();
@@ -133,7 +133,7 @@
 SItype
 __subvsi3 (SItype a, SItype b)
 {
-  const SItype w = a - b;
+  const SItype w = (USItype) a - (USItype) b;
 
   if (b >= 0 ? w > a : w < a)
     abort ();
@@ -147,7 +147,7 @@
 DWtype
 __subvDI3 (DWtype a, DWtype b)
 {
-  const DWtype w = a - b;
+  const DWtype w = (UDWtype) a - (UDWtype) b;
 
   if (b >= 0 ? w > a : w < a)
     abort ();
@@ -187,7 +187,7 @@
 Wtype
 __negvSI2 (Wtype a)
 {
-  const Wtype w = -a;
+  const Wtype w = -(UWtype) a;
 
   if (a >= 0 ? w > 0 : w < 0)
     abort ();
@@ -198,7 +198,7 @@
 SItype
 __negvsi2 (SItype a)
 {
-  const SItype w = -a;
+  const SItype w = -(USItype) a;
 
   if (a >= 0 ? w > 0 : w < 0)
     abort ();
@@ -212,7 +212,7 @@
 DWtype
 __negvDI2 (DWtype a)
 {
-  const DWtype w = -a;
+  const DWtype w = -(UDWtype) a;
 
   if (a >= 0 ? w > 0 : w < 0)
     abort ();
@@ -231,7 +231,7 @@
 #ifdef L_negvsi2
     w = __negvSI2 (a);
 #else
-    w = -a;
+    w = -(UWtype) a;
 
   if (w < 0)
     abort ();
@@ -249,7 +249,7 @@
 #ifdef L_negvsi2
     w = __negvsi2 (a);
 #else
-    w = -a;
+    w = -(USItype) a;
 
   if (w < 0)
     abort ();
@@ -270,7 +270,7 @@
 #ifdef L_negvdi2
     w = __negvDI2 (a);
 #else
-    w = -a;
+    w = -(UDWtype) a;
 
   if (w < 0)
     abort ();

-- 
Joseph S. Myers
joseph@codesourcery.com


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