Bootstrap failure because of warning in tc-i386.c

[Nick Clifton <nickc at redhat dot com>]

Hi H,J.

  I was trying to bootstrap the current mainline FSF gcc sources
  yesterday, using a combined tree with the latest binutils sources,
  when I ran into this error:

gas/config/tc-i386.c: In function 'optimize_imm':
gas/config/tc-i386.c:4222:53: error: result of '2l << 31' requires 34 bits to represent, but 'long int' only has 32 bits [-Werror=shift-overflow=]
   && ((i.op[op].imms->X_add_number & ~(((offsetT) 2 << 31) - 1))
                                                     ^~

gas/config/tc-i386.c: In function 'optimize_disp':
gas/config/tc-i386.c:4310:32: error: result of '2l << 31' requires 34 bits to represent, but 'long int' only has 32 bits [-Werror=shift-overflow=]
   && (op_disp & ~(((offsetT) 2 << 31) - 1)) == 0)
                                ^~

gas/config/tc-i386.c:4315:28: error: result of '2l << 31' requires 34 bits to represent, but 'long int' only has 32 bits [-Werror=shift-overflow=]
   op_disp &= (((offsetT) 2 << 31) - 1);
                            ^~

  I tried adding a check on the size of offsetT but that was
  insufficient - the compiler still complained even though the code
  would never be executed.  So in the end I opted for the patch below -
  which makes the code conditional on BFD64 being defined.  I am not
  happy with the patch though, as it means that assembler will behave
  differently depending upon whether it was built with 64-bit support
  enabled or not.  Please could you take a look and decide if the patch
  is OK, or if a better solution is needed.

Cheers
  Nick

PS.  Bootstrapping was on an x86_64 box running Fedora 23.


diff --git a/gas/config/tc-i386.c b/gas/config/tc-i386.c
index 1573043..c2d8029 100644
--- a/gas/config/tc-i386.c
+++ b/gas/config/tc-i386.c
@@ -4218,7 +4218,12 @@ optimize_imm (void)
 		i.op[op].imms->X_add_number =
 		  (((i.op[op].imms->X_add_number & 0xffff) ^ 0x8000) - 0x8000);
 	      }
-	    if ((i.types[op].bitfield.imm32)
+#ifdef BFD64
+	    /* Note: if offsetT only holds 32 bits then the left shift below will
+	       overflow.  On the other hand if offsetT only holds 32 bits then
+	       values bigger than that will be held as O_big not O_constant.  */
+	    if ((sizeof (offsetT) * CHAR_BIT) > 32
+		&& i.types[op].bitfield.imm32
 		&& ((i.op[op].imms->X_add_number & ~(((offsetT) 2 << 31) - 1))
 		    == 0))
 	      {
@@ -4226,6 +4231,7 @@ optimize_imm (void)
 						^ ((offsetT) 1 << 31))
 					       - ((offsetT) 1 << 31));
 	      }
+#endif
 	    i.types[op]
 	      = operand_type_or (i.types[op],
 				 smallest_imm_type (i.op[op].imms->X_add_number));
@@ -4306,7 +4312,12 @@ optimize_disp (void)
 		op_disp = (((op_disp & 0xffff) ^ 0x8000) - 0x8000);
 		i.types[op].bitfield.disp64 = 0;
 	      }
-	    if (i.types[op].bitfield.disp32
+#ifdef BFD64
+	    /* Note: if offsetT only holds 32 bits then the left shift below will
+	       overflow.  On the other hand if offsetT only holds 32 bits then
+	       values bigger than that will be held as O_big not O_constant.  */
+	    if ((sizeof (offsetT) * CHAR_BIT) > 32
+		&& i.types[op].bitfield.disp32
 		&& (op_disp & ~(((offsetT) 2 << 31) - 1)) == 0)
 	      {
 		/* If this operand is at most 32 bits, convert
@@ -4316,6 +4327,7 @@ optimize_disp (void)
 		op_disp = (op_disp ^ ((offsetT) 1 << 31)) - ((addressT) 1 << 31);
 		i.types[op].bitfield.disp64 = 0;
 	      }
+#endif
 	    if (!op_disp && i.types[op].bitfield.baseindex)
 	      {
 		i.types[op].bitfield.disp8 = 0;