Created attachment 26944 [details]
Reduced testcase

GMP cannot be compiled anymore on IA-64/Linux, the error being:

gcc -std=gnu99 -DHAVE_CONFIG_H -I. -I. -I.. -D__GMP_WITHIN_GMP -I.. -DOPERATION_redc_2 -O2 -pedantic -c 
redc_2.c -o redc_2.o
redc_2.c: In function '__gmpn_redc_2':
redc_2.c:87:7: error: 'asm' operand requires impossible reload
redc_2.c:87:7: error: 'asm' operand requires impossible reload
redc_2.c:87:7: error: 'asm' operand requires impossible reload
redc_2.c:87:7: error: 'asm' operand requires impossible reload
make[2]: *** [redc_2.lo] Error 1

The error is issued by this very old piece of code in reload_as_needed:

	      /* If this was an ASM, make sure that all the reload insns
		 we have generated are valid.  If not, give an error
		 and delete them.  */
	      if (asm_noperands (PATTERN (insn)) >= 0)
		for (p = NEXT_INSN (prev); p != next; p = NEXT_INSN (p))
		  if (p != insn && INSN_P (p)
		      && GET_CODE (PATTERN (p)) != USE
		      && (recog_memoized (p) < 0
			  || (extract_insn (p), ! constrain_operands (1))))
		    {
		      error_for_asm (insn,
				     "%<asm%> operand requires "
				     "impossible reload");
		      delete_insn (p);
		    }

Now it seems to overlook the case where the reload insns contain pseudos that 
didn't get hard regs and thus have equivalent memory references.  They will be 
replaced by these memory references only _after_ reload_as_needed has run.

Commenting out the piece code generates correct assembly AFAICS and the GMP 
testsuite is clean.  But it seems quite astonishing that this issue has never 
surfaced until now (the code was added by Richard Kenner almost 20 years ago).