Re: inline-asm/10857: Inlining a function with inline-asm: "error: impossible constraint in `asm'"

[ehrhardt@mathematik.uni-ulm.de]

Synopsis: Inlining a function with inline-asm: "error: impossible constraint in `asm'"

State-Changed-From-To: closed->open
State-Changed-By: cae
State-Changed-When: Mon May 19 17:53:20 2003
State-Changed-Why:
    Reopened based on submitter's comment. This is rejected by 3.3 at all
    optimization levels. I still don't think this should compile but previous
    versions of gcc accepted it. An arch independant example is below. Could
    someone please clarify if this supposed to compile at e.g. -S -O3?
    
    ----------------- cut -------------------------------
    #define PORTD 0x12
    
    static
    void
    write_byte(unsigned char adr, unsigned char data )
    {
    	__asm__ ("blah %0" : : "i" (adr));
    }
    
    int main(void)
    {
    	write_byte( PORTD, 4);
    	return 0;
    }
    ----------------- cut -------------------------------
    
    Both gcc-3.2 and older versions of gcc-3.4 accepted this if
    optimization level was high enough. It is rejected by gcc 3.3
    nomatter what. Note that __builtin_constant_p (adr) holds for
    the inlined copy of write_byte.
    
    The patch the prevented this from compiling at -O3 went into gcc-3.4
    between 20030331 and 20030519.
    
        regards  Christian

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=10857