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[Bug rtl-optimization/44288] [Extended inline asm] wrong assembly generation on IA32
- From: "jakub at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 27 May 2010 11:44:32 -0000
- Subject: [Bug rtl-optimization/44288] [Extended inline asm] wrong assembly generation on IA32
- References: <bug-44288-19237@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #7 from jakub at gcc dot gnu dot org 2010-05-27 11:44 -------
You are wrong. It is user's responsibility to choose correct constraints for
the inline assembly, the compiler doesn't try to understand what the inline
assembly is doing or even check its semantics, all it does is perform
replacements in it (replacing %0, %1, %2 in this case).
Not every constraint is suitable for every use in the assembly obviously,
otherwise we wouldn't need multiple constraints.
The "g" constraint allows a register, immediate or memory, all must be valid in
the instruction and it is up to the compiler which one it chooses.
"g" constraint is usable say for mov eax, %2; which can work well with
registers, immediates or memory. But as you use [%2] instead, memory isn't
valid, all that is valid is either a register or register + immediate or
register + X*register2 + immediate (the usual i?86 addressing modes).
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44288