[LLVMbugs] [Bug 10352] New: inline asm can't tie bool to "q" constraint

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Wed Jul 13 17:59:30 PDT 2011


           Summary: inline asm can't tie bool to "q" constraint
           Product: libraries
           Version: trunk
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: Backend: X86
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: nlewycky at google.com
                CC: llvmbugs at cs.uiuc.edu, echristo at gmail.com

Consider this code:

  template <typename T>
  inline void test(T desired) {
    __asm__ __volatile__("foo %0" : : "q" (desired));

  void helper() {
    bool v;  // char, short, float, double, unsigned long long all work

Note that the failure about "foo" not being a valid mnemonic is not a problem.
The problem is:

$ clang z.cc
fatal error: error in backend: Couldn't allocate input reg for constraint 'q'!

GCC thinks this is fine:

$ gcc z.cc
z.cc: Assembler messages:
z.cc:3: Error: no such instruction: `foo %al'

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