[LLVMbugs] [Bug 11045] New: clang does not support "o" inline asm constraint

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=11045

           Summary: clang does not support "o" inline asm constraint
           Product: clang
           Version: trunk
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: -New Bugs
        AssignedTo: unassignedclangbugs at nondot.org
        ReportedBy: nlewycky at google.com
                CC: llvmbugs at cs.uiuc.edu, rikka at google.com


The definition of the "o" constraint is "A memory operand is allowed, but only
if the address is offsettable. This means that adding a small integer
(actually, the width in bytes of the operand, as determined by its machine
mode) may be added to the address and the result is also a valid memory
address."

Testcase:

void test() {
    char tmp[256];
    __asm__ volatile(
        "movl 1+%0, %%eax"
        :
        :"o"(tmp[128]));
}

Here, tmp[128] maps to "(%rsp)" producing "movl 1+(%rsp), %eax", so that fails.

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