[llvm-bugs] [Bug 26411] New: __attribute__((interrupt)) trashes MMX registers

via llvm-bugs llvm-bugs at lists.llvm.org
Mon Feb 1 05:41:54 PST 2016


            Bug ID: 26411
           Summary: __attribute__((interrupt)) trashes MMX registers
           Product: new-bugs
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: new bugs
          Assignee: unassignedbugs at nondot.org
          Reporter: hjl.tools at gmail.com
                CC: kevin.b.smith at intel.com, llvm-bugs at lists.llvm.org
    Classification: Unclassified

[hjl at gnu-6 interrupt-8]$ cat z.i
typedef short __v4hi __attribute__ ((__vector_size__ (8)));
typedef int __m64 __attribute__ ((__vector_size__ (8), __may_alias__));

extern __m64 y, x;

fn1 (void *frame)
  x = (__m64) __builtin_ia32_packsswb ((__v4hi) x, (__v4hi) y);
[hjl at gnu-6 interrupt-8]$ make z.s
/export/build/gnu/llvm-clang-bootstrap/stage1/build-x86_64-linux/bin/clang -O2
-Wall -march=nehalem -S -o z.s z.i
[hjl at gnu-6 interrupt-8]$ cat z.s
    .file    "z.i"
    .globl    fn1
    .p2align    4, 0x90
    .type    fn1, at function
fn1:                                    # @fn1
# BB#0:
    movq    x(%rip), %mm0
    packsswb    y(%rip), %mm0
    movq    %mm0, x(%rip)
    .size    fn1, .Lfunc_end0-fn1

    .ident    "clang version 3.9.0 (http://llvm.org/git/clang.git
1f64ddbc4c5d1036b68ec896765a7535537ded85) (http://llvm.org/git/llvm.git
    .section    ".note.GNU-stack","", at progbits
[hjl at gnu-6 interrupt-8]$ 

Interrupt handler must preserve MMX and X87 states.  It shouldn't be
allowed to use MMX nor x87 registers.

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