[llvm-bugs] [Bug 33030] ARM: Builtins should use AAPCS ABI for non-windows platforms

via llvm-bugs llvm-bugs at lists.llvm.org
Mon May 15 11:04:57 PDT 2017


Manoj Gupta <manojgupta at google.com> changed:

           What    |Removed                     |Added
         Resolution|INVALID                     |---
             Status|RESOLVED                    |REOPENED

--- Comment #5 from Manoj Gupta <manojgupta at google.com> ---
Please note that I am referring only to builtins (__aeabi_* functions generally
provided in libgcc) that need aapcs ABI.
Other functions can use aapcs_vfp ABI, just not these builtins.

Here is an example to illustrate it.

$ cat arm_dltoul.c 
unsigned long long convert(double a) {
  return (unsigned long long)a;

$ bin/clang -target armv7a-unknown-linux-gnueabihf arm_dltoul.c -c -O2

$ objdump -d arm_dltoul.o 

arm_dltoul.o:     file format elf32-littlearm

Disassembly of section .text:

00000000 <convert>: // Convert function itself uses aapcs_vfp ABI. Arg is in d0
   0:   e92d4800        push    {fp, lr}
   4:   e1a0b00d        mov     fp, sp
   8:   ec510b10        vmov    r0, r1, d0 // d0 is moved to r0 and r1
   c:   ebfffffe        bl      0 <__aeabi_d2ulz> // __aebi_d2ulz expects args
in r0 and r1 using AAPCS ABI.
  10:   e8bd8800        pop     {fp, pc}

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