[PATCH] D48468: [SelectionDAG] Remove debug locations from ConstantSD(FP)Nodes

[Petr Pavlu via Phabricator via llvm-commits]

petpav01 added a comment.

Hi Vedant,

This change also made debug information for the following example slightly worse:

  $ cat test.c
  void bar(void);
  int foo(void) {
    bar();
    int i = 2;
    return i;
  }
  $ clang -target armv7a-none-eabi -g -c test.c main.c
  $ llvm-objdump -S test.o
  
  test.o: file format ELF32-arm-little
  
  Disassembly of section .text:
  foo:
  ; int foo(void) {
         0:       00 48 2d e9     push    {r11, lr}
         4:       0d b0 a0 e1     mov     r11, sp
         8:       08 d0 4d e2     sub     sp, sp, #8
  ; bar();
         c:       fe ff ff eb     bl      #-8 <foo+0xc>
        10:       02 e0 a0 e3     mov     lr, #2
  ; int i = 2;
        14:       04 e0 8d e5     str     lr, [sp, #4]
  ; return i;
        18:       04 00 9d e5     ldr     r0, [sp, #4]
        1c:       0b d0 a0 e1     mov     sp, r11
        20:       00 88 bd e8     pop     {r11, pc}

Instruction `mov lr, #2` is recorded as part of line 3 (`bar();`) but previously it was more accurately accounted as line 4 (`int i = 2;`).

Previous behaviour:

  $ llvm-objdump -S test.o
  
  test.o: file format ELF32-arm-little
  
  Disassembly of section .text:
  foo:
  ; int foo(void) {
         0:       00 48 2d e9     push    {r11, lr}
         4:       0d b0 a0 e1     mov     r11, sp
         8:       08 d0 4d e2     sub     sp, sp, #8
  ; bar();
         c:       fe ff ff eb     bl      #-8 <foo+0xc>
  ; int i = 2;
        10:       02 e0 a0 e3     mov     lr, #2
        14:       04 e0 8d e5     str     lr, [sp, #4]
  ; return i;
        18:       04 00 9d e5     ldr     r0, [sp, #4]
        1c:       0b d0 a0 e1     mov     sp, r11
        20:       00 88 bd e8     pop     {r11, pc}

It is not clear to me whether this is an expected change but I thought I would let you know about it if it actually isn't.

Thanks,
Petr


Repository:
  rL LLVM

https://reviews.llvm.org/D48468