https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99151
--- Comment #4 from Sebastian Huber <sebastian.hu...@embedded-brains.de> ---
(In reply to Andrew Pinski from comment #3)
> Is the nop due to alignment?
With -g and -coverage I get this code:
sparc-rtems7-gcc -O2 -o - -S unreachable.c -fverbose-asm -g -coverage
.file "unreachable.c"
! GNU C17 (GCC) version 11.0.0 20210205 (RTEMS 7, RSB
61dcadee0825867ebe51f9f367430ef75b8fe9c0, Newlib d4a756f) (sparc-rtems7)
! compiled by GNU C version 11.0.0 20201130 (experimental) [revision
b46314c78061a5156bac44a317c87d32b00d4295], GMP version 6.1.0, MPFR version
3.1.4, MPC version 1.0.3, isl version isl-0.18-GMP
! GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
! options passed: -mcpu=v7 -g -O2 -fprofile-arcs -ftest-coverage
.section ".text"
.LLtext0:
.cfi_sections .debug_frame
.align 4
.global g
.type g, #function
.proc 020
g:
.LLFB0:
.file 1 "unreachable.c"
.loc 1 5 1 view -0
.cfi_startproc
save %sp, -96, %sp !
.cfi_window_save
.cfi_register 15, 31
.cfi_def_cfa_register 30
sethi %hi(__gcov0.g), %g1 !, tmp112
ldd [%g1+%lo(__gcov0.g)], %i4 ! __gcov0.g[0], __gcov0.g[0]
addcc %i5, 1, %g3 ! __gcov0.g[0],, tmp115
addx %i4, 0, %g2 ! __gcov0.g[0],,
.loc 1 6 9 view .LLVU1
call r, 0 !,
.LLVL0:
std %g2, [%g1+%lo(__gcov0.g)] ! tmp115, __gcov0.g[0]
nop
In the the no-return function case, this nop has no line debug information and
there is no profiling counter increment.
.cfi_endproc
.LLFE0:
.size g, .-g
.align 4
.global f
.type f, #function
.proc 020
f:
.LLFB1:
.loc 1 11 1 view -0
.cfi_startproc
save %sp, -96, %sp !
.cfi_window_save
.cfi_register 15, 31
.cfi_def_cfa_register 30
sethi %hi(__gcov0.f), %g1 !, tmp114
ldd [%g1+%lo(__gcov0.f)], %i2 ! __gcov0.f[0], __gcov0.f[0]
addcc %i3, 1, %g3 ! __gcov0.f[0],, tmp117
addx %i2, 0, %g2 ! __gcov0.f[0],,
or %g1, %lo(__gcov0.f), %i5 ! tmp114,, tmp113
.loc 1 12 9 view .LLVU3
call u, 0 !,
.LLVL1:
std %g2, [%g1+%lo(__gcov0.f)] ! tmp117, __gcov0.f[0]
ldd [%i5+8], %i2 ! __gcov0.f[1], __gcov0.f[1]
addcc %i3, 1, %g3 ! __gcov0.f[1],, tmp123
addx %i2, 0, %g2 ! __gcov0.f[1],,
std %g2, [%i5+8] ! tmp123, __gcov0.f[1]
.loc 1 13 9 view .LLVU4
.cfi_endproc
.LLFE1:
.size f, .-f
In the __builtin_unreachable() case we don't have a nop, but a profiling
counter increment is there.
clang 9 generates this code:
clang -O2 -o - -S unreachable.c -fverbose-asm -g -coverage --target=sparc
.text
.file "unreachable.c"
.globl g ! -- Begin function g
.p2align 2
.type g,@function
g: ! @g
.Lfunc_begin0:
.file 1 "/home/EB/sebastian_h/src/rtems/unreachable.c"
.loc 1 5 0 ! unreachable.c:5:0
.cfi_startproc
! %bb.0:
save %sp, -96, %sp
.cfi_def_cfa_register %fp
.cfi_window_save
.cfi_register 15, 31
.Ltmp0:
.loc 1 6 9 prologue_end ! unreachable.c:6:9
sethi %hi(__llvm_gcov_ctr), %i0
ldd [%i0+%lo(__llvm_gcov_ctr)], %i2
addcc %i3, 1, %i5
addxcc %i2, 0, %i4
call r
std %i4, [%i0+%lo(__llvm_gcov_ctr)]
.Ltmp1:
.Lfunc_end0:
.size g, .Lfunc_end0-g
.cfi_endproc
! -- End function
.globl f ! -- Begin function f
.p2align 2
.type f,@function
f: ! @f
.Lfunc_begin1:
.loc 1 11 0 ! unreachable.c:11:0
.cfi_startproc
! %bb.0:
save %sp, -96, %sp
.cfi_def_cfa_register %fp
.cfi_window_save
.cfi_register 15, 31
.Ltmp2:
.loc 1 12 9 prologue_end ! unreachable.c:12:9
sethi %hi(__llvm_gcov_ctr.1), %i0
ldd [%i0+%lo(__llvm_gcov_ctr.1)], %i2
addcc %i3, 1, %i5
addxcc %i2, 0, %i4
call u
std %i4, [%i0+%lo(__llvm_gcov_ctr.1)]
.Ltmp3:
.Lfunc_end1:
.size f, .Lfunc_end1-f
.cfi_endproc
! -- End function
There are no nops and no unreachable profiling counter increments.
