https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85185
--- Comment #9 from Zev Weiss <zev+gccbug at bewilderbeest dot net> ---
I've just encountered another related-looking problem -- the inline asm sees
0xfffffffffffffffc here instead of the intended 0xfffc:
$ cat x.c
static inline void foo(unsigned short n)
{
__asm__("foo %0" :: "r" (n));
}
void bar(void)
{
foo(0xfffc);
}
$ riscv64-unknown-elf-gcc -S -o - -Og -fdump-rtl-expand x.c
.file "x.c"
.option nopic
.text
.align 2
.globl bar
.type bar, @function
bar:
li a5,-4
#APP
# 3 "x.c" 1
foo a5
# 0 "" 2
#NO_APP
ret
.size bar, .-bar
.ident "GCC: (GNU) 7.2.0"
$ cat x.c.229r.expand
;; Function bar (bar, funcdef_no=1, decl_uid=1412, cgraph_uid=1,
symbol_order=1)
;; Generating RTL for gimple basic block 2
try_optimize_cfg iteration 1
Merging block 3 into block 2...
Merged blocks 2 and 3.
Merged 2 and 3 without moving.
Merging block 4 into block 2...
Merged blocks 2 and 4.
Merged 2 and 4 without moving.
try_optimize_cfg iteration 2
;;
;; Full RTL generated for this function:
;;
(note 1 0 3 NOTE_INSN_DELETED)
(note 3 1 2 2 [bb 2] NOTE_INSN_BASIC_BLOCK)
(note 2 3 5 2 NOTE_INSN_FUNCTION_BEG)
(insn 5 2 6 2 (set (reg:HI 72)
(const_int -4 [0xfffffffffffffffc])) "x.c":3 -1
(nil))
(insn 6 5 0 2 (asm_operands/v ("foo %0") ("") 0 [
(reg:HI 72)
]
[
(asm_input:HI ("r") x.c:3)
]
[] x.c:3) "x.c":3 -1
(nil))
I don't really know how to read these RTL dumps, so I can't say for sure, but
my guess is that this is probably another manifestation of the same underlying
problem. Jim (or anyone else with input), can you confirm that's the case?
Unlike the original case, this one, for what it's worth, also occurs at -O1,
-O2, and -O3 in addition to -Og.
