man gcc:
Warn if in a loop with constant number of iterations the compiler
detects undefined behavior in some statement during one or more of
the iterations.
Milkymist pfpu has no jump instructions, so checking for
MICROCODE_WORDS
instructions should have kept us in bounds of s->microcode, but i++
allowed one loop too many,
hw/misc/milkymist-pfpu.c: In function ‘pfpu_write’:
hw/misc/milkymist-pfpu.c:365:20: error: loop exit may only be
reached after undefined behavior
[-Werror=aggressive-loop-optimizations]
if (i++ >= MICROCODE_WORDS) {
^
hw/misc/milkymist-pfpu.c:167:14: note: possible undefined statement
is here
uint32_t insn = s->microcode[pc];
^
The code can still access out of bounds, because it presumes that PC
register
always begins at 0, and we allow writing to it.
Signed-off-by: Radim Krčmář <address@hidden>
---
v2: used a simpler solution [Paolo, Peter]
hw/misc/milkymist-pfpu.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/hw/misc/milkymist-pfpu.c b/hw/misc/milkymist-pfpu.c
index 609f33f9cd14..08b604f13f4b 100644
--- a/hw/misc/milkymist-pfpu.c
+++ b/hw/misc/milkymist-pfpu.c
@@ -362,7 +362,7 @@ static void pfpu_start(MilkymistPFPUState *s)
i = 0;
while (pfpu_decode_insn(s)) {
/* decode at most MICROCODE_WORDS instructions */
- if (i++ >= MICROCODE_WORDS) {
+ if (++i >= MICROCODE_WORDS) {
error_report("milkymist_pfpu: too many
instructions "
"executed in microcode. No VECTOUT?");
break;