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milkymist-pfpu: fix GCC 5.0.0 aggressive-loop-optimizations warning

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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 <rkrcmar@redhat.com>
Acked-by: Michael Walle <michael@walle.cc>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
This commit is contained in:
Radim Krčmář 2015-02-20 17:06:16 +01:00 committed by Michael Tokarev
parent 8c1ac475e3
commit c6dc3dd72b
1 changed files with 1 additions and 1 deletions
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2
hw/misc/milkymist-pfpu.c
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@ -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;