[Qemu-devel] [PATCH 2/2] milkymist-pfpu: fix GCC 5.0.0 aggressive-loop-optimizations warning

["Radim Krčmář" <rkrcmar@redhat.com>]

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.

Refactored the code a bit to avoid the GCC warning, in an objectionable
way,
  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];
                ^

Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
---
 hw/misc/milkymist-pfpu.c | 18 ++++++++----------
 1 file changed, 8 insertions(+), 10 deletions(-)

diff --git a/hw/misc/milkymist-pfpu.c b/hw/misc/milkymist-pfpu.c
index 609f33f9cd14..133f5b8c5153 100644
--- a/hw/misc/milkymist-pfpu.c
+++ b/hw/misc/milkymist-pfpu.c
@@ -164,6 +164,13 @@ output_queue_advance(MilkymistPFPUState *s)
 static int pfpu_decode_insn(MilkymistPFPUState *s)
 {
     uint32_t pc = s->regs[R_PC];
+
+    if (pc > MICROCODE_WORDS) {
+        error_report("milkymist_pfpu: too many instructions "
+                     "executed in microcode. No VECTOUT?");
+        return 0;
+    }
+
     uint32_t insn = s->microcode[pc];
     uint32_t reg_a = (insn >> 18) & 0x7f;
     uint32_t reg_b = (insn >> 11) & 0x7f;
@@ -348,7 +355,6 @@ static int pfpu_decode_insn(MilkymistPFPUState *s)
 static void pfpu_start(MilkymistPFPUState *s)
 {
     int x, y;
-    int i;
 
     for (y = 0; y <= s->regs[R_VMESHLAST]; y++) {
         for (x = 0; x <= s->regs[R_HMESHLAST]; x++) {
@@ -359,15 +365,7 @@ static void pfpu_start(MilkymistPFPUState *s)
             s->gp_regs[GPR_Y] = y;
 
             /* run microcode on this position */
-            i = 0;
-            while (pfpu_decode_insn(s)) {
-                /* decode at most MICROCODE_WORDS instructions */
-                if (i++ >= MICROCODE_WORDS) {
-                    error_report("milkymist_pfpu: too many instructions "
-                            "executed in microcode. No VECTOUT?");
-                    break;
-                }
-            }
+            while (pfpu_decode_insn(s));
 
             /* reset pc for next run */
             s->regs[R_PC] = 0;
-- 
2.3.0