bpf: fix neg and neg32 BPF instructions in simulator

This patch fixes the semantics of the neg and neg32 BPF instructions
in the simulator, and also updates the corresponding tests
accordingly.

Tested in target bpf-unknown-none.

sim/bpf/bpf-sim.c

@@ -728,7 +728,7 @@ execute (SIM_CPU *cpu, struct bpf_insn *insn)
       break;
     case BPF_INSN_NEGR:
       BPF_TRACE ("BPF_INSN_NEGR\n");
-      bpf_regs[insn->dst] = - (int64_t) bpf_regs[insn->src];
+      bpf_regs[insn->dst] = - (int64_t) bpf_regs[insn->dst];
       break;
     case BPF_INSN_NEGI:
       BPF_TRACE ("BPF_INSN_NEGI\n");
@@ -865,7 +865,7 @@ execute (SIM_CPU *cpu, struct bpf_insn *insn)
       break;
     case BPF_INSN_NEG32R:
       BPF_TRACE ("BPF_INSN_NEG32R\n");
-      bpf_regs[insn->dst] = (uint32_t) (- (int32_t) bpf_regs[insn->src]);
+      bpf_regs[insn->dst] = (uint32_t) (- (int32_t) bpf_regs[insn->dst]);
       break;
     case BPF_INSN_NEG32I:
       BPF_TRACE ("BPF_INSN_NEG32I\n");

sim/testsuite/bpf/alu.s

@@ -112,10 +112,10 @@ main:
     fail_ne     %r1, 0
 
     ;; neg
-    neg         %r2, %r2
+    neg         %r2
     fail_ne     %r2, -5
     mov         %r1, -1025
-    neg         %r1, %r1
+    neg         %r1
     fail_ne     %r1, 1025
 
     pass

sim/testsuite/bpf/alu32.s

@@ -100,11 +100,11 @@ main:
     ;; neg
     mov32       %r1, -1
     mov32       %r2, 0x7fffffff
-    neg32       %r1, %r1
-    neg32       %r2, %r2
+    neg32       %r1
+    neg32       %r2
     fail_ne32   %r1, 1
     fail_ne     %r2, 0x80000001 ; Note: check for (bad) sign-extend
-    neg32       %r2, %r2
+    neg32       %r2
     fail_ne32   %r2, 0x7fffffff
 
     pass