bpf: print backward branch target properly

Currently, it prints the backward branch offset as unsigned value
like below:
       7:       7d 34 0b 00 00 00 00 00         if r4 s>= r3 goto 11 <LBB0_3>
       8:       b7 00 00 00 00 00 00 00         r0 = 0
LBB0_2:
       9:       07 00 00 00 01 00 00 00         r0 += 1
      ......
      17:       bf 31 00 00 00 00 00 00         r1 = r3
      18:       6d 32 f6 ff 00 00 00 00         if r2 s> r3 goto 65526 <LBB0_3+0x7FFB0>

The correct print insn 18 should be:
      18:       6d 32 f6 ff 00 00 00 00         if r2 s> r3 goto -10 <LBB0_2>

To provide better clarity and be consistent with kernel verifier output,
the insn 7 output is changed to the following with "+" added to
non-negative branch offset:
       7:       7d 34 0b 00 00 00 00 00         if r4 s>= r3 goto +11 <LBB0_3>

Signed-off-by: Yonghong Song <yhs@fb.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@318442 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 42 insertions, 3 deletions

diff --git a/test/CodeGen/BPF/objdump_cond_op.ll b/test/CodeGen/BPF/objdump_cond_op.ll
index 3abbb76ccc9..b9dc122fe20 100644
--- a/test/CodeGen/BPF/objdump_cond_op.ll
+++ b/test/CodeGen/BPF/objdump_cond_op.ll
@@ -27,7 +27,7 @@ define i32 @test(i32, i32) local_unnamed_addr #0 {
   br label %13
 ; CHECK: r1 <<= 32
 ; CHECK: r1 >>= 32
-; CHECK: if r1 != 2 goto 6 <LBB0_2>
+; CHECK: if r1 != 2 goto +6 <LBB0_2>
 
 ; <label>:8:                                      ; preds = %2
   %9 = icmp eq i32 %0, %1
@@ -38,7 +38,7 @@ define i32 @test(i32, i32) local_unnamed_addr #0 {
 ; CHECK: r0 = *(u32 *)(r1 + 0)
 ; CHECK: r0 *= r0
 ; CHECK: r0 <<= 1
-; CHECK: goto 7 <LBB0_4>
+; CHECK: goto +7 <LBB0_4>
 
 ; <label>:11:                                     ; preds = %8
   %12 = shl nsw i32 %10, 2
@@ -49,7 +49,7 @@ define i32 @test(i32, i32) local_unnamed_addr #0 {
 ; CHECK: r0 = *(u32 *)(r3 + 0)
 ; CHECK: r2 <<= 32
 ; CHECK: r2 >>= 32
-; CHECK: if r1 == r2 goto 4 <LBB0_5>
+; CHECK: if r1 == r2 goto +4 <LBB0_5>
 ; CHECK: r0 <<= 2
 
 ; <label>:13:                                     ; preds = %4, %11
diff --git a/test/CodeGen/BPF/objdump_cond_op_2.ll b/test/CodeGen/BPF/objdump_cond_op_2.ll
new file mode 100644
index 00000000000..618fb6ce187
--- /dev/null
+++ b/test/CodeGen/BPF/objdump_cond_op_2.ll
@@ -0,0 +1,39 @@
+; RUN: llc -march=bpfel -filetype=obj -o - %s | llvm-objdump -d - | FileCheck %s
+
+; Source Code:
+; int test(int a, int b) {
+;   int s = 0;
+;   while (a < b) { s++; a += s; b -= s; }
+;   return s;
+; }
+
+define i32 @test(i32, i32) local_unnamed_addr #0 {
+; CHECK-LABEL: test:
+  %3 = icmp slt i32 %0, %1
+  br i1 %3, label %4, label %13
+
+; <label>:4:                                      ; preds = %2
+  br label %5
+; CHECK: if r4 s>= r3 goto +11 <LBB0_3>
+; CHECK: r0 = 0
+; CHECK-LABEL: LBB0_2:
+
+; <label>:5:                                      ; preds = %4, %5
+  %6 = phi i32 [ %9, %5 ], [ 0, %4 ]
+  %7 = phi i32 [ %11, %5 ], [ %1, %4 ]
+  %8 = phi i32 [ %10, %5 ], [ %0, %4 ]
+  %9 = add nuw nsw i32 %6, 1
+  %10 = add nsw i32 %9, %8
+  %11 = sub nsw i32 %7, %9
+  %12 = icmp slt i32 %10, %11
+  br i1 %12, label %5, label %13
+; CHECK: r1 = r3
+; CHECK: if r2 s> r3 goto -10 <LBB0_2>
+
+; <label>:13:                                     ; preds = %5, %2
+  %14 = phi i32 [ 0, %2 ], [ %9, %5 ]
+  ret i32 %14
+; CHECK-LABEL: LBB0_3:
+; CHECK: exit
+}
+attributes #0 = { norecurse nounwind readnone }