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

7 files changed, 81 insertions, 26 deletions

diff --git a/lib/Target/BPF/BPFInstrInfo.td b/lib/Target/BPF/BPFInstrInfo.td
index a3ad2ee5e80..27b26b987fa 100644
--- a/lib/Target/BPF/BPFInstrInfo.td
+++ b/lib/Target/BPF/BPFInstrInfo.td
@@ -46,7 +46,9 @@ def BPFWrapper      : SDNode<"BPFISD::Wrapper", SDT_BPFWrapper>;
 def BPFIsLittleEndian : Predicate<"CurDAG->getDataLayout().isLittleEndian()">;
 def BPFIsBigEndian    : Predicate<"!CurDAG->getDataLayout().isLittleEndian()">;
 
-def brtarget : Operand<OtherVT>;
+def brtarget : Operand<OtherVT> {
+  let PrintMethod = "printBrTargetOperand";
+}
 def calltarget : Operand<i64>;
 
 def u64imm   : Operand<i64> {
diff --git a/lib/Target/BPF/InstPrinter/BPFInstPrinter.cpp b/lib/Target/BPF/InstPrinter/BPFInstPrinter.cpp
index 536ae4df937..6f81e020b99 100644
--- a/lib/Target/BPF/InstPrinter/BPFInstPrinter.cpp
+++ b/lib/Target/BPF/InstPrinter/BPFInstPrinter.cpp
@@ -94,3 +94,16 @@ void BPFInstPrinter::printImm64Operand(const MCInst *MI, unsigned OpNo,
   else
     O << Op;
 }
+
+void BPFInstPrinter::printBrTargetOperand(const MCInst *MI, unsigned OpNo,
+                                       raw_ostream &O) {
+  const MCOperand &Op = MI->getOperand(OpNo);
+  if (Op.isImm()) {
+    int16_t Imm = Op.getImm();
+    O << ((Imm >= 0) ? "+" : "") << Imm;
+  } else if (Op.isExpr()) {
+    printExpr(Op.getExpr(), O);
+  } else {
+    O << Op;
+  }
+}
diff --git a/lib/Target/BPF/InstPrinter/BPFInstPrinter.h b/lib/Target/BPF/InstPrinter/BPFInstPrinter.h
index 4276d0858c2..bb0b0d71da5 100644
--- a/lib/Target/BPF/InstPrinter/BPFInstPrinter.h
+++ b/lib/Target/BPF/InstPrinter/BPFInstPrinter.h
@@ -30,6 +30,7 @@ public:
   void printMemOperand(const MCInst *MI, int OpNo, raw_ostream &O,
                        const char *Modifier = nullptr);
   void printImm64Operand(const MCInst *MI, unsigned OpNo, raw_ostream &O);
+  void printBrTargetOperand(const MCInst *MI, unsigned OpNo, raw_ostream &O);
 
   // Autogenerated by tblgen.
   void printInstruction(const MCInst *MI, raw_ostream &O);
diff --git a/lib/Target/BPF/MCTargetDesc/BPFMCTargetDesc.cpp b/lib/Target/BPF/MCTargetDesc/BPFMCTargetDesc.cpp
index 5c3bba6e669..cbf1ea7d7fb 100644
--- a/lib/Target/BPF/MCTargetDesc/BPFMCTargetDesc.cpp
+++ b/lib/Target/BPF/MCTargetDesc/BPFMCTargetDesc.cpp
@@ -79,7 +79,7 @@ public:
   bool evaluateBranch(const MCInst &Inst, uint64_t Addr, uint64_t Size,
                       uint64_t &Target) const override {
     // The target is the 3rd operand of cond inst and the 1st of uncond inst.
-    int64_t Imm;
+    int16_t Imm;
     if (isConditionalBranch(Inst)) {
       Imm = Inst.getOperand(2).getImm();
     } else if (isUnconditionalBranch(Inst))
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 }
diff --git a/test/MC/BPF/insn-unit.s b/test/MC/BPF/insn-unit.s
index a750facb8b9..75cb93b9513 100644
--- a/test/MC/BPF/insn-unit.s
+++ b/test/MC/BPF/insn-unit.s
@@ -57,55 +57,55 @@
   goto Llabel0               // BPF_JA
   call 1                     // BPF_CALL
   exit                       // BPF_EXIT
-// CHECK: 05 00 1a 00 00 00 00 00 	goto 26
+// CHECK: 05 00 1a 00 00 00 00 00 	goto +26
 // CHECK: 85 00 00 00 01 00 00 00 	call 1
 // CHECK: 95 00 00 00 00 00 00 00 	exit
 
   if r0 == r1 goto Llabel0   // BPF_JEQ  | BPF_X
   if r3 != r4 goto Llabel0   // BPF_JNE  | BPF_X
-// CHECK: 1d 10 17 00 00 00 00 00 	if r0 == r1 goto 23
-// CHECK: 5d 43 16 00 00 00 00 00 	if r3 != r4 goto 22
+// CHECK: 1d 10 17 00 00 00 00 00 	if r0 == r1 goto +23
+// CHECK: 5d 43 16 00 00 00 00 00 	if r3 != r4 goto +22
 
   if r1 > r2 goto Llabel0    // BPF_JGT  | BPF_X
   if r2 >= r3 goto Llabel0   // BPF_JGE  | BPF_X
   if r4 s> r5 goto Llabel0   // BPF_JSGT | BPF_X
   if r5 s>= r6 goto Llabel0  // BPF_JSGE | BPF_X
-// CHECK: 2d 21 15 00 00 00 00 00 	if r1 > r2 goto 21
-// CHECK: 3d 32 14 00 00 00 00 00 	if r2 >= r3 goto 20
-// CHECK: 6d 54 13 00 00 00 00 00 	if r4 s> r5 goto 19
-// CHECK: 7d 65 12 00 00 00 00 00 	if r5 s>= r6 goto 18
+// CHECK: 2d 21 15 00 00 00 00 00 	if r1 > r2 goto +21
+// CHECK: 3d 32 14 00 00 00 00 00 	if r2 >= r3 goto +20
+// CHECK: 6d 54 13 00 00 00 00 00 	if r4 s> r5 goto +19
+// CHECK: 7d 65 12 00 00 00 00 00 	if r5 s>= r6 goto +18
 
   if r6 < r7 goto Llabel0    // BPF_JLT  | BPF_X
   if r7 <= r8 goto Llabel0   // BPF_JLE  | BPF_X
   if r8 s< r9 goto Llabel0   // BPF_JSLT | BPF_X
   if r9 s<= r10 goto Llabel0 // BPF_JSLE | BPF_X
-// CHECK: ad 76 11 00 00 00 00 00 	if r6 < r7 goto 17
-// CHECK: bd 87 10 00 00 00 00 00 	if r7 <= r8 goto 16
-// CHECK: cd 98 0f 00 00 00 00 00 	if r8 s< r9 goto 15
-// CHECK: dd a9 0e 00 00 00 00 00 	if r9 s<= r10 goto 14
+// CHECK: ad 76 11 00 00 00 00 00 	if r6 < r7 goto +17
+// CHECK: bd 87 10 00 00 00 00 00 	if r7 <= r8 goto +16
+// CHECK: cd 98 0f 00 00 00 00 00 	if r8 s< r9 goto +15
+// CHECK: dd a9 0e 00 00 00 00 00 	if r9 s<= r10 goto +14
 
   if r0 == 0 goto Llabel0           // BPF_JEQ  | BPF_K
   if r3 != -1 goto Llabel0          // BPF_JNE  | BPF_K
-// CHECK: 15 00 0d 00 00 00 00 00 	if r0 == 0 goto 13
-// CHECK: 55 03 0c 00 ff ff ff ff 	if r3 != -1 goto 12
+// CHECK: 15 00 0d 00 00 00 00 00 	if r0 == 0 goto +13
+// CHECK: 55 03 0c 00 ff ff ff ff 	if r3 != -1 goto +12
 
   if r1 > 64 goto Llabel0           // BPF_JGT  | BPF_K
   if r2 >= 0xffffffff goto Llabel0  // BPF_JGE  | BPF_K
   if r4 s> 0xffffffff goto Llabel0  // BPF_JSGT | BPF_K
   if r5 s>= 0x7fffffff goto Llabel0 // BPF_JSGE | BPF_K
-// CHECK: 25 01 0b 00 40 00 00 00 	if r1 > 64 goto 11
-// CHECK: 35 02 0a 00 ff ff ff ff 	if r2 >= -1 goto 10
-// CHECK: 65 04 09 00 ff ff ff ff 	if r4 s> -1 goto 9
-// CHECK: 75 05 08 00 ff ff ff 7f 	if r5 s>= 2147483647 goto 8
+// CHECK: 25 01 0b 00 40 00 00 00 	if r1 > 64 goto +11
+// CHECK: 35 02 0a 00 ff ff ff ff 	if r2 >= -1 goto +10
+// CHECK: 65 04 09 00 ff ff ff ff 	if r4 s> -1 goto +9
+// CHECK: 75 05 08 00 ff ff ff 7f 	if r5 s>= 2147483647 goto +8
 
   if r6 < 0xff goto Llabel0         // BPF_JLT  | BPF_K
   if r7 <= 0xffff goto Llabel0      // BPF_JLE  | BPF_K
   if r8 s< 0 goto Llabel0           // BPF_JSLT | BPF_K
   if r9 s<= -1 goto Llabel0         // BPF_JSLE | BPF_K
-// CHECK: a5 06 07 00 ff 00 00 00 	if r6 < 255 goto 7
-// CHECK: b5 07 06 00 ff ff 00 00 	if r7 <= 65535 goto 6
-// CHECK: c5 08 05 00 00 00 00 00 	if r8 s< 0 goto 5
-// CHECK: d5 09 04 00 ff ff ff ff 	if r9 s<= -1 goto 4
+// CHECK: a5 06 07 00 ff 00 00 00 	if r6 < 255 goto +7
+// CHECK: b5 07 06 00 ff ff 00 00 	if r7 <= 65535 goto +6
+// CHECK: c5 08 05 00 00 00 00 00 	if r8 s< 0 goto +5
+// CHECK: d5 09 04 00 ff ff ff ff 	if r9 s<= -1 goto +4
 
 // ======== BPF_ALU64 Class ========
   r0 += r1    // BPF_ADD  | BPF_X