From 0df1955fdb388964e250c6f3af89fa0e8b3104a6 Mon Sep 17 00:00:00 2001
From: Yonghong Song <yhs@fb.com>
Date: Thu, 16 Nov 2017 00:52:30 +0000
Subject: [PATCH] bpf: enable llvm-objdump to print out symbolized jmp target

Add hook in BPF backend so that llvm-objdump can print out
the jmp target with label names, e.g.,
  ...
  if r1 != 2 goto 6 <LBB0_2>
  ...
  goto 7 <LBB0_4>
  ...
 LBB0_2:
  ...
 LBB0_4:
  ...

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@318358 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/BPF/MCTargetDesc/BPFMCTargetDesc.cpp | 34 ++++++++++++
 test/CodeGen/BPF/objdump_cond_op.ll             | 69 +++++++++++++++++++++++++
 2 files changed, 103 insertions(+)
 create mode 100644 test/CodeGen/BPF/objdump_cond_op.ll

diff --git a/lib/Target/BPF/MCTargetDesc/BPFMCTargetDesc.cpp b/lib/Target/BPF/MCTargetDesc/BPFMCTargetDesc.cpp
index c8fbc0c2207..5c3bba6e669 100644
--- a/lib/Target/BPF/MCTargetDesc/BPFMCTargetDesc.cpp
+++ b/lib/Target/BPF/MCTargetDesc/BPFMCTargetDesc.cpp
@@ -15,6 +15,7 @@
 #include "BPF.h"
 #include "InstPrinter/BPFInstPrinter.h"
 #include "MCTargetDesc/BPFMCAsmInfo.h"
+#include "llvm/MC/MCInstrAnalysis.h"
 #include "llvm/MC/MCInstrInfo.h"
 #include "llvm/MC/MCRegisterInfo.h"
 #include "llvm/MC/MCSubtargetInfo.h"
@@ -68,6 +69,35 @@ static MCInstPrinter *createBPFMCInstPrinter(const Triple &T,
   return nullptr;
 }
 
+namespace {
+
+class BPFMCInstrAnalysis : public MCInstrAnalysis {
+public:
+  explicit BPFMCInstrAnalysis(const MCInstrInfo *Info)
+      : MCInstrAnalysis(Info) {}
+
+  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;
+    if (isConditionalBranch(Inst)) {
+      Imm = Inst.getOperand(2).getImm();
+    } else if (isUnconditionalBranch(Inst))
+      Imm = Inst.getOperand(0).getImm();
+    else
+      return false;
+
+    Target = Addr + Size + Imm * Size;
+    return true;
+  }
+};
+
+} // end anonymous namespace
+
+static MCInstrAnalysis *createBPFInstrAnalysis(const MCInstrInfo *Info) {
+  return new BPFMCInstrAnalysis(Info);
+}
+
 extern "C" void LLVMInitializeBPFTargetMC() {
   for (Target *T :
        {&getTheBPFleTarget(), &getTheBPFbeTarget(), &getTheBPFTarget()}) {
@@ -89,6 +119,9 @@ extern "C" void LLVMInitializeBPFTargetMC() {
 
     // Register the MCInstPrinter.
     TargetRegistry::RegisterMCInstPrinter(*T, createBPFMCInstPrinter);
+
+    // Register the MC instruction analyzer.
+    TargetRegistry::RegisterMCInstrAnalysis(*T, createBPFInstrAnalysis);
   }
 
   // Register the MC code emitter
@@ -114,4 +147,5 @@ extern "C" void LLVMInitializeBPFTargetMC() {
     TargetRegistry::RegisterMCAsmBackend(getTheBPFTarget(),
                                          createBPFbeAsmBackend);
   }
+
 }
diff --git a/test/CodeGen/BPF/objdump_cond_op.ll b/test/CodeGen/BPF/objdump_cond_op.ll
new file mode 100644
index 00000000000..3abbb76ccc9
--- /dev/null
+++ b/test/CodeGen/BPF/objdump_cond_op.ll
@@ -0,0 +1,69 @@
+; RUN: llc -march=bpfel -filetype=obj -o - %s | llvm-objdump -d - | FileCheck %s
+
+; Source Code:
+; int gbl;
+; int test(int a, int b) {
+;   if (a == 2) {
+;     gbl = gbl * gbl * 2;
+;     goto out;
+;   }
+;   if (a != b) {
+;     gbl = gbl * 4;
+;   }
+; out:
+;   return gbl;
+; }
+
+@gbl = common local_unnamed_addr global i32 0, align 4
+
+define i32 @test(i32, i32) local_unnamed_addr #0 {
+  %3 = icmp eq i32 %0, 2
+  br i1 %3, label %4, label %8
+
+; <label>:4:                                      ; preds = %2
+  %5 = load i32, i32* @gbl, align 4
+  %6 = shl i32 %5, 1
+  %7 = mul i32 %6, %5
+  br label %13
+; CHECK: r1 <<= 32
+; CHECK: r1 >>= 32
+; CHECK: if r1 != 2 goto 6 <LBB0_2>
+
+; <label>:8:                                      ; preds = %2
+  %9 = icmp eq i32 %0, %1
+  %10 = load i32, i32* @gbl, align 4
+  br i1 %9, label %15, label %11
+
+; CHECK: r1 = 0 ll
+; CHECK: r0 = *(u32 *)(r1 + 0)
+; CHECK: r0 *= r0
+; CHECK: r0 <<= 1
+; CHECK: goto 7 <LBB0_4>
+
+; <label>:11:                                     ; preds = %8
+  %12 = shl nsw i32 %10, 2
+  br label %13
+
+; CHECK-LABEL: LBB0_2:
+; CHECK: r3 = 0 ll
+; CHECK: r0 = *(u32 *)(r3 + 0)
+; CHECK: r2 <<= 32
+; CHECK: r2 >>= 32
+; CHECK: if r1 == r2 goto 4 <LBB0_5>
+; CHECK: r0 <<= 2
+
+; <label>:13:                                     ; preds = %4, %11
+  %14 = phi i32 [ %12, %11 ], [ %7, %4 ]
+  store i32 %14, i32* @gbl, align 4
+  br label %15
+; CHECK-LABEL: LBB0_4:
+; CHECK: r1 = 0 ll
+; CHECK: *(u32 *)(r1 + 0) = r0
+
+; <label>:15:                                     ; preds = %8, %13
+  %16 = phi i32 [ %14, %13 ], [ %10, %8 ]
+  ret i32 %16
+; CHECK-LABEL: LBB0_5:
+; CHECK: exit
+}
+attributes #0 = { norecurse nounwind }
-- 
2.11.0