From 64d083c81add9243be14ac3e0833e02754c42c1e Mon Sep 17 00:00:00 2001
From: Simon Atanasyan <simon@atanasyan.com>
Date: Thu, 24 Mar 2016 17:18:14 +0000
Subject: [PATCH] [MC][mips] Add MipsMCInstrAnalysis class and register it as
 MC instruction analyzer

The `MipsMCInstrAnalysis` class overrides the `evaluateBranch` method
and calculates target addresses for branch and calls instructions.
That allows llvm-objdump to print functions' names in branch instructions
in the disassemble mode.

Differential Revision: http://reviews.llvm.org/D18209

llvm-svn: 264309
---
 .../Mips/MCTargetDesc/MipsMCTargetDesc.cpp    | 36 +++++++++++++++++++
 test/MC/Mips/instr-analysis.s                 | 36 +++++++++++++++++++
 2 files changed, 72 insertions(+)
 create mode 100644 test/MC/Mips/instr-analysis.s

diff --git a/lib/Target/Mips/MCTargetDesc/MipsMCTargetDesc.cpp b/lib/Target/Mips/MCTargetDesc/MipsMCTargetDesc.cpp
index 949ee1474f9..f1b81814b7c 100644
--- a/lib/Target/Mips/MCTargetDesc/MipsMCTargetDesc.cpp
+++ b/lib/Target/Mips/MCTargetDesc/MipsMCTargetDesc.cpp
@@ -20,6 +20,7 @@
 #include "llvm/ADT/Triple.h"
 #include "llvm/MC/MCCodeGenInfo.h"
 #include "llvm/MC/MCELFStreamer.h"
+#include "llvm/MC/MCInstrAnalysis.h"
 #include "llvm/MC/MCInstrInfo.h"
 #include "llvm/MC/MCRegisterInfo.h"
 #include "llvm/MC/MCSubtargetInfo.h"
@@ -129,6 +130,38 @@ createMipsObjectTargetStreamer(MCStreamer &S, const MCSubtargetInfo &STI) {
   return new MipsTargetELFStreamer(S, STI);
 }
 
+namespace {
+
+class MipsMCInstrAnalysis : public MCInstrAnalysis {
+public:
+  MipsMCInstrAnalysis(const MCInstrInfo *Info) : MCInstrAnalysis(Info) {}
+
+  bool evaluateBranch(const MCInst &Inst, uint64_t Addr, uint64_t Size,
+                      uint64_t &Target) const override {
+    unsigned NumOps = Inst.getNumOperands();
+    if (NumOps == 0)
+      return false;
+    switch (Info->get(Inst.getOpcode()).OpInfo[NumOps - 1].OperandType) {
+    case MCOI::OPERAND_UNKNOWN:
+    case MCOI::OPERAND_IMMEDIATE:
+      // jal, bal ...
+      Target = Inst.getOperand(NumOps - 1).getImm();
+      return true;
+    case MCOI::OPERAND_PCREL:
+      // b, j, beq ...
+      Target = Addr + Inst.getOperand(NumOps - 1).getImm();
+      return true;
+    default:
+      return false;
+    }
+  }
+};
+}
+
+static MCInstrAnalysis *createMipsMCInstrAnalysis(const MCInstrInfo *Info) {
+  return new MipsMCInstrAnalysis(Info);
+}
+
 extern "C" void LLVMInitializeMipsTargetMC() {
   for (Target *T : {&TheMipsTarget, &TheMipselTarget, &TheMips64Target,
                     &TheMips64elTarget}) {
@@ -156,6 +189,9 @@ extern "C" void LLVMInitializeMipsTargetMC() {
     // Register the MC subtarget info.
     TargetRegistry::RegisterMCSubtargetInfo(*T, createMipsMCSubtargetInfo);
 
+    // Register the MC instruction analyzer.
+    TargetRegistry::RegisterMCInstrAnalysis(*T, createMipsMCInstrAnalysis);
+
     // Register the MCInstPrinter.
     TargetRegistry::RegisterMCInstPrinter(*T, createMipsMCInstPrinter);
 
diff --git a/test/MC/Mips/instr-analysis.s b/test/MC/Mips/instr-analysis.s
new file mode 100644
index 00000000000..58abfd0f472
--- /dev/null
+++ b/test/MC/Mips/instr-analysis.s
@@ -0,0 +1,36 @@
+# RUN: llvm-mc -filetype=obj -triple=mips-unknown-linux %s -o - \
+# RUN:   | llvm-objdump -d - | FileCheck %s
+
+# CHECK:      foo:
+# CHECK-NEXT:        0:       0c 00 00 02     jal     8 <loc1>
+# CHECK-NEXT:        4:       00 00 00 00     nop
+#
+# CHECK:      loc1:
+# CHECK-NEXT:        8:       0c 00 00 06     jal     24 <loc3>
+# CHECK-NEXT:        c:       00 00 00 00     nop
+#
+# CHECK:      loc2:
+# CHECK-NEXT:       10:       10 00 ff fd     b       -8 <loc1>
+# CHECK-NEXT:       14:       00 00 00 00     nop
+#
+# CHECK:      loc3:
+# CHECK-NEXT:       18:       10 43 ff fd     beq     $2, $3, -8 <loc2>
+# CHECK-NEXT:       1c:       00 00 00 00     nop
+# CHECK-NEXT:       20:       04 11 ff f9     bal     -24 <loc1>
+# CHECK-NEXT:       24:       00 00 00 00     nop
+# CHECK-NEXT:       28:       08 00 00 04     j       16 <loc2>
+
+  .text
+  .globl foo
+  .ent foo
+foo:
+  jal loc1
+loc1:
+  jal loc3
+loc2:
+  b   loc1
+loc3:
+  beq $2, $3, loc2
+  bal loc1
+  j   loc2
+  .end foo