From 8f90edde69e4b4635b1ec8197aa244e22bc9aac6 Mon Sep 17 00:00:00 2001
From: Seiya Nuta <nuta@seiya.me>
Date: Thu, 25 Jul 2019 06:57:09 +0000
Subject: [PATCH] [MC] Add MCInstrAnalysis::evaluateMemoryOperandAddress

Summary:
Add a new method which tries to compute the target address referenced by an operand.

This patch supports x86_64 RIP-relative addressing for now.

It is necessary to print referenced symbol names in llvm-objdump.

Reviewers: andreadb, MaskRay, grosbach, jgalenson, craig.topper

Reviewed By: MaskRay, craig.topper

Subscribers: bcain, rupprecht, jhenderson, hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D63847

llvm-svn: 366987
---
 include/llvm/MC/MCInstrAnalysis.h             |  6 ++++
 lib/MC/MCInstrAnalysis.cpp                    |  6 ++++
 .../X86/MCTargetDesc/X86MCTargetDesc.cpp      | 29 ++++++++++++++++++-
 3 files changed, 40 insertions(+), 1 deletion(-)

diff --git a/include/llvm/MC/MCInstrAnalysis.h b/include/llvm/MC/MCInstrAnalysis.h
index dfefd7e7277..898ca47b13b 100644
--- a/include/llvm/MC/MCInstrAnalysis.h
+++ b/include/llvm/MC/MCInstrAnalysis.h
@@ -152,6 +152,12 @@ public:
   evaluateBranch(const MCInst &Inst, uint64_t Addr, uint64_t Size,
                  uint64_t &Target) const;
 
+  /// Given an instruction tries to get the address of a memory operand. Returns
+  /// the address on success.
+  virtual Optional<uint64_t> evaluateMemoryOperandAddress(const MCInst &Inst,
+                                                          uint64_t Addr,
+                                                          uint64_t Size) const;
+
   /// Returns (PLT virtual address, GOT virtual address) pairs for PLT entries.
   virtual std::vector<std::pair<uint64_t, uint64_t>>
   findPltEntries(uint64_t PltSectionVA, ArrayRef<uint8_t> PltContents,
diff --git a/lib/MC/MCInstrAnalysis.cpp b/lib/MC/MCInstrAnalysis.cpp
index eca87f940bf..54741fdd686 100644
--- a/lib/MC/MCInstrAnalysis.cpp
+++ b/lib/MC/MCInstrAnalysis.cpp
@@ -33,3 +33,9 @@ bool MCInstrAnalysis::evaluateBranch(const MCInst &Inst, uint64_t Addr,
   Target = Addr+Size+Imm;
   return true;
 }
+
+Optional<uint64_t>
+MCInstrAnalysis::evaluateMemoryOperandAddress(const MCInst &Inst, uint64_t Addr,
+                                              uint64_t Size) const {
+  return None;
+}
diff --git a/lib/Target/X86/MCTargetDesc/X86MCTargetDesc.cpp b/lib/Target/X86/MCTargetDesc/X86MCTargetDesc.cpp
index ce05ad97450..c700ab31ba9 100644
--- a/lib/Target/X86/MCTargetDesc/X86MCTargetDesc.cpp
+++ b/lib/Target/X86/MCTargetDesc/X86MCTargetDesc.cpp
@@ -399,6 +399,9 @@ public:
   findPltEntries(uint64_t PltSectionVA, ArrayRef<uint8_t> PltContents,
                  uint64_t GotSectionVA,
                  const Triple &TargetTriple) const override;
+  Optional<uint64_t> evaluateMemoryOperandAddress(const MCInst &Inst,
+                                                  uint64_t Addr,
+                                                  uint64_t Size) const override;
 };
 
 #define GET_STIPREDICATE_DEFS_FOR_MC_ANALYSIS
@@ -511,7 +514,31 @@ std::vector<std::pair<uint64_t, uint64_t>> X86MCInstrAnalysis::findPltEntries(
       return findX86_64PltEntries(PltSectionVA, PltContents);
     default:
       return {};
-  }
+    }
+}
+
+Optional<uint64_t> X86MCInstrAnalysis::evaluateMemoryOperandAddress(
+    const MCInst &Inst, uint64_t Addr, uint64_t Size) const {
+  const MCInstrDesc &MCID = Info->get(Inst.getOpcode());
+  int MemOpStart = X86II::getMemoryOperandNo(MCID.TSFlags);
+  if (MemOpStart == -1)
+    return None;
+  MemOpStart += X86II::getOperandBias(MCID);
+
+  const MCOperand &SegReg = Inst.getOperand(MemOpStart + X86::AddrSegmentReg);
+  const MCOperand &BaseReg = Inst.getOperand(MemOpStart + X86::AddrBaseReg);
+  const MCOperand &IndexReg = Inst.getOperand(MemOpStart + X86::AddrIndexReg);
+  const MCOperand &ScaleAmt = Inst.getOperand(MemOpStart + X86::AddrScaleAmt);
+  const MCOperand &Disp = Inst.getOperand(MemOpStart + X86::AddrDisp);
+  if (SegReg.getReg() != 0 || IndexReg.getReg() != 0 || ScaleAmt.getImm() != 1 ||
+      !Disp.isImm())
+    return None;
+
+  // RIP-relative addressing.
+  if (BaseReg.getReg() == X86::RIP)
+    return Addr + Size + Disp.getImm();
+
+  return None;
 }
 
 } // end of namespace X86_MC