llvm-mc: Move AsmExpr into MC lib (as MCExpr).

llvm-svn: 80567

1 files changed, 162 insertions, 0 deletions

diff --git a/llvm/lib/MC/MCExpr.cpp b/llvm/lib/MC/MCExpr.cpp
new file mode 100644
index 00000000000..91ef7e77ec8
--- /dev/null
+++ b/llvm/lib/MC/MCExpr.cpp
@@ -0,0 +1,162 @@
+//===- MCExpr.cpp - Assembly Level Expression Implementation --------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/MC/MCExpr.h"
+#include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCSymbol.h"
+#include "llvm/MC/MCValue.h"
+using namespace llvm;
+
+MCExpr::~MCExpr() {
+}
+
+bool MCExpr::EvaluateAsAbsolute(MCContext &Ctx, int64_t &Res) const {
+  MCValue Value;
+  
+  if (!EvaluateAsRelocatable(Ctx, Value) || !Value.isAbsolute())
+    return false;
+
+  Res = Value.getConstant();
+  return true;
+}
+
+static bool EvaluateSymbolicAdd(const MCValue &LHS, const MCSymbol *RHS_A, 
+                                const MCSymbol *RHS_B, int64_t RHS_Cst,
+                                MCValue &Res) {
+  // We can't add or subtract two symbols.
+  if ((LHS.getSymA() && RHS_A) ||
+      (LHS.getSymB() && RHS_B))
+    return false;
+
+  const MCSymbol *A = LHS.getSymA() ? LHS.getSymA() : RHS_A;
+  const MCSymbol *B = LHS.getSymB() ? LHS.getSymB() : RHS_B;
+  if (B) {
+    // If we have a negated symbol, then we must have also have a non-negated
+    // symbol in order to encode the expression. We can do this check later to
+    // permit expressions which eventually fold to a representable form -- such
+    // as (a + (0 - b)) -- if necessary.
+    if (!A)
+      return false;
+  }
+  Res = MCValue::get(A, B, LHS.getConstant() + RHS_Cst);
+  return true;
+}
+
+bool MCExpr::EvaluateAsRelocatable(MCContext &Ctx, MCValue &Res) const {
+  switch (getKind()) {
+  default:
+    assert(0 && "Invalid assembly expression kind!");
+
+  case Constant:
+    Res = MCValue::get(cast<MCConstantExpr>(this)->getValue());
+    return true;
+
+  case SymbolRef: {
+    MCSymbol *Sym = cast<MCSymbolRefExpr>(this)->getSymbol();
+    if (const MCValue *Value = Ctx.GetSymbolValue(Sym))
+      Res = *Value;
+    else
+      Res = MCValue::get(Sym, 0, 0);
+    return true;
+  }
+
+  case Unary: {
+    const MCUnaryExpr *AUE = cast<MCUnaryExpr>(this);
+    MCValue Value;
+
+    if (!AUE->getSubExpr()->EvaluateAsRelocatable(Ctx, Value))
+      return false;
+
+    switch (AUE->getOpcode()) {
+    case MCUnaryExpr::LNot:
+      if (!Value.isAbsolute())
+        return false;
+      Res = MCValue::get(!Value.getConstant());
+      break;
+    case MCUnaryExpr::Minus:
+      /// -(a - b + const) ==> (b - a - const)
+      if (Value.getSymA() && !Value.getSymB())
+        return false;
+      Res = MCValue::get(Value.getSymB(), Value.getSymA(), 
+                         -Value.getConstant()); 
+      break;
+    case MCUnaryExpr::Not:
+      if (!Value.isAbsolute())
+        return false;
+      Res = MCValue::get(~Value.getConstant()); 
+      break;
+    case MCUnaryExpr::Plus:
+      Res = Value;
+      break;
+    }
+
+    return true;
+  }
+
+  case Binary: {
+    const MCBinaryExpr *ABE = cast<MCBinaryExpr>(this);
+    MCValue LHSValue, RHSValue;
+    
+    if (!ABE->getLHS()->EvaluateAsRelocatable(Ctx, LHSValue) ||
+        !ABE->getRHS()->EvaluateAsRelocatable(Ctx, RHSValue))
+      return false;
+
+    // We only support a few operations on non-constant expressions, handle
+    // those first.
+    if (!LHSValue.isAbsolute() || !RHSValue.isAbsolute()) {
+      switch (ABE->getOpcode()) {
+      default:
+        return false;
+      case MCBinaryExpr::Sub:
+        // Negate RHS and add.
+        return EvaluateSymbolicAdd(LHSValue,
+                                   RHSValue.getSymB(), RHSValue.getSymA(),
+                                   -RHSValue.getConstant(),
+                                   Res);
+
+      case MCBinaryExpr::Add:
+        return EvaluateSymbolicAdd(LHSValue,
+                                   RHSValue.getSymA(), RHSValue.getSymB(),
+                                   RHSValue.getConstant(),
+                                   Res);
+      }
+    }
+
+    // FIXME: We need target hooks for the evaluation. It may be limited in
+    // width, and gas defines the result of comparisons differently from Apple
+    // as (the result is sign extended).
+    int64_t LHS = LHSValue.getConstant(), RHS = RHSValue.getConstant();
+    int64_t Result = 0;
+    switch (ABE->getOpcode()) {
+    case MCBinaryExpr::Add:  Result = LHS + RHS; break;
+    case MCBinaryExpr::And:  Result = LHS & RHS; break;
+    case MCBinaryExpr::Div:  Result = LHS / RHS; break;
+    case MCBinaryExpr::EQ:   Result = LHS == RHS; break;
+    case MCBinaryExpr::GT:   Result = LHS > RHS; break;
+    case MCBinaryExpr::GTE:  Result = LHS >= RHS; break;
+    case MCBinaryExpr::LAnd: Result = LHS && RHS; break;
+    case MCBinaryExpr::LOr:  Result = LHS || RHS; break;
+    case MCBinaryExpr::LT:   Result = LHS < RHS; break;
+    case MCBinaryExpr::LTE:  Result = LHS <= RHS; break;
+    case MCBinaryExpr::Mod:  Result = LHS % RHS; break;
+    case MCBinaryExpr::Mul:  Result = LHS * RHS; break;
+    case MCBinaryExpr::NE:   Result = LHS != RHS; break;
+    case MCBinaryExpr::Or:   Result = LHS | RHS; break;
+    case MCBinaryExpr::Shl:  Result = LHS << RHS; break;
+    case MCBinaryExpr::Shr:  Result = LHS >> RHS; break;
+    case MCBinaryExpr::Sub:  Result = LHS - RHS; break;
+    case MCBinaryExpr::Xor:  Result = LHS ^ RHS; break;
+    }
+
+    Res = MCValue::get(Result);
+    return true;
+  }
+  }
+}
+