Subzero: Change -asm-verbose output to print more useful info.

src/IceCfg.cpp

@@ -743,6 +743,14 @@ void Cfg::emit() {
 
   emitTextHeader(MangledName, Ctx, Asm);
   deleteJumpTableInsts();
+  if (Ctx->getFlags().getDecorateAsm()) {
+    for (Variable *Var : getVariables()) {
+      if (Var->getStackOffset()) {
+        Str << "\t" << Var->getSymbolicStackOffset(this) << " = "
+            << Var->getStackOffset() << "\n";
+      }
+    }
+  }
   for (CfgNode *Node : Nodes) {
     if (NeedSandboxing && Node->needsAlignment()) {
       Str << "\t" << Asm->getAlignDirective() << " "

src/IceCfgNode.cpp

@@ -978,7 +978,7 @@ void CfgNode::emit(Cfg *Func) const {
   Func->setCurrentNode(this);
   Ostream &Str = Func->getContext()->getStrEmit();
   Liveness *Liveness = Func->getLiveness();
-  bool DecorateAsm =
+  const bool DecorateAsm =
       Liveness && Func->getContext()->getFlags().getDecorateAsm();
   Str << getAsmName() << ":\n";
   // LiveRegCount keeps track of the number of currently live variables that
@@ -989,6 +989,20 @@ void CfgNode::emit(Cfg *Func) const {
   if (DecorateAsm) {
     constexpr bool IsLiveIn = true;
     emitRegisterUsage(Str, Func, this, IsLiveIn, LiveRegCount);
+    if (getInEdges().size()) {
+      Str << "\t\t\t\t# preds=";
+      bool First = true;
+      for (CfgNode *I : getInEdges()) {
+        if (!First)
+          Str << ",";
+        First = false;
+        Str << I->getAsmName();
+      }
+      Str << "\n";
+    }
+    if (getLoopNestDepth()) {
+      Str << "\t\t\t\t# loop depth=" << getLoopNestDepth() << "\n";
+    }
   }
 
   for (const Inst &I : Phis) {

src/IceOperand.h

@@ -442,6 +442,11 @@ public:
 
   int32_t getStackOffset() const { return StackOffset; }
   void setStackOffset(int32_t Offset) { StackOffset = Offset; }
+  /// Returns the variable's stack offset in symbolic form, to improve
+  /// readability in DecorateAsm mode.
+  IceString getSymbolicStackOffset(const Cfg *Func) const {
+    return "lv$" + getName(Func);
+  }
 
   static const int32_t NoRegister = -1;
   bool hasReg() const { return getRegNum() != NoRegister; }

src/IceTargetLoweringX86BaseImpl.h

@@ -746,15 +746,35 @@ void TargetX86Base<Machine>::emitVariable(const Variable *Var) const {
   if (Var->mustHaveReg()) {
     llvm_unreachable("Infinite-weight Variable has no register assigned");
   }
-  int32_t Offset = Var->getStackOffset();
+  const int32_t Offset = Var->getStackOffset();
+  int32_t OffsetAdj = 0;
   int32_t BaseRegNum = Var->getBaseRegNum();
   if (BaseRegNum == Variable::NoRegister) {
     BaseRegNum = getFrameOrStackReg();
     if (!hasFramePointer())
-      Offset += getStackAdjustment();
+      OffsetAdj = getStackAdjustment();
+  }
+  // Print in the form "OffsetAdj+Offset(%reg)", taking care that:
+  //   - OffsetAdj may be 0
+  //   - Offset is never printed when it is 0
+  //   - Offset may be positive or symbolic, so a "+" might be needed
+
+  // Only print nonzero OffsetAdj.
+  if (OffsetAdj) {
+    Str << OffsetAdj;
+  }
+  const bool DecorateAsm = Func->getContext()->getFlags().getDecorateAsm();
+  // Only print Offset when it is nonzero, regardless of DecorateAsm.
+  if (Offset) {
+    if (OffsetAdj && (DecorateAsm || Offset > 0)) {
+      Str << "+";
+    }
+    if (DecorateAsm) {
+      Str << Var->getSymbolicStackOffset(Func);
+    } else {
+      Str << Offset;
+    }
   }
-  if (Offset)
-    Str << Offset;
   const Type FrameSPTy = Traits::WordType;
   Str << "(%" << getRegName(BaseRegNum, FrameSPTy) << ")";
 }