Don't DCE FreeInst's. We were using those! Patch from Owen Anderson.

[oota-llvm.git] / lib / Transforms / IPO / StripSymbols.cpp

diff --git a/lib/Transforms/IPO/StripSymbols.cpp b/lib/Transforms/IPO/StripSymbols.cpp
index 00cfc513b66370fbc078e48d17afff70a7214ed1..cd2396258c41f8b6d99ca1b07bb245cfdebcfbb7 100644 (file)
--- a/lib/Transforms/IPO/StripSymbols.cpp
+++ b/lib/Transforms/IPO/StripSymbols.cpp
@@ -2,23 +2,21 @@
 //
 //                     The LLVM Compiler Infrastructure
 //
-// This file was developed by the LLVM research group and is distributed under
-// the University of Illinois Open Source License. See LICENSE.TXT for details.
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
-// This file implements stripping symbols out of symbol tables.
+// The StripSymbols transformation implements code stripping. Specifically, it
+// can delete:
+// 
+//   * names for virtual registers
+//   * symbols for internal globals and functions
+//   * debug information
 //
-// Specifically, this allows you to strip all of the symbols out of:
-//   * All functions in a module
-//   * All non-essential symbols in a module (all function symbols + all module
-//     scope symbols)
-//   * Debug information.
-//
-// Notice that:
-//   * This pass makes code much less readable, so it should only be used in
-//     situations where the 'strip' utility would be used (such as reducing
-//     code size, and making it harder to reverse engineer code).
+// Note that this transformation makes code much less readable, so it should
+// only be used in situations where the 'strip' utility would be used, such as
+// reducing code size or making it harder to reverse engineer code.
 //
 //===----------------------------------------------------------------------===//
 
@@ -30,13 +28,17 @@
 #include "llvm/Pass.h"
 #include "llvm/ValueSymbolTable.h"
 #include "llvm/TypeSymbolTable.h"
+#include "llvm/Support/Compiler.h"
+#include "llvm/ADT/SmallPtrSet.h"
 using namespace llvm;
 
 namespace {
-  class StripSymbols : public ModulePass {
+  class VISIBILITY_HIDDEN StripSymbols : public ModulePass {
     bool OnlyDebugInfo;
   public:
-    StripSymbols(bool ODI = false) : OnlyDebugInfo(ODI) {}
+    static char ID; // Pass identification, replacement for typeid
+    explicit StripSymbols(bool ODI = false) 
+      : ModulePass((intptr_t)&ID), OnlyDebugInfo(ODI) {}
 
     virtual bool runOnModule(Module &M);
 
@@ -44,6 +46,8 @@ namespace {
       AU.setPreservesAll();
     }
   };
+
+  char StripSymbols::ID = 0;
   RegisterPass<StripSymbols> X("strip", "Strip all symbols from a module");
 }
 
@@ -72,23 +76,64 @@ static void RemoveDeadConstant(Constant *C) {
   }
 }
 
+// Strip the symbol table of its names.
+//
+static void StripSymtab(ValueSymbolTable &ST) {
+  for (ValueSymbolTable::iterator VI = ST.begin(), VE = ST.end(); VI != VE; ) {
+    Value *V = VI->getValue();
+    ++VI;
+    if (!isa<GlobalValue>(V) || cast<GlobalValue>(V)->hasInternalLinkage()) {
+      // Set name to "", removing from symbol table!
+      V->setName("");
+    }
+  }
+}
+
+// Strip the symbol table of its names.
+static void StripTypeSymtab(TypeSymbolTable &ST) {
+  for (TypeSymbolTable::iterator TI = ST.begin(), E = ST.end(); TI != E; )
+    ST.remove(TI++);
+}
+
+
+
 bool StripSymbols::runOnModule(Module &M) {
   // If we're not just stripping debug info, strip all symbols from the
   // functions and the names from any internal globals.
   if (!OnlyDebugInfo) {
+    SmallPtrSet<const GlobalValue*, 8> llvmUsedValues;
+    if (GlobalVariable *LLVMUsed = M.getGlobalVariable("llvm.used")) {
+      llvmUsedValues.insert(LLVMUsed);
+      // Collect values that are preserved as per explicit request.
+      // llvm.used is used to list these values.
+      if (ConstantArray *Inits = 
+            dyn_cast<ConstantArray>(LLVMUsed->getInitializer())) {
+        for (unsigned i = 0, e = Inits->getNumOperands(); i != e; ++i) {
+          if (GlobalValue *GV = dyn_cast<GlobalValue>(Inits->getOperand(i)))
+            llvmUsedValues.insert(GV);
+          else if (ConstantExpr *CE =
+                       dyn_cast<ConstantExpr>(Inits->getOperand(i)))
+            if (CE->getOpcode() == Instruction::BitCast)
+              if (GlobalValue *GV = dyn_cast<GlobalValue>(CE->getOperand(0)))
+                llvmUsedValues.insert(GV);
+        }
+      }
+    }
+
     for (Module::global_iterator I = M.global_begin(), E = M.global_end();
-         I != E; ++I)
-      if (I->hasInternalLinkage())
+         I != E; ++I) {
+      if (I->hasInternalLinkage() && llvmUsedValues.count(I) == 0)
         I->setName("");     // Internal symbols can't participate in linkage
+    }
 
     for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) {
-      if (I->hasInternalLinkage())
+      if (I->hasInternalLinkage() && llvmUsedValues.count(I) == 0)
         I->setName("");     // Internal symbols can't participate in linkage
-      I->getValueSymbolTable().strip();
+      StripSymtab(I->getValueSymbolTable());
     }
     
     // Remove all names from types.
-    M.getTypeSymbolTable().strip();
+    StripTypeSymtab(M.getTypeSymbolTable());
   }
 
   // Strip debug info in the module if it exists.  To do this, we remove