recommit r172363 & r171325 (reverted in r172756)

This adds minimalistic support for PHI nodes to llvm.objectsize() evaluation

fingers crossed so that it does break clang boostrap again..

llvm-svn: 176408

include/llvm/Analysis/MemoryBuiltins.h

@@ -161,12 +161,14 @@ typedef std::pair<APInt, APInt> SizeOffsetType;
 class ObjectSizeOffsetVisitor
   : public InstVisitor<ObjectSizeOffsetVisitor, SizeOffsetType> {
 
+  typedef DenseMap<const Value*, SizeOffsetType> CacheMapTy;
+
   const DataLayout *TD;
   const TargetLibraryInfo *TLI;
   bool RoundToAlign;
   unsigned IntTyBits;
   APInt Zero;
-  SmallPtrSet<Instruction *, 8> SeenInsts;
+  CacheMapTy CacheMap;
 
   APInt align(APInt Size, uint64_t Align);
 

lib/Analysis/MemoryBuiltins.cpp

@@ -405,16 +405,23 @@ ObjectSizeOffsetVisitor::ObjectSizeOffsetVisitor(const DataLayout *TD,
 
 SizeOffsetType ObjectSizeOffsetVisitor::compute(Value *V) {
   V = V->stripPointerCasts();
-  if (Instruction *I = dyn_cast<Instruction>(V)) {
-    // If we have already seen this instruction, bail out. Cycles can happen in
-    // unreachable code after constant propagation.
-    if (!SeenInsts.insert(I))
-      return unknown();
 
+  if (isa<Instruction>(V) || isa<GEPOperator>(V)) {
+    // Return cached value or insert unknown in cache if size of V was not
+    // computed yet in order to avoid recursions in PHis.
+    std::pair<CacheMapTy::iterator, bool> CacheVal =
+      CacheMap.insert(std::make_pair(V, unknown()));
+    if (!CacheVal.second)
+      return CacheVal.first->second;
+
+    SizeOffsetType Result;
     if (GEPOperator *GEP = dyn_cast<GEPOperator>(V))
-      return visitGEPOperator(*GEP);
+      Result = visitGEPOperator(*GEP);
-    return visit(*I);
+    else
+      Result = visit(cast<Instruction>(*V));
+    return CacheMap[V] = Result;
   }
+
   if (Argument *A = dyn_cast<Argument>(V))
     return visitArgument(*A);
   if (ConstantPointerNull *P = dyn_cast<ConstantPointerNull>(V))
@@ -428,8 +435,6 @@ SizeOffsetType ObjectSizeOffsetVisitor::compute(Value *V) {
   if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
     if (CE->getOpcode() == Instruction::IntToPtr)
       return unknown(); // clueless
-    if (CE->getOpcode() == Instruction::GetElementPtr)
-      return visitGEPOperator(cast<GEPOperator>(*CE));
   }
 
   DEBUG(dbgs() << "ObjectSizeOffsetVisitor::compute() unhandled value: " << *V
@@ -563,9 +568,21 @@ SizeOffsetType ObjectSizeOffsetVisitor::visitLoadInst(LoadInst&) {
   return unknown();
 }
 
-SizeOffsetType ObjectSizeOffsetVisitor::visitPHINode(PHINode&) {
+SizeOffsetType ObjectSizeOffsetVisitor::visitPHINode(PHINode &PHI) {
-  // too complex to analyze statically.
+  if (PHI.getNumIncomingValues() == 0)
     return unknown();
+
+  SizeOffsetType Ret = compute(PHI.getIncomingValue(0));
+  if (!bothKnown(Ret))
+    return unknown();
+
+  // Verify that all PHI incoming pointers have the same size and offset.
+  for (unsigned i = 1, e = PHI.getNumIncomingValues(); i != e; ++i) {
+    SizeOffsetType EdgeData = compute(PHI.getIncomingValue(i));
+    if (!bothKnown(EdgeData) || EdgeData != Ret)
+      return unknown();
+  }
+  return Ret;
 }
 
 SizeOffsetType ObjectSizeOffsetVisitor::visitSelectInst(SelectInst &I) {

test/Transforms/InstCombine/objsize.ll

@@ -256,3 +256,131 @@ xpto:
 return:
   ret i32 7
 }
+
+declare noalias i8* @valloc(i32) nounwind
+
+; CHECK: @test14
+; CHECK: ret i32 6
+define i32 @test14(i32 %a) nounwind {
+  switch i32 %a, label %sw.default [
+    i32 1, label %sw.bb
+    i32 2, label %sw.bb1
+  ]
+
+sw.bb:
+  %call = tail call noalias i8* @malloc(i32 6) nounwind
+  br label %sw.epilog
+
+sw.bb1:
+  %call2 = tail call noalias i8* @calloc(i32 3, i32 2) nounwind
+  br label %sw.epilog
+
+sw.default:
+  %call3 = tail call noalias i8* @valloc(i32 6) nounwind
+  br label %sw.epilog
+
+sw.epilog:
+  %b.0 = phi i8* [ %call3, %sw.default ], [ %call2, %sw.bb1 ], [ %call, %sw.bb ]
+  %1 = tail call i32 @llvm.objectsize.i32(i8* %b.0, i1 false)
+  ret i32 %1
+}
+
+; CHECK: @test15
+; CHECK: llvm.objectsize
+define i32 @test15(i32 %a) nounwind {
+  switch i32 %a, label %sw.default [
+    i32 1, label %sw.bb
+    i32 2, label %sw.bb1
+  ]
+
+sw.bb:
+  %call = tail call noalias i8* @malloc(i32 3) nounwind
+  br label %sw.epilog
+
+sw.bb1:
+  %call2 = tail call noalias i8* @calloc(i32 2, i32 1) nounwind
+  br label %sw.epilog
+
+sw.default:
+  %call3 = tail call noalias i8* @valloc(i32 3) nounwind
+  br label %sw.epilog
+
+sw.epilog:
+  %b.0 = phi i8* [ %call3, %sw.default ], [ %call2, %sw.bb1 ], [ %call, %sw.bb ]
+  %1 = tail call i32 @llvm.objectsize.i32(i8* %b.0, i1 false)
+  ret i32 %1
+}
+
+; CHECK: @test16
+; CHECK: llvm.objectsize
+define i32 @test16(i8* %a, i32 %n) nounwind {
+  %b = alloca [5 x i8], align 1
+  %c = alloca [5 x i8], align 1
+  switch i32 %n, label %sw.default [
+    i32 1, label %sw.bb
+    i32 2, label %sw.bb1
+  ]
+
+sw.bb:
+  %bp = bitcast [5 x i8]* %b to i8*
+  br label %sw.epilog
+
+sw.bb1:
+  %cp = bitcast [5 x i8]* %c to i8*
+  br label %sw.epilog
+
+sw.default:
+  br label %sw.epilog
+
+sw.epilog:
+  %phi = phi i8* [ %a, %sw.default ], [ %cp, %sw.bb1 ], [ %bp, %sw.bb ]
+  %sz = call i32 @llvm.objectsize.i32(i8* %phi, i1 false)
+  ret i32 %sz
+}
+
+; CHECK: @test17
+; CHECK: ret i32 5
+define i32 @test17(i32 %n) nounwind {
+  %b = alloca [5 x i8], align 1
+  %c = alloca [5 x i8], align 1
+  %bp = bitcast [5 x i8]* %b to i8*
+  switch i32 %n, label %sw.default [
+    i32 1, label %sw.bb
+    i32 2, label %sw.bb1
+  ]
+
+sw.bb:
+  br label %sw.epilog
+
+sw.bb1:
+  %cp = bitcast [5 x i8]* %c to i8*
+  br label %sw.epilog
+
+sw.default:
+  br label %sw.epilog
+
+sw.epilog:
+  %phi = phi i8* [ %bp, %sw.default ], [ %cp, %sw.bb1 ], [ %bp, %sw.bb ]
+  %sz = call i32 @llvm.objectsize.i32(i8* %phi, i1 false)
+  ret i32 %sz
+}
+
+@globalalias = alias internal [60 x i8]* @a
+
+; CHECK: @test18
+; CHECK-NEXT: ret i32 60
+define i32 @test18() {
+  %bc = bitcast [60 x i8]* @globalalias to i8*
+  %1 = call i32 @llvm.objectsize.i32(i8* %bc, i1 false)
+  ret i32 %1
+}
+
+@globalalias2 = alias weak [60 x i8]* @a
+
+; CHECK: @test19
+; CHECK: llvm.objectsize
+define i32 @test19() {
+  %bc = bitcast [60 x i8]* @globalalias2 to i8*
+  %1 = call i32 @llvm.objectsize.i32(i8* %bc, i1 false)
+  ret i32 %1
+}