From: Alexey Samsonov <vonosmas@gmail.com>
Date: Thu, 23 Apr 2015 01:50:45 +0000 (+0000)
Subject: Unify the way we report overflow in increment/decrement operator.
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=8f0ae54cd2da17bbd785f48f240d3e7a37ce6db4;p=clang

Unify the way we report overflow in increment/decrement operator.

Summary:
Make sure signed overflow in "x--" is checked with
llvm.ssub.with.overflow intrinsic and is reported as:
  "-2147483648 - 1 cannot be represented in type 'int'"
instead of:
  "-2147483648 + -1 cannot be represented in type 'int'"
, like we do for unsigned overflow.

Test Plan: clang + compiler-rt regression test suite

Reviewers: rsmith

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D8236

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@235568 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/CGExprScalar.cpp b/lib/CodeGen/CGExprScalar.cpp
index 658bd3e7af..c4dc428ff1 100644
--- a/lib/CodeGen/CGExprScalar.cpp
+++ b/lib/CodeGen/CGExprScalar.cpp
@@ -349,10 +349,9 @@ public:
     return EmitScalarPrePostIncDec(E, LV, true, true);
   }
 
-  llvm::Value *EmitAddConsiderOverflowBehavior(const UnaryOperator *E,
-                                               llvm::Value *InVal,
-                                               llvm::Value *NextVal,
-                                               bool IsInc);
+  llvm::Value *EmitIncDecConsiderOverflowBehavior(const UnaryOperator *E,
+                                                  llvm::Value *InVal,
+                                                  bool IsInc);
 
   llvm::Value *EmitScalarPrePostIncDec(const UnaryOperator *E, LValue LV,
                                        bool isInc, bool isPre);
@@ -1610,26 +1609,32 @@ Value *ScalarExprEmitter::VisitStmtExpr(const StmtExpr *E) {
 //                             Unary Operators
 //===----------------------------------------------------------------------===//
 
-llvm::Value *ScalarExprEmitter::
-EmitAddConsiderOverflowBehavior(const UnaryOperator *E,
-                                llvm::Value *InVal,
-                                llvm::Value *NextVal, bool IsInc) {
+static BinOpInfo createBinOpInfoFromIncDec(const UnaryOperator *E,
+                                           llvm::Value *InVal, bool IsInc) {
+  BinOpInfo BinOp;
+  BinOp.LHS = InVal;
+  BinOp.RHS = llvm::ConstantInt::get(InVal->getType(), 1, false);
+  BinOp.Ty = E->getType();
+  BinOp.Opcode = IsInc ? BO_Add : BO_Sub;
+  BinOp.FPContractable = false;
+  BinOp.E = E;
+  return BinOp;
+}
+
+llvm::Value *ScalarExprEmitter::EmitIncDecConsiderOverflowBehavior(
+    const UnaryOperator *E, llvm::Value *InVal, bool IsInc) {
+  llvm::Value *Amount =
+      llvm::ConstantInt::get(InVal->getType(), IsInc ? 1 : -1, true);
+  StringRef Name = IsInc ? "inc" : "dec";
   switch (CGF.getLangOpts().getSignedOverflowBehavior()) {
   case LangOptions::SOB_Defined:
-    return Builder.CreateAdd(InVal, NextVal, IsInc ? "inc" : "dec");
+    return Builder.CreateAdd(InVal, Amount, Name);
   case LangOptions::SOB_Undefined:
     if (!CGF.SanOpts.has(SanitizerKind::SignedIntegerOverflow))
-      return Builder.CreateNSWAdd(InVal, NextVal, IsInc ? "inc" : "dec");
+      return Builder.CreateNSWAdd(InVal, Amount, Name);
     // Fall through.
   case LangOptions::SOB_Trapping:
-    BinOpInfo BinOp;
-    BinOp.LHS = InVal;
-    BinOp.RHS = NextVal;
-    BinOp.Ty = E->getType();
-    BinOp.Opcode = BO_Add;
-    BinOp.FPContractable = false;
-    BinOp.E = E;
-    return EmitOverflowCheckedBinOp(BinOp);
+    return EmitOverflowCheckedBinOp(createBinOpInfoFromIncDec(E, InVal, IsInc));
   }
   llvm_unreachable("Unknown SignedOverflowBehaviorTy");
 }
@@ -1707,27 +1712,20 @@ ScalarExprEmitter::EmitScalarPrePostIncDec(const UnaryOperator *E, LValue LV,
 
   // Most common case by far: integer increment.
   } else if (type->isIntegerType()) {
-
-    llvm::Value *amt = llvm::ConstantInt::get(value->getType(), amount, true);
-
     // Note that signed integer inc/dec with width less than int can't
     // overflow because of promotion rules; we're just eliding a few steps here.
     bool CanOverflow = value->getType()->getIntegerBitWidth() >=
                        CGF.IntTy->getIntegerBitWidth();
     if (CanOverflow && type->isSignedIntegerOrEnumerationType()) {
-      value = EmitAddConsiderOverflowBehavior(E, value, amt, isInc);
+      value = EmitIncDecConsiderOverflowBehavior(E, value, isInc);
     } else if (CanOverflow && type->isUnsignedIntegerType() &&
                CGF.SanOpts.has(SanitizerKind::UnsignedIntegerOverflow)) {
-      BinOpInfo BinOp;
-      BinOp.LHS = value;
-      BinOp.RHS = llvm::ConstantInt::get(value->getType(), 1, false);
-      BinOp.Ty = E->getType();
-      BinOp.Opcode = isInc ? BO_Add : BO_Sub;
-      BinOp.FPContractable = false;
-      BinOp.E = E;
-      value = EmitOverflowCheckedBinOp(BinOp);
-    } else
+      value =
+          EmitOverflowCheckedBinOp(createBinOpInfoFromIncDec(E, value, isInc));
+    } else {
+      llvm::Value *amt = llvm::ConstantInt::get(value->getType(), amount, true);
       value = Builder.CreateAdd(value, amt, isInc ? "inc" : "dec");
+    }
 
   // Next most common: pointer increment.
   } else if (const PointerType *ptr = type->getAs<PointerType>()) {
diff --git a/test/CodeGen/integer-overflow.c b/test/CodeGen/integer-overflow.c
index eee1da7937..de3b53f4b5 100644
--- a/test/CodeGen/integer-overflow.c
+++ b/test/CodeGen/integer-overflow.c
@@ -52,8 +52,8 @@ void test1() {
   
   // DEFAULT: add nsw i32 {{.*}}, -1
   // WRAPV: add i32 {{.*}}, -1
-  // TRAPV: llvm.sadd.with.overflow.i32({{.*}}, i32 -1)
-  // CATCH_UB: llvm.sadd.with.overflow.i32({{.*}}, i32 -1)
+  // TRAPV: llvm.ssub.with.overflow.i32({{.*}}, i32 1)
+  // CATCH_UB: llvm.ssub.with.overflow.i32({{.*}}, i32 1)
   // TRAPV_HANDLER: foo(
   --a;