Fix __builtin_assume_aligned with too large values.

Code to handle __builtin_assume_aligned was allowing larger values, but
would convert this to unsigned along the way. This patch removes the
EmitAssumeAligned overloads that take unsigned to do away with this
problem.

Additionally, it adds a warning that values greater than 1 <<29 are
ignored by LLVM.

Differential Revision: https://reviews.llvm.org/D68824

llvm-svn: 374450

diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index bcd059b..68f2b37 100644 (file)
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -2853,6 +2853,10 @@ def err_alignment_dependent_typedef_name : Error<
 
 def err_attribute_aligned_too_great : Error<
   "requested alignment must be %0 bytes or smaller">;
+def warn_assume_aligned_too_great
+    : Warning<"requested alignment must be %0 bytes or smaller; assumption "
+              "ignored">,
+      InGroup<DiagGroup<"builtin-assume-aligned-alignment">>;
 def warn_redeclaration_without_attribute_prev_attribute_ignored : Warning<
   "%q0 redeclared without %1 attribute: previous %1 ignored">,
   InGroup<MicrosoftInconsistentDllImport>;

diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
index 0562a62..e6369d8 100644 (file)
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -2048,11 +2048,10 @@ RValue CodeGenFunction::EmitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
 
     Value *AlignmentValue = EmitScalarExpr(E->getArg(1));
     ConstantInt *AlignmentCI = cast<ConstantInt>(AlignmentValue);
-    unsigned Alignment = (unsigned)AlignmentCI->getZExtValue();
 
     EmitAlignmentAssumption(PtrValue, Ptr,
                             /*The expr loc is sufficient.*/ SourceLocation(),
-                            Alignment, OffsetValue);
+                            AlignmentCI, OffsetValue);
     return RValue::get(PtrValue);
   }
   case Builtin::BI__assume:

diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp
index 682a7cc..2ec9e91 100644 (file)
--- a/clang/lib/CodeGen/CGCall.cpp
+++ b/clang/lib/CodeGen/CGCall.cpp
@@ -4569,7 +4569,7 @@ RValue CodeGenFunction::EmitCall(const CGFunctionInfo &CallInfo,
       llvm::Value *Alignment = EmitScalarExpr(AA->getAlignment());
       llvm::ConstantInt *AlignmentCI = cast<llvm::ConstantInt>(Alignment);
       EmitAlignmentAssumption(Ret.getScalarVal(), RetTy, Loc, AA->getLocation(),
-                              AlignmentCI->getZExtValue(), OffsetValue);
+                              AlignmentCI, OffsetValue);
     } else if (const auto *AA = TargetDecl->getAttr<AllocAlignAttr>()) {
       llvm::Value *AlignmentVal = CallArgs[AA->getParamIndex().getLLVMIndex()]
                                       .getRValue(*this)

diff --git a/clang/lib/CodeGen/CGExprScalar.cpp b/clang/lib/CodeGen/CGExprScalar.cpp
index 0b9271b..c7f279d 100644 (file)
--- a/clang/lib/CodeGen/CGExprScalar.cpp
+++ b/clang/lib/CodeGen/CGExprScalar.cpp
@@ -294,8 +294,7 @@ public:
 
     Value *AlignmentValue = CGF.EmitScalarExpr(AVAttr->getAlignment());
     llvm::ConstantInt *AlignmentCI = cast<llvm::ConstantInt>(AlignmentValue);
-    CGF.EmitAlignmentAssumption(V, E, AVAttr->getLocation(),
-                                AlignmentCI->getZExtValue());
+    CGF.EmitAlignmentAssumption(V, E, AVAttr->getLocation(), AlignmentCI);
   }
 
   /// EmitLoadOfLValue - Given an expression with complex type that represents a

diff --git a/clang/lib/CodeGen/CGStmtOpenMP.cpp b/clang/lib/CodeGen/CGStmtOpenMP.cpp
index e50cdb1..fa4304d 100644 (file)
--- a/clang/lib/CodeGen/CGStmtOpenMP.cpp
+++ b/clang/lib/CodeGen/CGStmtOpenMP.cpp
@@ -1519,14 +1519,14 @@ static void emitAlignedClause(CodeGenFunction &CGF,
   if (!CGF.HaveInsertPoint())
     return;
   for (const auto *Clause : D.getClausesOfKind<OMPAlignedClause>()) {
-    unsigned ClauseAlignment = 0;
+    size_t ClauseAlignment = 0;
     if (const Expr *AlignmentExpr = Clause->getAlignment()) {
       auto *AlignmentCI =
           cast<llvm::ConstantInt>(CGF.EmitScalarExpr(AlignmentExpr));
-      ClauseAlignment = static_cast<unsigned>(AlignmentCI->getZExtValue());
+      ClauseAlignment = AlignmentCI->getZExtValue();
     }
     for (const Expr *E : Clause->varlists()) {
-      unsigned Alignment = ClauseAlignment;
+      size_t Alignment = ClauseAlignment;
       if (Alignment == 0) {
         // OpenMP [2.8.1, Description]
         // If no optional parameter is specified, implementation-defined default
@@ -1542,7 +1542,8 @@ static void emitAlignedClause(CodeGenFunction &CGF,
       if (Alignment != 0) {
         llvm::Value *PtrValue = CGF.EmitScalarExpr(E);
         CGF.EmitAlignmentAssumption(
-            PtrValue, E, /*No second loc needed*/ SourceLocation(), Alignment);
+            PtrValue, E, /*No second loc needed*/ SourceLocation(),
+            llvm::ConstantInt::get(CGF.SizeTy, Alignment));
       }
     }
   }

diff --git a/clang/lib/CodeGen/CodeGenFunction.cpp b/clang/lib/CodeGen/CodeGenFunction.cpp
index 41b7f2f..3f9a52a 100644 (file)
--- a/clang/lib/CodeGen/CodeGenFunction.cpp
+++ b/clang/lib/CodeGen/CodeGenFunction.cpp
@@ -2057,24 +2057,9 @@ void CodeGenFunction::EmitAlignmentAssumption(llvm::Value *PtrValue,
 }
 
 void CodeGenFunction::EmitAlignmentAssumption(llvm::Value *PtrValue,
-                                              QualType Ty, SourceLocation Loc,
-                                              SourceLocation AssumptionLoc,
-                                              unsigned Alignment,
-                                              llvm::Value *OffsetValue) {
-  llvm::Value *TheCheck;
-  llvm::Instruction *Assumption = Builder.CreateAlignmentAssumption(
-      CGM.getDataLayout(), PtrValue, Alignment, OffsetValue, &TheCheck);
-  if (SanOpts.has(SanitizerKind::Alignment)) {
-    llvm::Value *AlignmentVal = llvm::ConstantInt::get(IntPtrTy, Alignment);
-    EmitAlignmentAssumptionCheck(PtrValue, Ty, Loc, AssumptionLoc, AlignmentVal,
-                                 OffsetValue, TheCheck, Assumption);
-  }
-}
-
-void CodeGenFunction::EmitAlignmentAssumption(llvm::Value *PtrValue,
                                               const Expr *E,
                                               SourceLocation AssumptionLoc,
-                                              unsigned Alignment,
+                                              llvm::Value *Alignment,
                                               llvm::Value *OffsetValue) {
   if (auto *CE = dyn_cast<CastExpr>(E))
     E = CE->getSubExprAsWritten();

diff --git a/clang/lib/CodeGen/CodeGenFunction.h b/clang/lib/CodeGen/CodeGenFunction.h
index ea78309..bb4fed8 100644 (file)
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/lib/CodeGen/CodeGenFunction.h
@@ -2829,13 +2829,8 @@ public:
                                llvm::Value *Alignment,
                                llvm::Value *OffsetValue = nullptr);
 
-  void EmitAlignmentAssumption(llvm::Value *PtrValue, QualType Ty,
-                               SourceLocation Loc, SourceLocation AssumptionLoc,
-                               unsigned Alignment,
-                               llvm::Value *OffsetValue = nullptr);
-
   void EmitAlignmentAssumption(llvm::Value *PtrValue, const Expr *E,
-                               SourceLocation AssumptionLoc, unsigned Alignment,
+                               SourceLocation AssumptionLoc, llvm::Value *Alignment,
                                llvm::Value *OffsetValue = nullptr);
 
   //===--------------------------------------------------------------------===//

diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
index 07d3648..b35d591 100644 (file)
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -6063,6 +6063,16 @@ bool Sema::SemaBuiltinAssumeAligned(CallExpr *TheCall) {
     if (!Result.isPowerOf2())
       return Diag(TheCall->getBeginLoc(), diag::err_alignment_not_power_of_two)
              << Arg->getSourceRange();
+
+    // FIXME: this should probably use llvm::Value::MaximumAlignment, however
+    // doing so results in a linking issue in GCC in a couple of assemblies.
+    // Alignment calculations can wrap around if it's greater than 2**28.
+    unsigned MaximumAlignment =
+        Context.getTargetInfo().getTriple().isOSBinFormatCOFF() ? 8192
+                                                                : 268435456;
+    if (Result > MaximumAlignment)
+      Diag(TheCall->getBeginLoc(), diag::warn_assume_aligned_too_great)
+          << Arg->getSourceRange() << MaximumAlignment;
   }
 
   if (NumArgs > 2) {

diff --git a/clang/test/Sema/builtin-assume-aligned.c b/clang/test/Sema/builtin-assume-aligned.c
index 057a500..a669ed1 100644 (file)
--- a/clang/test/Sema/builtin-assume-aligned.c
+++ b/clang/test/Sema/builtin-assume-aligned.c
@@ -58,3 +58,7 @@ void *test_no_fn_proto() __attribute__((assume_aligned)); // expected-error {{'a
 void *test_no_fn_proto() __attribute__((assume_aligned())); // expected-error {{'assume_aligned' attribute takes at least 1 argument}}
 void *test_no_fn_proto() __attribute__((assume_aligned(32, 45, 37))); // expected-error {{'assume_aligned' attribute takes no more than 2 arguments}}
 
+int pr43638(int *a) {
+  a = __builtin_assume_aligned(a, 4294967296); // expected-warning {{requested alignment must be 268435456 bytes or smaller; assumption ignored}}
+return a[0];
+}