Inline asm constraints: allow ICE-like pointers for the "n" constraint (PR40890)

Apparently GCC allows this, and there's code relying on it (see bug).

The idea is to allow expression that would have been allowed if they
were cast to int. So I based the code on how such a cast would be done
(the CK_PointerToIntegral case in IntExprEvaluator::VisitCastExpr()).

Differential Revision: https://reviews.llvm.org/D58821

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@355491 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/clang/AST/APValue.h b/include/clang/AST/APValue.h
index 5d26a11177c072aa5dfe59dd6be4e6dbe4c3b92d..de5546f9fd5eafa7b383267841ef7a359a96c6a9 100644 (file)
--- a/include/clang/AST/APValue.h
+++ b/include/clang/AST/APValue.h
@@ -262,6 +262,12 @@ public:
     return const_cast<APValue*>(this)->getInt();
   }
 
+  /// Try to convert this value to an integral constant. This works if it's an
+  /// integer, null pointer, or offset from a null pointer. Returns true on
+  /// success.
+  bool toIntegralConstant(APSInt &Result, QualType SrcTy,
+                          const ASTContext &Ctx) const;
+
   APFloat &getFloat() {
     assert(isFloat() && "Invalid accessor");
     return *(APFloat*)(char*)Data.buffer;

diff --git a/lib/AST/APValue.cpp b/lib/AST/APValue.cpp
index e1876a933dcb5ee68fd43c12235fd75057505053..f9cbf331b28594af7a9f207595f676fe51fdb60d 100644 (file)
--- a/lib/AST/APValue.cpp
+++ b/lib/AST/APValue.cpp
@@ -614,6 +614,26 @@ std::string APValue::getAsString(ASTContext &Ctx, QualType Ty) const {
   return Result;
 }
 
+bool APValue::toIntegralConstant(APSInt &Result, QualType SrcTy,
+                                 const ASTContext &Ctx) const {
+  if (isInt()) {
+    Result = getInt();
+    return true;
+  }
+
+  if (isLValue() && isNullPointer()) {
+    Result = Ctx.MakeIntValue(Ctx.getTargetNullPointerValue(SrcTy), SrcTy);
+    return true;
+  }
+
+  if (isLValue() && !getLValueBase()) {
+    Result = Ctx.MakeIntValue(getLValueOffset().getQuantity(), SrcTy);
+    return true;
+  }
+
+  return false;
+}
+
 const APValue::LValueBase APValue::getLValueBase() const {
   assert(isLValue() && "Invalid accessor");
   return ((const LV*)(const void*)Data.buffer)->Base;

diff --git a/lib/AST/ExprConstant.cpp b/lib/AST/ExprConstant.cpp
index 1a21ad2539da58a8157d8e4e23d4686bd536fdfa..111cffe373ef2230f476f584985e939606ebb618 100644 (file)
--- a/lib/AST/ExprConstant.cpp
+++ b/lib/AST/ExprConstant.cpp
@@ -9872,13 +9872,12 @@ bool IntExprEvaluator::VisitCastExpr(const CastExpr *E) {
       return true;
     }
 
-    uint64_t V;
-    if (LV.isNullPointer())
-      V = Info.Ctx.getTargetNullPointerValue(SrcType);
-    else
-      V = LV.getLValueOffset().getQuantity();
+    APSInt AsInt;
+    APValue V;
+    LV.moveInto(V);
+    if (!V.toIntegralConstant(AsInt, SrcType, Info.Ctx))
+      llvm_unreachable("Can't cast this!");
 
-    APSInt AsInt = Info.Ctx.MakeIntValue(V, SrcType);
     return Success(HandleIntToIntCast(Info, E, DestType, SrcType, AsInt), E);
   }
 

diff --git a/lib/CodeGen/CGStmt.cpp b/lib/CodeGen/CGStmt.cpp
index 5b5113b1e7e451a47a5e1456009ee17afd038aa4..b9905a2b3ccf4cbe318f548127a94a2bc295bb36 100644 (file)
--- a/lib/CodeGen/CGStmt.cpp
+++ b/lib/CodeGen/CGStmt.cpp
@@ -1838,8 +1838,15 @@ llvm::Value* CodeGenFunction::EmitAsmInput(
   // (immediate or symbolic), try to emit it as such.
   if (!Info.allowsRegister() && !Info.allowsMemory()) {
     if (Info.requiresImmediateConstant()) {
-      llvm::APSInt AsmConst = InputExpr->EvaluateKnownConstInt(getContext());
-      return llvm::ConstantInt::get(getLLVMContext(), AsmConst);
+      Expr::EvalResult EVResult;
+      InputExpr->EvaluateAsRValue(EVResult, getContext(), true);
+
+      llvm::APSInt IntResult;
+      if (!EVResult.Val.toIntegralConstant(IntResult, InputExpr->getType(),
+                                           getContext()))
+        llvm_unreachable("Invalid immediate constant!");
+
+      return llvm::ConstantInt::get(getLLVMContext(), IntResult);
     }
 
     Expr::EvalResult Result;

diff --git a/lib/Sema/SemaStmtAsm.cpp b/lib/Sema/SemaStmtAsm.cpp
index 0d38f48aa5a51031967499883d1f47077b706c56..8c6012573c64fb5c0cd37f2bd2efb521803b02c8 100644 (file)
--- a/lib/Sema/SemaStmtAsm.cpp
+++ b/lib/Sema/SemaStmtAsm.cpp
@@ -385,11 +385,20 @@ StmtResult Sema::ActOnGCCAsmStmt(SourceLocation AsmLoc, bool IsSimple,
           return StmtError(
               Diag(InputExpr->getBeginLoc(), diag::err_asm_immediate_expected)
               << Info.getConstraintStr() << InputExpr->getSourceRange());
-        llvm::APSInt Result = EVResult.Val.getInt();
-        if (!Info.isValidAsmImmediate(Result))
+
+        // For compatibility with GCC, we also allow pointers that would be
+        // integral constant expressions if they were cast to int.
+        llvm::APSInt IntResult;
+        if (!EVResult.Val.toIntegralConstant(IntResult, InputExpr->getType(),
+                                             Context))
+          return StmtError(
+              Diag(InputExpr->getBeginLoc(), diag::err_asm_immediate_expected)
+              << Info.getConstraintStr() << InputExpr->getSourceRange());
+
+        if (!Info.isValidAsmImmediate(IntResult))
           return StmtError(Diag(InputExpr->getBeginLoc(),
                                 diag::err_invalid_asm_value_for_constraint)
-                           << Result.toString(10) << Info.getConstraintStr()
+                           << IntResult.toString(10) << Info.getConstraintStr()
                            << InputExpr->getSourceRange());
       }
 

diff --git a/test/CodeGen/x86-64-inline-asm.c b/test/CodeGen/x86-64-inline-asm.c
index bb46eda633b705675c05f32969d299022d5a3a9b..79c1bd95f38b5477de7a3c442f35b124756005bc 100644 (file)
--- a/test/CodeGen/x86-64-inline-asm.c
+++ b/test/CodeGen/x86-64-inline-asm.c
@@ -1,6 +1,7 @@
 // REQUIRES: x86-registered-target
 // RUN: %clang_cc1 -triple x86_64 %s -S -o /dev/null -DWARN -verify
 // RUN: %clang_cc1 -triple x86_64 %s -S -o /dev/null -Werror -verify
+// RUN: %clang_cc1 -triple x86_64-linux-gnu %s -S -o - | FileCheck %s
 void f() {
   asm("movaps %xmm3, (%esi, 2)");
 // expected-note@1 {{instantiated into assembly here}}
@@ -15,3 +16,17 @@ static unsigned var[1] = {};
 void g(void) { asm volatile("movd %%xmm0, %0"
                             :
                             : "m"(var)); }
+
+void pr40890(void) {
+  struct s {
+    int a, b;
+  } s;
+  __asm__ __volatile__("\n#define S_A abcd%0\n" : : "n"(&((struct s*)0)->a));
+  __asm__ __volatile__("\n#define S_B abcd%0\n" : : "n"(&((struct s*)0)->b));
+  __asm__ __volatile__("\n#define BEEF abcd%0\n" : : "n"((int*)0xdeadbeeeeeef));
+
+// CHECK-LABEL: pr40890
+// CHECK: #define S_A abcd$0
+// CHECK: #define S_B abcd$4
+// CHECK: #define BEEF abcd$244837814038255
+}

diff --git a/test/Sema/inline-asm-validate-x86.c b/test/Sema/inline-asm-validate-x86.c
index 026216c92a455294a1fd52d7661461128fdb0f10..c6fa2e1b4fa8365ac9dbe31a815ae75956d035f0 100644 (file)
--- a/test/Sema/inline-asm-validate-x86.c
+++ b/test/Sema/inline-asm-validate-x86.c
@@ -1,5 +1,5 @@
 // RUN: %clang_cc1 -triple i686 -fsyntax-only -verify %s
-// RUN: %clang_cc1 -triple x86_64 -fsyntax-only -verify %s
+// RUN: %clang_cc1 -triple x86_64 -fsyntax-only -verify -DAMD64 %s
 
 void I(int i, int j) {
   static const int BelowMin = -1;
@@ -137,3 +137,21 @@ void O(int i, int j) {
           : "0"(i), "O"(64)); // expected-no-error
 }
 
+void pr40890(void) {
+  struct s {
+    int a, b;
+  };
+  static struct s s;
+  // This null pointer can be used as an integer constant expression.
+  __asm__ __volatile__("\n#define S_A abcd%0\n" : : "n"(&((struct s*)0)->a));
+  // This offset-from-null pointer can be used as an integer constant expression.
+  __asm__ __volatile__("\n#define S_B abcd%0\n" : : "n"(&((struct s*)0)->b));
+  // This pointer cannot be used as an integer constant expression.
+  __asm__ __volatile__("\n#define GLOBAL_A abcd%0\n" : : "n"(&s.a)); // expected-error{{constraint 'n' expects an integer constant expression}}
+  // Floating-point is also not okay.
+  __asm__ __volatile__("\n#define PI abcd%0\n" : : "n"(3.14f)); // expected-error{{constraint 'n' expects an integer constant expression}}
+#ifdef AMD64
+  // This arbitrary pointer is fine.
+  __asm__ __volatile__("\n#define BEEF abcd%0\n" : : "n"((int*)0xdeadbeeeeeef));
+#endif
+}