Reland r374450 with Richard Smith's comments and test fixed.

The behavior from the original patch has changed, since we're no longer
allowing LLVM to just ignore the alignment.  Instead, we're just
assuming the maximum possible alignment.

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

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@374562 91177308-0d34-0410-b5e6-96231b3b80d8

13 files changed, 46 insertions, 41 deletions

diff --git a/include/clang/Basic/DiagnosticSemaKinds.td b/include/clang/Basic/DiagnosticSemaKinds.td
index bcd059be91..47a1deef98 100644
--- a/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/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; maximum "
+              "alignment assumed">,
+      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/lib/CodeGen/CGBuiltin.cpp b/lib/CodeGen/CGBuiltin.cpp
index 0562a623ae..ddff595987 100644
--- a/lib/CodeGen/CGBuiltin.cpp
+++ b/lib/CodeGen/CGBuiltin.cpp
@@ -2048,11 +2048,13 @@ RValue CodeGenFunction::EmitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
 
     Value *AlignmentValue = EmitScalarExpr(E->getArg(1));
     ConstantInt *AlignmentCI = cast<ConstantInt>(AlignmentValue);
-    unsigned Alignment = (unsigned)AlignmentCI->getZExtValue();
+    if (AlignmentCI->getValue().ugt(llvm::Value::MaximumAlignment))
+      AlignmentCI = ConstantInt::get(AlignmentCI->getType(),
+                                     llvm::Value::MaximumAlignment);
 
     EmitAlignmentAssumption(PtrValue, Ptr,
                             /*The expr loc is sufficient.*/ SourceLocation(),
-                            Alignment, OffsetValue);
+                            AlignmentCI, OffsetValue);
     return RValue::get(PtrValue);
   }
   case Builtin::BI__assume:
diff --git a/lib/CodeGen/CGCall.cpp b/lib/CodeGen/CGCall.cpp
index 682a7ccb49..2ec9e91e31 100644
--- a/lib/CodeGen/CGCall.cpp
+++ b/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/lib/CodeGen/CGExprScalar.cpp b/lib/CodeGen/CGExprScalar.cpp
index 0b9271b1d3..c7f279d28e 100644
--- a/lib/CodeGen/CGExprScalar.cpp
+++ b/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/lib/CodeGen/CGStmtOpenMP.cpp b/lib/CodeGen/CGStmtOpenMP.cpp
index e50cdb1b67..2a4e89b9e2 100644
--- a/lib/CodeGen/CGStmtOpenMP.cpp
+++ b/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;
+    llvm::APInt ClauseAlignment(64, 0);
     if (const Expr *AlignmentExpr = Clause->getAlignment()) {
       auto *AlignmentCI =
           cast<llvm::ConstantInt>(CGF.EmitScalarExpr(AlignmentExpr));
-      ClauseAlignment = static_cast<unsigned>(AlignmentCI->getZExtValue());
+      ClauseAlignment = AlignmentCI->getValue();
     }
     for (const Expr *E : Clause->varlists()) {
-      unsigned Alignment = ClauseAlignment;
+      llvm::APInt Alignment(ClauseAlignment);
       if (Alignment == 0) {
         // OpenMP [2.8.1, Description]
         // If no optional parameter is specified, implementation-defined default
@@ -1537,12 +1537,13 @@ static void emitAlignedClause(CodeGenFunction &CGF,
                     E->getType()->getPointeeType()))
                 .getQuantity();
       }
-      assert((Alignment == 0 || llvm::isPowerOf2_32(Alignment)) &&
+      assert((Alignment == 0 || Alignment.isPowerOf2()) &&
              "alignment is not power of 2");
       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.getLLVMContext(), Alignment));
       }
     }
   }
diff --git a/lib/CodeGen/CodeGenFunction.cpp b/lib/CodeGen/CodeGenFunction.cpp
index 41b7f2f4b1..3f9a52ab76 100644
--- a/lib/CodeGen/CodeGenFunction.cpp
+++ b/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/lib/CodeGen/CodeGenFunction.h b/lib/CodeGen/CodeGenFunction.h
index ea78309a06..bb4fed8083 100644
--- a/lib/CodeGen/CodeGenFunction.h
+++ b/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/lib/Sema/SemaChecking.cpp b/lib/Sema/SemaChecking.cpp
index 07d3648dc9..dca81d1d27 100644
--- a/lib/Sema/SemaChecking.cpp
+++ b/lib/Sema/SemaChecking.cpp
@@ -6063,6 +6063,12 @@ bool Sema::SemaBuiltinAssumeAligned(CallExpr *TheCall) {
     if (!Result.isPowerOf2())
       return Diag(TheCall->getBeginLoc(), diag::err_alignment_not_power_of_two)
              << Arg->getSourceRange();
+
+    // Alignment calculations can wrap around if it's greater than 2**29.
+    unsigned MaximumAlignment = 536870912;
+    if (Result > MaximumAlignment)
+      Diag(TheCall->getBeginLoc(), diag::warn_assume_aligned_too_great)
+          << Arg->getSourceRange() << MaximumAlignment;
   }
 
   if (NumArgs > 2) {
diff --git a/test/CodeGen/builtin-assume-aligned.c b/test/CodeGen/builtin-assume-aligned.c
index 1d807a40ca..f6a89a20ec 100644
--- a/test/CodeGen/builtin-assume-aligned.c
+++ b/test/CodeGen/builtin-assume-aligned.c
@@ -65,3 +65,12 @@ int test6() {
 // CHECK: call void @llvm.assume(i1 [[MASKCOND6]])
 }
 
+// CHECK-LABEL: @pr43638
+int pr43638(int *a) {
+  a = __builtin_assume_aligned(a, 4294967296);
+return a[0];
+// CHECK: [[PTRINT7:%.+]] = ptrtoint
+// CHECK: [[MASKEDPTR7:%.+]] = and i64 [[PTRINT7]], 536870911
+// CHECK: [[MASKCOND7:%.+]] = icmp eq i64 [[MASKEDPTR7]], 0
+// CHECK: call void @llvm.assume(i1 [[MASKCOND7]])
+}
diff --git a/test/CodeGen/catch-alignment-assumption-builtin_assume_aligned-three-params-variable.cpp b/test/CodeGen/catch-alignment-assumption-builtin_assume_aligned-three-params-variable.cpp
index 4384b9ce72..4306e322f5 100644
--- a/test/CodeGen/catch-alignment-assumption-builtin_assume_aligned-three-params-variable.cpp
+++ b/test/CodeGen/catch-alignment-assumption-builtin_assume_aligned-three-params-variable.cpp
@@ -18,13 +18,13 @@ void *caller(char **x, unsigned long offset) {
   // CHECK-NEXT:                        %[[OFFSET_RELOADED:.*]] = load i64, i64* %[[OFFSET_ADDR]], align 8
   // CHECK-NEXT:                        %[[PTRINT:.*]] = ptrtoint i8* %[[BITCAST]] to i64
   // CHECK-NEXT:                        %[[OFFSETPTR:.*]] = sub i64 %[[PTRINT]], %[[OFFSET_RELOADED]]
-  // CHECK-NEXT:                        %[[MASKEDPTR:.*]] = and i64 %[[OFFSETPTR]], 2147483647
+  // CHECK-NEXT:                        %[[MASKEDPTR:.*]] = and i64 %[[OFFSETPTR]], 536870911
   // CHECK-NEXT:                        %[[MASKCOND:.*]] = icmp eq i64 %[[MASKEDPTR]], 0
   // CHECK-SANITIZE-NEXT:               %[[PTRINT_DUP:.*]] = ptrtoint i8* %[[BITCAST]] to i64, !nosanitize
   // CHECK-SANITIZE-NEXT:               br i1 %[[MASKCOND]], label %[[CONT:.*]], label %[[HANDLER_ALIGNMENT_ASSUMPTION:[^,]+]],{{.*}} !nosanitize
   // CHECK-SANITIZE:                  [[HANDLER_ALIGNMENT_ASSUMPTION]]:
-  // CHECK-SANITIZE-NORECOVER-NEXT:     call void @__ubsan_handle_alignment_assumption_abort(i8* bitcast ({ {{{.*}}}, {{{.*}}}, {{{.*}}}* }* @[[LINE_100_ALIGNMENT_ASSUMPTION]] to i8*), i64 %[[PTRINT_DUP]], i64 2147483648, i64 %[[OFFSET_RELOADED]]){{.*}}, !nosanitize
-  // CHECK-SANITIZE-RECOVER-NEXT:       call void @__ubsan_handle_alignment_assumption(i8* bitcast ({ {{{.*}}}, {{{.*}}}, {{{.*}}}* }* @[[LINE_100_ALIGNMENT_ASSUMPTION]] to i8*), i64 %[[PTRINT_DUP]], i64 2147483648, i64 %[[OFFSET_RELOADED]]){{.*}}, !nosanitize
+  // CHECK-SANITIZE-NORECOVER-NEXT:     call void @__ubsan_handle_alignment_assumption_abort(i8* bitcast ({ {{{.*}}}, {{{.*}}}, {{{.*}}}* }* @[[LINE_100_ALIGNMENT_ASSUMPTION]] to i8*), i64 %[[PTRINT_DUP]], i64 536870912, i64 %[[OFFSET_RELOADED]]){{.*}}, !nosanitize
+  // CHECK-SANITIZE-RECOVER-NEXT:       call void @__ubsan_handle_alignment_assumption(i8* bitcast ({ {{{.*}}}, {{{.*}}}, {{{.*}}}* }* @[[LINE_100_ALIGNMENT_ASSUMPTION]] to i8*), i64 %[[PTRINT_DUP]], i64 536870912, i64 %[[OFFSET_RELOADED]]){{.*}}, !nosanitize
   // CHECK-SANITIZE-TRAP-NEXT:          call void @llvm.trap(){{.*}}, !nosanitize
   // CHECK-SANITIZE-UNREACHABLE-NEXT:   unreachable, !nosanitize
   // CHECK-SANITIZE:                  [[CONT]]:
diff --git a/test/CodeGen/catch-alignment-assumption-builtin_assume_aligned-three-params.cpp b/test/CodeGen/catch-alignment-assumption-builtin_assume_aligned-three-params.cpp
index 18a573429d..27f53e92be 100644
--- a/test/CodeGen/catch-alignment-assumption-builtin_assume_aligned-three-params.cpp
+++ b/test/CodeGen/catch-alignment-assumption-builtin_assume_aligned-three-params.cpp
@@ -15,13 +15,13 @@ void *caller(char **x) {
   // CHECK-NEXT:                        %[[BITCAST:.*]] = bitcast i8** %[[X_RELOADED]] to i8*
   // CHECK-NEXT:                        %[[PTRINT:.*]] = ptrtoint i8* %[[BITCAST]] to i64
   // CHECK-NEXT:                        %[[OFFSETPTR:.*]] = sub i64 %[[PTRINT]], 42
-  // CHECK-NEXT:                        %[[MASKEDPTR:.*]] = and i64 %[[OFFSETPTR]], 2147483647
+  // CHECK-NEXT:                        %[[MASKEDPTR:.*]] = and i64 %[[OFFSETPTR]], 536870911
   // CHECK-NEXT:                        %[[MASKCOND:.*]] = icmp eq i64 %[[MASKEDPTR]], 0
   // CHECK-SANITIZE-NEXT:               %[[PTRINT_DUP:.*]] = ptrtoint i8* %[[BITCAST]] to i64, !nosanitize
   // CHECK-SANITIZE-NEXT:               br i1 %[[MASKCOND]], label %[[CONT:.*]], label %[[HANDLER_ALIGNMENT_ASSUMPTION:[^,]+]],{{.*}} !nosanitize
   // CHECK-SANITIZE:                  [[HANDLER_ALIGNMENT_ASSUMPTION]]:
-  // CHECK-SANITIZE-NORECOVER-NEXT:     call void @__ubsan_handle_alignment_assumption_abort(i8* bitcast ({ {{{.*}}}, {{{.*}}}, {{{.*}}}* }* @[[LINE_100_ALIGNMENT_ASSUMPTION]] to i8*), i64 %[[PTRINT_DUP]], i64 2147483648, i64 42){{.*}}, !nosanitize
-  // CHECK-SANITIZE-RECOVER-NEXT:       call void @__ubsan_handle_alignment_assumption(i8* bitcast ({ {{{.*}}}, {{{.*}}}, {{{.*}}}* }* @[[LINE_100_ALIGNMENT_ASSUMPTION]] to i8*), i64 %[[PTRINT_DUP]], i64 2147483648, i64 42){{.*}}, !nosanitize
+  // CHECK-SANITIZE-NORECOVER-NEXT:     call void @__ubsan_handle_alignment_assumption_abort(i8* bitcast ({ {{{.*}}}, {{{.*}}}, {{{.*}}}* }* @[[LINE_100_ALIGNMENT_ASSUMPTION]] to i8*), i64 %[[PTRINT_DUP]], i64 536870912, i64 42){{.*}}, !nosanitize
+  // CHECK-SANITIZE-RECOVER-NEXT:       call void @__ubsan_handle_alignment_assumption(i8* bitcast ({ {{{.*}}}, {{{.*}}}, {{{.*}}}* }* @[[LINE_100_ALIGNMENT_ASSUMPTION]] to i8*), i64 %[[PTRINT_DUP]], i64 536870912, i64 42){{.*}}, !nosanitize
   // CHECK-SANITIZE-TRAP-NEXT:          call void @llvm.trap(){{.*}}, !nosanitize
   // CHECK-SANITIZE-UNREACHABLE-NEXT:   unreachable, !nosanitize
   // CHECK-SANITIZE:                  [[CONT]]:
diff --git a/test/CodeGen/catch-alignment-assumption-builtin_assume_aligned-two-params.cpp b/test/CodeGen/catch-alignment-assumption-builtin_assume_aligned-two-params.cpp
index fe4384752c..5412270f37 100644
--- a/test/CodeGen/catch-alignment-assumption-builtin_assume_aligned-two-params.cpp
+++ b/test/CodeGen/catch-alignment-assumption-builtin_assume_aligned-two-params.cpp
@@ -14,13 +14,13 @@ void *caller(char **x) {
   // CHECK-NEXT:                        %[[X_RELOADED:.*]] = load i8**, i8*** %[[X_ADDR]], align 8
   // CHECK-NEXT:                        %[[BITCAST:.*]] = bitcast i8** %[[X_RELOADED]] to i8*
   // CHECK-NEXT:                        %[[PTRINT:.*]] = ptrtoint i8* %[[BITCAST]] to i64
-  // CHECK-NEXT:                        %[[MASKEDPTR:.*]] = and i64 %[[PTRINT]], 2147483647
+  // CHECK-NEXT:                        %[[MASKEDPTR:.*]] = and i64 %[[PTRINT]], 536870911
   // CHECK-NEXT:                        %[[MASKCOND:.*]] = icmp eq i64 %[[MASKEDPTR]], 0
   // CHECK-SANITIZE-NEXT:               %[[PTRINT_DUP:.*]] = ptrtoint i8* %[[BITCAST]] to i64, !nosanitize
   // CHECK-SANITIZE-NEXT:               br i1 %[[MASKCOND]], label %[[CONT:.*]], label %[[HANDLER_ALIGNMENT_ASSUMPTION:[^,]+]],{{.*}} !nosanitize
   // CHECK-SANITIZE:                  [[HANDLER_ALIGNMENT_ASSUMPTION]]:
-  // CHECK-SANITIZE-NORECOVER-NEXT:     call void @__ubsan_handle_alignment_assumption_abort(i8* bitcast ({ {{{.*}}}, {{{.*}}}, {{{.*}}}* }* @[[LINE_100_ALIGNMENT_ASSUMPTION]] to i8*), i64 %[[PTRINT_DUP]], i64 2147483648, i64 0){{.*}}, !nosanitize
-  // CHECK-SANITIZE-RECOVER-NEXT:       call void @__ubsan_handle_alignment_assumption(i8* bitcast ({ {{{.*}}}, {{{.*}}}, {{{.*}}}* }* @[[LINE_100_ALIGNMENT_ASSUMPTION]] to i8*), i64 %[[PTRINT_DUP]], i64 2147483648, i64 0){{.*}}, !nosanitize
+  // CHECK-SANITIZE-NORECOVER-NEXT:     call void @__ubsan_handle_alignment_assumption_abort(i8* bitcast ({ {{{.*}}}, {{{.*}}}, {{{.*}}}* }* @[[LINE_100_ALIGNMENT_ASSUMPTION]] to i8*), i64 %[[PTRINT_DUP]], i64 536870912, i64 0){{.*}}, !nosanitize
+  // CHECK-SANITIZE-RECOVER-NEXT:       call void @__ubsan_handle_alignment_assumption(i8* bitcast ({ {{{.*}}}, {{{.*}}}, {{{.*}}}* }* @[[LINE_100_ALIGNMENT_ASSUMPTION]] to i8*), i64 %[[PTRINT_DUP]], i64 536870912, i64 0){{.*}}, !nosanitize
   // CHECK-SANITIZE-TRAP-NEXT:          call void @llvm.trap(){{.*}}, !nosanitize
   // CHECK-SANITIZE-UNREACHABLE-NEXT:   unreachable, !nosanitize
   // CHECK-SANITIZE:                  [[CONT]]:
diff --git a/test/Sema/builtin-assume-aligned.c b/test/Sema/builtin-assume-aligned.c
index 057a500b32..9411cb4e63 100644
--- a/test/Sema/builtin-assume-aligned.c
+++ b/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 536870912 bytes or smaller; maximum alignment assumed}}
+return a[0];
+}