Fix miscompilation regarding VLAs; subscription of VLA pointers was incorrect.

Fixes rdar://8644873 & http://llvm.org/PR8567.

llvm-svn: 118468

2 files changed, 18 insertions, 8 deletions

diff --git a/clang/lib/CodeGen/CGExpr.cpp b/clang/lib/CodeGen/CGExpr.cpp
index 1d86036c797..355c18f79c5 100644
--- a/clang/lib/CodeGen/CGExpr.cpp
+++ b/clang/lib/CodeGen/CGExpr.cpp
@@ -1433,17 +1433,14 @@ LValue CodeGenFunction::EmitArraySubscriptExpr(const ArraySubscriptExpr *E) {
 
     Idx = Builder.CreateMul(Idx, VLASize);
 
-    QualType BaseType = getContext().getBaseElementType(VAT);
+    const llvm::Type *i8PTy = llvm::Type::getInt8PtrTy(VMContext);
 
-    CharUnits BaseTypeSize = getContext().getTypeSizeInChars(BaseType);
-    Idx = Builder.CreateUDiv(Idx,
-                             llvm::ConstantInt::get(Idx->getType(),
-                                 BaseTypeSize.getQuantity()));
-    
     // The base must be a pointer, which is not an aggregate.  Emit it.
     llvm::Value *Base = EmitScalarExpr(E->getBase());
     
-    Address = Builder.CreateInBoundsGEP(Base, Idx, "arrayidx");
+    Address = Builder.CreateInBoundsGEP(Builder.CreateBitCast(Base, i8PTy),
+                                        Idx, "arrayidx");
+    Address = Builder.CreateBitCast(Address, Base->getType());
   } else if (const ObjCObjectType *OIT = E->getType()->getAs<ObjCObjectType>()){
     // Indexing over an interface, as in "NSString *P; P[4];"
     llvm::Value *InterfaceSize =
diff --git a/clang/test/CodeGen/vla.c b/clang/test/CodeGen/vla.c
index fa7a22fd0bd..f1f5a70a5e6 100644
--- a/clang/test/CodeGen/vla.c
+++ b/clang/test/CodeGen/vla.c
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 %s -emit-llvm -o - | FileCheck %s
+// RUN: %clang_cc1 -triple i386-unknown-unknown %s -emit-llvm -o - | FileCheck %s
 
 int b(char* x);
 
@@ -85,3 +85,16 @@ int test2(int n)
   return GLOB;
 }
 
+// http://llvm.org/PR8567
+// CHECK: define double @test_PR8567
+double test_PR8567(int n, double (*p)[n][5]) {
+  // CHECK: store [[vla_type:.*]] %p,
+  // CHECK: load i32* %n
+  // CHECK-NEXT: mul i32 40
+  // CHECK-NEXT: [[byte_idx:%.*]] = mul i32 1
+  // CHECK-NEXT: [[tmp_1:%.*]] = load [[vla_type]]*
+  // CHECK-NEXT: [[tmp_2:%.*]] = bitcast [[vla_type]] [[tmp_1]] to i8*
+  // CHECK-NEXT: [[idx:%.*]] = getelementptr inbounds i8* [[tmp_2]], i32 [[byte_idx]]
+  // CHECK-NEXT: bitcast i8* [[idx]] to [[vla_type]]
+ return p[1][2][3];
+}