Make va_arg on x86-64 compute alignment the same way as argument passing.

Fixes <rdar://problem/10463281>.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@144966 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/TargetInfo.cpp b/lib/CodeGen/TargetInfo.cpp
index 88f8579b9aa2ff98378402fda0fff84df390d781..33291dd5527b1a92894434b9b371d4a2675e3b58 100644 (file)
--- a/lib/CodeGen/TargetInfo.cpp
+++ b/lib/CodeGen/TargetInfo.cpp
@@ -1983,19 +1983,17 @@ static llvm::Value *EmitVAArgFromMemory(llvm::Value *VAListAddr,
 
   // AMD64-ABI 3.5.7p5: Step 7. Align l->overflow_arg_area upwards to a 16
   // byte boundary if alignment needed by type exceeds 8 byte boundary.
+  // It isn't stated explicitly in the standard, but in practice we use
+  // alignment greater than 16 where necessary.
   uint64_t Align = CGF.getContext().getTypeAlign(Ty) / 8;
   if (Align > 8) {
-    // Note that we follow the ABI & gcc here, even though the type
-    // could in theory have an alignment greater than 16. This case
-    // shouldn't ever matter in practice.
-
-    // overflow_arg_area = (overflow_arg_area + 15) & ~15;
+    // overflow_arg_area = (overflow_arg_area + align - 1) & -align;
     llvm::Value *Offset =
-      llvm::ConstantInt::get(CGF.Int32Ty, 15);
+      llvm::ConstantInt::get(CGF.Int64Ty, Align - 1);
     overflow_arg_area = CGF.Builder.CreateGEP(overflow_arg_area, Offset);
     llvm::Value *AsInt = CGF.Builder.CreatePtrToInt(overflow_arg_area,
                                                     CGF.Int64Ty);
-    llvm::Value *Mask = llvm::ConstantInt::get(CGF.Int64Ty, ~15LL);
+    llvm::Value *Mask = llvm::ConstantInt::get(CGF.Int64Ty, -(uint64_t)Align);
     overflow_arg_area =
       CGF.Builder.CreateIntToPtr(CGF.Builder.CreateAnd(AsInt, Mask),
                                  overflow_arg_area->getType(),

diff --git a/test/CodeGen/x86_64-arguments.c b/test/CodeGen/x86_64-arguments.c
index 8571ac9655528052ff7d5912157ea6c54ca85a5a..ea7dd79c790919dd8c1520e6b7dbc0fb98ad89aa 100644 (file)
--- a/test/CodeGen/x86_64-arguments.c
+++ b/test/CodeGen/x86_64-arguments.c
@@ -304,3 +304,17 @@ extern void func42(SA s);
 void func43(SA s) {
   func42(s);
 }
+
+// CHECK: define i32 @f44
+// CHECK: ptrtoint
+// CHECK-NEXT: and {{.*}}, -32
+// CHECK-NEXT: inttoptr
+typedef int T44 __attribute((vector_size(32)));
+struct s44 { T44 x; int y; };
+int f44(int i, ...) {
+  __builtin_va_list ap;
+  __builtin_va_start(ap, i);
+  struct s44 s = __builtin_va_arg(ap, struct s44);
+  __builtin_va_end(ap);
+  return s.y;
+}