Relax assertion in x86_64 byval argument handling for 32-bit pointers

[dschuff]

Summary

Byval argument pair formation assumes that if a type is less than 8 bytes
it must be an integer and not a pointer, which is not true for x32 and NaCl.

Relax the assertion and add a test for a codegen case that triggered it.

[jvoung]

lib/CodeGen/TargetInfo.cpp

2500–2501

For the old "two sorts of types..." comment, technically a pointer type is still a separate type from i8/i16/i32, so it would be worth updating the comment for x32 pointers.

I assume that the rest of the code knows how to cast a pointer type to the wider i64 type.

[dschuff]

• update comment

lib/CodeGen/TargetInfo.cpp

2500–2501

Updated the comment.
And yes, the rest of the code handles this case just fine.

[jvoung]

LGTM

[dschuff]

Oops, this was rL240600 and rL240601 because I fail at git-svn.

lib/CodeGen/TargetInfo.cpp

GetX86_64ByValArgumentPair(llvm::Type *Lo, llvm::Type *Hi,
   unsigned HiAlign = TD.getABITypeAlignment(Hi);
   unsigned HiStart = llvm::RoundUpToAlignment(LoSize, HiAlign);
   assert(HiStart != 0 && HiStart <= 8 && "Invalid x86-64 argument pair!");
 
   // To handle this, we have to increase the size of the low part so that the
   // second element will start at an 8 byte offset.  We can't increase the size
   // of the second element because it might make us access off the end of the
   // struct.
   if (HiStart != 8) {
-    // There are only two sorts of types the ABI generation code can produce for
-    // the low part of a pair that aren't 8 bytes in size: float or i8/i16/i32.
+    // There are usually two sorts of types the ABI generation code can produce
+    // for the low part of a pair that aren't 8 bytes in size: float or
+    // i8/i16/i32.  This can also include pointers when they are 32-bit (X32 and
+    // NaCl).
     // Promote these to a larger type.
     if (Lo->isFloatTy())
       Lo = llvm::Type::getDoubleTy(Lo->getContext());
     else {
-      assert(Lo->isIntegerTy() && "Invalid/unknown lo type");
+      assert((Lo->isIntegerTy() || Lo->isPointerTy())
+             && "Invalid/unknown lo type");
       Lo = llvm::Type::getInt64Ty(Lo->getContext());
     }
   }
 
   llvm::StructType *Result = llvm::StructType::get(Lo, Hi, nullptr);
 
 
   // Verify that the second element is at an 8-byte offset.

test/CodeGenCXX/x86_64-arguments-nacl-x32.cpp

-// RUN: %clang_cc1 -triple x86_64-unknown-nacl -emit-llvm -o - %s | FileCheck %s
-// RUN: %clang_cc1 -triple=x86_64-unknown-linux-gnux32 -emit-llvm -o - %s | FileCheck %s
+// RUN: %clang_cc1 -std=c++11 -triple x86_64-unknown-nacl -emit-llvm -o - %s | FileCheck %s
+// RUN: %clang_cc1 -std=c++11 -triple=x86_64-unknown-linux-gnux32 -emit-llvm -o - %s | FileCheck %s
 
 struct test_struct {};
 typedef int test_struct::* test_struct_mdp;
 typedef int (test_struct::*test_struct_mfp)();
 
 // CHECK-LABEL: define i32 @{{.*}}f_mdp{{.*}}(i32 %a)
 test_struct_mdp f_mdp(test_struct_mdp a) { return a; }
 

 
 // CHECK-LABEL: define void @{{.*}}f_struct_with_mfp_too_much{{.*}}({{.*}} byval {{.*}} %a, i32 %x)
 struct struct_with_mfp_too_much {
   char *a; char *b; char *c; test_struct_mfp d;
 };
 void f_struct_with_mfp_too_much(struct_with_mfp_too_much a, int x) {
   (void)a;
 }
+
+/* Struct containing an empty struct */
+typedef struct { int* a; test_struct x; double *b; } struct_with_empty;
+
+// CHECK-LABEL: define void @{{.*}}f_pass_struct_with_empty{{.*}}(i64 %x{{.*}}, double* %x
+void f_pass_struct_with_empty(struct_with_empty x) {
+  (void) x;
+}
+
+// CHECK-LABEL: define { i64, double* } @{{.*}}f_return_struct_with_empty
+struct_with_empty f_return_struct_with_empty() {
+  return {0, {}, 0};
+}