[x32/NaCl] Check if method pointers straddle an eightbyte to classify Hi

Summary:
Currently, with struct my_struct { int x; method_ptr y; };
a call to foo(my_struct s) may end up dropping the last 4 bytes
of the method pointer for x86_64 NaCl and x32.

When checking Has64BitPointers, also check if the method pointer
straddles an eightbyte boundary and classify Hi as well as Lo if needed.

Test Plan: test/CodeGenCXX/x86_64-arguments-nacl-x32.cpp

Reviewers: dschuff, pavel.v.chupin

Subscribers: jfb

Differential Revision: http://reviews.llvm.org/D5555

llvm-svn: 218889

clang/lib/CodeGen/TargetInfo.cpp

@@ -1695,10 +1695,25 @@ void X86_64ABIInfo::classify(QualType Ty, uint64_t OffsetBase,
   }
 
   if (Ty->isMemberPointerType()) {
-    if (Ty->isMemberFunctionPointerType() && Has64BitPointers)
-      Lo = Hi = Integer;
-    else
+    if (Ty->isMemberFunctionPointerType()) {
+      if (Has64BitPointers) {
+        // If Has64BitPointers, this is an {i64, i64}, so classify both
+        // Lo and Hi now.
+        Lo = Hi = Integer;
+      } else {
+        // Otherwise, with 32-bit pointers, this is an {i32, i32}. If that
+        // straddles an eightbyte boundary, Hi should be classified as well.
+        uint64_t EB_FuncPtr = (OffsetBase) / 64;
+        uint64_t EB_ThisAdj = (OffsetBase + 64 - 1) / 64;
+        if (EB_FuncPtr != EB_ThisAdj) {
+          Lo = Hi = Integer;
+        } else {
+          Current = Integer;
+        }
+      }
+    } else {
       Current = Integer;
+    }
     return;
   }
 

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

@@ -0,0 +1,44 @@
+// 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
+
+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 {{.*}} @{{.*}}f_mfp{{.*}}(i64 %a.coerce)
+test_struct_mfp f_mfp(test_struct_mfp a) { return a; }
+
+// A struct with <= 12 bytes before a member data pointer should still
+// be allowed in registers, since the member data pointer is only 4 bytes.
+// CHECK-LABEL: define void @{{.*}}f_struct_with_mdp{{.*}}(i64 %a.coerce0, i64 %a.coerce1)
+struct struct_with_mdp { char *a; char *b; char *c; test_struct_mdp d; };
+void f_struct_with_mdp(struct_with_mdp a) { (void)a; }
+
+struct struct_with_mdp_too_much {
+  char *a; char *b; char *c; char *d; test_struct_mdp e;
+};
+// CHECK-LABEL: define void @{{.*}}f_struct_with_mdp_too_much{{.*}}({{.*}} byval {{.*}} %a)
+void f_struct_with_mdp_too_much(struct_with_mdp_too_much a) {
+  (void)a;
+}
+
+// A struct with <= 8 bytes before a member function pointer should still
+// be allowed in registers, since the member function pointer is only 8 bytes.
+// CHECK-LABEL: define void @{{.*}}f_struct_with_mfp_0{{.*}}(i64 %a.coerce0, i32 %a.coerce1)
+struct struct_with_mfp_0 { char *a; test_struct_mfp b; };
+void f_struct_with_mfp_0(struct_with_mfp_0 a) { (void)a; }
+
+// CHECK-LABEL: define void @{{.*}}f_struct_with_mfp_1{{.*}}(i64 %a.coerce0, i64 %a.coerce1)
+struct struct_with_mfp_1 { char *a; char *b; test_struct_mfp c; };
+void f_struct_with_mfp_1(struct_with_mfp_1 a) { (void)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;
+}

clang/test/CodeGenCXX/x86_64-arguments.cpp

@@ -32,6 +32,21 @@ typedef int (s4::*s4_mfp)();
 s4_mdp f4_0(s4_mdp a) { return a; }
 s4_mfp f4_1(s4_mfp a) { return a; }
 
+// A struct with <= one eightbyte before a member data pointer should still
+// be allowed in registers.
+// CHECK-LABEL: define void @{{.*}}f_struct_with_mdp{{.*}}(i8* %a.coerce0, i64 %a.coerce1)
+struct struct_with_mdp { char *a; s4_mdp b; };
+void f_struct_with_mdp(struct_with_mdp a) { (void)a; }
+
+// A struct with anything before a member function will be too big and
+// goes in memory.
+// CHECK-LABEL: define void @{{.*}}f_struct_with_mfp_0{{.*}}(%struct{{.*}} byval align 8 %a)
+struct struct_with_mfp_0 { char a; s4_mfp b; };
+void f_struct_with_mfp_0(struct_with_mfp_0 a) { (void)a; }
+
+// CHECK-LABEL: define void @{{.*}}f_struct_with_mfp_1{{.*}}(%struct{{.*}} byval align 8 %a)
+struct struct_with_mfp_1 { void *a; s4_mfp b; };
+void f_struct_with_mfp_1(struct_with_mfp_1 a) { (void)a; }
 
 namespace PR7523 {
 struct StringRef {