[CUDA] Tweak attribute-based overload resolution to match nvcc behavior.

This is an artefact of split-mode CUDA compilation that we need to
mimic. HD functions are sometimes allowed to call H or D functions. Due
to split compilation mode device-side compilation will not see host-only
function and thus they will not be considered at all. For clang both H
and D variants will become function overloads visible to
compiler. Normally target attribute is considered only if C++ rules can
not determine which function is better. However in this case we need to
ignore functions that would not be present during current compilation
phase before we apply normal overload resolution rules.

Changes:
* introduced another level of call preference to better describe
  possible call combinations.
* removed WrongSide functions from consideration if the set contains
  SameSide function.
* disabled H->D, D->H and G->H calls. These combinations are
  not allowed by CUDA and we were reluctantly allowing them to work
  around device-side calls to math functions in std namespace.
  We no longer need it after r258880.

Differential Revision: http://reviews.llvm.org/D16870

llvm-svn: 260697

1 files changed, 106 insertions, 17 deletions

diff --git a/clang/test/CodeGenCUDA/function-overload.cu b/clang/test/CodeGenCUDA/function-overload.cu
index a12ef82773a..3f8f930106f 100644
--- a/clang/test/CodeGenCUDA/function-overload.cu
+++ b/clang/test/CodeGenCUDA/function-overload.cu
@@ -7,7 +7,8 @@
 // RUN:     | FileCheck -check-prefix=CHECK-BOTH -check-prefix=CHECK-HOST %s
 // RUN: %clang_cc1 -triple nvptx64-nvidia-cuda -fcuda-is-device \
 // RUN:     -fcuda-target-overloads -emit-llvm -o - %s \
-// RUN:     | FileCheck -check-prefix=CHECK-BOTH -check-prefix=CHECK-DEVICE %s
+// RUN:     | FileCheck -check-prefix=CHECK-BOTH -check-prefix=CHECK-DEVICE \
+// RUN:       -check-prefix=CHECK-DEVICE-STRICT %s
 
 // Check target overloads handling with disabled call target checks.
 // RUN: %clang_cc1 -DNOCHECKS -triple x86_64-unknown-linux-gnu -emit-llvm \
@@ -77,12 +78,112 @@ extern "C" __host__ int ch(void) {return 13;}
 extern "C" __host__ __device__ int chd(void) {return 14;}
 // CHECK-BOTH:     ret i32 14
 
+// HD functions are sometimes allowed to call H or D functions -- this
+// is an artifact of the source-to-source splitting performed by nvcc
+// that we need to mimic. During device mode compilation in nvcc, host
+// functions aren't present at all, so don't participate in
+// overloading. But in clang, H and D functions are present in both
+// compilation modes. Clang normally uses the target attribute as a
+// tiebreaker between overloads with otherwise identical priority, but
+// in order to match nvcc's behavior, we sometimes need to wholly
+// discard overloads that would not be present during compilation
+// under nvcc.
+
+template <typename T> T template_vs_function(T arg) { return 15; }
+__device__ float template_vs_function(float arg) { return 16; }
+
+// Here we expect to call the templated function during host
+// compilation, even if -fcuda-disable-target-call-checks is passed,
+// and even though C++ overload rules prefer the non-templated
+// function.
+// CHECK-BOTH-LABEL: define void @_Z5hd_tfv()
+__host__ __device__ void hd_tf(void) {
+  template_vs_function(1.0f);
+  // CHECK-HOST: call float @_Z20template_vs_functionIfET_S0_(float
+  // CHECK-DEVICE: call float @_Z20template_vs_functionf(float
+  template_vs_function(2.0);
+  // CHECK-HOST: call double @_Z20template_vs_functionIdET_S0_(double
+  // CHECK-DEVICE: call float @_Z20template_vs_functionf(float
+}
+
+// Calls from __host__ and __device__ functions should always call the
+// overloaded function that matches their mode.
+// CHECK-HOST-LABEL: define void @_Z4h_tfv()
+__host__ void h_tf() {
+  template_vs_function(1.0f);
+  // CHECK-HOST: call float @_Z20template_vs_functionIfET_S0_(float
+  template_vs_function(2.0);
+  // CHECK-HOST: call double @_Z20template_vs_functionIdET_S0_(double
+}
+
+// CHECK-DEVICE-LABEL: define void @_Z4d_tfv()
+__device__ void d_tf() {
+  template_vs_function(1.0f);
+  // CHECK-DEVICE: call float @_Z20template_vs_functionf(float
+  template_vs_function(2.0);
+  // CHECK-DEVICE: call float @_Z20template_vs_functionf(float
+}
+
+// In case we have a mix of HD and H-only or D-only candidates in the
+// overload set, normal C++ overload resolution rules apply first.
+template <typename T> T template_vs_hd_function(T arg) { return 15; }
+__host__ __device__ float template_vs_hd_function(float arg) { return 16; }
+
+// CHECK-BOTH-LABEL: define void @_Z7hd_thdfv()
+__host__ __device__ void hd_thdf() {
+  template_vs_hd_function(1.0f);
+  // CHECK-HOST: call float @_Z23template_vs_hd_functionf(float
+  // CHECK-DEVICE: call float @_Z23template_vs_hd_functionf(float
+  template_vs_hd_function(1);
+  // CHECK-HOST: call i32 @_Z23template_vs_hd_functionIiET_S0_(i32
+  // CHECK-DEVICE-STRICT: call float @_Z23template_vs_hd_functionf(float
+  // CHECK-DEVICE-NC: call i32 @_Z23template_vs_hd_functionIiET_S0_(i32
+}
+
+// CHECK-HOST-LABEL: define void @_Z6h_thdfv()
+__host__ void h_thdf() {
+  template_vs_hd_function(1.0f);
+  // CHECK-HOST: call float @_Z23template_vs_hd_functionf(float
+  template_vs_hd_function(1);
+  // CHECK-HOST: call i32 @_Z23template_vs_hd_functionIiET_S0_(i32
+}
+
+// CHECK-DEVICE-LABEL: define void @_Z6d_thdfv()
+__device__ void d_thdf() {
+  template_vs_hd_function(1.0f);
+  // CHECK-DEVICE: call float @_Z23template_vs_hd_functionf(float
+  template_vs_hd_function(1);
+  // Host-only function template is not callable with strict call checks,
+  // so for device side HD function will be the only choice.
+  // CHECK-DEVICE: call float @_Z23template_vs_hd_functionf(float
+}
+
+// Check that overloads still work the same way on both host and
+// device side when the overload set contains only functions from one
+// side of compilation.
+__device__ float device_only_function(int arg) { return 17; }
+__device__ float device_only_function(float arg) { return 18; }
+
+__host__ float host_only_function(int arg) { return 19; }
+__host__ float host_only_function(float arg) { return 20; }
+
+// CHECK-BOTH-LABEL: define void @_Z6hd_dofv()
+__host__ __device__ void hd_dof() {
+#ifdef NOCHECKS
+  device_only_function(1.0f);
+  // CHECK-BOTH-NC: call float @_Z20device_only_functionf(float
+  device_only_function(1);
+  // CHECK-BOTH-NC: call float @_Z20device_only_functioni(i32
+  host_only_function(1.0f);
+  // CHECK-BOTH-NC: call float @_Z18host_only_functionf(float
+  host_only_function(1);
+  // CHECK-BOTH-NC: call float @_Z18host_only_functioni(i32
+#endif
+}
+
+
 // CHECK-HOST-LABEL: define void @_Z5hostfv()
 __host__ void hostf(void) {
-#if defined (NOCHECKS)
-  fp_t dp = d;   // CHECK-HOST-NC: store {{.*}} @_Z1dv, {{.*}} %dp,
-  fp_t cdp = cd; // CHECK-HOST-NC: store {{.*}} @cd, {{.*}} %cdp,
-#endif
   fp_t hp = h; // CHECK-HOST: store {{.*}} @_Z1hv, {{.*}} %hp,
   fp_t chp = ch; // CHECK-HOST: store {{.*}} @ch, {{.*}} %chp,
   fp_t dhp = dh; // CHECK-HOST: store {{.*}} @_Z2dhv, {{.*}} %dhp,
@@ -91,10 +192,6 @@ __host__ void hostf(void) {
   fp_t chdp = chd; // CHECK-HOST: store {{.*}} @chd, {{.*}} %chdp,
   gp_t gp = g; // CHECK-HOST: store {{.*}} @_Z1gv, {{.*}} %gp,
 
-#if defined (NOCHECKS)
-  d();     // CHECK-HOST-NC: call i32 @_Z1dv()
-  cd();    // CHECK-HOST-NC: call i32 @cd()
-#endif
   h();     // CHECK-HOST: call i32 @_Z1hv()
   ch();    // CHECK-HOST: call i32 @ch()
   dh();    // CHECK-HOST: call i32 @_Z2dhv()
@@ -106,10 +203,6 @@ __host__ void hostf(void) {
 __device__ void devicef(void) {
   fp_t dp = d;   // CHECK-DEVICE: store {{.*}} @_Z1dv, {{.*}} %dp,
   fp_t cdp = cd; // CHECK-DEVICE: store {{.*}} @cd, {{.*}} %cdp,
-#if defined (NOCHECKS)
-  fp_t hp = h; // CHECK-DEVICE-NC: store {{.*}} @_Z1hv, {{.*}} %hp,
-  fp_t chp = ch; // CHECK-DEVICE-NC: store {{.*}} @ch, {{.*}} %chp,
-#endif
   fp_t dhp = dh; // CHECK-DEVICE: store {{.*}} @_Z2dhv, {{.*}} %dhp,
   fp_t cdhp = cdh; // CHECK-DEVICE: store {{.*}} @cdh, {{.*}} %cdhp,
   fp_t hdp = hd; // CHECK-DEVICE: store {{.*}} @_Z2hdv, {{.*}} %hdp,
@@ -117,10 +210,6 @@ __device__ void devicef(void) {
 
   d();     // CHECK-DEVICE: call i32 @_Z1dv()
   cd();    // CHECK-DEVICE: call i32 @cd()
-#if defined (NOCHECKS)
-  h();     // CHECK-DEVICE-NC: call i32 @_Z1hv()
-  ch();    // CHECK-DEVICE-NC: call i32 @ch()
-#endif
   dh();    // CHECK-DEVICE: call i32 @_Z2dhv()
   cdh();   // CHECK-DEVICE: call i32 @cdh()
 }