Compiler-rt part of D26230: Add (constant) masked load/store support

[filcab]

Summary

Unfortunately, there is no way to emit an llvm masked load/store in
clang without optimizations, and AVX enabled. Unsure how we should go
about making sure this test only runs if it's possible to execute AVC
code.

[filcab]

I've tried pushing this test, but one of the buildbots (at least) doesn't have AVX support. And AVX/AVX2 are the only things on X86 that will generate those masked loads/stores.
I'd go with either:

No testing on compiler-rt (ASan doesn't behave differently in the face of masked ops, so we should be able to go by with only the tests from llvm)
Testing on compiler-rt using IR, *assuming* we can lower calls to masked.loads/stores even on non-AVX CPUs
Testing on compiler-rt using some other arch that's not X86 (I don't really have the hardware to try that out, though)

[kubamracek]

In D26506#611883, @filcab wrote:

I've tried pushing this test, but one of the buildbots (at least) doesn't have AVX support. And AVX/AVX2 are the only things on X86 that will generate those masked loads/stores.
I'd go with either:

No testing on compiler-rt (ASan doesn't behave differently in the face of masked ops, so we should be able to go by with only the tests from llvm)
Testing on compiler-rt using IR, *assuming* we can lower calls to masked.loads/stores even on non-AVX CPUs
Testing on compiler-rt using some other arch that's not X86 (I don't really have the hardware to try that out, though)

Can we just add "REQUIRES: avx" to the test and lit?

[filcab]

In D26506#612095, @kubabrecka wrote:

Can we just add "REQUIRES: avx" to the test and lit?

No. That feature is not detected at all and there's no cmake scaffolding to expose it.
I think this test is too specific, and piggybacking on things that are tested (we're testing the instrumentation itself in llvm-land, callbacks, etc, are the exact same as regular instrumentation).
Since this is a matter of instrument (the exact same way as regular loads/stores) vs. no instrument, I think it's not useful to add all the scaffolding for this test.
If the handling in compiler-rt were in some way different from regular loads/stores, then I think we should add it. But as it is, I'm not sure it's worth the effort.

[kubamracek]

In D26506#618226, @filcab wrote:

In D26506#612095, @kubabrecka wrote:

Can we just add "REQUIRES: avx" to the test and lit?

No. That feature is not detected at all and there's no cmake scaffolding to expose it.
I think this test is too specific, and piggybacking on things that are tested (we're testing the instrumentation itself in llvm-land, callbacks, etc, are the exact same as regular instrumentation).
Since this is a matter of instrument (the exact same way as regular loads/stores) vs. no instrument, I think it's not useful to add all the scaffolding for this test.
If the handling in compiler-rt were in some way different from regular loads/stores, then I think we should add it. But as it is, I'm not sure it's worth the effort.

I was thinking about running grep /proc/cpuinfo (and systl hw on Darwin) in lit.cfg to detect AVX. Anyway, I'm fine with dropping this test (and just having the instrumentation test).

test/asan/TestCases/masked-ops.cpp

+// We need optimization to convert target-specific masked loads/stores to llvm
+// generic loads/stores
+// RUN: %clangxx_asan -o %t %s -mavx -O1
+// RUN: not %run %t l1 2>&1 | FileCheck -check-prefix=CHECK-L1 %s
+// RUN: %run %t l6 | FileCheck -check-prefix=CHECK-L6 %s
+// RUN: %run %t la | FileCheck -check-prefix=CHECK-LA %s
+// RUN: not %run %t s1 2>&1 | FileCheck -check-prefix=CHECK-S1 %s
+// RUN: %run %t s6 | FileCheck -check-prefix=CHECK-S6 %s
+// RUN: %run %t sa | FileCheck -check-prefix=CHECK-SA %s
+// REQUIRES: x86-target-arch
+#include <assert.h>
+#include <stdio.h>
+#include <x86intrin.h>
+
+float g_vec3[3] = {1802398064.0, 1881171305.0, 25961.0};
+
+void maskedstore_ps_0110(__m128 a) {
+  _mm_maskstore_ps(g_vec3, (__v4si){0, -1, -1, 0}, a);
+}
+
+void maskedstore_ps_0001(__m128 a) {
+  _mm_maskstore_ps(g_vec3, (__v4si){0, 0, 0, -1}, a);
+}
+
+void maskedstore_ps_1010(__m128 a) {
+  _mm_maskstore_ps(g_vec3, (__v4si){-1, 0, -1, 0}, a);
+}
+
+__m128i maskedload_ps_0110() {
+  return _mm_maskload_ps(g_vec3, (__v4si){0, -1, -1, 0});
+}
+
+__m128i maskedload_ps_0001() {
+  return _mm_maskload_ps(g_vec3, (__v4si){0, 0, 0, -1});
+}
+
+__m128i maskedload_ps_1010() {
+  return _mm_maskload_ps(g_vec3, (__v4si){-1, 0, -1, 0});
+}
+
+__m128 a = (__v4sf){1.0, 2.0, 3.0, 4.0};
+
+void print_vector(__v4sf v) {
+  printf("%d,%d,%d,%d\n", (int)v[0], (int)v[1], (int)v[2], (int)v[3]);
+}
+void print_vector3(float * v) {
+  printf("%d,%d,%d\n", (int)v[0], (int)v[1], (int)v[2]);
+}
+
+int main(int argc, char **argv) {
+  assert(argc > 1);
+  bool isLoad = argv[1][0] == 'l';
+  assert(isLoad || argv[1][0] == 's');
+  if (isLoad) {
+    switch (argv[1][1]) {
+    case '1': {
+      // CHECK-L1: ERROR: AddressSanitizer
+      __v4sf v = maskedload_ps_0001();
+      print_vector(v);
+      // Should have blown up
+      break;
+    }
+    case '6': {
+      // Safe
+      __v4sf v = maskedload_ps_0110();
+      // CHECK-L6: 0,1881171328,25961,0
+      print_vector(v);
+      return 0;
+    }
+    case 'a': {
+      // TODO: Poison middle element
+      // Safe
+      __v4sf v = maskedload_ps_1010();
+      // CHECK-LA: 1802398080,0,25961,0
+      print_vector(v);
+      return 0;
+    }
+    }
+  } else {
+    switch (argv[1][1]) {
+    case '1':
+      // CHECK-S1: ERROR: AddressSanitizer
+      maskedstore_ps_0001(a);
+      // Should have blown up
+      break;
+    case '6':
+      // Safe
+      maskedstore_ps_0110(a);
+      // CHECK-S6: 1802398080,2,3
+      print_vector3(g_vec3);
+      return 0;
+    case 'a':
+      // TODO: Poison middle element
+      // Safe
+      maskedstore_ps_1010(a);
+      // CHECK-SA: 1,1881171328,3
+      print_vector3(g_vec3);
+      return 0;
+    }
+  }
+  assert(0);
+}