Add warning about missing but required CPU features

Useful to debug why you're getting SIGILL, like running under Valgrind:

Processor features:  sse3[required] sse2[required] ssse3[required] fma
cmpxchg16b sse4.1[required] sse4.2[required] movbe popcnt[required]
aes[required] avx[required] f16c[required] bmi[required] avx2[required]
bmi2[required]
!!!!!!!!!!!!!!!!!!!!
!!! Missing required features: rdrand rdseed
!!! Applications will likely crash with "Invalid Instruction"
!!!!!!!!!!!!!!!!!!!!

Change-Id: Ia3e896da908f42939148fffd14c556557419b091
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>

1 files changed, 8 insertions, 0 deletions

diff --git a/src/corelib/tools/qsimd.cpp b/src/corelib/tools/qsimd.cpp
index d4edf459de..4c6f08c774 100644
--- a/src/corelib/tools/qsimd.cpp
+++ b/src/corelib/tools/qsimd.cpp
@@ -721,6 +721,14 @@ void qDumpCPUFeatures()
             printf("%s%s", features_string + features_indices[i],
                    minFeature & (Q_UINT64_C(1) << i) ? "[required]" : "");
     }
+    if ((features = (qCompilerCpuFeatures & ~features))) {
+        printf("\n!!!!!!!!!!!!!!!!!!!!\n!!! Missing required features:");
+        for (int i = 0; i < features_count; ++i) {
+            if (features & (Q_UINT64_C(1) << i))
+                printf("%s", features_string + features_indices[i]);
+        }
+        printf("\n!!! Applications will likely crash with \"Invalid Instruction\"\n!!!!!!!!!!!!!!!!!!!!");
+    }
     puts("");
 }