From 8d68b18f9964be8be7ffe1ed18074eae7dc3c021 Mon Sep 17 00:00:00 2001
From: Nicholas Clark <nick@ccl4.org>
Date: Sat, 31 Oct 2020 11:23:29 +0000
Subject: [PATCH] A probe for compiler thread local storage support.

Not needed on Win32, as UV already exposes it there.
---
 Configure.pl      |   2 +
 build/config.h.in |   5 ++
 build/probe.pm    | 126 ++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 133 insertions(+)

diff --git a/Configure.pl b/Configure.pl
index f045a81e9d..29b00e190a 100755
--- a/Configure.pl
+++ b/Configure.pl
@@ -490,12 +490,14 @@ sub uniq {
 if ($config{crossconf}) {
     build::auto::detect_cross(\%config, \%defaults);
     build::probe::static_inline_cross(\%config, \%defaults);
+    build::probe::thread_local_cross(\%config, \%defaults);
     build::probe::unaligned_access_cross(\%config, \%defaults);
     build::probe::ptr_size_cross(\%config, \%defaults);
 }
 else {
     build::auto::detect_native(\%config, \%defaults);
     build::probe::static_inline_native(\%config, \%defaults);
+    build::probe::thread_local_native(\%config, \%defaults);
     build::probe::unaligned_access(\%config, \%defaults);
     build::probe::ptr_size_native(\%config, \%defaults);
 }
diff --git a/build/config.h.in b/build/config.h.in
index 658624b1bf..b16f39b27e 100644
--- a/build/config.h.in
+++ b/build/config.h.in
@@ -46,6 +46,11 @@
 /* How this compiler does static inline functions. */
 #define MVM_STATIC_INLINE @static_inline@
 
+#if @has_thread_local@
+/* How this compiler declares thread local storage. */
+#define MVM_THREAD_LOCAL @thread_local@
+#endif
+
 #if @can_unaligned_int32@
 #define MVM_CAN_UNALIGNED_INT32
 #endif
diff --git a/build/probe.pm b/build/probe.pm
index 7e6bfb92fe..7dc5440b7d 100644
--- a/build/probe.pm
+++ b/build/probe.pm
@@ -227,6 +227,132 @@ sub static_inline_cross {
     $config->{static_inline} = 'static';
 }
 
+sub thread_local_cross {
+    my ($config) = @_;
+    $config->{has_thread_local} = 0;
+    $config->{thread_local} = "";
+}
+
+sub thread_local_native {
+    my ($config) = @_;
+
+    # We don't need to probe for this on Win32, as UV sets it for us
+    if ($^O eq 'MSWin32') {
+        $config->{has_thread_local} = 0;
+        $config->{thread_local} = "";
+        return;
+    }
+
+    my $restore = _to_probe_dir();
+
+    print ::dots('    probing if your compiler offers thread local storage');
+    my $file = 'thread_local.c';
+    _spew($file, <<'EOT');
+#include <stdio.h>
+#include <stdlib.h>
+#include <pthread.h>
+
+static int plus_one = 1;
+static int minus_one = -1;
+
+THREAD_LOCAL int *minion;
+
+int callback (const void *a, const void *b) {
+    int val_a = *minion * *(const int *)a;
+    int val_b = *minion * *(const int *)b;
+    return val_a < val_b ? -1 : val_a > val_b;
+}
+
+#define SIZE 8
+
+void *thread_function(void *arg) {
+    /* thread local variables should start zeroed in each thread. */
+    if (minion != NULL) {
+        fprintf(stderr, "__thread variable started with %p, should be NULL\n",
+                minion);
+        exit(2);
+    }
+    minion = &minus_one;
+
+    int array[SIZE];
+    unsigned int i;
+    for (i = 0; i < SIZE; ++i) {
+        /* "Hash randomisation" - this array isn't in sorted order: */
+        array[i ^ 5] = i * i;
+    }
+
+    qsort(array, SIZE, sizeof(int), callback);
+
+    int bad = 0;
+    for (i = 0; i < SIZE; ++i) {
+        int want = (SIZE - 1 - i) * (SIZE - 1 - i);
+        int have = array[i];
+        if (want != have) {
+            ++bad;
+            fprintf(stderr, "array[%u] - want %i, have %i\n", i, want, have);
+        }
+    }
+    if (bad)
+        exit(3);
+
+    return NULL;
+}
+
+int main(int argc, char **argv) {
+    if (minion != NULL) {
+        fprintf(stderr, "__thread variable started with %p, should be NULL\n",
+                minion);
+        exit(4);
+    }
+
+    minion = &plus_one;
+
+    pthread_t tid;
+    int result = pthread_create(&tid, NULL, thread_function, NULL);
+    if (result) {
+        fprintf(stderr, "pthread_create failed (%d)\n", result);
+        exit(5);
+    }
+
+    result = pthread_join(tid, NULL);
+    if (result) {
+        fprintf(stderr, "pthread_join failed (%d)\n", result);
+        exit(6);
+    }
+
+    if (minion == NULL) {
+        fprintf(stderr, "__thread variable should not be NULL\n");
+        exit(7);
+    }
+    if (!(minion == &plus_one && *minion == 1)) {
+        fprintf(stderr, "__thread variable should be %d @ %p, not %d @ %p\n",
+                1, &plus_one, *minion, minion);
+        exit(8);
+    }
+
+    return 0;
+}
+EOT
+
+    my @try = qw(_Thread_local __thread);
+
+    my $t_l;
+    while ($t_l = shift @try) {
+        next unless compile($config, 'thread_local', ["THREAD_LOCAL=$t_l"]);
+        last if !system "./thread_local";
+    }
+
+    if ($t_l) {
+        print "$t_l\n";
+        $config->{has_thread_local} = 1;
+        $config->{thread_local} = $t_l;
+    } else {
+        print "it doesn't, so falling back to UV's API\n";
+        $config->{has_thread_local} = 0;
+        $config->{thread_local} = "";
+    }
+}
+
 sub specific_werror {
     my ($config) = @_;
     my $restore = _to_probe_dir();