Change the way module initialisation is done (#3252, #4417)

Previously the code generator generated small code fragments labelled
with __stginit_M for each module M, and these performed whatever
initialisation was necessary for that module and recursively invoked
the initialisation functions for imported modules.  This appraoch had
drawbacks:

 - FFI users had to call hs_add_root() to ensure the correct
   initialisation routines were called.  This is a non-standard,
   and ugly, API.

 - unless we were using -split-objs, the __stginit dependencies would
   entail linking the whole transitive closure of modules imported,
   whether they were actually used or not.  In an extreme case (#4387,
   #4417), a module from GHC might be imported for use in Template
   Haskell or an annotation, and that would force the whole of GHC to
   be needlessly linked into the final executable.

So now instead we do our initialisation with C functions marked with
__attribute__((constructor)), which are automatically invoked at
program startup time (or DSO load-time).  The C initialisers are
emitted into the stub.c file.  This means that every time we compile
with -prof or -hpc, we now get a stub file, but thanks to #3687 that
is now invisible to the user.

There are some refactorings in the RTS (particularly for HPC) to
handle the fact that initialisers now get run earlier than they did
before.

The __stginit symbols are still generated, and the hs_add_root()
function still exists (but does nothing), for backwards compatibility.

1 files changed, 128 insertions, 90 deletions

diff --git a/rts/Hpc.c b/rts/Hpc.c
index 81c802cea2..c4ff8d3be1 100644
--- a/rts/Hpc.c
+++ b/rts/Hpc.c
@@ -6,6 +6,8 @@
 #include "Rts.h"
 
 #include "Trace.h"
+#include "Hash.h"
+#include "RtsUtils.h"
 
 #include <stdio.h>
 #include <ctype.h>
@@ -36,11 +38,11 @@ static pid_t hpc_pid = 0;		// pid of this process at hpc-boot time.
 static FILE *tixFile;			// file being read/written
 static int tix_ch;			// current char
 
+static HashTable * moduleHash = NULL;   // module name -> HpcModuleInfo
+
 HpcModuleInfo *modules = 0;
-HpcModuleInfo *nextModule = 0;
-int totalTixes = 0;		// total number of tix boxes.
 
-static char *tixFilename;
+static char *tixFilename = NULL;
 
 static void GNU_ATTRIBUTE(__noreturn__)
 failure(char *msg) {
@@ -78,7 +80,7 @@ static void ws(void) {
 }
 
 static char *expectString(void) {
-  char tmp[256], *res;
+  char tmp[256], *res; // XXX
   int tmp_ix = 0;
   expect('"');
   while (tix_ch != '"') {
@@ -87,7 +89,7 @@ static char *expectString(void) {
   }
   tmp[tmp_ix++] = 0;
   expect('"');
-  res = malloc(tmp_ix);
+  res = stgMallocBytes(tmp_ix,"Hpc.expectString");
   strcpy(res,tmp);
   return res;
 }
@@ -104,10 +106,8 @@ static StgWord64 expectWord64(void) {
 static void
 readTix(void) {
   unsigned int i;
-  HpcModuleInfo *tmpModule;
+  HpcModuleInfo *tmpModule, *lookup;
 
-  totalTixes = 0;
-    
   ws();
   expect('T');
   expect('i');
@@ -117,7 +117,9 @@ readTix(void) {
   ws();
   
   while(tix_ch != ']') {
-    tmpModule = (HpcModuleInfo *)calloc(1,sizeof(HpcModuleInfo));
+    tmpModule = (HpcModuleInfo *)stgMallocBytes(sizeof(HpcModuleInfo),
+                                                "Hpc.readTix");
+    tmpModule->from_file = rtsTrue;
     expect('T');
     expect('i');
     expect('x');
@@ -134,8 +136,6 @@ readTix(void) {
     ws();
     tmpModule -> tickCount = (int)expectWord64();
     tmpModule -> tixArr = (StgWord64 *)calloc(tmpModule->tickCount,sizeof(StgWord64));
-    tmpModule -> tickOffset = totalTixes;
-    totalTixes += tmpModule -> tickCount;
     ws();
     expect('[');
     ws();
@@ -150,13 +150,32 @@ readTix(void) {
     expect(']');
     ws();
     
-    if (!modules) {
-      modules = tmpModule;
+    lookup = lookupHashTable(moduleHash, (StgWord)tmpModule->modName);
+    if (tmpModule == NULL) {
+        debugTrace(DEBUG_hpc,"readTix: new HpcModuleInfo for %s",
+                   tmpModule->modName);
+        insertHashTable(moduleHash, (StgWord)tmpModule->modName, tmpModule);
     } else {
-      nextModule->next=tmpModule;
+        ASSERT(lookup->tixArr != 0);
+        ASSERT(!strcmp(tmpModule->modName, lookup->modName));
+        debugTrace(DEBUG_hpc,"readTix: existing HpcModuleInfo for %s",
+                   tmpModule->modName);
+        if (tmpModule->hashNo != lookup->hashNo) {
+            fprintf(stderr,"in module '%s'\n",tmpModule->modName);
+            failure("module mismatch with .tix/.mix file hash number");
+            if (tixFilename != NULL) {
+                fprintf(stderr,"(perhaps remove %s ?)\n",tixFilename);
+            }
+            stg_exit(EXIT_FAILURE);
+        }
+        for (i=0; i < tmpModule->tickCount; i++) {
+            lookup->tixArr[i] = tmpModule->tixArr[i];
+        }
+        stgFree(tmpModule->tixArr);
+        stgFree(tmpModule->modName);
+        stgFree(tmpModule);
     }
-    nextModule=tmpModule;
-    
+
     if (tix_ch == ',') {
       expect(',');
       ws();
@@ -166,9 +185,18 @@ readTix(void) {
   fclose(tixFile);
 }
 
-static void hpc_init(void) {
+void
+startupHpc(void)
+{
   char *hpc_tixdir;
   char *hpc_tixfile;
+
+  if (moduleHash == NULL) {
+      // no modules were registered with hs_hpc_module, so don't bother
+      // creating the .tix file.
+      return;
+  }
+
   if (hpc_inited != 0) {
     return;
   }
@@ -177,6 +205,8 @@ static void hpc_init(void) {
   hpc_tixdir = getenv("HPCTIXDIR");
   hpc_tixfile = getenv("HPCTIXFILE");
 
+  debugTrace(DEBUG_hpc,"startupHpc");
+
   /* XXX Check results of mallocs/strdups, and check we are requesting
          enough bytes */
   if (hpc_tixfile != NULL) {
@@ -192,10 +222,13 @@ static void hpc_init(void) {
 #endif
     /* Then, try open the file
      */
-    tixFilename = (char *) malloc(strlen(hpc_tixdir) + strlen(prog_name) + 12);
+    tixFilename = (char *) stgMallocBytes(strlen(hpc_tixdir) +
+                                          strlen(prog_name) + 12,
+                                          "Hpc.startupHpc");
     sprintf(tixFilename,"%s/%s-%d.tix",hpc_tixdir,prog_name,(int)hpc_pid);
   } else {
-    tixFilename = (char *) malloc(strlen(prog_name) + 6);
+    tixFilename = (char *) stgMallocBytes(strlen(prog_name) + 6,
+                                          "Hpc.startupHpc");
     sprintf(tixFilename, "%s.tix", prog_name);
   }
 
@@ -204,90 +237,80 @@ static void hpc_init(void) {
   }
 }
 
-/* Called on a per-module basis, at startup time, declaring where the tix boxes are stored in memory.
- * This memory can be uninitized, because we will initialize it with either the contents
- * of the tix file, or all zeros.
+/*
+ * Called on a per-module basis, by a constructor function compiled
+ * with each module (see Coverage.hpcInitCode), declaring where the
+ * tix boxes are stored in memory.  This memory can be uninitized,
+ * because we will initialize it with either the contents of the tix
+ * file, or all zeros.
+ *
+ * Note that we might call this before reading the .tix file, or after
+ * in the case where we loaded some Haskell code from a .so with
+ * dlopen().  So we must handle the case where we already have an
+ * HpcModuleInfo for the module which was read from the .tix file.
  */
 
-int
+void
 hs_hpc_module(char *modName,
 	      StgWord32 modCount,
 	      StgWord32 modHashNo,
-	      StgWord64 *tixArr) {
-  HpcModuleInfo *tmpModule, *lastModule;
-  unsigned int i;
-  int offset = 0;
-  
-  debugTrace(DEBUG_hpc,"hs_hpc_module(%s,%d)",modName,(nat)modCount);
+              StgWord64 *tixArr)
+{
+  HpcModuleInfo *tmpModule;
+  nat i;
 
-  hpc_init();
+  if (moduleHash == NULL) {
+      moduleHash = allocStrHashTable();
+  }
 
-  tmpModule = modules;
-  lastModule = 0;
-  
-  for(;tmpModule != 0;tmpModule = tmpModule->next) {
-    if (!strcmp(tmpModule->modName,modName)) {
+  tmpModule = lookupHashTable(moduleHash, (StgWord)modName);
+  if (tmpModule == NULL)
+  {
+      // Did not find entry so add one on.
+      tmpModule = (HpcModuleInfo *)stgMallocBytes(sizeof(HpcModuleInfo),
+                                                  "Hpc.hs_hpc_module");
+      tmpModule->modName = modName;
+      tmpModule->tickCount = modCount;
+      tmpModule->hashNo = modHashNo;
+
+      tmpModule->tixArr = tixArr;
+      for(i=0;i < modCount;i++) {
+          tixArr[i] = 0;
+      }
+      tmpModule->next = modules;
+      tmpModule->from_file = rtsFalse;
+      modules = tmpModule;
+      insertHashTable(moduleHash, (StgWord)modName, tmpModule);
+  }
+  else
+  {
       if (tmpModule->tickCount != modCount) {
-	failure("inconsistent number of tick boxes");
+          failure("inconsistent number of tick boxes");
       }
-      assert(tmpModule->tixArr != 0);	
+      ASSERT(tmpModule->tixArr != 0);
       if (tmpModule->hashNo != modHashNo) {
-	fprintf(stderr,"in module '%s'\n",tmpModule->modName);
-	failure("module mismatch with .tix/.mix file hash number");
-	fprintf(stderr,"(perhaps remove %s ?)\n",tixFilename);
-	stg_exit(1);
-
+          fprintf(stderr,"in module '%s'\n",tmpModule->modName);
+          failure("module mismatch with .tix/.mix file hash number");
+          if (tixFilename != NULL) {
+              fprintf(stderr,"(perhaps remove %s ?)\n",tixFilename);
+          }
+          stg_exit(EXIT_FAILURE);
       }
+      // The existing tixArr was made up when we read the .tix file,
+      // whereas this is the real tixArr, so copy the data from the
+      // .tix into the real tixArr.
       for(i=0;i < modCount;i++) {
-	tixArr[i] = tmpModule->tixArr[i];
+          tixArr[i] = tmpModule->tixArr[i];
       }
-      tmpModule->tixArr = tixArr;
-      return tmpModule->tickOffset;
-    }
-    lastModule = tmpModule;
-  }
-  // Did not find entry so add one on.
-  tmpModule = (HpcModuleInfo *)calloc(1,sizeof(HpcModuleInfo));
-  tmpModule->modName = modName;
-  tmpModule->tickCount = modCount;
-  tmpModule->hashNo = modHashNo;
-  if (lastModule) {
-    tmpModule->tickOffset = lastModule->tickOffset + lastModule->tickCount;
-  } else {
-    tmpModule->tickOffset = 0;
-  }
-  tmpModule->tixArr = tixArr;
-  for(i=0;i < modCount;i++) {
-    tixArr[i] = 0;
-  }
-  tmpModule->next = 0;
-
-  if (!modules) {
-    modules = tmpModule;
-  } else {
-    lastModule->next=tmpModule;
-  }
-
-  debugTrace(DEBUG_hpc,"end: hs_hpc_module");
-
-  return offset;
-}
-
 
-/* This is called after all the modules have registered their local tixboxes,
- * and does a sanity check: are we good to go?
- */
-
-void
-startupHpc(void) {
-  debugTrace(DEBUG_hpc,"startupHpc");
- 
- if (hpc_inited == 0) {
-    return;
+      if (tmpModule->from_file) {
+          stgFree(tmpModule->modName);
+          stgFree(tmpModule->tixArr);
+      }
+      tmpModule->from_file = rtsFalse;
   }
 }
 
-
 static void
 writeTix(FILE *f) {
   HpcModuleInfo *tmpModule;  
@@ -311,11 +334,10 @@ writeTix(FILE *f) {
 	   tmpModule->modName,
 	    (nat)tmpModule->hashNo,
 	    (nat)tmpModule->tickCount);
-    debugTrace(DEBUG_hpc,"%s: %u (offset=%u) (hash=%u)\n",
+    debugTrace(DEBUG_hpc,"%s: %u (hash=%u)\n",
 	       tmpModule->modName,
 	       (nat)tmpModule->tickCount,
-	       (nat)tmpModule->hashNo,
-	       (nat)tmpModule->tickOffset);
+               (nat)tmpModule->hashNo);
 
     inner_comma = 0;
     for(i = 0;i < tmpModule->tickCount;i++) {
@@ -338,7 +360,17 @@ writeTix(FILE *f) {
   fclose(f);
 }
 
-/* Called at the end of execution, to write out the Hpc *.tix file  
+static void
+freeHpcModuleInfo (HpcModuleInfo *mod)
+{
+    if (mod->from_file) {
+        stgFree(mod->modName);
+        stgFree(mod->tixArr);
+    }
+    stgFree(mod);
+}
+
+/* Called at the end of execution, to write out the Hpc *.tix file
  * for this exection. Safe to call, even if coverage is not used.
  */
 void
@@ -357,6 +389,12 @@ exitHpc(void) {
     FILE *f = fopen(tixFilename,"w");
     writeTix(f);
   }
+
+  freeHashTable(moduleHash, (void (*)(void *))freeHpcModuleInfo);
+  moduleHash = NULL;
+
+  stgFree(tixFilename);
+  tixFilename = NULL;
 }
 
 //////////////////////////////////////////////////////////////////////////////