Enable memory alignment management via compiler options

builtins.cpp

@@ -996,6 +996,11 @@ DefineStdlib(SymbolTable *symbolTable, llvm::LLVMContext *ctx, llvm::Module *mod
     lDefineConstantInt("__have_native_transcendentals", g->target->hasTranscendentals(),
                        module, symbolTable);
 
+    if (g->forceAlignment != -1) {
+        llvm::GlobalVariable *alignment = module->getGlobalVariable("memory_alignment", true);
+        alignment->setInitializer(LLVMInt32(g->forceAlignment));
+    }
+
     if (includeStdlibISPC) {
         // If the user wants the standard library to be included, parse the
         // serialized version of the stdlib.ispc file to get its

ispc.cpp

@@ -747,6 +747,7 @@ Globals::Globals() {
     if (getcwd(currentDirectory, sizeof(currentDirectory)) == NULL)
         FATAL("Current directory path too long!");
 #endif
+    forceAlignment = -1;
 }
 
 ///////////////////////////////////////////////////////////////////////////

ispc.h

@@ -551,6 +551,10 @@ struct Globals {
     /** Additional user-provided directories to search when processing
         #include directives in the preprocessor. */
     std::vector<std::string> includePath;
+
+    /** Indicates that alignment in memory allocation routines should be
+        forced to have given value. -1 value means natural alignment for the platforms. */
+    int forceAlignment;
 };
 
 enum {

main.cpp

@@ -98,6 +98,7 @@ usage(int ret) {
     printf("    [--emit-c++]\t\t\tEmit a C++ source file as output\n");
     printf("    [--emit-llvm]\t\t\tEmit LLVM bitode file as output\n");
     printf("    [--emit-obj]\t\t\tGenerate object file file as output (default)\n");
+    printf("    [--force-alignment=<value>]\t\tForce alignment in memory allocations routine to be <value>\n");
     printf("    [-g]\t\t\t\tGenerate debugging information\n");
     printf("    [--help]\t\t\t\tPrint help\n");
     printf("    [--help-dev]\t\t\tPrint help for developer options\n");
@@ -393,6 +394,9 @@ int main(int Argc, char *Argv[]) {
                 usage(1);
             }
         }
+        else if (!strncmp(argv[i], "--force-alignment=", 18)) {
+            g->forceAlignment = atoi(argv[i] + 18);
+        }
         else if (!strcmp(argv[i], "--woff") || !strcmp(argv[i], "-woff")) {
             g->disableWarnings = true;
             g->emitPerfWarnings = false;