Add command-line option to specify position-independent codegen

ispc.cpp

@@ -72,7 +72,7 @@ Module *m;
 
 bool
 Target::GetTarget(const char *arch, const char *cpu, const char *isa,
-                  Target *t) {
+                  bool pic, Target *t) {
     if (cpu == NULL) {
         std::string hostCPU = llvm::sys::getHostCPUName();
         if (hostCPU.size() > 0)
@@ -100,6 +100,8 @@ Target::GetTarget(const char *arch, const char *cpu, const char *isa,
 
     bool error = false;
 
+    t->generatePIC = pic;
+
     // Make sure the target architecture is a known one; print an error
     // with the valid ones otherwise.
     t->target = NULL;
@@ -228,14 +230,17 @@ llvm::TargetMachine *
 Target::GetTargetMachine() const {
     std::string triple = GetTripleString();
 
+    llvm::Reloc::Model relocModel = generatePIC ? llvm::Reloc::PIC_ : 
+                                                  llvm::Reloc::Default;
 #if defined(LLVM_3_0svn) || defined(LLVM_3_0)
     std::string featuresString = attributes;
     llvm::TargetMachine *targetMachine = 
-        target->createTargetMachine(triple, cpu, featuresString);
+        target->createTargetMachine(triple, cpu, featuresString, relocModel);
 #else
     std::string featuresString = cpu + std::string(",") + attributes;
     llvm::TargetMachine *targetMachine = 
         target->createTargetMachine(triple, featuresString);
+    targetMachine->setRelocationModel(relocModel);
 #endif
     assert(targetMachine != NULL);
 

ispc.h

@@ -162,7 +162,7 @@ struct Target {
         name, if the name is a known target.  Returns true if the
         target was initialized and false if the name is unknown. */
     static bool GetTarget(const char *arch, const char *cpu, const char *isa,
-                          Target *);
+                          bool pic, Target *);
 
     /** Returns a comma-delimited string giving the names of the currently
         supported target ISAs. */
@@ -215,8 +215,12 @@ struct Target {
         integer multiple of the native vector width, for example if we're
         "doubling up" and compiling 8-wide on a 4-wide SSE system. */
     int vectorWidth;
+
+    /** Indicates whether position independent code should be generated. */
+    bool generatePIC;
 };
 
+
 /** @brief Structure that collects optimization options
 
     This structure collects all of the options related to optimization of

main.cpp

@@ -98,6 +98,7 @@ static void usage(int ret) {
     printf("        disable-uniform-memory-optimizations\tDisable uniform-based coherent memory access\n");
     printf("        disable-masked-store-optimizations\tDisable lowering to regular stores when possible\n");
 #endif
+    printf("    [--pic]\t\t\t\tGenerate position-independent code\n");
     printf("    [--target=<isa>]\t\t\tSelect target ISA. <isa>={%s}\n", Target::SupportedTargetISAs());
     printf("    [--version]\t\t\t\tPrint ispc version\n");
     printf("    [--woff]\t\t\t\tDisable warnings\n");
@@ -184,8 +185,9 @@ int main(int Argc, char *Argv[]) {
 
     bool debugSet = false, optSet = false;
     Module::OutputType ot = Module::Object;
-
+    bool generatePIC = false;
     const char *arch = NULL, *cpu = NULL, *target = NULL;
+
     for (int i = 1; i < argc; ++i) {
         if (!strcmp(argv[i], "--help"))
             usage(0);
@@ -286,6 +288,8 @@ int main(int Argc, char *Argv[]) {
             g->includeStdlib = false;
         else if (!strcmp(argv[i], "--nocpp"))
             g->runCPP = false;
+        else if (!strcmp(argv[i], "--pic"))
+            generatePIC = true;
         else if (!strcmp(argv[i], "-v") || !strcmp(argv[i], "--version")) {
             printf("Intel(r) SPMD Program Compiler (ispc) build %s (%s)\n", 
                    BUILD_DATE, BUILD_VERSION);
@@ -307,7 +311,7 @@ int main(int Argc, char *Argv[]) {
     if (debugSet && !optSet)
         g->opt.level = 0;
 
-    if (!Target::GetTarget(arch, cpu, target, &g->target))
+    if (!Target::GetTarget(arch, cpu, target, generatePIC, &g->target))
         usage(1);
 
     m = new Module(file);