Do not add DWARF version before LLVM 3.5

ispc.cpp

@@ -1102,10 +1102,13 @@ Target::Target(const char *arch, const char *cpu, const char *isa, bool pic, boo
 #else /* LLVM 3.7+ */
         m_targetMachine->Options.MCOptions.AsmVerbose = true;
 #endif
+
+#if ISPC_LLVM_VERSION >= ISPC_LLVM_3_5
         // Change default version of generated DWARF.
         if (g->generateDWARFVersion != 0) {
             m_targetMachine->Options.MCOptions.DwarfVersion = g->generateDWARFVersion;
         }
+#endif
 
         // Initialize TargetData/DataLayout in 3 steps.
         // 1. Get default data layout first
@@ -1522,7 +1525,9 @@ Globals::Globals() {
     emitPerfWarnings = true;
     emitInstrumentation = false;
     generateDebuggingSymbols = false;
+#if ISPC_LLVM_VERSION >= ISPC_LLVM_3_5
     generateDWARFVersion = 0;
+#endif
     enableFuzzTest = false;
     fuzzTestSeed = -1;
     mangleFunctionsWithTarget = false;

ispc.h

@@ -612,7 +612,9 @@ struct Globals {
     // readelf --debug-dump=info object.o | grep -A 2 'Compilation Unit @'
     // on Mac:
     // xcrun dwarfdump -r0 object.o
+#if ISPC_LLVM_VERSION >= ISPC_LLVM_3_5
     int generateDWARFVersion;
+#endif
 
     /** If true, function names are mangled by appending the target ISA and
         vector width to them. */

main.cpp

@@ -104,7 +104,9 @@ usage(int ret) {
 #ifdef ISPC_IS_WINDOWS
     printf("    [--dllexport]\t\t\tMake non-static functions DLL exported.  Windows only.\n");
 #endif
+#if ISPC_LLVM_VERSION >= ISPC_LLVM_3_5
     printf("    [--dwarf-version={2,3,4}]\t\tGenerate source-level debug information with given DWARF version (triggers -g)\n");
+#endif
     printf("    [--emit-asm]\t\t\tGenerate assembly language file as output\n");
     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");
@@ -388,6 +390,7 @@ int main(int Argc, char *Argv[]) {
         else if (!strcmp(argv[i], "--dllexport"))
             g->dllExport = true;
 #endif
+#if ISPC_LLVM_VERSION >= ISPC_LLVM_3_5
         else if (!strncmp(argv[i], "--dwarf-version=", 16)) {
             int val = atoi(argv[i] + 16);
             if (2 <= val && val <=4) {
@@ -398,7 +401,9 @@ int main(int Argc, char *Argv[]) {
                         "only 2, 3 and 4 are allowed.\n", argv[i]+16);
                 usage(1);
             }
-        } else if (!strcmp(argv[i], "--print-target"))
+        }
+#endif
+        else if (!strcmp(argv[i], "--print-target"))
             g->printTarget = true;
         else if (!strcmp(argv[i], "--no-omit-frame-pointer"))
             g->NoOmitFramePointer = true;