rustc: Fix support for LLVM 3.3

The llvm.copysign and llvm.round intrinsics weren't added until LLVM 3.4, so if
we're on LLVM 3.3 we lower these to calls in libm instead of LLVM intrinsics.

This should fix our travis failures.

Author: alexcrichton

src/librustc/lib/llvm.rs

@@ -1771,6 +1771,7 @@ pub mod llvm {
         pub fn LLVMRustDestroyArchive(AR: ArchiveRef);
 
         pub fn LLVMRustSetDLLExportStorageClass(V: ValueRef);
+        pub fn LLVMVersionMinor() -> c_int;
     }
 }
 

src/librustc/middle/trans/base.rs

@@ -2286,8 +2286,6 @@ pub fn declare_intrinsics(llmod: ModuleRef) -> HashMap<&'static str, ValueRef> {
 
     ifn!(intrinsics, "llvm.fabs.f32", [Type::f32()], Type::f32());
     ifn!(intrinsics, "llvm.fabs.f64", [Type::f64()], Type::f64());
-    ifn!(intrinsics, "llvm.copysign.f32", [Type::f32(), Type::f32()], Type::f32());
-    ifn!(intrinsics, "llvm.copysign.f64", [Type::f64(), Type::f64()], Type::f64());
 
     ifn!(intrinsics, "llvm.floor.f32",[Type::f32()], Type::f32());
     ifn!(intrinsics, "llvm.floor.f64",[Type::f64()], Type::f64());
@@ -2300,8 +2298,6 @@ pub fn declare_intrinsics(llmod: ModuleRef) -> HashMap<&'static str, ValueRef> {
     ifn!(intrinsics, "llvm.rint.f64", [Type::f64()], Type::f64());
     ifn!(intrinsics, "llvm.nearbyint.f32", [Type::f32()], Type::f32());
     ifn!(intrinsics, "llvm.nearbyint.f64", [Type::f64()], Type::f64());
-    ifn!(intrinsics, "llvm.round.f32", [Type::f32()], Type::f32());
-    ifn!(intrinsics, "llvm.round.f64", [Type::f64()], Type::f64());
 
     ifn!(intrinsics, "llvm.ctpop.i8", [Type::i8()], Type::i8());
     ifn!(intrinsics, "llvm.ctpop.i16",[Type::i16()], Type::i16());
@@ -2378,6 +2374,32 @@ pub fn declare_intrinsics(llmod: ModuleRef) -> HashMap<&'static str, ValueRef> {
 
     ifn!(intrinsics, "llvm.expect.i1", [Type::i1(), Type::i1()], Type::i1());
 
+    // Some intrinsics were introduced in later versions of LLVM, but they have
+    // fallbacks in libc or libm and such. Currently, all of these intrinsics
+    // were introduced in LLVM 3.4, so we case on that.
+    macro_rules! compatible_ifn (
+        ($intrinsics:ident, $name:expr, $cname:expr, $args:expr, $ret:expr) => ({
+            let name = $name;
+            if unsafe { llvm::LLVMVersionMinor() >= 4 } {
+                ifn!($intrinsics, $name, $args, $ret);
+            } else {
+                let f = decl_cdecl_fn(llmod, $cname,
+                                      Type::func($args, &$ret),
+                                      ty::mk_nil());
+                $intrinsics.insert(name, f);
+            }
+        })
+    )
+
+    compatible_ifn!(intrinsics, "llvm.copysign.f32", "copysignf",
+                    [Type::f32(), Type::f32()], Type::f32());
+    compatible_ifn!(intrinsics, "llvm.copysign.f64", "copysign",
+                    [Type::f64(), Type::f64()], Type::f64());
+    compatible_ifn!(intrinsics, "llvm.round.f32", "roundf",
+                    [Type::f32()], Type::f32());
+    compatible_ifn!(intrinsics, "llvm.round.f64", "round",
+                    [Type::f64()], Type::f64());
+
     return intrinsics;
 }
 

src/rustllvm/RustWrapper.cpp

@@ -652,3 +652,8 @@ LLVMRustSetDLLExportStorageClass(LLVMValueRef Value) {
     LLVMSetLinkage(Value, LLVMDLLExportLinkage);
 }
 #endif
+
+extern "C" int
+LLVMVersionMinor() {
+    return LLVM_VERSION_MINOR;
+}