Revert "runtime: remove some redundant libm functions copied inline."

This reverts commit fee75bd50f.

LLVM does not have lround as a libcall and this inhibits LICM.

artiq/compiler/transforms/llvm_ir_generator.py

@@ -323,6 +323,8 @@ class LLVMIRGenerator:
             llty = ll.FunctionType(llvoid, [])
         elif name == "llvm.floor.f64":
             llty = ll.FunctionType(lldouble, [lldouble])
+        elif name == "llvm.round.f64":
+            llty = ll.FunctionType(lldouble, [lldouble])
         elif name == "llvm.pow.f64":
             llty = ll.FunctionType(lldouble, [lldouble, lldouble])
         elif name == "llvm.powi.f64":
@@ -347,8 +349,6 @@ class LLVMIRGenerator:
             llty = ll.FunctionType(lli32, [llptr])
         elif name == "strcmp":
             llty = ll.FunctionType(lli32, [llptr, llptr])
-        elif name == "lround":
-            llty = ll.FunctionType(lli32, [lldouble])
         elif name == "send_rpc":
             llty = ll.FunctionType(llvoid, [lli32, llptr, llptrptr])
         elif name == "send_async_rpc":
@@ -1044,8 +1044,9 @@ class LLVMIRGenerator:
                                          name=insn.name)
         elif insn.op == "round":
             llarg = self.map(insn.operands[0])
-            return self.llbuilder.call(self.llbuiltin("lround"), [llarg],
-                                       name=insn.name)
+            llvalue = self.llbuilder.call(self.llbuiltin("llvm.round.f64"), [llarg])
+            return self.llbuilder.fptosi(llvalue, self.llty_of_type(insn.type),
+                                         name=insn.name)
         elif insn.op == "globalenv":
             def get_outer(llenv, env_ty):
                 if "$outer" in env_ty.params:

artiq/runtime.rs/libksupport/api.rs

@@ -74,7 +74,7 @@ static mut API: &'static [(&'static str, *const ())] = &[
 
     /* libm */
     api!(sqrt),
-    api!(lround),
+    api!(round),
 
     /* exceptions */
     api!(_Unwind_Resume),

artiq/runtime/ksupport_glue.c

@@ -70,10 +70,33 @@ int dl_iterate_phdr (int (*callback)(struct dl_phdr_info *, size_t, void *), voi
 }
 
 /* called by kernel */
-long lround(double x);
-long lround(double x)
+double round(double x);
+double round(double x)
 {
-    return x < 0 ? floor(x) : ceil(x);
+    union {double f; uint64_t i;} u = {x};
+    int e = u.i >> 52 & 0x7ff;
+    double y;
+
+    if (e >= 0x3ff+52)
+        return x;
+    if (u.i >> 63)
+        x = -x;
+    if (e < 0x3ff-1) {
+        /* we don't do it in ARTIQ */
+        /* raise inexact if x!=0 */
+        // FORCE_EVAL(x + 0x1p52);
+        return 0*u.f;
+    }
+    y = (double)(x + 0x1p52) - 0x1p52 - x;
+    if (y > 0.5)
+        y = y + x - 1;
+    else if (y <= -0.5)
+        y = y + x + 1;
+    else
+        y = y + x;
+    if (u.i >> 63)
+        y = -y;
+    return y;
 }
 
 /* called by kernel */