compiler: support disabling now-pinning

artiq/compiler/targets.py

@@ -78,13 +78,15 @@ class Target:
     :var little_endian: (boolean)
         Whether the code will be executed on a little-endian machine. This cannot be always
         determined from data_layout due to JIT.
+    :var now_pinning: (boolean)
+        Whether the target implements the now-pinning RTIO optimization.
     """
     triple = "unknown"
     data_layout = ""
     features = []
     print_function = "printf"
     little_endian = False
-
+    now_pinning = True
 
     def __init__(self):
         self.llcontext = ll.Context()
@@ -254,6 +256,7 @@ class OR1KTarget(Target):
     features = ["mul", "div", "ffl1", "cmov", "addc"]
     print_function = "core_log"
     little_endian = False
+    now_pinning = True
 
 class CortexA9Target(Target):
     triple = "armv7-unknown-linux-gnueabihf"
@@ -261,3 +264,4 @@ class CortexA9Target(Target):
     features = ["dsp", "fp16", "neon", "vfp3"]
     print_function = "core_log"
     little_endian = True
+    now_pinning = False

artiq/compiler/transforms/llvm_ir_generator.py

@@ -380,8 +380,19 @@ class LLVMIRGenerator:
             llty = ll.FunctionType(llvoid, [lli32, llsliceptr, llptrptr])
         elif name == "rpc_recv":
             llty = ll.FunctionType(lli32, [llptr])
+
+        # with now-pinning
         elif name == "now":
             llty = lli64
+
+        # without now-pinning
+        elif name == "now_mu":
+            llty = ll.FunctionType(lli64, [])
+        elif name == "at_mu":
+            llty = ll.FunctionType(llvoid, [lli64])
+        elif name == "delay_mu":
+            llty = ll.FunctionType(llvoid, [lli64])
+
         elif name == "watchdog_set":
             llty = ll.FunctionType(lli32, [lli64])
         elif name == "watchdog_clear":
@@ -1174,11 +1185,14 @@ class LLVMIRGenerator:
             # This is an identity cast at LLVM IR level.
             return self.map(insn.operands[0])
         elif insn.op == "now_mu":
-            llnow = self.llbuilder.load(self.llbuiltin("now"), name=insn.name)
+            if self.target.now_pinning:
-            return llnow
+                return self.llbuilder.load(self.llbuiltin("now"), name=insn.name)
+            else:
+                return self.llbuilder.call(self.llbuiltin("now_mu"), [])
         elif insn.op == "at_mu":
             time, = insn.operands
             lltime = self.map(time)
+            if self.target.now_pinning:
                 lltime_hi = self.llbuilder.trunc(self.llbuilder.lshr(lltime, ll.Constant(lli64, 32)), lli32)
                 lltime_lo = self.llbuilder.trunc(lltime, lli32)
                 llnow_hiptr = self.llbuilder.bitcast(self.llbuiltin("now"), lli32.as_pointer())
@@ -1188,12 +1202,15 @@ class LLVMIRGenerator:
                 llstore_hi = self.llbuilder.store_atomic(lltime_hi, llnow_hiptr, ordering="seq_cst", align=4)
                 llstore_lo = self.llbuilder.store_atomic(lltime_lo, llnow_loptr, ordering="seq_cst", align=4)
                 return llstore_lo
+            else:
+                return self.llbuilder.call(self.llbuiltin("at_mu"), [lltime])
         elif insn.op == "delay_mu":
             interval, = insn.operands
+            llinterval = self.map(interval)
+            if self.target.now_pinning:
                 llnowptr = self.llbuiltin("now")
                 llnow = self.llbuilder.load(llnowptr, name="now.old")
-            lladjusted = self.llbuilder.add(llnow, self.map(interval), name="now.new")
+                lladjusted = self.llbuilder.add(llnow, llinterval, name="now.new")
-
                 lladjusted_hi = self.llbuilder.trunc(self.llbuilder.lshr(lladjusted, ll.Constant(lli64, 32)), lli32)
                 lladjusted_lo = self.llbuilder.trunc(lladjusted, lli32)
                 llnow_hiptr = self.llbuilder.bitcast(llnowptr, lli32.as_pointer())
@@ -1203,6 +1220,8 @@ class LLVMIRGenerator:
                 llstore_hi = self.llbuilder.store_atomic(lladjusted_hi, llnow_hiptr, ordering="seq_cst", align=4)
                 llstore_lo = self.llbuilder.store_atomic(lladjusted_lo, llnow_loptr, ordering="seq_cst", align=4)
                 return llstore_lo
+            else:
+                return self.llbuilder.call(self.llbuiltin("delay_mu"), [llinterval])
         elif insn.op == "watchdog_set":
             interval, = insn.operands
             return self.llbuilder.call(self.llbuiltin("watchdog_set"), [self.map(interval)])