From 7f914a057c407a8ee786607a99d3dc0f8097295b Mon Sep 17 00:00:00 2001
From: whitequark <whitequark@whitequark.org>
Date: Sun, 10 Jan 2016 17:31:59 +0000
Subject: [PATCH] transforms.llvm_ir_generator: use sret attribute.

---
 .../compiler/transforms/llvm_ir_generator.py  | 42 +++++++++----------
 1 file changed, 20 insertions(+), 22 deletions(-)

diff --git a/artiq/compiler/transforms/llvm_ir_generator.py b/artiq/compiler/transforms/llvm_ir_generator.py
index 25b572c2d..685918981 100644
--- a/artiq/compiler/transforms/llvm_ir_generator.py
+++ b/artiq/compiler/transforms/llvm_ir_generator.py
@@ -193,6 +193,10 @@ class LLVMIRGenerator:
         else:
             return True
 
+    def has_sret(self, functy):
+        llretty = self.llty_of_type(functy.ret, for_return=True)
+        return self.needs_sret(llretty)
+
     def llty_of_type(self, typ, bare=False, for_return=False):
         typ = typ.find()
         if types.is_tuple(typ):
@@ -219,22 +223,14 @@ class LLVMIRGenerator:
                                          for arg in typ.optargs],
                                    return_type=llretty)
 
-            # TODO: actually mark the first argument as sret (also noalias nocapture).
-            # llvmlite currently does not have support for this;
-            # https://github.com/numba/llvmlite/issues/91.
-            if sretarg:
-                llty.__has_sret = True
-            else:
-                llty.__has_sret = False
-
             if bare:
                 return llty
             else:
                 return ll.LiteralStructType([envarg, llty.as_pointer()])
         elif types.is_method(typ):
-            llfuncty = self.llty_of_type(types.get_method_function(typ))
+            llfunty  = self.llty_of_type(types.get_method_function(typ))
             llselfty = self.llty_of_type(types.get_method_self(typ))
-            return ll.LiteralStructType([llfuncty, llselfty])
+            return ll.LiteralStructType([llfunty, llselfty])
         elif builtins.is_none(typ):
             if for_return:
                 return llvoid
@@ -400,8 +396,13 @@ class LLVMIRGenerator:
         elif isinstance(value, ir.Function):
             llfun = self.llmodule.get_global(value.name)
             if llfun is None:
-                llfun = ll.Function(self.llmodule, self.llty_of_type(value.type, bare=True),
-                                    value.name)
+                llfunty = self.llty_of_type(value.type, bare=True)
+                llfun   = ll.Function(self.llmodule, llfunty, value.name)
+
+                llretty = self.llty_of_type(value.type.ret, for_return=True)
+                if self.needs_sret(llretty):
+                    llfun.args[0].add_attribute('sret')
+
             return llfun
         else:
             assert False
@@ -516,11 +517,7 @@ class LLVMIRGenerator:
 
     def process_function(self, func):
         try:
-            self.llfunction = self.llmodule.get_global(func.name)
-
-            if self.llfunction is None:
-                llfunty = self.llty_of_type(func.type, bare=True)
-                self.llfunction = ll.Function(self.llmodule, llfunty, func.name)
+            self.llfunction = self.map(func)
 
             if func.is_internal:
                 self.llfunction.linkage = 'internal'
@@ -533,7 +530,7 @@ class LLVMIRGenerator:
             disubprogram = self.debug_info_emitter.emit_subprogram(func, self.llfunction)
 
             # First, map arguments.
-            if self.llfunction.type.pointee.__has_sret:
+            if self.has_sret(func.type):
                 llactualargs = self.llfunction.args[1:]
             else:
                 llactualargs = self.llfunction.args
@@ -1095,7 +1092,7 @@ class LLVMIRGenerator:
         else:
             llfun, llargs = self._prepare_closure_call(insn)
 
-            if llfun.type.pointee.__has_sret:
+            if self.has_sret(insn.target_function().type):
                 llstackptr = self.llbuilder.call(self.llbuiltin("llvm.stacksave"), [])
 
                 llresultslot = self.llbuilder.alloca(llfun.type.pointee.args[0].pointee)
@@ -1221,11 +1218,12 @@ class LLVMIRGenerator:
         if builtins.is_none(insn.value().type):
             return self.llbuilder.ret_void()
         else:
-            if self.llfunction.type.pointee.__has_sret:
-                self.llbuilder.store(self.map(insn.value()), self.llfunction.args[0])
+            llvalue = self.map(insn.value())
+            if self.needs_sret(llvalue):
+                self.llbuilder.store(llvalue, self.llfunction.args[0])
                 return self.llbuilder.ret_void()
             else:
-                return self.llbuilder.ret(self.map(insn.value()))
+                return self.llbuilder.ret(llvalue)
 
     def process_Unreachable(self, insn):
         return self.llbuilder.unreachable()