From 9f90088fa6d677370bc12cb6af55a09bc8d176a9 Mon Sep 17 00:00:00 2001 From: pca006132 Date: Thu, 6 Jan 2022 13:36:19 +0800 Subject: [PATCH] compiler: generate appropriate landingpad IR When used together with modified personality function, we got ~20% performance improvement in exception unwinding with zynq. --- artiq/compiler/ir.py | 1 + .../compiler/transforms/artiq_ir_generator.py | 2 + .../compiler/transforms/llvm_ir_generator.py | 43 +++++++++++++------ 3 files changed, 32 insertions(+), 14 deletions(-) diff --git a/artiq/compiler/ir.py b/artiq/compiler/ir.py index 3f984606f..ae786f8a8 100644 --- a/artiq/compiler/ir.py +++ b/artiq/compiler/ir.py @@ -1347,6 +1347,7 @@ class LandingPad(Terminator): def __init__(self, cleanup, name=""): super().__init__([cleanup], builtins.TException(), name) self.types = [] + self.has_cleanup = True def copy(self, mapper): self_copy = super().copy(mapper) diff --git a/artiq/compiler/transforms/artiq_ir_generator.py b/artiq/compiler/transforms/artiq_ir_generator.py index 4520ec049..5873664ed 100644 --- a/artiq/compiler/transforms/artiq_ir_generator.py +++ b/artiq/compiler/transforms/artiq_ir_generator.py @@ -718,6 +718,8 @@ class ARTIQIRGenerator(algorithm.Visitor): cleanup = self.add_block('handler.cleanup') landingpad = dispatcher.append(ir.LandingPad(cleanup)) + if not any(node.finalbody): + landingpad.has_cleanup = False handlers = [] for handler_node in node.handlers: diff --git a/artiq/compiler/transforms/llvm_ir_generator.py b/artiq/compiler/transforms/llvm_ir_generator.py index 521e0de14..1a206391e 100644 --- a/artiq/compiler/transforms/llvm_ir_generator.py +++ b/artiq/compiler/transforms/llvm_ir_generator.py @@ -1722,7 +1722,8 @@ class LLVMIRGenerator: def process_LandingPad(self, insn): # Layout on return from landing pad: {%_Unwind_Exception*, %Exception*} lllandingpadty = ll.LiteralStructType([llptr, llptr]) - lllandingpad = self.llbuilder.landingpad(lllandingpadty, cleanup=True) + lllandingpad = self.llbuilder.landingpad(lllandingpadty, + cleanup=insn.has_cleanup) llrawexn = self.llbuilder.extract_value(lllandingpad, 1) llexn = self.llbuilder.bitcast(llrawexn, self.llty_of_type(insn.type)) llexnnameptr = self.llbuilder.gep(llexn, [self.llindex(0), self.llindex(0)], @@ -1731,23 +1732,34 @@ class LLVMIRGenerator: for target, typ in insn.clauses(): if typ is None: - exnname = "" # see the comment in ksupport/eh.rs + # we use a null pointer here, similar to how cpp does it + # https://llvm.org/docs/ExceptionHandling.html#try-catch + # > If @ExcType is null, any exception matches, so the + # landingpad should always be entered. This is used for C++ + # catch-all blocks (“catch (...)”). + lllandingpad.add_clause( + ll.CatchClause( + ll.Constant(lli32, 0).inttoptr(llptr) + ) + ) else: exnname = "{}:{}".format(typ.id, typ.name) - llclauseexnname = self.llconst_of_const( - ir.Constant(exnname, builtins.TStr())) - llclauseexnnameptr = self.llmodule.globals.get("exn.{}".format(exnname)) - if llclauseexnnameptr is None: - llclauseexnnameptr = ll.GlobalVariable(self.llmodule, llclauseexnname.type, - name="exn.{}".format(exnname)) - llclauseexnnameptr.global_constant = True - llclauseexnnameptr.initializer = llclauseexnname - llclauseexnnameptr.linkage = "private" - llclauseexnnameptr.unnamed_addr = True - lllandingpad.add_clause(ll.CatchClause(llclauseexnnameptr)) + llclauseexnname = self.llconst_of_const( + ir.Constant(exnname, builtins.TStr())) + llclauseexnnameptr = self.llmodule.globals.get("exn.{}".format(exnname)) + if llclauseexnnameptr is None: + llclauseexnnameptr = ll.GlobalVariable(self.llmodule, llclauseexnname.type, + name="exn.{}".format(exnname)) + llclauseexnnameptr.global_constant = True + llclauseexnnameptr.initializer = llclauseexnname + llclauseexnnameptr.linkage = "private" + llclauseexnnameptr.unnamed_addr = True + lllandingpad.add_clause(ll.CatchClause(llclauseexnnameptr)) if typ is None: + # typ is None means that we match all exceptions, so no need to + # compare self.llbuilder.branch(self.map(target)) else: llexnlen = self.llbuilder.extract_value(llexnname, 1) @@ -1764,6 +1776,9 @@ class LLVMIRGenerator: self.llbuilder.branch(self.map(target)) if self.llbuilder.basic_block.terminator is None: - self.llbuilder.branch(self.map(insn.cleanup())) + if insn.has_cleanup: + self.llbuilder.branch(self.map(insn.cleanup())) + else: + self.llbuilder.resume(lllandingpad) return llexn