From ebb3c53316538e6799f727ade65ce95606f3cd05 Mon Sep 17 00:00:00 2001 From: Reid Kleckner Date: Mon, 6 Apr 2015 18:50:38 +0000 Subject: [PATCH] [WinEH] Don't sink allocas into child handlers The uselist isn't enough to infer anything about the lifetime of such allocas. If we want to re-add this optimization, we will need to leverage lifetime markers to do it. Fixes PR23122. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@234196 91177308-0d34-0410-b5e6-96231b3b80d8 --- .../SelectionDAG/SelectionDAGBuilder.cpp | 6 +- lib/CodeGen/WinEHPrepare.cpp | 14 +- test/CodeGen/WinEH/cppeh-alloca-sink.ll | 180 ++++++++++++++++++ 3 files changed, 187 insertions(+), 13 deletions(-) create mode 100644 test/CodeGen/WinEH/cppeh-alloca-sink.ll diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp index 710d8073fed..626101bcf60 100644 --- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp +++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp @@ -5404,8 +5404,10 @@ SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I, unsigned Intrinsic) { // Directly emit some FRAME_ALLOC machine instrs. Label assignment emission // is the same on all targets. for (unsigned Idx = 0, E = I.getNumArgOperands(); Idx < E; ++Idx) { - AllocaInst *Slot = - cast(I.getArgOperand(Idx)->stripPointerCasts()); + Value *Arg = I.getArgOperand(Idx)->stripPointerCasts(); + if (isa(Arg)) + continue; // Skip null pointers. They represent a hole in index space. + AllocaInst *Slot = cast(Arg); assert(FuncInfo.StaticAllocaMap.count(Slot) && "can only escape static allocas"); int FI = FuncInfo.StaticAllocaMap[Slot]; diff --git a/lib/CodeGen/WinEHPrepare.cpp b/lib/CodeGen/WinEHPrepare.cpp index 9ebe8a2fc10..ab4f5cde030 100644 --- a/lib/CodeGen/WinEHPrepare.cpp +++ b/lib/CodeGen/WinEHPrepare.cpp @@ -561,17 +561,9 @@ bool WinEHPrepare::prepareExceptionHandlers( } } - // If the parent alloca is used by exactly one handler and is not a catch - // parameter, erase the parent and leave the copy in the outlined handler. - // Catch parameters are indicated by a single null pointer in Allocas. - if (ParentAlloca->getNumUses() == 0 && Allocas.size() == 1 && - Allocas[0] != getCatchObjectSentinel()) { - ParentAlloca->eraseFromParent(); - // FIXME: Put a null entry in the llvm.frameescape call because we've - // already created llvm.eh.actions calls with indices into it. - AllocasToEscape.push_back(Constant::getNullValue(Int8PtrType)); - continue; - } + // FIXME: We should try to sink unescaped allocas from the parent frame into + // the child frame. If the alloca is escaped, we have to use the lifetime + // markers to ensure that the alloca is only live within the child frame. // Add this alloca to the list of things to escape. AllocasToEscape.push_back(ParentAlloca); diff --git a/test/CodeGen/WinEH/cppeh-alloca-sink.ll b/test/CodeGen/WinEH/cppeh-alloca-sink.ll new file mode 100644 index 00000000000..93c410fbdb6 --- /dev/null +++ b/test/CodeGen/WinEH/cppeh-alloca-sink.ll @@ -0,0 +1,180 @@ +; RUN: opt -mtriple=x86_64-pc-windows-msvc -winehprepare -S -o - < %s | FileCheck %s + +; This test describes two difficult cases in sinking allocas into child frames. +; We don't currently do this optimization, but we'll need to tweak these tests +; when we do. + +; This test is based on the following code: +; +; // In this case we can sink the alloca from the parent into the catch because +; // the lifetime is limited to the catch. +; extern "C" void may_throw(); +; extern "C" void sink_alloca_to_catch() { +; try { +; may_throw(); +; } catch (int) { +; volatile int only_used_in_catch = 42; +; } +; } +; +; // In this case we cannot. The variable should live as long as the parent +; // frame lives. +; extern "C" void use_catch_var(int *); +; extern "C" void dont_sink_alloca_to_catch(int n) { +; int live_in_out_catch = 0; +; while (n > 0) { +; try { +; may_throw(); +; } catch (int) { +; use_catch_var(&live_in_out_catch); +; } +; n--; +; } +; } + +target datalayout = "e-m:w-i64:64-f80:128-n8:16:32:64-S128" +target triple = "x86_64-pc-windows-msvc" + +declare void @may_throw() #1 +declare i32 @__CxxFrameHandler3(...) +declare i32 @llvm.eh.typeid.for(i8*) #2 +declare void @llvm.eh.begincatch(i8* nocapture, i8* nocapture) #3 +declare void @llvm.eh.endcatch() #3 + +%rtti.TypeDescriptor2 = type { i8**, i8*, [3 x i8] } +%eh.CatchHandlerType = type { i32, i8* } + +$"\01??_R0H@8" = comdat any + +@"\01??_7type_info@@6B@" = external constant i8* +@"\01??_R0H@8" = linkonce_odr global %rtti.TypeDescriptor2 { i8** @"\01??_7type_info@@6B@", i8* null, [3 x i8] c".H\00" }, comdat +@llvm.eh.handlertype.H.0 = private unnamed_addr constant %eh.CatchHandlerType { i32 0, i8* bitcast (%rtti.TypeDescriptor2* @"\01??_R0H@8" to i8*) }, section "llvm.metadata" + +; Function Attrs: uwtable +define void @sink_alloca_to_catch() #0 { +entry: + %0 = alloca i32 + %only_used_in_catch = alloca i32, align 4 + invoke void @may_throw() + to label %try.cont unwind label %lpad + +lpad: ; preds = %entry + %1 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__CxxFrameHandler3 to i8*) + catch %eh.CatchHandlerType* @llvm.eh.handlertype.H.0 + %2 = extractvalue { i8*, i32 } %1, 1 + %3 = tail call i32 @llvm.eh.typeid.for(i8* bitcast (%eh.CatchHandlerType* @llvm.eh.handlertype.H.0 to i8*)) #3 + %matches = icmp eq i32 %2, %3 + br i1 %matches, label %catch, label %eh.resume + +catch: ; preds = %lpad + %4 = extractvalue { i8*, i32 } %1, 0 + call void @llvm.eh.begincatch(i8* %4, i8* null) #3 + store volatile i32 42, i32* %only_used_in_catch, align 4 + tail call void @llvm.eh.endcatch() #3 + br label %try.cont + +try.cont: ; preds = %entry, %catch + ret void + +eh.resume: ; preds = %lpad + resume { i8*, i32 } %1 +} + +; CHECK-LABEL: define void @sink_alloca_to_catch() +; CHECK: call void (...)* @llvm.frameescape(i32* %only_used_in_catch) + +declare void @use_catch_var(i32*) #1 + +; Function Attrs: uwtable +define void @dont_sink_alloca_to_catch(i32 %n) #0 { +entry: + %0 = alloca i32 + %n.addr = alloca i32, align 4 + %live_in_out_catch = alloca i32, align 4 + %exn.slot = alloca i8* + %ehselector.slot = alloca i32 + store i32 %n, i32* %n.addr, align 4 + br label %while.cond + +while.cond: ; preds = %try.cont, %entry + %1 = load i32, i32* %n.addr, align 4 + %cmp = icmp sgt i32 %1, 0 + br i1 %cmp, label %while.body, label %while.end + +while.body: ; preds = %while.cond + invoke void @may_throw() + to label %invoke.cont unwind label %lpad + +invoke.cont: ; preds = %while.body + br label %try.cont + +lpad: ; preds = %while.body + %2 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__CxxFrameHandler3 to i8*) + catch i8* bitcast (%eh.CatchHandlerType* @llvm.eh.handlertype.H.0 to i8*) + %3 = extractvalue { i8*, i32 } %2, 0 + store i8* %3, i8** %exn.slot + %4 = extractvalue { i8*, i32 } %2, 1 + store i32 %4, i32* %ehselector.slot + br label %catch.dispatch + +catch.dispatch: ; preds = %lpad + %sel = load i32, i32* %ehselector.slot + %5 = call i32 @llvm.eh.typeid.for(i8* bitcast (%eh.CatchHandlerType* @llvm.eh.handlertype.H.0 to i8*)) #3 + %matches = icmp eq i32 %sel, %5 + br i1 %matches, label %catch, label %eh.resume + +catch: ; preds = %catch.dispatch + %exn = load i8*, i8** %exn.slot + call void @llvm.eh.begincatch(i8* %exn, i8* null) #3 + invoke void @use_catch_var(i32* %live_in_out_catch) + to label %invoke.cont2 unwind label %lpad1 + +invoke.cont2: ; preds = %catch + call void @llvm.eh.endcatch() #3 + br label %try.cont + +try.cont: ; preds = %invoke.cont2, %invoke.cont + %6 = load i32, i32* %0 + %7 = load i32, i32* %n.addr, align 4 + %dec = add nsw i32 %7, -1 + store i32 %dec, i32* %n.addr, align 4 + br label %while.cond + +lpad1: ; preds = %catch + %8 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__CxxFrameHandler3 to i8*) + cleanup + %9 = extractvalue { i8*, i32 } %8, 0 + store i8* %9, i8** %exn.slot + %10 = extractvalue { i8*, i32 } %8, 1 + store i32 %10, i32* %ehselector.slot + call void @llvm.eh.endcatch() #3 + br label %eh.resume + +while.end: ; preds = %while.cond + ret void + +eh.resume: ; preds = %lpad1, %catch.dispatch + %exn3 = load i8*, i8** %exn.slot + %sel4 = load i32, i32* %ehselector.slot + %lpad.val = insertvalue { i8*, i32 } undef, i8* %exn3, 0 + %lpad.val5 = insertvalue { i8*, i32 } %lpad.val, i32 %sel4, 1 + resume { i8*, i32 } %lpad.val5 +} + +; CHECK-LABEL: define void @dont_sink_alloca_to_catch(i32 %n) +; CHECK: call void (...)* @llvm.frameescape(i32* %live_in_out_catch) + +; CHECK-LABEL: define internal i8* @sink_alloca_to_catch.catch(i8*, i8*) +; CHECK: %only_used_in_catch.i8 = call i8* @llvm.framerecover({{.*}}, i32 0) +; CHECK: %only_used_in_catch = bitcast + +; CHECK-LABEL: define internal i8* @dont_sink_alloca_to_catch.catch(i8*, i8*) +; CHECK: %live_in_out_catch.i8 = call i8* @llvm.framerecover({{.*}}, i32 0) +; CHECK: %live_in_out_catch = bitcast + + + +attributes #0 = { uwtable "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "unsafe-fp-math"="false" "use-soft-float"="false" } +attributes #1 = { "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "unsafe-fp-math"="false" "use-soft-float"="false" } +attributes #2 = { nounwind readnone } +attributes #3 = { nounwind } -- 2.34.1