[llvm] r234196 - [WinEH] Don't sink allocas into child handlers
Reid Kleckner
reid at kleckner.net
Mon Apr 6 11:50:38 PDT 2015
Author: rnk
Date: Mon Apr 6 13:50:38 2015
New Revision: 234196
URL: http://llvm.org/viewvc/llvm-project?rev=234196&view=rev
Log:
[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.
Added:
llvm/trunk/test/CodeGen/WinEH/cppeh-alloca-sink.ll
Modified:
llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
llvm/trunk/lib/CodeGen/WinEHPrepare.cpp
Modified: llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp?rev=234196&r1=234195&r2=234196&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp Mon Apr 6 13:50:38 2015
@@ -5404,8 +5404,10 @@ SelectionDAGBuilder::visitIntrinsicCall(
// 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<AllocaInst>(I.getArgOperand(Idx)->stripPointerCasts());
+ Value *Arg = I.getArgOperand(Idx)->stripPointerCasts();
+ if (isa<ConstantPointerNull>(Arg))
+ continue; // Skip null pointers. They represent a hole in index space.
+ AllocaInst *Slot = cast<AllocaInst>(Arg);
assert(FuncInfo.StaticAllocaMap.count(Slot) &&
"can only escape static allocas");
int FI = FuncInfo.StaticAllocaMap[Slot];
Modified: llvm/trunk/lib/CodeGen/WinEHPrepare.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/WinEHPrepare.cpp?rev=234196&r1=234195&r2=234196&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/WinEHPrepare.cpp (original)
+++ llvm/trunk/lib/CodeGen/WinEHPrepare.cpp Mon Apr 6 13:50:38 2015
@@ -561,17 +561,9 @@ bool WinEHPrepare::prepareExceptionHandl
}
}
- // 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);
Added: llvm/trunk/test/CodeGen/WinEH/cppeh-alloca-sink.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/WinEH/cppeh-alloca-sink.ll?rev=234196&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/WinEH/cppeh-alloca-sink.ll (added)
+++ llvm/trunk/test/CodeGen/WinEH/cppeh-alloca-sink.ll Mon Apr 6 13:50:38 2015
@@ -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 at 8" = comdat any
+
+@"\01??_7type_info@@6B@" = external constant i8*
+@"\01??_R0H at 8" = linkonce_odr global %rtti.TypeDescriptor2 { i8** @"\01??_7type_info@@6B@", i8* null, [3 x i8] c".H\00" }, comdat
+ at llvm.eh.handlertype.H.0 = private unnamed_addr constant %eh.CatchHandlerType { i32 0, i8* bitcast (%rtti.TypeDescriptor2* @"\01??_R0H at 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 }
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