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[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. llvm-svn: 234196
This commit is contained in:
Reid Kleckner
parent
497a3115c3
commit
b881568c8b
@ -5404,8 +5404,10 @@ SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I, unsigned Intrinsic) {
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// Directly emit some FRAME_ALLOC machine instrs. Label assignment emission
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// is the same on all targets.
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for (unsigned Idx = 0, E = I.getNumArgOperands(); Idx < E; ++Idx) {
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AllocaInst *Slot =
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cast<AllocaInst>(I.getArgOperand(Idx)->stripPointerCasts());
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Value *Arg = I.getArgOperand(Idx)->stripPointerCasts();
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if (isa<ConstantPointerNull>(Arg))
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continue; // Skip null pointers. They represent a hole in index space.
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AllocaInst *Slot = cast<AllocaInst>(Arg);
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assert(FuncInfo.StaticAllocaMap.count(Slot) &&
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"can only escape static allocas");
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int FI = FuncInfo.StaticAllocaMap[Slot];
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@ -561,17 +561,9 @@ bool WinEHPrepare::prepareExceptionHandlers(
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}
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}
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// If the parent alloca is used by exactly one handler and is not a catch
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// parameter, erase the parent and leave the copy in the outlined handler.
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// Catch parameters are indicated by a single null pointer in Allocas.
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if (ParentAlloca->getNumUses() == 0 && Allocas.size() == 1 &&
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Allocas[0] != getCatchObjectSentinel()) {
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ParentAlloca->eraseFromParent();
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// FIXME: Put a null entry in the llvm.frameescape call because we've
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// already created llvm.eh.actions calls with indices into it.
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AllocasToEscape.push_back(Constant::getNullValue(Int8PtrType));
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continue;
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}
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// FIXME: We should try to sink unescaped allocas from the parent frame into
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// the child frame. If the alloca is escaped, we have to use the lifetime
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// markers to ensure that the alloca is only live within the child frame.
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// Add this alloca to the list of things to escape.
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AllocasToEscape.push_back(ParentAlloca);
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180
test/CodeGen/WinEH/cppeh-alloca-sink.ll
Normal file
180
test/CodeGen/WinEH/cppeh-alloca-sink.ll
Normal file
@ -0,0 +1,180 @@
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; RUN: opt -mtriple=x86_64-pc-windows-msvc -winehprepare -S -o - < %s | FileCheck %s
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; This test describes two difficult cases in sinking allocas into child frames.
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; We don't currently do this optimization, but we'll need to tweak these tests
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; when we do.
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; This test is based on the following code:
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;
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; // In this case we can sink the alloca from the parent into the catch because
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; // the lifetime is limited to the catch.
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; extern "C" void may_throw();
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; extern "C" void sink_alloca_to_catch() {
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; try {
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; may_throw();
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; } catch (int) {
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; volatile int only_used_in_catch = 42;
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; }
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; }
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;
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; // In this case we cannot. The variable should live as long as the parent
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; // frame lives.
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; extern "C" void use_catch_var(int *);
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; extern "C" void dont_sink_alloca_to_catch(int n) {
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; int live_in_out_catch = 0;
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; while (n > 0) {
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; try {
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; may_throw();
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; } catch (int) {
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; use_catch_var(&live_in_out_catch);
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; }
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; n--;
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; }
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; }
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target datalayout = "e-m:w-i64:64-f80:128-n8:16:32:64-S128"
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target triple = "x86_64-pc-windows-msvc"
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declare void @may_throw() #1
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declare i32 @__CxxFrameHandler3(...)
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declare i32 @llvm.eh.typeid.for(i8*) #2
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declare void @llvm.eh.begincatch(i8* nocapture, i8* nocapture) #3
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declare void @llvm.eh.endcatch() #3
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%rtti.TypeDescriptor2 = type { i8**, i8*, [3 x i8] }
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%eh.CatchHandlerType = type { i32, i8* }
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$"\01??_R0H@8" = comdat any
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@"\01??_7type_info@@6B@" = external constant i8*
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@"\01??_R0H@8" = linkonce_odr global %rtti.TypeDescriptor2 { i8** @"\01??_7type_info@@6B@", i8* null, [3 x i8] c".H\00" }, comdat
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@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"
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; Function Attrs: uwtable
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define void @sink_alloca_to_catch() #0 {
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entry:
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%0 = alloca i32
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%only_used_in_catch = alloca i32, align 4
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invoke void @may_throw()
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to label %try.cont unwind label %lpad
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lpad: ; preds = %entry
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%1 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__CxxFrameHandler3 to i8*)
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catch %eh.CatchHandlerType* @llvm.eh.handlertype.H.0
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%2 = extractvalue { i8*, i32 } %1, 1
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%3 = tail call i32 @llvm.eh.typeid.for(i8* bitcast (%eh.CatchHandlerType* @llvm.eh.handlertype.H.0 to i8*)) #3
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%matches = icmp eq i32 %2, %3
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br i1 %matches, label %catch, label %eh.resume
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catch: ; preds = %lpad
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%4 = extractvalue { i8*, i32 } %1, 0
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call void @llvm.eh.begincatch(i8* %4, i8* null) #3
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store volatile i32 42, i32* %only_used_in_catch, align 4
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tail call void @llvm.eh.endcatch() #3
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br label %try.cont
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try.cont: ; preds = %entry, %catch
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ret void
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eh.resume: ; preds = %lpad
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resume { i8*, i32 } %1
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}
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; CHECK-LABEL: define void @sink_alloca_to_catch()
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; CHECK: call void (...)* @llvm.frameescape(i32* %only_used_in_catch)
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declare void @use_catch_var(i32*) #1
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; Function Attrs: uwtable
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define void @dont_sink_alloca_to_catch(i32 %n) #0 {
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entry:
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%0 = alloca i32
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%n.addr = alloca i32, align 4
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%live_in_out_catch = alloca i32, align 4
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%exn.slot = alloca i8*
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%ehselector.slot = alloca i32
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store i32 %n, i32* %n.addr, align 4
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br label %while.cond
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while.cond: ; preds = %try.cont, %entry
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%1 = load i32, i32* %n.addr, align 4
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%cmp = icmp sgt i32 %1, 0
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br i1 %cmp, label %while.body, label %while.end
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while.body: ; preds = %while.cond
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invoke void @may_throw()
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to label %invoke.cont unwind label %lpad
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invoke.cont: ; preds = %while.body
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br label %try.cont
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lpad: ; preds = %while.body
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%2 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__CxxFrameHandler3 to i8*)
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catch i8* bitcast (%eh.CatchHandlerType* @llvm.eh.handlertype.H.0 to i8*)
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%3 = extractvalue { i8*, i32 } %2, 0
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store i8* %3, i8** %exn.slot
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%4 = extractvalue { i8*, i32 } %2, 1
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store i32 %4, i32* %ehselector.slot
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br label %catch.dispatch
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catch.dispatch: ; preds = %lpad
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%sel = load i32, i32* %ehselector.slot
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%5 = call i32 @llvm.eh.typeid.for(i8* bitcast (%eh.CatchHandlerType* @llvm.eh.handlertype.H.0 to i8*)) #3
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%matches = icmp eq i32 %sel, %5
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br i1 %matches, label %catch, label %eh.resume
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catch: ; preds = %catch.dispatch
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%exn = load i8*, i8** %exn.slot
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call void @llvm.eh.begincatch(i8* %exn, i8* null) #3
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invoke void @use_catch_var(i32* %live_in_out_catch)
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to label %invoke.cont2 unwind label %lpad1
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invoke.cont2: ; preds = %catch
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call void @llvm.eh.endcatch() #3
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br label %try.cont
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try.cont: ; preds = %invoke.cont2, %invoke.cont
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%6 = load i32, i32* %0
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%7 = load i32, i32* %n.addr, align 4
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%dec = add nsw i32 %7, -1
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store i32 %dec, i32* %n.addr, align 4
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br label %while.cond
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lpad1: ; preds = %catch
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%8 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__CxxFrameHandler3 to i8*)
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cleanup
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%9 = extractvalue { i8*, i32 } %8, 0
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store i8* %9, i8** %exn.slot
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%10 = extractvalue { i8*, i32 } %8, 1
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store i32 %10, i32* %ehselector.slot
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call void @llvm.eh.endcatch() #3
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br label %eh.resume
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while.end: ; preds = %while.cond
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ret void
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eh.resume: ; preds = %lpad1, %catch.dispatch
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%exn3 = load i8*, i8** %exn.slot
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%sel4 = load i32, i32* %ehselector.slot
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%lpad.val = insertvalue { i8*, i32 } undef, i8* %exn3, 0
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%lpad.val5 = insertvalue { i8*, i32 } %lpad.val, i32 %sel4, 1
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resume { i8*, i32 } %lpad.val5
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}
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; CHECK-LABEL: define void @dont_sink_alloca_to_catch(i32 %n)
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; CHECK: call void (...)* @llvm.frameescape(i32* %live_in_out_catch)
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; CHECK-LABEL: define internal i8* @sink_alloca_to_catch.catch(i8*, i8*)
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; CHECK: %only_used_in_catch.i8 = call i8* @llvm.framerecover({{.*}}, i32 0)
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; CHECK: %only_used_in_catch = bitcast
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; CHECK-LABEL: define internal i8* @dont_sink_alloca_to_catch.catch(i8*, i8*)
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; CHECK: %live_in_out_catch.i8 = call i8* @llvm.framerecover({{.*}}, i32 0)
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; CHECK: %live_in_out_catch = bitcast
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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" }
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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" }
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attributes #2 = { nounwind readnone }
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attributes #3 = { nounwind }
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