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[Windows SEH] Fix the frame-ptr of a nested-filter within a _finally 

This change fixed a SEH bug (exposed by test58 & test61 in MSVC test xcpt4u.c);
when an Except-filter is located inside a finally, the frame-pointer generated today
via intrinsic @llvm.eh.recoverfp is the frame-pointer of the immediate
parent _finally, not the frame-ptr of outermost host function.

The fix is to retrieve the Establisher's frame-pointer that was previously saved in
parent's frame.
The prolog of a filter inside a _finally should be like code below:

%0 = call i8* @llvm.eh.recoverfp(i8* bitcast (@"?fin$0@0@main@@"), i8*%frame_pointer)
%1 = call i8* @llvm.localrecover(i8* bitcast (@"?fin$0@0@main@@"), i8*%0, i32 0)
%2 = bitcast i8* %1 to i8**
%3 = load i8*, i8** %2, align 8

Differential Revision: https://reviews.llvm.org/D77982
This commit is contained in:
Ten Tzen 2020-07-12 01:37:56 -07:00
parent 6634aef71f
commit 66f1dcd872
3 changed files with 82 additions and 0 deletions
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43
clang/lib/CodeGen/CGException.cpp
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@ -1815,6 +1815,48 @@ void CodeGenFunction::EmitCapturedLocals(CodeGenFunction &ParentCGF,
llvm::Constant *ParentI8Fn =
llvm::ConstantExpr::getBitCast(ParentCGF.CurFn, Int8PtrTy);
ParentFP = Builder.CreateCall(RecoverFPIntrin, {ParentI8Fn, EntryFP});
// if the parent is a _finally, the passed-in ParentFP is the FP
// of parent _finally, not Establisher's FP (FP of outermost function).
// Establkisher FP is 2nd paramenter passed into parent _finally.
// Fortunately, it's always saved in parent's frame. The following
// code retrieves it, and escapes it so that spill instruction won't be
// optimized away.
if (ParentCGF.ParentCGF != nullptr) {
// Locate and escape Parent's frame_pointer.addr alloca
// Depending on target, should be 1st/2nd one in LocalDeclMap.
// Let's just scan for ImplicitParamDecl with VoidPtrTy.
llvm::AllocaInst *FramePtrAddrAlloca = nullptr;
for (auto &I : ParentCGF.LocalDeclMap) {
const VarDecl *D = cast<VarDecl>(I.first);
if (isa<ImplicitParamDecl>(D) &&
D->getType() == getContext().VoidPtrTy) {
assert(D->getName().startswith("frame_pointer"));
FramePtrAddrAlloca = cast<llvm::AllocaInst>(I.second.getPointer());
break;
}
}
assert(FramePtrAddrAlloca);
auto InsertPair = ParentCGF.EscapedLocals.insert(
std::make_pair(FramePtrAddrAlloca, ParentCGF.EscapedLocals.size()));
int FrameEscapeIdx = InsertPair.first->second;
// an example of a filter's prolog::
// %0 = call i8* @llvm.eh.recoverfp(bitcast(@"?fin$0@0@main@@"),..)
// %1 = call i8* @llvm.localrecover(bitcast(@"?fin$0@0@main@@"),..)
// %2 = bitcast i8* %1 to i8**
// %3 = load i8*, i8* *%2, align 8
// ==> %3 is the frame-pointer of outermost host function
llvm::Function *FrameRecoverFn = llvm::Intrinsic::getDeclaration(
&CGM.getModule(), llvm::Intrinsic::localrecover);
llvm::Constant *ParentI8Fn =
llvm::ConstantExpr::getBitCast(ParentCGF.CurFn, Int8PtrTy);
ParentFP = Builder.CreateCall(
FrameRecoverFn, {ParentI8Fn, ParentFP,
llvm::ConstantInt::get(Int32Ty, FrameEscapeIdx)});
ParentFP = Builder.CreateBitCast(ParentFP, CGM.VoidPtrPtrTy);
ParentFP = Builder.CreateLoad(Address(ParentFP, getPointerAlign()));
}
}
// Create llvm.localrecover calls for all captures.
@ -2013,6 +2055,7 @@ void CodeGenFunction::pushSEHCleanup(CleanupKind Kind,
void CodeGenFunction::EnterSEHTryStmt(const SEHTryStmt &S) {
CodeGenFunction HelperCGF(CGM, /*suppressNewContext=*/true);
HelperCGF.ParentCGF = this;
if (const SEHFinallyStmt *Finally = S.getFinallyHandler()) {
// Outline the finally block.
llvm::Function *FinallyFunc =

3
clang/lib/CodeGen/CodeGenFunction.h
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@ -264,6 +264,9 @@ public:
CodeGenModule &CGM; // Per-module state.
const TargetInfo &Target;
// For EH/SEH outlined funclets, this field points to parent's CGF
CodeGenFunction *ParentCGF = nullptr;
typedef std::pair<llvm::Value *, llvm::Value *> ComplexPairTy;
LoopInfoStack LoopStack;
CGBuilderTy Builder;

36
clang/test/CodeGen/windows-seh-filter-inFinally.c Normal file
View File

@ -0,0 +1,36 @@
// RUN: %clang_cc1 -triple x86_64-windows -fms-extensions -Wno-implicit-function-declaration -S -emit-llvm %s -o - | FileCheck %s
// CHECK: %[[dst:[0-9-]+]] = call i8* @llvm.eh.recoverfp(i8* bitcast (void (i8, i8*)* @"?fin$0@0@main@@" to i8*), i8* %frame_pointer)
// CHECK-NEXT: %[[dst1:[0-9-]+]] = call i8* @llvm.localrecover(i8* bitcast (void (i8, i8*)* @"?fin$0@0@main@@" to i8*), i8* %[[dst]], i32 0)
// CHECK-NEXT: %[[dst2:[0-9-]+]] = bitcast i8* %[[dst1]] to i8**
// CHECK-NEXT: = load i8*, i8** %[[dst2]], align 8
int
main(int argc, char *argv[])
{
int Counter = 0;
//
// Try/except within the finally clause of a try/finally.
//
__try {
Counter -= 1;
}
__finally {
__try {
Counter += 2;
// RtlRaiseStatus(STATUS_INTEGER_OVERFLOW);
} __except(Counter) {
__try {
Counter += 3;
}
__finally {
if (abnormal_termination() == 1) {
Counter += 5;
}
}
}
}
// expect Counter == 9
return 1;
}