[clang] 66f1dcd - [Windows SEH] Fix the frame-ptr of a nested-filter within a _finally
Ten Tzen via cfe-commits
cfe-commits at lists.llvm.org
Sun Jul 12 01:39:53 PDT 2020
Author: Ten Tzen
Date: 2020-07-12T01:37:56-07:00
New Revision: 66f1dcd872dba189ee054fb016f4bff535fb5afc
URL: https://github.com/llvm/llvm-project/commit/66f1dcd872dba189ee054fb016f4bff535fb5afc
DIFF: https://github.com/llvm/llvm-project/commit/66f1dcd872dba189ee054fb016f4bff535fb5afc.diff
LOG: [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 at 0@main@@"), i8*%frame_pointer)
%1 = call i8* @llvm.localrecover(i8* bitcast (@"?fin$0 at 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
Added:
clang/test/CodeGen/windows-seh-filter-inFinally.c
Modified:
clang/lib/CodeGen/CGException.cpp
clang/lib/CodeGen/CodeGenFunction.h
Removed:
################################################################################
diff --git a/clang/lib/CodeGen/CGException.cpp b/clang/lib/CodeGen/CGException.cpp
index 2494f38b3159..bdf70252b5ad 100644
--- a/clang/lib/CodeGen/CGException.cpp
+++ b/clang/lib/CodeGen/CGException.cpp
@@ -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 at 0@main@@"),..)
+ // %1 = call i8* @llvm.localrecover(bitcast(@"?fin$0 at 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 =
diff --git a/clang/lib/CodeGen/CodeGenFunction.h b/clang/lib/CodeGen/CodeGenFunction.h
index b1841d646643..1fc2ed76ca9e 100644
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/lib/CodeGen/CodeGenFunction.h
@@ -264,6 +264,9 @@ class CodeGenFunction : public CodeGenTypeCache {
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;
diff --git a/clang/test/CodeGen/windows-seh-filter-inFinally.c b/clang/test/CodeGen/windows-seh-filter-inFinally.c
new file mode 100644
index 000000000000..f9dfca14f020
--- /dev/null
+++ b/clang/test/CodeGen/windows-seh-filter-inFinally.c
@@ -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 at 0@main@@" to i8*), i8* %frame_pointer)
+// CHECK-NEXT: %[[dst1:[0-9-]+]] = call i8* @llvm.localrecover(i8* bitcast (void (i8, i8*)* @"?fin$0 at 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;
+}
+
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