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[MergeFunc] Prevent silent miscompile of vararg functions

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The function merging pass miscompiles identical vararg functions. The
forwarding thunk it emits doesn't forward the full variable-length list
of arguments. Disable merging for vararg functions for now.

I've filed llvm.org/PR40345 to track the issue.

rdar://47326238

llvm-svn: 351411
This commit is contained in:
Vedant Kumar 2019-01-17 02:15:05 +00:00
parent 27982aa1e1
commit f667646768
2 changed files with 96 additions and 1 deletions
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8
lib/Transforms/IPO/MergeFunctions.cpp
View File

@ -383,6 +383,12 @@ bool MergeFunctions::doSanityCheck(std::vector<WeakTrackingVH> &Worklist) {
}
#endif
/// Check whether \p F is eligible for function merging.
static bool isEligibleForMerging(Function &F) {
return !F.isDeclaration() && !F.hasAvailableExternallyLinkage() &&
!F.isVarArg();
}
bool MergeFunctions::runOnModule(Module &M) {
if (skipModule(M))
return false;
@ -394,7 +400,7 @@ bool MergeFunctions::runOnModule(Module &M) {
std::vector<std::pair<FunctionComparator::FunctionHash, Function *>>
HashedFuncs;
for (Function &Func : M) {
if (!Func.isDeclaration() && !Func.hasAvailableExternallyLinkage()) {
if (isEligibleForMerging(Func)) {
HashedFuncs.push_back({FunctionComparator::functionHash(Func), &Func});
}
}

89
test/Transforms/MergeFunc/va_arg.ll Normal file
View File

@ -0,0 +1,89 @@
; RUN: opt -S -mergefunc < %s | FileCheck %s
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
%struct.__va_list_tag = type { i32, i32, i8*, i8* }
; CHECK-LABEL: define {{.*}}@_Z9simple_vaPKcz
; CHECK: call void @llvm.va_start
; CHECK: call void @llvm.va_end
define dso_local void @_Z9simple_vaPKcz(i8* nocapture readnone, ...) local_unnamed_addr {
%2 = alloca [1 x %struct.__va_list_tag], align 16
%3 = bitcast [1 x %struct.__va_list_tag]* %2 to i8*
call void @llvm.va_start(i8* nonnull %3)
%4 = getelementptr inbounds [1 x %struct.__va_list_tag], [1 x %struct.__va_list_tag]* %2, i64 0, i64 0, i32 0
%5 = load i32, i32* %4, align 16
%6 = icmp ult i32 %5, 41
br i1 %6, label %7, label %13
; <label>:7: ; preds = %1
%8 = getelementptr inbounds [1 x %struct.__va_list_tag], [1 x %struct.__va_list_tag]* %2, i64 0, i64 0, i32 3
%9 = load i8*, i8** %8, align 16
%10 = sext i32 %5 to i64
%11 = getelementptr i8, i8* %9, i64 %10
%12 = add i32 %5, 8
store i32 %12, i32* %4, align 16
br label %17
; <label>:13: ; preds = %1
%14 = getelementptr inbounds [1 x %struct.__va_list_tag], [1 x %struct.__va_list_tag]* %2, i64 0, i64 0, i32 2
%15 = load i8*, i8** %14, align 8
%16 = getelementptr i8, i8* %15, i64 8
store i8* %16, i8** %14, align 8
br label %17
; <label>:17: ; preds = %13, %7
%18 = phi i8* [ %11, %7 ], [ %15, %13 ]
%19 = bitcast i8* %18 to i32*
%20 = load i32, i32* %19, align 4
call void @_Z6escapei(i32 %20)
call void @llvm.va_end(i8* nonnull %3)
ret void
}
; Function Attrs: nounwind
declare void @llvm.va_start(i8*)
; Function Attrs: minsize optsize
declare dso_local void @_Z6escapei(i32) local_unnamed_addr
; Function Attrs: nounwind
declare void @llvm.va_end(i8*)
; CHECK-LABEL: define {{.*}}@_Z10simple_va2PKcz
; CHECK: call void @llvm.va_start
; CHECK: call void @llvm.va_end
define dso_local void @_Z10simple_va2PKcz(i8* nocapture readnone, ...) local_unnamed_addr {
%2 = alloca [1 x %struct.__va_list_tag], align 16
%3 = bitcast [1 x %struct.__va_list_tag]* %2 to i8*
call void @llvm.va_start(i8* nonnull %3)
%4 = getelementptr inbounds [1 x %struct.__va_list_tag], [1 x %struct.__va_list_tag]* %2, i64 0, i64 0, i32 0
%5 = load i32, i32* %4, align 16
%6 = icmp ult i32 %5, 41
br i1 %6, label %7, label %13
; <label>:7: ; preds = %1
%8 = getelementptr inbounds [1 x %struct.__va_list_tag], [1 x %struct.__va_list_tag]* %2, i64 0, i64 0, i32 3
%9 = load i8*, i8** %8, align 16
%10 = sext i32 %5 to i64
%11 = getelementptr i8, i8* %9, i64 %10
%12 = add i32 %5, 8
store i32 %12, i32* %4, align 16
br label %17
; <label>:13: ; preds = %1
%14 = getelementptr inbounds [1 x %struct.__va_list_tag], [1 x %struct.__va_list_tag]* %2, i64 0, i64 0, i32 2
%15 = load i8*, i8** %14, align 8
%16 = getelementptr i8, i8* %15, i64 8
store i8* %16, i8** %14, align 8
br label %17
; <label>:17: ; preds = %13, %7
%18 = phi i8* [ %11, %7 ], [ %15, %13 ]
%19 = bitcast i8* %18 to i32*
%20 = load i32, i32* %19, align 4
call void @_Z6escapei(i32 %20)
call void @llvm.va_end(i8* nonnull %3)
ret void
}