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[CFL-AA] CFL-AA should not assert on an va_arg instruction

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The CFL-AA implementation was missing a visit* routine for va_arg instructions,
causing it to assert when run on a function that had one. For now, handle these
in a conservative way.

Fixes PR20954.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219718 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Hal Finkel 2014-10-14 20:51:26 +00:00
parent 3f349b2ba8
commit 2a77e6bdd1
2 changed files with 40 additions and 0 deletions
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11
lib/Analysis/CFLAliasAnalysis.cpp
View File

@ -317,6 +317,17 @@ public:
Output.push_back(Edge(Ptr, Val, EdgeType::Dereference, AttrNone));
}
void visitVAArgInst(VAArgInst &Inst) {
// We can't fully model va_arg here. For *Ptr = Inst.getOperand(0), it does
// two things:
// 1. Loads a value from *((T*)*Ptr).
// 2. Increments (stores to) *Ptr by some target-specific amount.
// For now, we'll handle this like a landingpad instruction (by placing the
// result in its own group, and having that group alias externals).
auto *Val = &Inst;
Output.push_back(Edge(Val, Val, EdgeType::Assign, AttrAll));
}
static bool isFunctionExternal(Function *Fn) {
return Fn->isDeclaration() || !Fn->hasLocalLinkage();
}

29
test/Analysis/CFLAliasAnalysis/va.ll Normal file
View File

@ -0,0 +1,29 @@
; RUN: opt < %s -cfl-aa -aa-eval -print-may-aliases -disable-output 2>&1 | FileCheck %s
; CHECK-LABEL: Function: test1
; CHECK: 0 no alias responses
define i32 @test1(i32 %X, ...) {
; Initialize variable argument processing
%ap = alloca i8*
%ap2 = bitcast i8** %ap to i8*
call void @llvm.va_start(i8* %ap2)
; Read a single integer argument
%tmp = va_arg i8** %ap, i32
; Demonstrate usage of llvm.va_copy and llvm.va_end
%aq = alloca i8*
%aq2 = bitcast i8** %aq to i8*
call void @llvm.va_copy(i8* %aq2, i8* %ap2)
call void @llvm.va_end(i8* %aq2)
; Stop processing of arguments.
call void @llvm.va_end(i8* %ap2)
ret i32 %tmp
}
declare void @llvm.va_start(i8*)
declare void @llvm.va_copy(i8*, i8*)
declare void @llvm.va_end(i8*)