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[GlobalsAA] Don't assume anything about functions that may be overridden

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Weak linkage and friends allow a symbol to be overriden outside the
code generator's model, so GlobalsAA shouldn't assume that anything it
can compute about such a symbol is valid.

llvm-svn: 250156
This commit is contained in:
James Molloy 2015-10-13 10:43:33 +00:00
parent 9edee2b861
commit 7b355004c3
2 changed files with 26 additions and 2 deletions
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4
lib/Analysis/GlobalsModRef.cpp
View File

@ -480,8 +480,8 @@ void GlobalsAAResult::AnalyzeCallGraph(CallGraph &CG, Module &M) {
const std::vector<CallGraphNode *> &SCC = *I;
assert(!SCC.empty() && "SCC with no functions?");
if (!SCC[0]->getFunction()) {
// Calls externally - can't say anything useful. Remove any existing
if (!SCC[0]->getFunction() || SCC[0]->getFunction()->mayBeOverridden()) {
// Calls externally or is weak - can't say anything useful. Remove any existing
// function records (may have been created when scanning globals).
for (auto *Node : SCC)
FunctionInfos.erase(Node->getFunction());

24
test/Analysis/GlobalsModRef/weak-interposition.ll Normal file
View File

@ -0,0 +1,24 @@
; RUN: opt -S -O1 -enable-non-lto-gmr=true < %s | FileCheck %s
@a = common global i32 0, align 4
; @hook_me is weak, so GMR must not eliminate the reload of @a in @f,
; even though @hook_me doesn't mod or ref @a.
; Function Attrs: nounwind ssp uwtable
define weak i32 @hook_me() {
ret i32 0
}
; Function Attrs: nounwind ssp uwtable
define i32 @f() {
%1 = alloca i32, align 4
store i32 4, i32* @a, align 4
%2 = call i32 @hook_me()
; CHECK: load i32, i32* @a, align 4
%3 = load i32, i32* @a, align 4
%4 = add nsw i32 %3, %2
store i32 %4, i32* @a, align 4
%5 = load i32, i32* %1
ret i32 %5
}