http://llvm.org/bugs/show_bug.cgi?id=14320
Bug #: 14320
Summary: SROA increases stack usage when used with ASan
Product: new-bugs
Version: trunk
Platform: All
OS/Version: All
Status: NEW
Severity: enhancement
Priority: P
Component: new bugs
AssignedTo: [email protected]
ReportedBy: [email protected]
CC: [email protected], [email protected],
[email protected]
Classification: Unclassified
$ cat sroa.cc
void f(volatile int *arg) {}
int main() {
volatile int b[20] = {0, 1};
f(b);
}
$ clang++ -O2 -fsanitize=address sroa.cc -S -emit-llvm -mllvm -print-after-all
-o sroa.ll 2>log.ll
$ cat sroa.ll
<...>
define i32 @main() nounwind uwtable address_safety {
%MyAlloca = alloca [288 x i8], align 32
%1 = ptrtoint [288 x i8]* %MyAlloca to i64
%2 = add i64 %1, 32
%3 = inttoptr i64 %2 to i32* <---------- int
%4 = add i64 %1, 96
%5 = inttoptr i64 %4 to i32* <---------- int
%6 = add i64 %1, 160
%7 = inttoptr i64 %6 to [18 x i32]* <---- int[18]
%8 = inttoptr i64 %1 to i64*
Looks like SROA changes this:
%b = alloca [20 x i32], align 16
to this:
%b.sroa.0 = alloca i32, align 16
%b.sroa.1 = alloca i32
%b.sroa.2 = alloca [18 x i32], align 8
and ASan inserts large redzones between this fake "different" local variables.
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