https://llvm.org/bugs/show_bug.cgi?id=23517
Bug ID: 23517
Summary: UBSan breaks target intrinsics taking constants:
should we fold overflow intrinsics? Where?
Product: clang
Version: trunk
Hardware: PC
OS: All
Status: NEW
Severity: normal
Priority: P
Component: LLVM Codegen
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Classification: Unclassified
Consider:
#include <arm_neon.h>
int32x2_t test(int64x2_t a) {
return vqrshrn_n_s64(a, 31 - 2);
}
clang -fsanitize=undefined -target arm64-apple-darwin -O0
will generate:
%3 = call { i32, i1 } @llvm.ssub.with.overflow.i32(i32 31, i32 2)
%4 = extractvalue { i32, i1 } %3, 0
...
%vqrshrn_n1 = call <2 x i32> @llvm.aarch64.neon.sqrshrn.v2i32(<2 x i64>
%vqrshrn_n, i32 %4)
Which is not OK, and breaks various assumptions in clang and LLVM (and will
causes us to eventually crash).
With -O0, we can't expect any pass to fold these; in fact, clang itself
assumes these intrinsics *will* take Constants, so we have to deal with this
during IR gen.
I see two alternatives:
- teach ConstantFolder to deal with overflow intrinsics (messy, because it's
implemented in terms of ConstantExprs)
- teach the UBSan clang CodeGen to do the folding (which sounds wrong)
--
You are receiving this mail because:
You are on the CC list for the bug.
_______________________________________________
LLVMbugs mailing list
[email protected]
http://lists.cs.uiuc.edu/mailman/listinfo/llvmbugs
