http://llvm.org/bugs/show_bug.cgi?id=20535
Bug ID: 20535
Summary: UBSan breaks compilation of inline asm
Product: clang
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P
Component: LLVM Codegen
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected], [email protected]
Classification: Unclassified
$ cat tmp/ubsan/asm.c
void clear_blocks_sse() {
__asm__ volatile (
"" : : "i"(128 * 6)
);
}
$ ./bin/clang -c -fsanitize=undefined tmp/ubsan/asm.c -o asm.o
tmp/ubsan/asm.c:3:9: error: invalid operand for inline asm constraint 'i'
"" : : "i"(128 * 6)
^
1 error generated.
This happens because 128 * 6 is not a compiled-time constant anymore - it is
instead a regular Value calculated by @llvm.smul.with.overflow.i32 intrinsic.
I'm not sure what is the best approach for fixing this. Should we check for
overflow statically if both operands of the checked binary op are constants?
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