http://llvm.org/bugs/show_bug.cgi?id=15674
Bug ID: 15674
Summary: Broken switch when compiling with optimizations
Product: clang
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: release blocker
Priority: P
Component: LLVM Codegen
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Classification: Unclassified
Created attachment 10288
--> http://llvm.org/bugs/attachment.cgi?id=10288&action=edit
Bug with switch statements.
The attached test case is extracted from a much larger production code. When
compiled and run, the expected output is:
> ./t
> 1 1 1 1
However, if built with any -O level above zero, it outputs:
> ./t
> 1 0 0 0
It seems that the ::memcpy() is confusing the optimizer. I'm not sure at what
stage this happens, so logging against clang.
I can work around this by rewriting the code like below, but this seems like a
rather critical bug.
---- 8< ----
void quantize(char *data, float *src, int nb_src, int vsize)
{
unsigned char *i8 = (unsigned char *)data;
switch(vsize)
{
case 4: i8[3] = (unsigned char)src[3];
case 3: i8[2] = (unsigned char)src[2];
i8[1] = (unsigned char)src[1];
case 1: i8[0] = (unsigned char)src[0];
}
}
---- 8< ----
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