https://bugs.llvm.org/show_bug.cgi?id=41875
Bug ID: 41875
Summary: Incorrect code is generated for rotation of 32-bit
value to 32-bits
Product: clang
Version: 8.0
Hardware: PC
OS: All
Status: NEW
Severity: normal
Priority: P
Component: -New Bugs
Assignee: unassignedclangb...@nondot.org
Reporter: esol...@gmail.com
CC: htmldevelo...@gmail.com, llvm-bugs@lists.llvm.org,
neeil...@live.com, richard-l...@metafoo.co.uk
I'm using https://clang.godbolt.org/ with the following settings:
Compiler: x86-64 clang 8.0.0
Options: -Os
Test code:
```
#include <stdint.h>
extern uint32_t v32;
void rotate_32 (void)
{
uint32_t x = v32;
int n = 32;
v32 = (x >> n) | (x << (32 - n)); /* rotate right to 32-bits */
}
```
Disassembly:
```
rotate_32: # @rotate_32
mov dword ptr [rip + v32], -1
ret
```
I expect that value in v32 does not change, but -1 is loaded instead.
Also can be observed with other clang version and other optimization levels
(-O1, -O2, -O3).
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