https://bugs.llvm.org/show_bug.cgi?id=52049
Bug ID: 52049
Summary: Missing combine of shl+bswap to rol
Product: libraries
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: Scalar Optimizations
Assignee: unassignedb...@nondot.org
Reporter: david.bolvan...@gmail.com
CC: llvm-bugs@lists.llvm.org
unsigned read_be16 (unsigned char *data)
{
return *(data + 1) | (*data << 8);
}
LLVM
read_be16(unsigned char*): # @read_be16(unsigned char*)
movzx eax, word ptr [rdi]
shl eax, 16
bswap eax
ret
GCC
read_be16(unsigned char*):
movzx eax, WORD PTR [rdi]
rol ax, 8
movzx eax, ax
ret
https://godbolt.org/z/s8ha55Y7W
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