https://bugs.llvm.org/show_bug.cgi?id=41098
Bug ID: 41098
Summary: Missed rotate oportunity
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
Not sure if reported or not.. please close if a duplicate..
struct edge {
unsigned char from;
unsigned char to;
};
void reverse_edge(struct edge *e) {
unsigned char tmp = e->from;
e->from = e->to;
e->to = tmp;
}
Clang -O3:
reverse_edge(edge*): # @reverse_edge(edge*)
mov al, byte ptr [rdi]
mov cl, byte ptr [rdi + 1]
mov byte ptr [rdi], cl
mov byte ptr [rdi + 1], al
ret
GCC generates
reverse_edge(edge*):
rol WORD PTR [rdi], 8
ret
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