http://llvm.org/bugs/show_bug.cgi?id=17955
Bug ID: 17955
Summary: LLVM 3.3 misses bitfield optimization
Product: new-bugs
Version: trunk
Hardware: PC
OS: All
Status: NEW
Severity: normal
Priority: P
Component: new bugs
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Classification: Unclassified
consider:
struct foo {
int f_x : 1;
int f_y : 1;
};
int fun(struct foo *f) {
return f->f_x || f->f_y;
}
we get:
movb (%rdi), %al
movb $1, %cl
testb $1, %al
jne .LBB0_2
andb $2, %al
shrb %al
movb %al, %cl
.LBB0_2:
movzbl %cl, %eax
ret
it would be nicer to get:
movl (%rdi), %eax
andl $3, %eax
GCC 4.9 gets pretty close.
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