| Issue |
142071
|
| Summary |
[AArch64] We can materialize some immediates using add or sub
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
AZero13
|
add and sub have different immediate operand rules than mov.
We can use this to materialize certain operands in a single instruction.
define i64 @mov_basic_6() nounwind {
; CHECK-LABEL: mov_basic_6:
; CHECK: // %bb.0:
; CHECK-NEXT: mov x0, #-20481 // =0xffffffffffffafff
; CHECK-NEXT: movk x0, #65468, lsl #16
; CHECK-NEXT: ret
ret i64 -4411393
}
We can encode this in one:
sub X0, xzr, #imm12, LSL #12
Because 0xFFFFFFFF`FFXXXFFF
If it is 32 bits we can use the w register to our advantage
0x00000000`FFXXXFFF
And if it is something like 0x00000000`00XXX000
We can use
add w0, wzr, X, LSL 12
![]()
_______________________________________________
llvm-bugs mailing list
llvm-bugs@lists.llvm.org
https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-bugs
