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arm64: Improve constant generation, with tests.

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This commit is contained in:
Edmund Grimley Evans
2015-03-02 20:39:28 +00:00
parent 883fd365c7
commit 86e8dcd5e2
3 changed files with 55 additions and 8 deletions
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30
arm64-gen.c
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@ -204,16 +204,30 @@ static void arm64_movimm(int r, uint64_t x)
{
uint32_t i;
if ((i = arm64_movi(r, x)))
o(i);
o(i); // a single MOV
else {
// This could be improved:
o(0x52800000 | r | (x & 0xffff) << 5); // movz w(r),#(x & 0xffff)
for (i = 1; i < 4; i++)
if (x >> 16 * i & 0xffff) {
o(0xf2800000 | r | (x >> 16 * i & 0xffff) << 5 | i << 21);
// movk w(r),#(*),lsl #(*)
// MOVZ/MOVN and 1-3 MOVKs
int z = 0, m = 0;
uint32_t mov1 = 0xd2800000; // movz
uint64_t x1 = x;
for (i = 0; i < 64; i += 16) {
z += !(x >> i & 0xffff);
m += !(~x >> i & 0xffff);
}
if (m > z) {
x1 = ~x;
mov1 = 0x92800000; // movn
}
for (i = 0; i < 64; i += 16)
if (x1 >> i & 0xffff) {
o(mov1 | r | (x1 >> i & 0xffff) << 5 | i << 17);
// movz/movn x(r),#(*),lsl #(i)
break;
}
for (i += 16; i < 64; i += 16)
if (x1 >> i & 0xffff)
o(0xf2800000 | r | (x >> i & 0xffff) << 5 | i << 17);
// movk x(r),#(*),lsl #(i)
}
}