| Message ID | 20190902094244.486-1-abrodkin@synopsys.com |
|---|---|
| State | New |
| Headers | show |
| Series | arc: libgcc: Import __udivdi3 & __udivmoddi4 to allow 64-bit division | expand |
Hi, > -----Original Message----- > From: Alexey Brodkin <abrodkin@synopsys.com> > Sent: Monday, September 2, 2019 12:43 PM > To: u-boot@lists.denx.de > Cc: uboot-snps-arc@synopsys.com; linux-snps-arc@lists.infradead.org; Alexey Brodkin > <abrodkin@synopsys.com>; Kever Yang <kever.yang@rock-chips.com> > Subject: [PATCH] arc: libgcc: Import __udivdi3 & __udivmoddi4 to allow 64-bit division > > As reported by Kever here [1] we were unable to compile 64-bit division > code due to missing definition of __udivdi3(). > > Import its implementation and __udivmoddi4() as its direct dependency > from today's libgcc [2]. > > [1] https://patchwork.ozlabs.org/patch/1146845/ > [2] https://github.com/gcc-mirror/gcc/commit/5d8723600bc0eed41226b5a6785bc02a053b45d5 > > Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com> > Cc: Kever Yang <kever.yang@rock-chips.com> For the record for EM SDP (emsdp_defconfig) building still fails this way: ----------------------------->8------------------------- arc-linux-ld.bfd: arch/arc/lib/lib.a(libgcc2.o): in function `__udivmoddi4': .../arch/arc/lib/libgcc2.c:195: undefined reference to `__clzdi2' arc-linux-ld.bfd: .../arch/arc/lib/libgcc2.c:195: undefined reference to `__clzdi2' arc-linux-ld.bfd: .../arch/arc/lib/libgcc2.c:196: undefined reference to `__clzdi2' arc-linux-ld.bfd: .../arch/arc/lib/libgcc2.c:196: undefined reference to `__clzdi2' ----------------------------->8------------------------- That happens because we use a very simple -mcpu=arcem which doesn't use HW normalizer unit. I'm preparing a patch that will improve EM SDP's compiler options. -Alexey
diff --git a/arch/arc/lib/libgcc2.c b/arch/arc/lib/libgcc2.c index b92a841a37..ab1dbe1c13 100644 --- a/arch/arc/lib/libgcc2.c +++ b/arch/arc/lib/libgcc2.c @@ -158,3 +158,78 @@ __umodsi3(long a, long b) { return udivmodsi4(a, b, 1); } + +UDWtype +__udivmoddi4(UDWtype n, UDWtype d, UDWtype *rp) +{ + UDWtype q = 0, r = n, y = d; + UWtype lz1, lz2, i, k; + + /* + * Implements align divisor shift dividend method. This algorithm + * aligns the divisor under the dividend and then perform number of + * test-subtract iterations which shift the dividend left. Number of + * iterations is k + 1 where k is the number of bit positions the + * divisor must be shifted left to align it under the dividend. + * quotient bits can be saved in the rightmost positions of the + * dividend as it shifts left on each test-subtract iteration. + */ + + if (y <= r) { + lz1 = __builtin_clzll(d); + lz2 = __builtin_clzll(n); + + k = lz1 - lz2; + y = (y << k); + + /* + * Dividend can exceed 2 ^ (width - 1) - 1 but still be less + * than the aligned divisor. Normal iteration can drops the + * high order bit of the dividend. Therefore, first + * test-subtract iteration is a special case, saving its + * quotient bit in a separate location and not shifting + * the dividend. + */ + + if (r >= y) { + r = r - y; + q = (1ULL << k); + } + + if (k > 0) { + y = y >> 1; + + /* + * k additional iterations where k regular test + * subtract shift dividend iterations are done. + */ + i = k; + do { + if (r >= y) + r = ((r - y) << 1) + 1; + else + r = (r << 1); + i = i - 1; + } while (i != 0); + + /* + * First quotient bit is combined with the quotient + * bits resulting from the k regular iterations. + */ + q = q + r; + r = r >> k; + q = q - (r << k); + } + } + + if (rp) + *rp = r; + + return q; +} + +UDWtype +__udivdi3(UDWtype n, UDWtype d) +{ + return __udivmoddi4(n, d, (UDWtype *)0); +}
As reported by Kever here [1] we were unable to compile 64-bit division code due to missing definition of __udivdi3(). Import its implementation and __udivmoddi4() as its direct dependency from today's libgcc [2]. [1] https://patchwork.ozlabs.org/patch/1146845/ [2] https://github.com/gcc-mirror/gcc/commit/5d8723600bc0eed41226b5a6785bc02a053b45d5 Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com> Cc: Kever Yang <kever.yang@rock-chips.com> --- arch/arc/lib/libgcc2.c | 75 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 75 insertions(+)