convert divcoeff.c to D rebooted #7714
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| Original file line number | Diff line number | Diff line change |
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@@ -2,38 +2,47 @@ | |
| * Compiler implementation of the | ||
| * $(LINK2 http://www.dlang.org, D programming language). | ||
| * | ||
| * Copyright: Copyright (c) 2013-2018 by The D Language Foundation, All Rights Reserved | ||
| * Authors: $(LINK2 http://www.digitalmars.com, Walter Bright) | ||
| * License: $(LINK2 http://www.boost.org/LICENSE_1_0.txt, Boost License 1.0) | ||
| * Source: $(LINK2 https://github.com/dlang/dmd/blob/master/src/dmd/backend/divcoeff.d, backend/divcoeff.d) | ||
| */ | ||
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| /*************************************************** | ||
| * Algorithms from "Division by Invariant Integers using Multiplication" | ||
| * by Torbjoern Granlund and Peter L. Montgomery | ||
| */ | ||
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| import core.stdc.stdio; | ||
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| extern (C++): | ||
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| alias ullong = ulong; | ||
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| /* unsigned 128 bit math | ||
| */ | ||
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| bool SIGN64(ullong x) | ||
| { | ||
| return cast(long)x < 0; | ||
| } | ||
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| void SHL128(out ullong dh, out ullong dl, ullong xh,ullong xl) | ||
| { | ||
| dh = (xh << 1) | SIGN64(xl); | ||
| dl = xl << 1; | ||
| } | ||
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| void SHR128(out ullong dh, out ullong dl, ullong xh,ullong xl) | ||
| { | ||
| dl = (xl >> 1) | ((xh & 1) << 63); | ||
| dh = xh >> 1; | ||
| } | ||
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| bool XltY128(ullong xh, ullong xl, ullong yh, ullong yl) | ||
| { | ||
| return xh < yh || (xh == yh && xl < yl); | ||
| } | ||
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| void u128Div(ullong xh, ullong xl, ullong yh, ullong yl, ullong *pqh, ullong *pql) | ||
| { | ||
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@@ -43,10 +52,10 @@ void u128Div(ullong xh, ullong xl, ullong yh, ullong yl, ullong *pqh, ullong *pq | |
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| //ullong xxh = xh, xxl = xl, yyh = yh, yyl = yl; | ||
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| // assert(yh || yl); // no div-by-0 bugs | ||
|
There was a problem hiding this comment. Why not use the Or maybe @CyberShadow can update DAutoTest to use 2.068.2 as initial bootstrap compiler? There was a problem hiding this comment. I don't want to redo the asserts, as that doesn't scale to the rest of the back end. What's needed is to upgrade the boot compiler to 2.074. But that's for after this PR. There was a problem hiding this comment.
Well, I thought it helps porting when the |
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| // left justify y | ||
| uint shiftcount = 1; | ||
| if (!yh) | ||
| { yh = yl; | ||
| yl = 0; | ||
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@@ -85,31 +94,32 @@ void u128Div(ullong xh, ullong xl, ullong yh, ullong yl, ullong *pqh, ullong *pq | |
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| // Remainder is xh,xl | ||
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| version (none) | ||
| { | ||
| printf("%016llx_%016llx / %016llx_%016llx = %016llx_%016llx\n", xxh,xxl,yyh,yyl,qh,ql); | ||
| if (xxh == 0 && yyh == 0) | ||
| printf("should be %llx\n", xxl / yyl); | ||
| } | ||
| } | ||
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| /************************************ | ||
| * Implement Algorithm 6.2: Selection of multiplier and shift count | ||
| * Params: | ||
| * N = 32 or 64 | ||
| * d = divisor (must not be 0 or a power of 2) | ||
| * prec = bits of precision desired | ||
| * Output: | ||
| * *pm = factor | ||
| * *pshpost = post shift | ||
| * Returns: | ||
| * true m >= 2**N | ||
| */ | ||
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| extern (C) bool choose_multiplier(int N, ullong d, int prec, ullong *pm, int *pshpost) | ||
| { | ||
| // assert(N == 32 || N == 64); | ||
| // assert(prec <= N); | ||
| // assert(d > 1 && (d & (d - 1))); | ||
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| // Compute b such that 2**(b-1) < d <= 2**b | ||
| // which is the number of significant bits in d | ||
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@@ -127,10 +137,10 @@ bool choose_multiplier(int N, ullong d, int prec, ullong *pm, int *pshpost) | |
| if (N == 32) | ||
| { | ||
| // mlow = (2**(N + b)) / d | ||
| ullong mlow = (1UL << (N + b)) / d; | ||
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| // uhigh = (2**(N + b) + 2**(N + b - prec)) / d | ||
| ullong mhigh = ((1UL << (N + b)) + (1UL << (N + b - prec))) / d; | ||
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| while (mlow/2 < mhigh/2 && shpost) | ||
| { | ||
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@@ -140,27 +150,27 @@ bool choose_multiplier(int N, ullong d, int prec, ullong *pm, int *pshpost) | |
| } | ||
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| *pm = mhigh & 0xFFFFFFFF; | ||
| mhighbit = (mhigh >> N) != 0; | ||
| } | ||
| else if (N == 64) | ||
| { | ||
| // Same as for N==32, but use 128 bit unsigned arithmetic | ||
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| // mlow = (2**(N + b)) / d | ||
| ullong mlowl = 0; | ||
| ullong mlowh = 1UL << b; | ||
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| // mlow /= d | ||
| u128Div(mlowh, mlowl, 0, d, &mlowh, &mlowl); | ||
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| // mhigh = (2**(N + b) + 2**(N + b - prec)) / d | ||
| ullong mhighl = 0; | ||
| ullong mhighh = 1UL << b; | ||
| int e = N + b - prec; | ||
| if (e < 64) | ||
| mhighl = 1UL << e; | ||
| else | ||
| mhighh |= 1UL << (e - 64); | ||
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| // mhigh /= d | ||
| u128Div(mhighh, mhighl, 0, d, &mhighh, &mhighl); | ||
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@@ -195,8 +205,8 @@ bool choose_multiplier(int N, ullong d, int prec, ullong *pm, int *pshpost) | |
| *pm = mhighl; | ||
| mhighbit = mhighh & 1; | ||
| } | ||
| // else | ||
| // assert(0); | ||
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| *pshpost = shpost; | ||
| return mhighbit; | ||
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@@ -221,12 +231,8 @@ bool choose_multiplier(int N, ullong d, int prec, ullong *pm, int *pshpost) | |
| * q = SRL(MULUH(m, SRL(n, shpre)), shpost) | ||
| */ | ||
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| extern (C) bool udiv_coefficients(int N, ullong d, int *pshpre, ullong *pm, int *pshpost) | ||
| { | ||
| bool mhighbit = choose_multiplier(N, d, N, pm, pshpost); | ||
| if (mhighbit && (d & 1) == 0) | ||
| { | ||
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@@ -237,21 +243,15 @@ bool udiv_coefficients(int N, ullong d, int *pshpre, ullong *pm, int *pshpost) | |
| } | ||
| *pshpre = e; | ||
| mhighbit = choose_multiplier(N, d, N - e, pm, pshpost); | ||
| // assert(mhighbit == false); | ||
| } | ||
| else | ||
| *pshpre = 0; | ||
| return mhighbit; | ||
| } | ||
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| unittest | ||
| { | ||
| struct S | ||
| { | ||
| int N; | ||
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@@ -260,10 +260,10 @@ void test_udiv_coefficients() | |
| int highbit; | ||
| ullong m; | ||
| int shpost; | ||
| } | ||
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| static immutable S[14] table = | ||
| [ | ||
| { 32, 10, 0, 0, 0xCCCCCCCD, 3 }, | ||
| { 32, 13, 0, 0, 0x4EC4EC4F, 2 }, | ||
| { 32, 14, 1, 0, 0x92492493, 2 }, | ||
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@@ -279,39 +279,40 @@ void test_udiv_coefficients() | |
| { 64, 17, 0, 0, 0xF0F0F0F0F0F0F0F1, 4 }, | ||
| { 64, 100, 2, 0, 0x28F5C28F5C28F5C3, 2 }, | ||
| { 64, 14007, 0, 1, 0x2B71840C5ADF02C3, 14 }, | ||
| ]; | ||
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| for (int i = 0; i < table.length; i++) | ||
| { const ps = &table[i]; | ||
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| ullong m; | ||
| int shpre; | ||
| int shpost; | ||
| bool mhighbit = udiv_coefficients(ps.N, ps.d, &shpre, &m, &shpost); | ||
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| //printf("[%d] %d %d %llx %d\n", i, shpre, mhighbit, m, shpost); | ||
| // assert(shpre == ps.shpre); | ||
| // assert(mhighbit == ps.highbit); | ||
| // assert(m == ps.m); | ||
| // assert(shpost == ps.shpost); | ||
| } | ||
| } | ||
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| version (none) | ||
| { | ||
| import core.stdc.stdlib; | ||
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| extern (D) int main(string[] args) | ||
| { | ||
| if (args.length == 2) | ||
| { | ||
| ullong d = atoi(args[1].ptr); | ||
| ullong m; | ||
| int shpre; | ||
| int shpost; | ||
| bool mhighbit = udiv_coefficients(64, d, &shpre, &m, &shpost); | ||
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| printf("%d %d %llx, %d\n", shpre, mhighbit, m, shpost); | ||
| } | ||
| return 0; | ||
| } | ||
| } | ||
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FYI: auto-tester needs to be bumped too, see the discussion on the previous PR and the NG discussion - especially Martin's reply.