[PATCH v3 10/16] util: move 256-by-128 division helpers to int128

From: marcandre.lureau@redhat.com
To: qemu-devel@nongnu.org
Cc: "Markus Armbruster" <armbru@redhat.com>,
	"Peter Maydell" <peter.maydell@linaro.org>,
	"Cleber Rosa" <crosa@redhat.com>,
	"Michael Roth" <michael.roth@amd.com>,
	"John Snow" <jsnow@redhat.com>,
	"Xie Yongji" <xieyongji@bytedance.com>,
	"Paolo Bonzini" <pbonzini@redhat.com>,
	"Marc-André Lureau" <marcandre.lureau@redhat.com>
Subject: [PATCH v3 10/16] util: move 256-by-128 division helpers to int128
Date: Wed, 10 Aug 2022 16:48:51 +0400	[thread overview]
Message-ID: <20220810124857.1360211-11-marcandre.lureau@redhat.com> (raw)
In-Reply-To: <20220810124857.1360211-1-marcandre.lureau@redhat.com>

From: Marc-André Lureau <marcandre.lureau@redhat.com>

Break a cyclic dependency between int128 and host-utils.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Lucas Mateus Castro <lucas.araujo@eldorado.org.br>
---
 include/qemu/host-utils.h |   3 -
 include/qemu/int128.h     |   3 +
 util/host-utils.c         | 180 --------------------------------------
 util/int128.c             | 180 ++++++++++++++++++++++++++++++++++++++
 4 files changed, 183 insertions(+), 183 deletions(-)

diff --git a/include/qemu/host-utils.h b/include/qemu/host-utils.h
index 88d476161c..e8162fb6b0 100644
--- a/include/qemu/host-utils.h
+++ b/include/qemu/host-utils.h
@@ -32,7 +32,6 @@
 
 #include "qemu/compiler.h"
 #include "qemu/bswap.h"
-#include "qemu/int128.h"
 
 #ifdef CONFIG_INT128
 static inline void mulu64(uint64_t *plow, uint64_t *phigh,
@@ -784,6 +783,4 @@ static inline uint64_t udiv_qrnnd(uint64_t *r, uint64_t n1,
 #endif
 }
 
-Int128 divu256(Int128 *plow, Int128 *phigh, Int128 divisor);
-Int128 divs256(Int128 *plow, Int128 *phigh, Int128 divisor);
 #endif
diff --git a/include/qemu/int128.h b/include/qemu/int128.h
index d2b76ca6ac..823c61edb0 100644
--- a/include/qemu/int128.h
+++ b/include/qemu/int128.h
@@ -472,4 +472,7 @@ static inline void bswap128s(Int128 *s)
 #define INT128_MAX int128_make128(UINT64_MAX, INT64_MAX)
 #define INT128_MIN int128_make128(0, INT64_MIN)
 
+Int128 divu256(Int128 *plow, Int128 *phigh, Int128 divisor);
+Int128 divs256(Int128 *plow, Int128 *phigh, Int128 divisor);
+
 #endif /* INT128_H */
diff --git a/util/host-utils.c b/util/host-utils.c
index fb91bcba82..96d5dc0bed 100644
--- a/util/host-utils.c
+++ b/util/host-utils.c
@@ -266,183 +266,3 @@ void ulshift(uint64_t *plow, uint64_t *phigh, int32_t shift, bool *overflow)
         *plow = *plow << shift;
     }
 }
-
-/*
- * Unsigned 256-by-128 division.
- * Returns the remainder via r.
- * Returns lower 128 bit of quotient.
- * Needs a normalized divisor (most significant bit set to 1).
- *
- * Adapted from include/qemu/host-utils.h udiv_qrnnd,
- * from the GNU Multi Precision Library - longlong.h __udiv_qrnnd
- * (https://gmplib.org/repo/gmp/file/tip/longlong.h)
- *
- * Licensed under the GPLv2/LGPLv3
- */
-static Int128 udiv256_qrnnd(Int128 *r, Int128 n1, Int128 n0, Int128 d)
-{
-    Int128 d0, d1, q0, q1, r1, r0, m;
-    uint64_t mp0, mp1;
-
-    d0 = int128_make64(int128_getlo(d));
-    d1 = int128_make64(int128_gethi(d));
-
-    r1 = int128_remu(n1, d1);
-    q1 = int128_divu(n1, d1);
-    mp0 = int128_getlo(q1);
-    mp1 = int128_gethi(q1);
-    mulu128(&mp0, &mp1, int128_getlo(d0));
-    m = int128_make128(mp0, mp1);
-    r1 = int128_make128(int128_gethi(n0), int128_getlo(r1));
-    if (int128_ult(r1, m)) {
-        q1 = int128_sub(q1, int128_one());
-        r1 = int128_add(r1, d);
-        if (int128_uge(r1, d)) {
-            if (int128_ult(r1, m)) {
-                q1 = int128_sub(q1, int128_one());
-                r1 = int128_add(r1, d);
-            }
-        }
-    }
-    r1 = int128_sub(r1, m);
-
-    r0 = int128_remu(r1, d1);
-    q0 = int128_divu(r1, d1);
-    mp0 = int128_getlo(q0);
-    mp1 = int128_gethi(q0);
-    mulu128(&mp0, &mp1, int128_getlo(d0));
-    m = int128_make128(mp0, mp1);
-    r0 = int128_make128(int128_getlo(n0), int128_getlo(r0));
-    if (int128_ult(r0, m)) {
-        q0 = int128_sub(q0, int128_one());
-        r0 = int128_add(r0, d);
-        if (int128_uge(r0, d)) {
-            if (int128_ult(r0, m)) {
-                q0 = int128_sub(q0, int128_one());
-                r0 = int128_add(r0, d);
-            }
-        }
-    }
-    r0 = int128_sub(r0, m);
-
-    *r = r0;
-    return int128_or(int128_lshift(q1, 64), q0);
-}
-
-/*
- * Unsigned 256-by-128 division.
- * Returns the remainder.
- * Returns quotient via plow and phigh.
- * Also returns the remainder via the function return value.
- */
-Int128 divu256(Int128 *plow, Int128 *phigh, Int128 divisor)
-{
-    Int128 dhi = *phigh;
-    Int128 dlo = *plow;
-    Int128 rem, dhighest;
-    int sh;
-
-    if (!int128_nz(divisor) || !int128_nz(dhi)) {
-        *plow  = int128_divu(dlo, divisor);
-        *phigh = int128_zero();
-        return int128_remu(dlo, divisor);
-    } else {
-        sh = clz128(divisor);
-
-        if (int128_ult(dhi, divisor)) {
-            if (sh != 0) {
-                /* normalize the divisor, shifting the dividend accordingly */
-                divisor = int128_lshift(divisor, sh);
-                dhi = int128_or(int128_lshift(dhi, sh),
-                                int128_urshift(dlo, (128 - sh)));
-                dlo = int128_lshift(dlo, sh);
-            }
-
-            *phigh = int128_zero();
-            *plow = udiv256_qrnnd(&rem, dhi, dlo, divisor);
-        } else {
-            if (sh != 0) {
-                /* normalize the divisor, shifting the dividend accordingly */
-                divisor = int128_lshift(divisor, sh);
-                dhighest = int128_rshift(dhi, (128 - sh));
-                dhi = int128_or(int128_lshift(dhi, sh),
-                                int128_urshift(dlo, (128 - sh)));
-                dlo = int128_lshift(dlo, sh);
-
-                *phigh = udiv256_qrnnd(&dhi, dhighest, dhi, divisor);
-            } else {
-                /*
-                 * dhi >= divisor
-                 * Since the MSB of divisor is set (sh == 0),
-                 * (dhi - divisor) < divisor
-                 *
-                 * Thus, the high part of the quotient is 1, and we can
-                 * calculate the low part with a single call to udiv_qrnnd
-                 * after subtracting divisor from dhi
-                 */
-                dhi = int128_sub(dhi, divisor);
-                *phigh = int128_one();
-            }
-
-            *plow = udiv256_qrnnd(&rem, dhi, dlo, divisor);
-        }
-
-        /*
-         * since the dividend/divisor might have been normalized,
-         * the remainder might also have to be shifted back
-         */
-        rem = int128_urshift(rem, sh);
-        return rem;
-    }
-}
-
-/*
- * Signed 256-by-128 division.
- * Returns quotient via plow and phigh.
- * Also returns the remainder via the function return value.
- */
-Int128 divs256(Int128 *plow, Int128 *phigh, Int128 divisor)
-{
-    bool neg_quotient = false, neg_remainder = false;
-    Int128 unsig_hi = *phigh, unsig_lo = *plow;
-    Int128 rem;
-
-    if (!int128_nonneg(*phigh)) {
-        neg_quotient = !neg_quotient;
-        neg_remainder = !neg_remainder;
-
-        if (!int128_nz(unsig_lo)) {
-            unsig_hi = int128_neg(unsig_hi);
-        } else {
-            unsig_hi = int128_not(unsig_hi);
-            unsig_lo = int128_neg(unsig_lo);
-        }
-    }
-
-    if (!int128_nonneg(divisor)) {
-        neg_quotient = !neg_quotient;
-
-        divisor = int128_neg(divisor);
-    }
-
-    rem = divu256(&unsig_lo, &unsig_hi, divisor);
-
-    if (neg_quotient) {
-        if (!int128_nz(unsig_lo)) {
-            *phigh = int128_neg(unsig_hi);
-            *plow = int128_zero();
-        } else {
-            *phigh = int128_not(unsig_hi);
-            *plow = int128_neg(unsig_lo);
-        }
-    } else {
-        *phigh = unsig_hi;
-        *plow = unsig_lo;
-    }
-
-    if (neg_remainder) {
-        return int128_neg(rem);
-    } else {
-        return rem;
-    }
-}
diff --git a/util/int128.c b/util/int128.c
index ed8f25fef1..482c63b655 100644
--- a/util/int128.c
+++ b/util/int128.c
@@ -145,3 +145,183 @@ Int128 int128_rems(Int128 a, Int128 b)
 }
 
 #endif
+
+/*
+ * Unsigned 256-by-128 division.
+ * Returns the remainder via r.
+ * Returns lower 128 bit of quotient.
+ * Needs a normalized divisor (most significant bit set to 1).
+ *
+ * Adapted from include/qemu/host-utils.h udiv_qrnnd,
+ * from the GNU Multi Precision Library - longlong.h __udiv_qrnnd
+ * (https://gmplib.org/repo/gmp/file/tip/longlong.h)
+ *
+ * Licensed under the GPLv2/LGPLv3
+ */
+static Int128 udiv256_qrnnd(Int128 *r, Int128 n1, Int128 n0, Int128 d)
+{
+    Int128 d0, d1, q0, q1, r1, r0, m;
+    uint64_t mp0, mp1;
+
+    d0 = int128_make64(int128_getlo(d));
+    d1 = int128_make64(int128_gethi(d));
+
+    r1 = int128_remu(n1, d1);
+    q1 = int128_divu(n1, d1);
+    mp0 = int128_getlo(q1);
+    mp1 = int128_gethi(q1);
+    mulu128(&mp0, &mp1, int128_getlo(d0));
+    m = int128_make128(mp0, mp1);
+    r1 = int128_make128(int128_gethi(n0), int128_getlo(r1));
+    if (int128_ult(r1, m)) {
+        q1 = int128_sub(q1, int128_one());
+        r1 = int128_add(r1, d);
+        if (int128_uge(r1, d)) {
+            if (int128_ult(r1, m)) {
+                q1 = int128_sub(q1, int128_one());
+                r1 = int128_add(r1, d);
+            }
+        }
+    }
+    r1 = int128_sub(r1, m);
+
+    r0 = int128_remu(r1, d1);
+    q0 = int128_divu(r1, d1);
+    mp0 = int128_getlo(q0);
+    mp1 = int128_gethi(q0);
+    mulu128(&mp0, &mp1, int128_getlo(d0));
+    m = int128_make128(mp0, mp1);
+    r0 = int128_make128(int128_getlo(n0), int128_getlo(r0));
+    if (int128_ult(r0, m)) {
+        q0 = int128_sub(q0, int128_one());
+        r0 = int128_add(r0, d);
+        if (int128_uge(r0, d)) {
+            if (int128_ult(r0, m)) {
+                q0 = int128_sub(q0, int128_one());
+                r0 = int128_add(r0, d);
+            }
+        }
+    }
+    r0 = int128_sub(r0, m);
+
+    *r = r0;
+    return int128_or(int128_lshift(q1, 64), q0);
+}
+
+/*
+ * Unsigned 256-by-128 division.
+ * Returns the remainder.
+ * Returns quotient via plow and phigh.
+ * Also returns the remainder via the function return value.
+ */
+Int128 divu256(Int128 *plow, Int128 *phigh, Int128 divisor)
+{
+    Int128 dhi = *phigh;
+    Int128 dlo = *plow;
+    Int128 rem, dhighest;
+    int sh;
+
+    if (!int128_nz(divisor) || !int128_nz(dhi)) {
+        *plow  = int128_divu(dlo, divisor);
+        *phigh = int128_zero();
+        return int128_remu(dlo, divisor);
+    } else {
+        sh = clz128(divisor);
+
+        if (int128_ult(dhi, divisor)) {
+            if (sh != 0) {
+                /* normalize the divisor, shifting the dividend accordingly */
+                divisor = int128_lshift(divisor, sh);
+                dhi = int128_or(int128_lshift(dhi, sh),
+                                int128_urshift(dlo, (128 - sh)));
+                dlo = int128_lshift(dlo, sh);
+            }
+
+            *phigh = int128_zero();
+            *plow = udiv256_qrnnd(&rem, dhi, dlo, divisor);
+        } else {
+            if (sh != 0) {
+                /* normalize the divisor, shifting the dividend accordingly */
+                divisor = int128_lshift(divisor, sh);
+                dhighest = int128_rshift(dhi, (128 - sh));
+                dhi = int128_or(int128_lshift(dhi, sh),
+                                int128_urshift(dlo, (128 - sh)));
+                dlo = int128_lshift(dlo, sh);
+
+                *phigh = udiv256_qrnnd(&dhi, dhighest, dhi, divisor);
+            } else {
+                /*
+                 * dhi >= divisor
+                 * Since the MSB of divisor is set (sh == 0),
+                 * (dhi - divisor) < divisor
+                 *
+                 * Thus, the high part of the quotient is 1, and we can
+                 * calculate the low part with a single call to udiv_qrnnd
+                 * after subtracting divisor from dhi
+                 */
+                dhi = int128_sub(dhi, divisor);
+                *phigh = int128_one();
+            }
+
+            *plow = udiv256_qrnnd(&rem, dhi, dlo, divisor);
+        }
+
+        /*
+         * since the dividend/divisor might have been normalized,
+         * the remainder might also have to be shifted back
+         */
+        rem = int128_urshift(rem, sh);
+        return rem;
+    }
+}
+
+/*
+ * Signed 256-by-128 division.
+ * Returns quotient via plow and phigh.
+ * Also returns the remainder via the function return value.
+ */
+Int128 divs256(Int128 *plow, Int128 *phigh, Int128 divisor)
+{
+    bool neg_quotient = false, neg_remainder = false;
+    Int128 unsig_hi = *phigh, unsig_lo = *plow;
+    Int128 rem;
+
+    if (!int128_nonneg(*phigh)) {
+        neg_quotient = !neg_quotient;
+        neg_remainder = !neg_remainder;
+
+        if (!int128_nz(unsig_lo)) {
+            unsig_hi = int128_neg(unsig_hi);
+        } else {
+            unsig_hi = int128_not(unsig_hi);
+            unsig_lo = int128_neg(unsig_lo);
+        }
+    }
+
+    if (!int128_nonneg(divisor)) {
+        neg_quotient = !neg_quotient;
+
+        divisor = int128_neg(divisor);
+    }
+
+    rem = divu256(&unsig_lo, &unsig_hi, divisor);
+
+    if (neg_quotient) {
+        if (!int128_nz(unsig_lo)) {
+            *phigh = int128_neg(unsig_hi);
+            *plow = int128_zero();
+        } else {
+            *phigh = int128_not(unsig_hi);
+            *plow = int128_neg(unsig_lo);
+        }
+    } else {
+        *phigh = unsig_hi;
+        *plow = unsig_lo;
+    }
+
+    if (neg_remainder) {
+        return int128_neg(rem);
+    } else {
+        return rem;
+    }
+}
-- 
2.37.1


