From e7ebdc8fb66e04717b15af4cf6719ae23b03aad1 Mon Sep 17 00:00:00 2001
From: Quentin Carbonneaux <quentin@c9x.me>
Date: Mon, 17 Jun 2024 13:17:39 +0200
Subject: [PATCH] qbe has its own magic
---
simpl.c | 18 +++++++--------
tools/log2.c | 64 ++++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 73 insertions(+), 9 deletions(-)
create mode 100644 tools/log2.c
diff --git a/simpl.c b/simpl.c
index f22d491..99e09df 100644
--- a/simpl.c
+++ b/simpl.c
@@ -32,20 +32,20 @@ blit(Ref sd[2], int sz, Fn *fn)
static int
ulog2_tab64[64] = {
- 63, 0, 58, 1, 59, 47, 53, 2,
- 60, 39, 48, 27, 54, 33, 42, 3,
- 61, 51, 37, 40, 49, 18, 28, 20,
- 55, 30, 34, 11, 43, 14, 22, 4,
- 62, 57, 46, 52, 38, 26, 32, 41,
- 50, 36, 17, 19, 29, 10, 13, 21,
- 56, 45, 25, 31, 35, 16, 9, 12,
- 44, 24, 15, 8, 23, 7, 6, 5
+ 63, 0, 1, 41, 37, 2, 16, 42,
+ 38, 29, 32, 3, 12, 17, 43, 55,
+ 39, 35, 30, 53, 33, 21, 4, 23,
+ 13, 9, 18, 6, 25, 44, 48, 56,
+ 62, 40, 36, 15, 28, 31, 11, 54,
+ 34, 52, 20, 22, 8, 5, 24, 47,
+ 61, 14, 27, 10, 51, 19, 7, 46,
+ 60, 26, 50, 45, 59, 49, 58, 57,
};
static int
ulog2(uint64_t pow2)
{
- return ulog2_tab64[(pow2 * 0x07EDD5E59A4E28C2) >> 58];
+ return ulog2_tab64[(pow2 * 0x5b31ab928877a7e) >> 58];
}
static int
diff --git a/tools/log2.c b/tools/log2.c
new file mode 100644
index 0000000..05f97c9
--- /dev/null
+++ b/tools/log2.c
@@ -0,0 +1,64 @@
+#include <assert.h>
+#include <stdio.h>
+
+typedef unsigned long long ullong;
+
+char seen[64];
+ullong rbg = 0x1e0298f7a7e;
+
+int
+bit()
+{
+ int bit;
+
+ bit = rbg & 1;
+ rbg >>= 1;
+ return bit;
+}
+
+int
+search(ullong n, int b, ullong *out)
+{
+ int i, x;
+ ullong y, z;
+
+ if (b == 64) {
+ *out = n;
+ return 1;
+ }
+
+ x = 63 & ((n << (63 - b)) >> 58);
+ assert(!(x & 0) && x <= 62);
+ y = bit();
+
+ for (i=0; i<2; i++) {
+ z = x | (y << 5);
+ if (!seen[z]) {
+ seen[z] = (63-b)+1;
+ if (search(n | (y << b), b+1, out))
+ return 1;
+ seen[z] = 0;
+ }
+ y ^= 1;
+ }
+
+ return 0;
+}
+
+int
+main()
+{
+ ullong out;
+ int i;
+
+ if (search(0, 0, &out)) {
+ printf("0x%llx\n", out);
+ for (i=0; i<64; i++) {
+ printf((i&7) == 0 ? "\t" : " ");
+ printf("%2d,", seen[i]-1);
+ if ((i&7) == 7)
+ printf("\n");
+ }
+ } else
+ puts("not found");
+}