Use 32-bit comparisons for "decnet dst" when possible.

gen_dnhostop() already compares PLENGTH and FLAGS in parallel, so
compare the destination address as well when it is within reach (that
is, for the short frame encoding).  Fix and expand my earlier comment to
document gen_dnhostop() better.

This changes the resulting bytecode: it now takes 4 fewer instructions
to test a destination DECnet address (thus the corresponding accept
tests change), but the behaviour remains the same (thus no apply tests
change).

diff --git a/gencode.c b/gencode.c
index d413e4a2a052b9e46b5b722adb929de2e9f5b384..c05185bc7539d3ee5ad7bee484fa120c00125be7 100644 (file)
--- a/gencode.c
+++ b/gencode.c
@@ -5066,9 +5066,14 @@ gen_dnhostop(compiler_state_t *cstate, bpf_u_int32 addr, int dir)
         * the header.  "Short header" means bits 0-2 of the bitmap encode the
         * integer value 2 (SFDP), and "long header" means value 6 (LFDP).
         *
+        * To test PLENGTH and FLAGS, use multiple-byte constants with the
+        * values and the masks, this maps to the required single bytes of
+        * the message correctly on both big-endian and little-endian hosts.
         * For the DECnet address use SWAPSHORT(), which always swaps bytes,
-        * because the wire encoding is little-endian and this function always
-        * receives a big-endian address value.
+        * because the wire encoding is little-endian and BPF multiple-byte
+        * loads are big-endian.  When the destination address is near enough
+        * to PLENGTH and FLAGS, generate one 32-bit comparison instead of two
+        * smaller ones.
         */
        /* Check for pad = 1, long header case */
        tmp = gen_mcmp(cstate, OR_LINKPL, 2, BPF_H, 0x8106U, 0xFF07U);
@@ -5082,16 +5087,28 @@ gen_dnhostop(compiler_state_t *cstate, bpf_u_int32 addr, int dir)
        gen_and(tmp, b2);
        gen_or(b2, b1);
        /* Check for pad = 1, short header case */
-       tmp = gen_mcmp(cstate, OR_LINKPL, 2, BPF_H, 0x8102U, 0xFF07U);
-       b2 = gen_cmp(cstate, OR_LINKPL, 2 + 1 + offset_sh, BPF_H,
-           SWAPSHORT(addr));
-       gen_and(tmp, b2);
+       if (dir == Q_DST) {
+               b2 = gen_mcmp(cstate, OR_LINKPL, 2, BPF_W,
+                   0x81020000U | SWAPSHORT(addr),
+                   0xFF07FFFFU);
+       } else {
+               tmp = gen_mcmp(cstate, OR_LINKPL, 2, BPF_H, 0x8102U, 0xFF07U);
+               b2 = gen_cmp(cstate, OR_LINKPL, 2 + 1 + offset_sh, BPF_H,
+                   SWAPSHORT(addr));
+               gen_and(tmp, b2);
+       }
        gen_or(b2, b1);
        /* Check for pad = 0, short header case */
-       tmp = gen_mcmp(cstate, OR_LINKPL, 2, BPF_B, 0x02U, 0x07U);
-       b2 = gen_cmp(cstate, OR_LINKPL, 2 + offset_sh, BPF_H,
-           SWAPSHORT(addr));
-       gen_and(tmp, b2);
+       if (dir == Q_DST) {
+               b2 = gen_mcmp(cstate, OR_LINKPL, 2, BPF_W,
+                   0x02000000U | SWAPSHORT(addr) << 8,
+                   0x07FFFF00U);
+       } else {
+               tmp = gen_mcmp(cstate, OR_LINKPL, 2, BPF_B, 0x02U, 0x07U);
+               b2 = gen_cmp(cstate, OR_LINKPL, 2 + offset_sh, BPF_H,
+                   SWAPSHORT(addr));
+               gen_and(tmp, b2);
+       }
        gen_or(b2, b1);
 
        return b1;

diff --git a/testprogs/TESTrun b/testprogs/TESTrun
index ab5d5f0aee1bbce01e099b0c9a598116e4e42609..b427a109dba5383174ae092a65db255c471d665e 100755 (executable)
--- a/testprogs/TESTrun
+++ b/testprogs/TESTrun
@@ -3765,95 +3765,87 @@ my %accept_blocks = (
                expr => 'decnet host 50.764',
                opt => <<~'EOF',
                        (000) ldh      [12]
-                       (001) jeq      #0x6003          jt 2    jf 43
+                       (001) jeq      #0x6003          jt 2    jf 39
                        (002) ldb      [16]
                        (003) and      #0x7
                        (004) jeq      #0x2             jt 5    jf 7
                        (005) ldh      [19]
-                       (006) jeq      #0xfcca          jt 42   jf 7
+                       (006) jeq      #0xfcca          jt 38   jf 7
                        (007) ldh      [16]
                        (008) and      #0xff07
                        (009) jeq      #0x8102          jt 10   jf 12
                        (010) ldh      [20]
-                       (011) jeq      #0xfcca          jt 42   jf 12
+                       (011) jeq      #0xfcca          jt 38   jf 12
                        (012) ldb      [16]
                        (013) and      #0x7
                        (014) jeq      #0x6             jt 15   jf 17
                        (015) ldh      [31]
-                       (016) jeq      #0xfcca          jt 42   jf 17
+                       (016) jeq      #0xfcca          jt 38   jf 17
                        (017) ldh      [16]
                        (018) and      #0xff07
                        (019) jeq      #0x8106          jt 20   jf 22
                        (020) ldh      [32]
-                       (021) jeq      #0xfcca          jt 42   jf 22
-                       (022) ldb      [16]
-                       (023) and      #0x7
-                       (024) jeq      #0x2             jt 25   jf 27
-                       (025) ldh      [17]
-                       (026) jeq      #0xfcca          jt 42   jf 27
-                       (027) ldh      [16]
-                       (028) and      #0xff07
-                       (029) jeq      #0x8102          jt 30   jf 32
-                       (030) ldh      [18]
-                       (031) jeq      #0xfcca          jt 42   jf 32
-                       (032) ldb      [16]
-                       (033) and      #0x7
-                       (034) jeq      #0x6             jt 35   jf 37
-                       (035) ldh      [23]
-                       (036) jeq      #0xfcca          jt 42   jf 37
-                       (037) ldh      [16]
-                       (038) and      #0xff07
-                       (039) jeq      #0x8106          jt 40   jf 43
-                       (040) ldh      [24]
-                       (041) jeq      #0xfcca          jt 42   jf 43
-                       (042) ret      #262144
-                       (043) ret      #0
+                       (021) jeq      #0xfcca          jt 38   jf 22
+                       (022) ld       [16]
+                       (023) and      #0x7ffff00
+                       (024) jeq      #0x2fcca00       jt 38   jf 25
+                       (025) ld       [16]
+                       (026) and      #0xff07ffff
+                       (027) jeq      #0x8102fcca      jt 38   jf 28
+                       (028) ldb      [16]
+                       (029) and      #0x7
+                       (030) jeq      #0x6             jt 31   jf 33
+                       (031) ldh      [23]
+                       (032) jeq      #0xfcca          jt 38   jf 33
+                       (033) ldh      [16]
+                       (034) and      #0xff07
+                       (035) jeq      #0x8106          jt 36   jf 39
+                       (036) ldh      [24]
+                       (037) jeq      #0xfcca          jt 38   jf 39
+                       (038) ret      #262144
+                       (039) ret      #0
                        EOF
                unopt => <<~'EOF',
                        (000) ldh      [12]
-                       (001) jeq      #0x6003          jt 2    jf 43
+                       (001) jeq      #0x6003          jt 2    jf 39
                        (002) ldb      [16]
                        (003) and      #0x7
                        (004) jeq      #0x2             jt 5    jf 7
                        (005) ldh      [19]
-                       (006) jeq      #0xfcca          jt 42   jf 7
+                       (006) jeq      #0xfcca          jt 38   jf 7
                        (007) ldh      [16]
                        (008) and      #0xff07
                        (009) jeq      #0x8102          jt 10   jf 12
                        (010) ldh      [20]
-                       (011) jeq      #0xfcca          jt 42   jf 12
+                       (011) jeq      #0xfcca          jt 38   jf 12
                        (012) ldb      [16]
                        (013) and      #0x7
                        (014) jeq      #0x6             jt 15   jf 17
                        (015) ldh      [31]
-                       (016) jeq      #0xfcca          jt 42   jf 17
+                       (016) jeq      #0xfcca          jt 38   jf 17
                        (017) ldh      [16]
                        (018) and      #0xff07
                        (019) jeq      #0x8106          jt 20   jf 22
                        (020) ldh      [32]
-                       (021) jeq      #0xfcca          jt 42   jf 22
-                       (022) ldb      [16]
-                       (023) and      #0x7
-                       (024) jeq      #0x2             jt 25   jf 27
-                       (025) ldh      [17]
-                       (026) jeq      #0xfcca          jt 42   jf 27
-                       (027) ldh      [16]
-                       (028) and      #0xff07
-                       (029) jeq      #0x8102          jt 30   jf 32
-                       (030) ldh      [18]
-                       (031) jeq      #0xfcca          jt 42   jf 32
-                       (032) ldb      [16]
-                       (033) and      #0x7
-                       (034) jeq      #0x6             jt 35   jf 37
-                       (035) ldh      [23]
-                       (036) jeq      #0xfcca          jt 42   jf 37
-                       (037) ldh      [16]
-                       (038) and      #0xff07
-                       (039) jeq      #0x8106          jt 40   jf 43
-                       (040) ldh      [24]
-                       (041) jeq      #0xfcca          jt 42   jf 43
-                       (042) ret      #262144
-                       (043) ret      #0
+                       (021) jeq      #0xfcca          jt 38   jf 22
+                       (022) ld       [16]
+                       (023) and      #0x7ffff00
+                       (024) jeq      #0x2fcca00       jt 38   jf 25
+                       (025) ld       [16]
+                       (026) and      #0xff07ffff
+                       (027) jeq      #0x8102fcca      jt 38   jf 28
+                       (028) ldb      [16]
+                       (029) and      #0x7
+                       (030) jeq      #0x6             jt 31   jf 33
+                       (031) ldh      [23]
+                       (032) jeq      #0xfcca          jt 38   jf 33
+                       (033) ldh      [16]
+                       (034) and      #0xff07
+                       (035) jeq      #0x8106          jt 36   jf 39
+                       (036) ldh      [24]
+                       (037) jeq      #0xfcca          jt 38   jf 39
+                       (038) ret      #262144
+                       (039) ret      #0
                        EOF
        }, # decnet_host
        decnet_src_host => {
@@ -3893,29 +3885,25 @@ my %accept_blocks = (
                aliases => ['decnet dst 50.764'],
                unopt => <<~'EOF',
                        (000) ldh      [12]
-                       (001) jeq      #0x6003          jt 2    jf 23
-                       (002) ldb      [16]
-                       (003) and      #0x7
-                       (004) jeq      #0x2             jt 5    jf 7
-                       (005) ldh      [17]
-                       (006) jeq      #0xfcca          jt 22   jf 7
-                       (007) ldh      [16]
-                       (008) and      #0xff07
-                       (009) jeq      #0x8102          jt 10   jf 12
-                       (010) ldh      [18]
-                       (011) jeq      #0xfcca          jt 22   jf 12
-                       (012) ldb      [16]
-                       (013) and      #0x7
-                       (014) jeq      #0x6             jt 15   jf 17
-                       (015) ldh      [23]
-                       (016) jeq      #0xfcca          jt 22   jf 17
-                       (017) ldh      [16]
-                       (018) and      #0xff07
-                       (019) jeq      #0x8106          jt 20   jf 23
-                       (020) ldh      [24]
-                       (021) jeq      #0xfcca          jt 22   jf 23
-                       (022) ret      #262144
-                       (023) ret      #0
+                       (001) jeq      #0x6003          jt 2    jf 19
+                       (002) ld       [16]
+                       (003) and      #0x7ffff00
+                       (004) jeq      #0x2fcca00       jt 18   jf 5
+                       (005) ld       [16]
+                       (006) and      #0xff07ffff
+                       (007) jeq      #0x8102fcca      jt 18   jf 8
+                       (008) ldb      [16]
+                       (009) and      #0x7
+                       (010) jeq      #0x6             jt 11   jf 13
+                       (011) ldh      [23]
+                       (012) jeq      #0xfcca          jt 18   jf 13
+                       (013) ldh      [16]
+                       (014) and      #0xff07
+                       (015) jeq      #0x8106          jt 16   jf 19
+                       (016) ldh      [24]
+                       (017) jeq      #0xfcca          jt 18   jf 19
+                       (018) ret      #262144
+                       (019) ret      #0
                        EOF
        }, # decnet_dst_host