git: a42d8fe001b9 - main - radix_trie: simplify trimkey functions

The branch main has been updated by dougm:

URL: https://cgit.FreeBSD.org/src/commit/?id=a42d8fe001b912a5e4efdd4020d9bfadc07f6c7f

commit a42d8fe001b912a5e4efdd4020d9bfadc07f6c7f
Author:     Doug Moore <dougm@FreeBSD.org>
AuthorDate: 2023-06-25 17:49:15 +0000
Commit:     Doug Moore <dougm@FreeBSD.org>
CommitDate: 2023-06-25 17:49:15 +0000

    radix_trie: simplify trimkey functions
    
    Replacing a branch and two shifts with a single masking operation saves 64 bytes the pair of functions lookup_le and lookup_ge on amd64.  Refresh the associated comments.
    Reviewed by:    alc
    Differential Revision:  https://reviews.freebsd.org/D40722
---
 sys/kern/subr_pctrie.c | 11 ++---------
 sys/vm/vm_radix.c      | 11 ++---------
 2 files changed, 4 insertions(+), 18 deletions(-)

diff --git a/sys/kern/subr_pctrie.c b/sys/kern/subr_pctrie.c
index 043c31ad9501..44a00a9eef77 100644
--- a/sys/kern/subr_pctrie.c
+++ b/sys/kern/subr_pctrie.c
@@ -156,18 +156,11 @@ pctrie_slot(uint64_t index, uint16_t level)
 	return ((index >> (level * PCTRIE_WIDTH)) & PCTRIE_MASK);
 }
 
-/* Trims the key after the specified level. */
+/* Computes the key (index) with the low-order 'level' radix-digits zeroed. */
 static __inline uint64_t
 pctrie_trimkey(uint64_t index, uint16_t level)
 {
-	uint64_t ret;
-
-	ret = index;
-	if (level > 0) {
-		ret >>= level * PCTRIE_WIDTH;
-		ret <<= level * PCTRIE_WIDTH;
-	}
-	return (ret);
+	return (index & -PCTRIE_UNITLEVEL(level));
 }
 
 /*
diff --git a/sys/vm/vm_radix.c b/sys/vm/vm_radix.c
index cc932a6cc80d..7d3408226be1 100644
--- a/sys/vm/vm_radix.c
+++ b/sys/vm/vm_radix.c
@@ -181,18 +181,11 @@ vm_radix_slot(vm_pindex_t index, uint16_t level)
 	return ((index >> (level * VM_RADIX_WIDTH)) & VM_RADIX_MASK);
 }
 
-/* Trims the key after the specified level. */
+/* Computes the key (index) with the low-order 'level' radix-digits zeroed. */
 static __inline vm_pindex_t
 vm_radix_trimkey(vm_pindex_t index, uint16_t level)
 {
-	vm_pindex_t ret;
-
-	ret = index;
-	if (level > 0) {
-		ret >>= level * VM_RADIX_WIDTH;
-		ret <<= level * VM_RADIX_WIDTH;
-	}
-	return (ret);
+	return (index & -VM_RADIX_UNITLEVEL(level));
 }
 
 /*