runtime: replace all uses of CtzXX with TrailingZerosXX

Replace all uses of Ctz64/32/8 with TrailingZeros64/32/8, because they
are the same and maybe duplicated. Also renamed CtzXX functions in 386
assembly code.

Change-Id: I19290204858083750f4be589bb0923393950ae6d
Reviewed-on: https://go-review.googlesource.com/c/go/+/438935
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Bryan Mills <bcmills@google.com>
Auto-Submit: Keith Randall <khr@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@google.com>
Run-TryBot: Keith Randall <khr@golang.org>

diff --git a/src/cmd/compile/internal/ssagen/ssa.go b/src/cmd/compile/internal/ssagen/ssa.go
index 77307f4c2dfddfffd9e53346a9738da7c92f4667..871530d7d59b31bf5f7792562b126d71b4046946 100644 (file)
--- a/src/cmd/compile/internal/ssagen/ssa.go
+++ b/src/cmd/compile/internal/ssagen/ssa.go
@@ -4003,16 +4003,6 @@ func InitTables() {
                sys.ARM64, sys.PPC64)
 
        /******** runtime/internal/sys ********/
-       addF("runtime/internal/sys", "Ctz32",
-               func(s *state, n *ir.CallExpr, args []*ssa.Value) *ssa.Value {
-                       return s.newValue1(ssa.OpCtz32, types.Types[types.TINT], args[0])
-               },
-               sys.AMD64, sys.ARM64, sys.ARM, sys.S390X, sys.MIPS, sys.PPC64)
-       addF("runtime/internal/sys", "Ctz64",
-               func(s *state, n *ir.CallExpr, args []*ssa.Value) *ssa.Value {
-                       return s.newValue1(ssa.OpCtz64, types.Types[types.TINT], args[0])
-               },
-               sys.AMD64, sys.ARM64, sys.ARM, sys.S390X, sys.MIPS, sys.PPC64)
        addF("runtime/internal/sys", "Bswap32",
                func(s *state, n *ir.CallExpr, args []*ssa.Value) *ssa.Value {
                        return s.newValue1(ssa.OpBswap32, types.Types[types.TUINT32], args[0])
@@ -4750,8 +4740,8 @@ func InitTables() {
                sys.AMD64)
        alias("math/bits", "Div", "math/bits", "Div64", sys.ArchAMD64)
 
-       alias("runtime/internal/sys", "Ctz8", "math/bits", "TrailingZeros8", all...)
        alias("runtime/internal/sys", "TrailingZeros8", "math/bits", "TrailingZeros8", all...)
+       alias("runtime/internal/sys", "TrailingZeros32", "math/bits", "TrailingZeros32", all...)
        alias("runtime/internal/sys", "TrailingZeros64", "math/bits", "TrailingZeros64", all...)
        alias("runtime/internal/sys", "Len8", "math/bits", "Len8", all...)
        alias("runtime/internal/sys", "Len64", "math/bits", "Len64", all...)

diff --git a/src/cmd/compile/internal/test/inl_test.go b/src/cmd/compile/internal/test/inl_test.go
index 285052c0dab0d3f916b2944dd266870c8fe81132..c73f49eeb7ff45edc8be858c3f6f3e160821e867 100644 (file)
--- a/src/cmd/compile/internal/test/inl_test.go
+++ b/src/cmd/compile/internal/test/inl_test.go
@@ -212,19 +212,19 @@ func TestIntendedInlining(t *testing.T) {
        }
 
        if runtime.GOARCH != "386" && runtime.GOARCH != "loong64" && runtime.GOARCH != "mips64" && runtime.GOARCH != "mips64le" && runtime.GOARCH != "riscv64" {
-               // nextFreeFast calls sys.Ctz64, which on 386 is implemented in asm and is not inlinable.
+               // nextFreeFast calls sys.TrailingZeros64, which on 386 is implemented in asm and is not inlinable.
                // We currently don't have midstack inlining so nextFreeFast is also not inlinable on 386.
-               // On loong64, mips64x and riscv64, Ctz64 is not intrinsified and causes nextFreeFast too expensive
-               // to inline (Issue 22239).
+               // On loong64, mips64x and riscv64, TrailingZeros64 is not intrinsified and causes nextFreeFast
+               // too expensive to inline (Issue 22239).
                want["runtime"] = append(want["runtime"], "nextFreeFast")
                // Same behavior for heapBits.nextFast.
                want["runtime"] = append(want["runtime"], "heapBits.nextFast")
        }
        if runtime.GOARCH != "386" {
-               // As explained above, Ctz64 and Ctz32 are not Go code on 386.
+               // As explained above, TrailingZeros64 and TrailingZeros32 are not Go code on 386.
                // The same applies to Bswap32.
-               want["runtime/internal/sys"] = append(want["runtime/internal/sys"], "Ctz64")
-               want["runtime/internal/sys"] = append(want["runtime/internal/sys"], "Ctz32")
+               want["runtime/internal/sys"] = append(want["runtime/internal/sys"], "TrailingZeros64")
+               want["runtime/internal/sys"] = append(want["runtime/internal/sys"], "TrailingZeros32")
                want["runtime/internal/sys"] = append(want["runtime/internal/sys"], "Bswap32")
        }
        if bits.UintSize == 64 {

diff --git a/src/runtime/internal/sys/intrinsics.go b/src/runtime/internal/sys/intrinsics.go
index 5af49011e9e65549e10829b6358617a0c6b20172..902d893178889c1918d4b3ab0195b6a3a2e762c1 100644 (file)
--- a/src/runtime/internal/sys/intrinsics.go
+++ b/src/runtime/internal/sys/intrinsics.go
@@ -5,56 +5,75 @@
 //go:build !386
 
 // TODO finish intrinsifying 386, deadcode the assembly, remove build tags, merge w/ intrinsics_common
-// TODO replace all uses of CtzXX with TrailingZerosXX; they are the same.
 
 package sys
 
-// Using techniques from http://supertech.csail.mit.edu/papers/debruijn.pdf
+// Copied from math/bits to avoid dependence.
 
-const deBruijn64ctz = 0x0218a392cd3d5dbf
-
-var deBruijnIdx64ctz = [64]byte{
-       0, 1, 2, 7, 3, 13, 8, 19,
-       4, 25, 14, 28, 9, 34, 20, 40,
-       5, 17, 26, 38, 15, 46, 29, 48,
-       10, 31, 35, 54, 21, 50, 41, 57,
-       63, 6, 12, 18, 24, 27, 33, 39,
-       16, 37, 45, 47, 30, 53, 49, 56,
-       62, 11, 23, 32, 36, 44, 52, 55,
-       61, 22, 43, 51, 60, 42, 59, 58,
+var deBruijn32tab = [32]byte{
+       0, 1, 28, 2, 29, 14, 24, 3, 30, 22, 20, 15, 25, 17, 4, 8,
+       31, 27, 13, 23, 21, 19, 16, 7, 26, 12, 18, 6, 11, 5, 10, 9,
 }
 
-const deBruijn32ctz = 0x04653adf
+const deBruijn32 = 0x077CB531
 
-var deBruijnIdx32ctz = [32]byte{
-       0, 1, 2, 6, 3, 11, 7, 16,
-       4, 14, 12, 21, 8, 23, 17, 26,
-       31, 5, 10, 15, 13, 20, 22, 25,
-       30, 9, 19, 24, 29, 18, 28, 27,
+var deBruijn64tab = [64]byte{
+       0, 1, 56, 2, 57, 49, 28, 3, 61, 58, 42, 50, 38, 29, 17, 4,
+       62, 47, 59, 36, 45, 43, 51, 22, 53, 39, 33, 30, 24, 18, 12, 5,
+       63, 55, 48, 27, 60, 41, 37, 16, 46, 35, 44, 21, 52, 32, 23, 11,
+       54, 26, 40, 15, 34, 20, 31, 10, 25, 14, 19, 9, 13, 8, 7, 6,
 }
 
-// Ctz64 counts trailing (low-order) zeroes,
-// and if all are zero, then 64.
-func Ctz64(x uint64) int {
-       x &= -x                       // isolate low-order bit
-       y := x * deBruijn64ctz >> 58  // extract part of deBruijn sequence
-       i := int(deBruijnIdx64ctz[y]) // convert to bit index
-       z := int((x - 1) >> 57 & 64)  // adjustment if zero
-       return i + z
+const deBruijn64 = 0x03f79d71b4ca8b09
+
+const ntz8tab = "" +
+       "\x08\x00\x01\x00\x02\x00\x01\x00\x03\x00\x01\x00\x02\x00\x01\x00" +
+       "\x04\x00\x01\x00\x02\x00\x01\x00\x03\x00\x01\x00\x02\x00\x01\x00" +
+       "\x05\x00\x01\x00\x02\x00\x01\x00\x03\x00\x01\x00\x02\x00\x01\x00" +
+       "\x04\x00\x01\x00\x02\x00\x01\x00\x03\x00\x01\x00\x02\x00\x01\x00" +
+       "\x06\x00\x01\x00\x02\x00\x01\x00\x03\x00\x01\x00\x02\x00\x01\x00" +
+       "\x04\x00\x01\x00\x02\x00\x01\x00\x03\x00\x01\x00\x02\x00\x01\x00" +
+       "\x05\x00\x01\x00\x02\x00\x01\x00\x03\x00\x01\x00\x02\x00\x01\x00" +
+       "\x04\x00\x01\x00\x02\x00\x01\x00\x03\x00\x01\x00\x02\x00\x01\x00" +
+       "\x07\x00\x01\x00\x02\x00\x01\x00\x03\x00\x01\x00\x02\x00\x01\x00" +
+       "\x04\x00\x01\x00\x02\x00\x01\x00\x03\x00\x01\x00\x02\x00\x01\x00" +
+       "\x05\x00\x01\x00\x02\x00\x01\x00\x03\x00\x01\x00\x02\x00\x01\x00" +
+       "\x04\x00\x01\x00\x02\x00\x01\x00\x03\x00\x01\x00\x02\x00\x01\x00" +
+       "\x06\x00\x01\x00\x02\x00\x01\x00\x03\x00\x01\x00\x02\x00\x01\x00" +
+       "\x04\x00\x01\x00\x02\x00\x01\x00\x03\x00\x01\x00\x02\x00\x01\x00" +
+       "\x05\x00\x01\x00\x02\x00\x01\x00\x03\x00\x01\x00\x02\x00\x01\x00" +
+       "\x04\x00\x01\x00\x02\x00\x01\x00\x03\x00\x01\x00\x02\x00\x01\x00"
+
+// TrailingZeros32 returns the number of trailing zero bits in x; the result is 32 for x == 0.
+func TrailingZeros32(x uint32) int {
+       if x == 0 {
+               return 32
+       }
+       // see comment in TrailingZeros64
+       return int(deBruijn32tab[(x&-x)*deBruijn32>>(32-5)])
 }
 
-// Ctz32 counts trailing (low-order) zeroes,
-// and if all are zero, then 32.
-func Ctz32(x uint32) int {
-       x &= -x                       // isolate low-order bit
-       y := x * deBruijn32ctz >> 27  // extract part of deBruijn sequence
-       i := int(deBruijnIdx32ctz[y]) // convert to bit index
-       z := int((x - 1) >> 26 & 32)  // adjustment if zero
-       return i + z
+// TrailingZeros64 returns the number of trailing zero bits in x; the result is 64 for x == 0.
+func TrailingZeros64(x uint64) int {
+       if x == 0 {
+               return 64
+       }
+       // If popcount is fast, replace code below with return popcount(^x & (x - 1)).
+       //
+       // x & -x leaves only the right-most bit set in the word. Let k be the
+       // index of that bit. Since only a single bit is set, the value is two
+       // to the power of k. Multiplying by a power of two is equivalent to
+       // left shifting, in this case by k bits. The de Bruijn (64 bit) constant
+       // is such that all six bit, consecutive substrings are distinct.
+       // Therefore, if we have a left shifted version of this constant we can
+       // find by how many bits it was shifted by looking at which six bit
+       // substring ended up at the top of the word.
+       // (Knuth, volume 4, section 7.3.1)
+       return int(deBruijn64tab[(x&-x)*deBruijn64>>(64-6)])
 }
 
-// Ctz8 returns the number of trailing zero bits in x; the result is 8 for x == 0.
-func Ctz8(x uint8) int {
+// TrailingZeros8 returns the number of trailing zero bits in x; the result is 8 for x == 0.
+func TrailingZeros8(x uint8) int {
        return int(ntz8tab[x])
 }
 

diff --git a/src/runtime/internal/sys/intrinsics_386.s b/src/runtime/internal/sys/intrinsics_386.s
index 784b246a0156171d063dc53ad02a420e5a7f6b20..f33ade0a3abf528e05a7ee63b19e1f78c367235c 100644 (file)
--- a/src/runtime/internal/sys/intrinsics_386.s
+++ b/src/runtime/internal/sys/intrinsics_386.s
@@ -4,7 +4,7 @@
 
 #include "textflag.h"
 
-TEXT runtime∕internal∕sys·Ctz64(SB), NOSPLIT, $0-12
+TEXT runtime∕internal∕sys·TrailingZeros64(SB), NOSPLIT, $0-12
        // Try low 32 bits.
        MOVL    x_lo+0(FP), AX
        BSFL    AX, AX
@@ -26,7 +26,7 @@ none:
        MOVL    $64, ret+8(FP)
        RET
 
-TEXT runtime∕internal∕sys·Ctz32(SB), NOSPLIT, $0-8
+TEXT runtime∕internal∕sys·TrailingZeros32(SB), NOSPLIT, $0-8
        MOVL    x+0(FP), AX
        BSFL    AX, AX
        JNZ     2(PC)
@@ -34,7 +34,7 @@ TEXT runtime∕internal∕sys·Ctz32(SB), NOSPLIT, $0-8
        MOVL    AX, ret+4(FP)
        RET
 
-TEXT runtime∕internal∕sys·Ctz8(SB), NOSPLIT, $0-8
+TEXT runtime∕internal∕sys·TrailingZeros8(SB), NOSPLIT, $0-8
        MOVBLZX x+0(FP), AX
        BSFL    AX, AX
        JNZ     2(PC)

diff --git a/src/runtime/internal/sys/intrinsics_common.go b/src/runtime/internal/sys/intrinsics_common.go
index 7d7af20906790b57bfff828b9480ac494fb49869..709ec23f9debc759f9cac6d34f38ca7abf7cbf1c 100644 (file)
--- a/src/runtime/internal/sys/intrinsics_common.go
+++ b/src/runtime/internal/sys/intrinsics_common.go
@@ -6,43 +6,23 @@ package sys
 
 // Copied from math/bits to avoid dependence.
 
-var len8tab = [256]uint8{
-       0x00, 0x01, 0x02, 0x02, 0x03, 0x03, 0x03, 0x03, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04,
-       0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05,
-       0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06,
-       0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06,
-       0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07,
-       0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07,
-       0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07,
-       0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07,
-       0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08,
-       0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08,
-       0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08,
-       0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08,
-       0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08,
-       0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08,
-       0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08,
-       0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08,
-}
-
-var ntz8tab = [256]uint8{
-       0x08, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x03, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00,
-       0x04, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x03, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00,
-       0x05, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x03, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00,
-       0x04, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x03, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00,
-       0x06, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x03, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00,
-       0x04, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x03, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00,
-       0x05, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x03, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00,
-       0x04, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x03, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00,
-       0x07, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x03, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00,
-       0x04, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x03, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00,
-       0x05, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x03, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00,
-       0x04, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x03, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00,
-       0x06, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x03, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00,
-       0x04, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x03, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00,
-       0x05, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x03, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00,
-       0x04, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x03, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00,
-}
+const len8tab = "" +
+       "\x00\x01\x02\x02\x03\x03\x03\x03\x04\x04\x04\x04\x04\x04\x04\x04" +
+       "\x05\x05\x05\x05\x05\x05\x05\x05\x05\x05\x05\x05\x05\x05\x05\x05" +
+       "\x06\x06\x06\x06\x06\x06\x06\x06\x06\x06\x06\x06\x06\x06\x06\x06" +
+       "\x06\x06\x06\x06\x06\x06\x06\x06\x06\x06\x06\x06\x06\x06\x06\x06" +
+       "\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07" +
+       "\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07" +
+       "\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07" +
+       "\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07" +
+       "\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08" +
+       "\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08" +
+       "\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08" +
+       "\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08" +
+       "\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08" +
+       "\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08" +
+       "\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08" +
+       "\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08"
 
 // len64 returns the minimum number of bits required to represent x; the result is 0 for x == 0.
 //
@@ -102,45 +82,12 @@ func OnesCount64(x uint64) int {
        return int(x) & (1<<7 - 1)
 }
 
-var deBruijn64tab = [64]byte{
-       0, 1, 56, 2, 57, 49, 28, 3, 61, 58, 42, 50, 38, 29, 17, 4,
-       62, 47, 59, 36, 45, 43, 51, 22, 53, 39, 33, 30, 24, 18, 12, 5,
-       63, 55, 48, 27, 60, 41, 37, 16, 46, 35, 44, 21, 52, 32, 23, 11,
-       54, 26, 40, 15, 34, 20, 31, 10, 25, 14, 19, 9, 13, 8, 7, 6,
-}
-
-const deBruijn64 = 0x03f79d71b4ca8b09
-
-// TrailingZeros64 returns the number of trailing zero bits in x; the result is 64 for x == 0.
-func TrailingZeros64(x uint64) int {
-       if x == 0 {
-               return 64
-       }
-       // If popcount is fast, replace code below with return popcount(^x & (x - 1)).
-       //
-       // x & -x leaves only the right-most bit set in the word. Let k be the
-       // index of that bit. Since only a single bit is set, the value is two
-       // to the power of k. Multiplying by a power of two is equivalent to
-       // left shifting, in this case by k bits. The de Bruijn (64 bit) constant
-       // is such that all six bit, consecutive substrings are distinct.
-       // Therefore, if we have a left shifted version of this constant we can
-       // find by how many bits it was shifted by looking at which six bit
-       // substring ended up at the top of the word.
-       // (Knuth, volume 4, section 7.3.1)
-       return int(deBruijn64tab[(x&-x)*deBruijn64>>(64-6)])
-}
-
 // LeadingZeros64 returns the number of leading zero bits in x; the result is 64 for x == 0.
 func LeadingZeros64(x uint64) int { return 64 - Len64(x) }
 
 // LeadingZeros8 returns the number of leading zero bits in x; the result is 8 for x == 0.
 func LeadingZeros8(x uint8) int { return 8 - Len8(x) }
 
-// TrailingZeros8 returns the number of trailing zero bits in x; the result is 8 for x == 0.
-func TrailingZeros8(x uint8) int {
-       return int(ntz8tab[x])
-}
-
 // Len8 returns the minimum number of bits required to represent x; the result is 0 for x == 0.
 func Len8(x uint8) int {
        return int(len8tab[x])

diff --git a/src/runtime/internal/sys/intrinsics_stubs.go b/src/runtime/internal/sys/intrinsics_stubs.go
index a020652f7604b39c40798983b66fcfd03e210f9a..66cfcded409f2083ceb2280ce345eefad67a0e03 100644 (file)
--- a/src/runtime/internal/sys/intrinsics_stubs.go
+++ b/src/runtime/internal/sys/intrinsics_stubs.go
@@ -6,8 +6,8 @@
 
 package sys
 
-func Ctz64(x uint64) int
-func Ctz32(x uint32) int
-func Ctz8(x uint8) int
+func TrailingZeros64(x uint64) int
+func TrailingZeros32(x uint32) int
+func TrailingZeros8(x uint8) int
 func Bswap64(x uint64) uint64
 func Bswap32(x uint32) uint32

diff --git a/src/runtime/internal/sys/intrinsics_test.go b/src/runtime/internal/sys/intrinsics_test.go
index 0444183e9dc129d09b54e0aff08f6061ff80a0c9..bf75f198489ec188ad5134230720cfe0ef2403d9 100644 (file)
--- a/src/runtime/internal/sys/intrinsics_test.go
+++ b/src/runtime/internal/sys/intrinsics_test.go
@@ -5,19 +5,19 @@ import (
        "testing"
 )
 
-func TestCtz64(t *testing.T) {
+func TestTrailingZeros64(t *testing.T) {
        for i := 0; i <= 64; i++ {
                x := uint64(5) << uint(i)
-               if got := sys.Ctz64(x); got != i {
-                       t.Errorf("Ctz64(%d)=%d, want %d", x, got, i)
+               if got := sys.TrailingZeros64(x); got != i {
+                       t.Errorf("TrailingZeros64(%d)=%d, want %d", x, got, i)
                }
        }
 }
-func TestCtz32(t *testing.T) {
+func TestTrailingZeros32(t *testing.T) {
        for i := 0; i <= 32; i++ {
                x := uint32(5) << uint(i)
-               if got := sys.Ctz32(x); got != i {
-                       t.Errorf("Ctz32(%d)=%d, want %d", x, got, i)
+               if got := sys.TrailingZeros32(x); got != i {
+                       t.Errorf("TrailingZeros32(%d)=%d, want %d", x, got, i)
                }
        }
 }

diff --git a/src/runtime/malloc.go b/src/runtime/malloc.go
index cece04eecaac45188e197a49b0db5fc83276c43b..70a13d0576bd0877b40cc1910ef9a1ffd528c884 100644 (file)
--- a/src/runtime/malloc.go
+++ b/src/runtime/malloc.go
@@ -816,7 +816,7 @@ var zerobase uintptr
 // nextFreeFast returns the next free object if one is quickly available.
 // Otherwise it returns 0.
 func nextFreeFast(s *mspan) gclinkptr {
-       theBit := sys.Ctz64(s.allocCache) // Is there a free object in the allocCache?
+       theBit := sys.TrailingZeros64(s.allocCache) // Is there a free object in the allocCache?
        if theBit < 64 {
                result := s.freeindex + uintptr(theBit)
                if result < s.nelems {

diff --git a/src/runtime/mbitmap.go b/src/runtime/mbitmap.go
index 8a4a61c27d2d106322bab23c86db6d2b99a92ddf..7cc22309f1bb1a1e585a6a82ef260816aa782c0a 100644 (file)
--- a/src/runtime/mbitmap.go
+++ b/src/runtime/mbitmap.go
@@ -147,7 +147,7 @@ func (s *mspan) nextFreeIndex() uintptr {
 
        aCache := s.allocCache
 
-       bitIndex := sys.Ctz64(aCache)
+       bitIndex := sys.TrailingZeros64(aCache)
        for bitIndex == 64 {
                // Move index to start of next cached bits.
                sfreeindex = (sfreeindex + 64) &^ (64 - 1)
@@ -159,7 +159,7 @@ func (s *mspan) nextFreeIndex() uintptr {
                // Refill s.allocCache with the next 64 alloc bits.
                s.refillAllocCache(whichByte)
                aCache = s.allocCache
-               bitIndex = sys.Ctz64(aCache)
+               bitIndex = sys.TrailingZeros64(aCache)
                // nothing available in cached bits
                // grab the next 8 bytes and try again.
        }
@@ -452,9 +452,9 @@ func (h heapBits) next() (heapBits, uintptr) {
                if h.mask != 0 {
                        var i int
                        if goarch.PtrSize == 8 {
-                               i = sys.Ctz64(uint64(h.mask))
+                               i = sys.TrailingZeros64(uint64(h.mask))
                        } else {
-                               i = sys.Ctz32(uint32(h.mask))
+                               i = sys.TrailingZeros32(uint32(h.mask))
                        }
                        h.mask ^= uintptr(1) << (i & (ptrBits - 1))
                        return h, h.addr + uintptr(i)*goarch.PtrSize
@@ -494,9 +494,9 @@ func (h heapBits) nextFast() (heapBits, uintptr) {
        // BSFQ
        var i int
        if goarch.PtrSize == 8 {
-               i = sys.Ctz64(uint64(h.mask))
+               i = sys.TrailingZeros64(uint64(h.mask))
        } else {
-               i = sys.Ctz32(uint32(h.mask))
+               i = sys.TrailingZeros32(uint32(h.mask))
        }
        // BTCQ
        h.mask ^= uintptr(1) << (i & (ptrBits - 1))

diff --git a/src/runtime/slice.go b/src/runtime/slice.go
index 134d14f1a0a75114a275484a94bbd0e749903e82..459dc8891e0fd9ad803591435fa3e06ae3a85721 100644 (file)
--- a/src/runtime/slice.go
+++ b/src/runtime/slice.go
@@ -225,9 +225,9 @@ func growslice(oldPtr unsafe.Pointer, newLen, oldCap, num int, et *_type) slice
                var shift uintptr
                if goarch.PtrSize == 8 {
                        // Mask shift for better code generation.
-                       shift = uintptr(sys.Ctz64(uint64(et.size))) & 63
+                       shift = uintptr(sys.TrailingZeros64(uint64(et.size))) & 63
                } else {
-                       shift = uintptr(sys.Ctz32(uint32(et.size))) & 31
+                       shift = uintptr(sys.TrailingZeros32(uint32(et.size))) & 31
                }
                lenmem = uintptr(oldLen) << shift
                newlenmem = uintptr(newLen) << shift

diff --git a/src/runtime/stack.go b/src/runtime/stack.go
index 10c45045d903456bc7a5ba3ad2227ae86c5b8568..87d8e519bdd2211fb989574f65852389536fe78d 100644 (file)
--- a/src/runtime/stack.go
+++ b/src/runtime/stack.go
@@ -617,7 +617,7 @@ func adjustpointers(scanp unsafe.Pointer, bv *bitvector, adjinfo *adjustinfo, f
                }
                b := *(addb(bv.bytedata, i/8))
                for b != 0 {
-                       j := uintptr(sys.Ctz8(b))
+                       j := uintptr(sys.TrailingZeros8(b))
                        b &= b - 1
                        pp := (*uintptr)(add(scanp, (i+j)*goarch.PtrSize))
                retry:

diff --git a/test/intrinsic.dir/main.go b/test/intrinsic.dir/main.go
index 4340dd4b11e898b1b01e865496affe10fc8a6898..951aa159d6709a2c9a6453ff90c9e858fcf858c6 100644 (file)
--- a/test/intrinsic.dir/main.go
+++ b/test/intrinsic.dir/main.go
@@ -23,26 +23,26 @@ func logf(f string, args ...interface{}) {
 }
 
 func test(i int, x uint64) {
-       t := T.Ctz64(x) // ERROR "intrinsic substitution for Ctz64"
+       t := T.TrailingZeros64(x) // ERROR "intrinsic substitution for TrailingZeros64"
        if i != t {
-               logf("Ctz64(0x%x) expected %d but got %d\n", x, i, t)
+               logf("TrailingZeros64(0x%x) expected %d but got %d\n", x, i, t)
        }
        x = -x
-       t = T.Ctz64(x) // ERROR "intrinsic substitution for Ctz64"
+       t = T.TrailingZeros64(x) // ERROR "intrinsic substitution for TrailingZeros64"
        if i != t {
-               logf("Ctz64(0x%x) expected %d but got %d\n", x, i, t)
+               logf("TrailingZeros64(0x%x) expected %d but got %d\n", x, i, t)
        }
 
        if i <= 32 {
                x32 := uint32(x)
-               t32 := T.Ctz32(x32) // ERROR "intrinsic substitution for Ctz32"
+               t32 := T.TrailingZeros32(x32) // ERROR "intrinsic substitution for TrailingZeros32"
                if i != t32 {
-                       logf("Ctz32(0x%x) expected %d but got %d\n", x32, i, t32)
+                       logf("TrailingZeros32(0x%x) expected %d but got %d\n", x32, i, t32)
                }
                x32 = -x32
-               t32 = T.Ctz32(x32) // ERROR "intrinsic substitution for Ctz32"
+               t32 = T.TrailingZeros32(x32) // ERROR "intrinsic substitution for TrailingZeros32"
                if i != t32 {
-                       logf("Ctz32(0x%x) expected %d but got %d\n", x32, i, t32)
+                       logf("TrailingZeros32(0x%x) expected %d but got %d\n", x32, i, t32)
                }
        }
 }
@@ -76,11 +76,11 @@ func main() {
        }
 
        // Zero is a special case, be sure it is done right.
-       if T.Ctz32(0) != 32 { // ERROR "intrinsic substitution for Ctz32"
-               logf("ctz32(0) != 32")
+       if T.TrailingZeros32(0) != 32 { // ERROR "intrinsic substitution for TrailingZeros32"
+               logf("TrailingZeros32(0) != 32")
        }
-       if T.Ctz64(0) != 64 { // ERROR "intrinsic substitution for Ctz64"
-               logf("ctz64(0) != 64")
+       if T.TrailingZeros64(0) != 64 { // ERROR "intrinsic substitution for TrailingZeros64"
+               logf("TrailingZeros64(0) != 64")
        }
 
        for i := 0; i <= 64; i++ {