[dev.cmdgo] all: merge master (5e6a7e9) into dev.cmdgo

Merge List:

+ 2021-08-26 5e6a7e9b86 embed: remove reference to global variables in docs
+ 2021-08-26 166b691b65 cmd/compile/internal/types2: remove need for instance (struct)
+ 2021-08-26 d6bdae33e9 cmd/compile/internal/types2: address some TODOs (cleanup)
+ 2021-08-26 770df2e18d crypto/tls: fix typo in PreferServerCipherSuites comment
+ 2021-08-26 a6ff433d6a cmd/go: pass -gcflags after other flags generated by the go command
+ 2021-08-25 4f2620285d cmd/compile/internal/types2: fix type set printing and add test
+ 2021-08-25 0ac64f6d70 cmd/compile/internal/types2: rename IsMethodSet to IsConstraint (cleanup)
+ 2021-08-25 4068fb6c21 cmd/compile: always accept 1.18 syntax but complain if not 1.18
+ 2021-08-25 bf0bc4122f go/types, types2: don't re-evaluate context string for each function argument (optimization)
+ 2021-08-25 4158e88f64 cmd/compile/internal/syntax: fix position of type parameter field
+ 2021-08-25 647bef6c59 go/types: implement NewTypeList and use it instead of composite literals
+ 2021-08-25 6cf1d5d0fa cmd/compile: generic SSA rules for simplifying 2 and 3 operand integer arithmetic expressions
+ 2021-08-25 5baf60d472 bytes, strings: optimize Trim for single byte cutsets
+ 2021-08-25 3d667671ad cmd/compile: fix function contains no TParam in generic function
+ 2021-08-25 4f2ebfe34b cmd/compile: allow embed into any byte slice type
+ 2021-08-25 d2f002cb39 time/format: avoid growslice in time.String()/time.GoString()
+ 2021-08-25 08d4cc20ca cmd/compile: fix stencil call expression.
+ 2021-08-25 099b819085 cmd/compile: fix CheckSize() calculation for -G=3 and stencils
+ 2021-08-25 e1fcf8857e test: add test that caused gofrontend compiler crash
+ 2021-08-25 d37b8dedf7 test: add test case that gofrontend miscompiled
+ 2021-08-25 41b99dab0f os/user: don't skip TestLookupGroup if supported
+ 2021-08-25 de1c934b97 cmd/compile: fix checkptr false positive for (*[Big]T)(ptr)[:n:n] pattern
+ 2021-08-24 54cdef1f10 reflect: add MapIter.SetKey and MapIter.SetValue
+ 2021-08-24 5d863f89fe cmd/compile: simplify bad conversion check

Change-Id: I29ab927f0e47f44d82f9307c642900f75f4f678f

2 files changed, 32 insertions, 5 deletions

diff --git a/src/bytes/bytes.go b/src/bytes/bytes.go
index ce52649f13..cd859d086d 100644
--- a/src/bytes/bytes.go
+++ b/src/bytes/bytes.go
@@ -888,11 +888,6 @@ func (as *asciiSet) contains(c byte) bool {
 }
 
 func makeCutsetFunc(cutset string) func(r rune) bool {
-	if len(cutset) == 1 && cutset[0] < utf8.RuneSelf {
-		return func(r rune) bool {
-			return r == rune(cutset[0])
-		}
-	}
 	if as, isASCII := makeASCIISet(cutset); isASCII {
 		return func(r rune) bool {
 			return r < utf8.RuneSelf && as.contains(byte(r))
@@ -911,21 +906,44 @@ func makeCutsetFunc(cutset string) func(r rune) bool {
 // Trim returns a subslice of s by slicing off all leading and
 // trailing UTF-8-encoded code points contained in cutset.
 func Trim(s []byte, cutset string) []byte {
+	if len(cutset) == 1 && cutset[0] < utf8.RuneSelf {
+		return trimLeftByte(trimRightByte(s, cutset[0]), cutset[0])
+	}
 	return TrimFunc(s, makeCutsetFunc(cutset))
 }
 
 // TrimLeft returns a subslice of s by slicing off all leading
 // UTF-8-encoded code points contained in cutset.
 func TrimLeft(s []byte, cutset string) []byte {
+	if len(cutset) == 1 && cutset[0] < utf8.RuneSelf {
+		return trimLeftByte(s, cutset[0])
+	}
 	return TrimLeftFunc(s, makeCutsetFunc(cutset))
 }
 
+func trimLeftByte(s []byte, c byte) []byte {
+	for len(s) > 0 && s[0] == c {
+		s = s[1:]
+	}
+	return s
+}
+
 // TrimRight returns a subslice of s by slicing off all trailing
 // UTF-8-encoded code points that are contained in cutset.
 func TrimRight(s []byte, cutset string) []byte {
+	if len(cutset) == 1 && cutset[0] < utf8.RuneSelf {
+		return trimRightByte(s, cutset[0])
+	}
 	return TrimRightFunc(s, makeCutsetFunc(cutset))
 }
 
+func trimRightByte(s []byte, c byte) []byte {
+	for len(s) > 0 && s[len(s)-1] == c {
+		s = s[:len(s)-1]
+	}
+	return s
+}
+
 // TrimSpace returns a subslice of s by slicing off all leading and
 // trailing white space, as defined by Unicode.
 func TrimSpace(s []byte) []byte {
diff --git a/src/bytes/bytes_test.go b/src/bytes/bytes_test.go
index 544ee46f90..850b2ed061 100644
--- a/src/bytes/bytes_test.go
+++ b/src/bytes/bytes_test.go
@@ -1251,7 +1251,9 @@ var trimTests = []TrimTest{
 	{"TrimLeft", "abba", "ab", ""},
 	{"TrimRight", "abba", "ab", ""},
 	{"TrimLeft", "abba", "a", "bba"},
+	{"TrimLeft", "abba", "b", "abba"},
 	{"TrimRight", "abba", "a", "abb"},
+	{"TrimRight", "abba", "b", "abba"},
 	{"Trim", "<tag>", "<>", "tag"},
 	{"Trim", "* listitem", " *", "listitem"},
 	{"Trim", `"quote"`, `"`, "quote"},
@@ -1963,6 +1965,13 @@ func BenchmarkTrimASCII(b *testing.B) {
 	}
 }
 
+func BenchmarkTrimByte(b *testing.B) {
+	x := []byte("  the quick brown fox   ")
+	for i := 0; i < b.N; i++ {
+		Trim(x, " ")
+	}
+}
+
 func BenchmarkIndexPeriodic(b *testing.B) {
 	key := []byte{1, 1}
 	for _, skip := range [...]int{2, 4, 8, 16, 32, 64} {