runtime: use max/min func

Change-Id: I3f0b7209621b39cee69566a5cc95e4343b4f1f20
GitHub-Last-Rev: af9dbbe69ad74e8c210254dafa260a886b690853
GitHub-Pull-Request: golang/go#63321
Reviewed-on: https://go-review.googlesource.com/c/go/+/531916
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Mauri de Souza Meneguzzo <mauri870@gmail.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Keith Randall <khr@golang.org>

10 files changed, 39 insertions, 68 deletions

diff --git a/src/runtime/export_test.go b/src/runtime/export_test.go
index fc681b140e..6d1d3c4537 100644
--- a/src/runtime/export_test.go
+++ b/src/runtime/export_test.go
@@ -806,7 +806,7 @@ func (b *PallocBits) PopcntRange(i, n uint) uint { return (*pageBits)(b).popcntR
 // SummarizeSlow is a slow but more obviously correct implementation
 // of (*pallocBits).summarize. Used for testing.
 func SummarizeSlow(b *PallocBits) PallocSum {
-	var start, max, end uint
+	var start, most, end uint
 
 	const N = uint(len(b)) * 64
 	for start < N && (*pageBits)(b).get(start) == 0 {
@@ -822,11 +822,9 @@ func SummarizeSlow(b *PallocBits) PallocSum {
 		} else {
 			run = 0
 		}
-		if run > max {
-			max = run
-		}
+		most = max(most, run)
 	}
-	return PackPallocSum(start, max, end)
+	return PackPallocSum(start, most, end)
 }
 
 // Expose non-trivial helpers for testing.
diff --git a/src/runtime/memmove_test.go b/src/runtime/memmove_test.go
index 21236d19da..587e03d385 100644
--- a/src/runtime/memmove_test.go
+++ b/src/runtime/memmove_test.go
@@ -488,9 +488,7 @@ func BenchmarkMemclrRange(b *testing.B) {
 		maxLen := 0
 
 		for _, clrLen := range t.data {
-			if clrLen > maxLen {
-				maxLen = clrLen
-			}
+			maxLen = max(maxLen, clrLen)
 			if clrLen < minLen || minLen == 0 {
 				minLen = clrLen
 			}
diff --git a/src/runtime/mfixalloc.go b/src/runtime/mfixalloc.go
index 1a249e5981..7760ada397 100644
--- a/src/runtime/mfixalloc.go
+++ b/src/runtime/mfixalloc.go
@@ -57,9 +57,7 @@ func (f *fixalloc) init(size uintptr, first func(arg, p unsafe.Pointer), arg uns
 	if size > _FixAllocChunk {
 		throw("runtime: fixalloc size too large")
 	}
-	if min := unsafe.Sizeof(mlink{}); size < min {
-		size = min
-	}
+	size = max(size, unsafe.Sizeof(mlink{}))
 
 	f.size = size
 	f.first = first
diff --git a/src/runtime/mgcmark.go b/src/runtime/mgcmark.go
index 9ab3b48f2f..aff6c2fb99 100644
--- a/src/runtime/mgcmark.go
+++ b/src/runtime/mgcmark.go
@@ -1326,9 +1326,7 @@ func scanobject(b uintptr, gcw *gcWork) {
 		// must be a large object, s.base() is the beginning
 		// of the object.
 		n = s.base() + s.elemsize - b
-		if n > maxObletBytes {
-			n = maxObletBytes
-		}
+		n = min(n, maxObletBytes)
 	}
 
 	hbits := heapBitsForAddr(b, n)
diff --git a/src/runtime/mgcpacer.go b/src/runtime/mgcpacer.go
index 1850811865..10767df26c 100644
--- a/src/runtime/mgcpacer.go
+++ b/src/runtime/mgcpacer.go
@@ -1137,9 +1137,7 @@ func (c *gcControllerState) trigger() (uint64, uint64) {
 	if goal > defaultHeapMinimum && goal-defaultHeapMinimum > maxTrigger {
 		maxTrigger = goal - defaultHeapMinimum
 	}
-	if maxTrigger < minTrigger {
-		maxTrigger = minTrigger
-	}
+	maxTrigger = max(maxTrigger, minTrigger)
 
 	// Compute the trigger from our bounds and the runway stored by commit.
 	var trigger uint64
@@ -1149,12 +1147,8 @@ func (c *gcControllerState) trigger() (uint64, uint64) {
 	} else {
 		trigger = goal - runway
 	}
-	if trigger < minTrigger {
-		trigger = minTrigger
-	}
-	if trigger > maxTrigger {
-		trigger = maxTrigger
-	}
+	trigger = max(trigger, minTrigger)
+	trigger = min(trigger, maxTrigger)
 	if trigger > goal {
 		print("trigger=", trigger, " heapGoal=", goal, "\n")
 		print("minTrigger=", minTrigger, " maxTrigger=", maxTrigger, "\n")
diff --git a/src/runtime/mgcscavenge.go b/src/runtime/mgcscavenge.go
index 5df36d0d16..e6725b4622 100644
--- a/src/runtime/mgcscavenge.go
+++ b/src/runtime/mgcscavenge.go
@@ -893,12 +893,12 @@ func fillAligned(x uint64, m uint) uint64 {
 // will round up). That is, even if max is small, the returned size is not guaranteed
 // to be equal to max. max is allowed to be less than min, in which case it is as if
 // max == min.
-func (m *pallocData) findScavengeCandidate(searchIdx uint, min, max uintptr) (uint, uint) {
-	if min&(min-1) != 0 || min == 0 {
-		print("runtime: min = ", min, "\n")
+func (m *pallocData) findScavengeCandidate(searchIdx uint, minimum, max uintptr) (uint, uint) {
+	if minimum&(minimum-1) != 0 || minimum == 0 {
+		print("runtime: min = ", minimum, "\n")
 		throw("min must be a non-zero power of 2")
-	} else if min > maxPagesPerPhysPage {
-		print("runtime: min = ", min, "\n")
+	} else if minimum > maxPagesPerPhysPage {
+		print("runtime: min = ", minimum, "\n")
 		throw("min too large")
 	}
 	// max may not be min-aligned, so we might accidentally truncate to
@@ -907,16 +907,16 @@ func (m *pallocData) findScavengeCandidate(searchIdx uint, min, max uintptr) (ui
 	// a power of 2). This also prevents max from ever being less than
 	// min, unless it's zero, so handle that explicitly.
 	if max == 0 {
-		max = min
+		max = minimum
 	} else {
-		max = alignUp(max, min)
+		max = alignUp(max, minimum)
 	}
 
 	i := int(searchIdx / 64)
 	// Start by quickly skipping over blocks of non-free or scavenged pages.
 	for ; i >= 0; i-- {
 		// 1s are scavenged OR non-free => 0s are unscavenged AND free
-		x := fillAligned(m.scavenged[i]|m.pallocBits[i], uint(min))
+		x := fillAligned(m.scavenged[i]|m.pallocBits[i], uint(minimum))
 		if x != ^uint64(0) {
 			break
 		}
@@ -929,7 +929,7 @@ func (m *pallocData) findScavengeCandidate(searchIdx uint, min, max uintptr) (ui
 	// extend further. Loop until we find the extent of it.
 
 	// 1s are scavenged OR non-free => 0s are unscavenged AND free
-	x := fillAligned(m.scavenged[i]|m.pallocBits[i], uint(min))
+	x := fillAligned(m.scavenged[i]|m.pallocBits[i], uint(minimum))
 	z1 := uint(sys.LeadingZeros64(^x))
 	run, end := uint(0), uint(i)*64+(64-z1)
 	if x<<z1 != 0 {
@@ -942,7 +942,7 @@ func (m *pallocData) findScavengeCandidate(searchIdx uint, min, max uintptr) (ui
 		// word so it may extend into further words.
 		run = 64 - z1
 		for j := i - 1; j >= 0; j-- {
-			x := fillAligned(m.scavenged[j]|m.pallocBits[j], uint(min))
+			x := fillAligned(m.scavenged[j]|m.pallocBits[j], uint(minimum))
 			run += uint(sys.LeadingZeros64(x))
 			if x != 0 {
 				// The run stopped in this word.
@@ -953,10 +953,7 @@ func (m *pallocData) findScavengeCandidate(searchIdx uint, min, max uintptr) (ui
 
 	// Split the run we found if it's larger than max but hold on to
 	// our original length, since we may need it later.
-	size := run
-	if size > uint(max) {
-		size = uint(max)
-	}
+	size := min(run, uint(max))
 	start := end - size
 
 	// Each huge page is guaranteed to fit in a single palloc chunk.
diff --git a/src/runtime/mksizeclasses.go b/src/runtime/mksizeclasses.go
index 156e61315f..26ca49e6eb 100644
--- a/src/runtime/mksizeclasses.go
+++ b/src/runtime/mksizeclasses.go
@@ -278,14 +278,12 @@ func printComment(w io.Writer, classes []class) {
 }
 
 func maxObjsPerSpan(classes []class) int {
-	max := 0
+	most := 0
 	for _, c := range classes[1:] {
 		n := c.npages * pageSize / c.size
-		if n > max {
-			max = n
-		}
+		most = max(most, n)
 	}
-	return max
+	return most
 }
 
 func printClasses(w io.Writer, classes []class) {
diff --git a/src/runtime/mpagealloc.go b/src/runtime/mpagealloc.go
index 3e789ab85c..f87565417f 100644
--- a/src/runtime/mpagealloc.go
+++ b/src/runtime/mpagealloc.go
@@ -1038,8 +1038,8 @@ func mergeSummaries(sums []pallocSum, logMaxPagesPerSum uint) pallocSum {
 	// Merge the summaries in sums into one.
 	//
 	// We do this by keeping a running summary representing the merged
-	// summaries of sums[:i] in start, max, and end.
-	start, max, end := sums[0].unpack()
+	// summaries of sums[:i] in start, most, and end.
+	start, most, end := sums[0].unpack()
 	for i := 1; i < len(sums); i++ {
 		// Merge in sums[i].
 		si, mi, ei := sums[i].unpack()
@@ -1055,12 +1055,7 @@ func mergeSummaries(sums []pallocSum, logMaxPagesPerSum uint) pallocSum {
 		// across the boundary between the running sum and sums[i]
 		// and at the max sums[i], taking the greatest of those two
 		// and the max of the running sum.
-		if end+si > max {
-			max = end + si
-		}
-		if mi > max {
-			max = mi
-		}
+		most = max(most, end+si, mi)
 
 		// Merge in end by checking if this new summary is totally
 		// free. If it is, then we want to extend the running sum's
@@ -1073,5 +1068,5 @@ func mergeSummaries(sums []pallocSum, logMaxPagesPerSum uint) pallocSum {
 			end = ei
 		}
 	}
-	return packPallocSum(start, max, end)
+	return packPallocSum(start, most, end)
 }
diff --git a/src/runtime/mpallocbits.go b/src/runtime/mpallocbits.go
index 2f35ce007c..6b5f15dbd8 100644
--- a/src/runtime/mpallocbits.go
+++ b/src/runtime/mpallocbits.go
@@ -134,7 +134,7 @@ type pallocBits pageBits
 
 // summarize returns a packed summary of the bitmap in pallocBits.
 func (b *pallocBits) summarize() pallocSum {
-	var start, max, cur uint
+	var start, most, cur uint
 	const notSetYet = ^uint(0) // sentinel for start value
 	start = notSetYet
 	for i := 0; i < len(b); i++ {
@@ -151,9 +151,7 @@ func (b *pallocBits) summarize() pallocSum {
 		if start == notSetYet {
 			start = cur
 		}
-		if cur > max {
-			max = cur
-		}
+		most = max(most, cur)
 		// Final region that might span to next uint64
 		cur = l
 	}
@@ -162,12 +160,11 @@ func (b *pallocBits) summarize() pallocSum {
 		const n = uint(64 * len(b))
 		return packPallocSum(n, n, n)
 	}
-	if cur > max {
-		max = cur
-	}
-	if max >= 64-2 {
+	most = max(most, cur)
+
+	if most >= 64-2 {
 		// There is no way an internal run of zeros could beat max.
-		return packPallocSum(start, max, cur)
+		return packPallocSum(start, most, cur)
 	}
 	// Now look inside each uint64 for runs of zeros.
 	// All uint64s must be nonzero, or we would have aborted above.
@@ -188,7 +185,7 @@ outer:
 
 		// Strategy: shrink all runs of zeros by max. If any runs of zero
 		// remain, then we've identified a larger maximum zero run.
-		p := max     // number of zeros we still need to shrink by.
+		p := most    // number of zeros we still need to shrink by.
 		k := uint(1) // current minimum length of runs of ones in x.
 		for {
 			// Shrink all runs of zeros by p places (except the top zeros).
@@ -217,14 +214,14 @@ outer:
 			x >>= j & 63                       // remove trailing ones
 			j = uint(sys.TrailingZeros64(x))   // count contiguous trailing zeros
 			x >>= j & 63                       // remove zeros
-			max += j                           // we have a new maximum!
+			most += j                          // we have a new maximum!
 			if x&(x+1) == 0 {                  // no more zeros (except at the top).
 				continue outer
 			}
 			p = j // remove j more zeros from each zero run.
 		}
 	}
-	return packPallocSum(start, max, cur)
+	return packPallocSum(start, most, cur)
 }
 
 // find searches for npages contiguous free pages in pallocBits and returns
diff --git a/src/runtime/symtab.go b/src/runtime/symtab.go
index 0cc3085f6a..60adb37eac 100644
--- a/src/runtime/symtab.go
+++ b/src/runtime/symtab.go
@@ -1043,16 +1043,14 @@ func funcMaxSPDelta(f funcInfo) int32 {
 	p := datap.pctab[f.pcsp:]
 	pc := f.entry()
 	val := int32(-1)
-	max := int32(0)
+	most := int32(0)
 	for {
 		var ok bool
 		p, ok = step(p, &pc, &val, pc == f.entry())
 		if !ok {
-			return max
-		}
-		if val > max {
-			max = val
+			return most
 		}
+		most = max(most, val)
 	}
 }