diff --git a/src/runtime/mgc.go b/src/runtime/mgc.go
index f65402e94c..4750a74bc7 100644
--- a/src/runtime/mgc.go
+++ b/src/runtime/mgc.go
@@ -328,6 +328,10 @@ var work struct {
 	nFlushCacheRoots                               int
 	nDataRoots, nBSSRoots, nSpanRoots, nStackRoots int
 
+	// Base indexes of each root type. Set by gcMarkRootPrepare.
+	baseFlushCache                                    uint32
+	baseData, baseBSS, baseSpans, baseStacks, baseEnd uint32
+
 	// Each type of GC state transition is protected by a lock.
 	// Since multiple threads can simultaneously detect the state
 	// transition condition, any thread that detects a transition
diff --git a/src/runtime/mgcmark.go b/src/runtime/mgcmark.go
index b3c1e00ca5..45ccc806bd 100644
--- a/src/runtime/mgcmark.go
+++ b/src/runtime/mgcmark.go
@@ -106,6 +106,14 @@ func gcMarkRootPrepare() {
 
 	work.markrootNext = 0
 	work.markrootJobs = uint32(fixedRootCount + work.nFlushCacheRoots + work.nDataRoots + work.nBSSRoots + work.nSpanRoots + work.nStackRoots)
+
+	// Calculate base indexes of each root type
+	work.baseFlushCache = uint32(fixedRootCount)
+	work.baseData = work.baseFlushCache + uint32(work.nFlushCacheRoots)
+	work.baseBSS = work.baseData + uint32(work.nDataRoots)
+	work.baseSpans = work.baseBSS + uint32(work.nBSSRoots)
+	work.baseStacks = work.baseSpans + uint32(work.nSpanRoots)
+	work.baseEnd = work.baseStacks + uint32(work.nStackRoots)
 }
 
 // gcMarkRootCheck checks that all roots have been scanned. It is
@@ -149,28 +157,19 @@ var oneptrmask = [...]uint8{1}
 //
 //go:nowritebarrier
 func markroot(gcw *gcWork, i uint32) {
-	// TODO(austin): This is a bit ridiculous. Compute and store
-	// the bases in gcMarkRootPrepare instead of the counts.
-	baseFlushCache := uint32(fixedRootCount)
-	baseData := baseFlushCache + uint32(work.nFlushCacheRoots)
-	baseBSS := baseData + uint32(work.nDataRoots)
-	baseSpans := baseBSS + uint32(work.nBSSRoots)
-	baseStacks := baseSpans + uint32(work.nSpanRoots)
-	end := baseStacks + uint32(work.nStackRoots)
-
 	// Note: if you add a case here, please also update heapdump.go:dumproots.
 	switch {
-	case baseFlushCache <= i && i < baseData:
-		flushmcache(int(i - baseFlushCache))
+	case work.baseFlushCache <= i && i < work.baseData:
+		flushmcache(int(i - work.baseFlushCache))
 
-	case baseData <= i && i < baseBSS:
+	case work.baseData <= i && i < work.baseBSS:
 		for _, datap := range activeModules() {
-			markrootBlock(datap.data, datap.edata-datap.data, datap.gcdatamask.bytedata, gcw, int(i-baseData))
+			markrootBlock(datap.data, datap.edata-datap.data, datap.gcdatamask.bytedata, gcw, int(i-work.baseData))
 		}
 
-	case baseBSS <= i && i < baseSpans:
+	case work.baseBSS <= i && i < work.baseSpans:
 		for _, datap := range activeModules() {
-			markrootBlock(datap.bss, datap.ebss-datap.bss, datap.gcbssmask.bytedata, gcw, int(i-baseBSS))
+			markrootBlock(datap.bss, datap.ebss-datap.bss, datap.gcbssmask.bytedata, gcw, int(i-work.baseBSS))
 		}
 
 	case i == fixedRootFinalizers:
@@ -184,18 +183,18 @@ func markroot(gcw *gcWork, i uint32) {
 		// stackfree.
 		systemstack(markrootFreeGStacks)
 
-	case baseSpans <= i && i < baseStacks:
+	case work.baseSpans <= i && i < work.baseStacks:
 		// mark mspan.specials
-		markrootSpans(gcw, int(i-baseSpans))
+		markrootSpans(gcw, int(i-work.baseSpans))
 
 	default:
 		// the rest is scanning goroutine stacks
 		var gp *g
-		if baseStacks <= i && i < end {
+		if work.baseStacks <= i && i < work.baseEnd {
 			// N.B. Atomic read of allglen in gcMarkRootPrepare
 			// acts as a barrier to ensure that allgs must be large
 			// enough to contain all relevant Gs.
-			gp = allgs[i-baseStacks]
+			gp = allgs[i-work.baseStacks]
 		} else {
 			throw("markroot: bad index")
 		}