return 0 is compare function of sortBlocks when blocks are equal (#2026)

Signed-off-by: Achille Roussel <[email protected]>

internal/engine/wazevo/ssa/basic_block_sort.go

@@ -8,16 +8,27 @@ import (
 
 func sortBlocks(blocks []*basicBlock) {
 	slices.SortFunc(blocks, func(i, j *basicBlock) int {
-		if j.ReturnBlock() {
+		jIsReturn := j.ReturnBlock()
+		iIsReturn := i.ReturnBlock()
+		if iIsReturn && jIsReturn {
+			return 0
+		}
+		if jIsReturn {
 			return 1
 		}
-		if i.ReturnBlock() {
+		if iIsReturn {
 			return -1
 		}
 		iRoot, jRoot := i.rootInstr, j.rootInstr
-		if iRoot == nil || jRoot == nil { // For testing.
+		if iRoot == nil && jRoot == nil { // For testing.
+			return 0
+		}
+		if jRoot == nil {
 			return 1
 		}
+		if iRoot == nil {
+			return -1
+		}
 		return i.rootInstr.id - j.rootInstr.id
 	})
 }