fix: staticcheck and deadcode findings repo-wide, modernize counting loops

verify/abi_amd64.go

@@ -17,7 +17,12 @@ import (
 var abiResult uint64
 
 // savedBP holds the caller's frame pointer across the ABI-checked JIT call.
-// Referenced by enterJITChecked to satisfy go vet's save-before-clobber rule.
+// Written and read by enterJITChecked/leaveJITChecked (abi_amd64.s); no Go
+// code references it, which GoLand cannot see inside assembly.
+//
+// noinspection GoUnusedGlobalVariable
+//
+//lint:ignore U1000 written and read by the assembly
 var savedBP uintptr
 
 // leaveCheckedPtr is initialised by the linker from the GLOBL/DATA in
@@ -26,7 +31,10 @@ var savedBP uintptr
 var leaveCheckedPtr uintptr
 
 // enterJITChecked sets sentinels in BP and R14, switches to the prepared
-// stack and jumps to fn.
+// stack and jumps to fn.  The body lives in abi_amd64.s and reads the
+// parameters from the frame by name, which GoLand cannot see.
+//
+// noinspection GoUnusedParameter
 //
 //go:nosplit
 func enterJITChecked(fn uintptr, stack uintptr)
@@ -37,6 +45,9 @@ func enterJITChecked(fn uintptr, stack uintptr)
 // declaration would generate.  The declaration exists solely to satisfy
 // go vet's "missing Go declaration" check.
 //
+// noinspection GoUnusedFunction
+//
+//lint:ignore U1000 the assembly obtains this address through leaveCheckedPtr
 //go:nosplit
 func leaveJITCheckedRaw()
 
@@ -95,10 +106,10 @@ func CallChecked(fnAddr uintptr, args []byte) ([]byte, ABIReport, error) {
 	if err != nil {
 		return nil, report, fmt.Errorf("verify: stack mmap: %w", err)
 	}
-	defer syscall.Munmap(stackMem)
+	defer func() { _ = syscall.Munmap(stackMem) }()
 
 	// Fill the red zone with the canary pattern.
-	for i := 0; i < redZoneSize; i++ {
+	for i := range redZoneSize {
 		stackMem[i] = redZoneFill
 	}
 
@@ -116,7 +127,7 @@ func CallChecked(fnAddr uintptr, args []byte) ([]byte, ABIReport, error) {
 	report.R14Clobbered = res&2 != 0
 
 	// Check the red zone.
-	for i := 0; i < redZoneSize; i++ {
+	for i := range redZoneSize {
 		if stackMem[i] != redZoneFill {
 			report.RedZoneHit = true
 			break