diff --git a/src/cmd/compile/internal/ssa/deadstore.go b/src/cmd/compile/internal/ssa/deadstore.go index 9e67e833999..d0adff788c0 100644 --- a/src/cmd/compile/internal/ssa/deadstore.go +++ b/src/cmd/compile/internal/ssa/deadstore.go @@ -7,6 +7,7 @@ package ssa import ( "cmd/compile/internal/ir" "cmd/compile/internal/types" + "cmd/internal/obj" ) // dse does dead-store elimination on the Function. @@ -213,7 +214,7 @@ func elimDeadAutosGeneric(f *Func) { case OpAddr, OpLocalAddr: // Propagate the address if it points to an auto. n, ok := v.Aux.(*ir.Name) - if !ok || n.Class != ir.PAUTO { + if !ok || (n.Class != ir.PAUTO && !isABIInternalParam(f, n)) { return } if addr[v] == nil { @@ -224,7 +225,7 @@ func elimDeadAutosGeneric(f *Func) { case OpVarDef: // v should be eliminated if we eliminate the auto. n, ok := v.Aux.(*ir.Name) - if !ok || n.Class != ir.PAUTO { + if !ok || (n.Class != ir.PAUTO && !isABIInternalParam(f, n)) { return } if elim[v] == nil { @@ -240,7 +241,7 @@ func elimDeadAutosGeneric(f *Func) { // may not be used by the inline code, but will be used by // panic processing). n, ok := v.Aux.(*ir.Name) - if !ok || n.Class != ir.PAUTO { + if !ok || (n.Class != ir.PAUTO && !isABIInternalParam(f, n)) { return } if !used.Has(n) { @@ -373,7 +374,7 @@ func elimUnreadAutos(f *Func) { if !ok { continue } - if n.Class != ir.PAUTO { + if n.Class != ir.PAUTO && !isABIInternalParam(f, n) { continue } @@ -413,3 +414,16 @@ func elimUnreadAutos(f *Func) { store.Op = OpCopy } } + +// isABIInternalParam returns whether n is a parameter of an ABIInternal +// function. For dead store elimination, we can treat parameters the same +// way as autos. Storing to a parameter can be removed if it is not read +// or address-taken. +// +// We check ABI here because for a cgo_unsafe_arg function (which is ABI0), +// all the args are effectively address-taken, but not necessarily have +// an Addr or LocalAddr op. We could probably just check for cgo_unsafe_arg, +// but ABIInternal is mostly what matters. +func isABIInternalParam(f *Func, n *ir.Name) bool { + return n.Class == ir.PPARAM && f.ABISelf.Which() == obj.ABIInternal +} diff --git a/src/runtime/testdata/testprog/badtraceback.go b/src/runtime/testdata/testprog/badtraceback.go index 09aa2b877ec..455118a5437 100644 --- a/src/runtime/testdata/testprog/badtraceback.go +++ b/src/runtime/testdata/testprog/badtraceback.go @@ -44,6 +44,8 @@ func badLR2(arg int) { lrPtr := (*uintptr)(unsafe.Pointer(uintptr(unsafe.Pointer(&arg)) - lrOff)) *lrPtr = 0xbad + runtime.KeepAlive(lrPtr) // prevent dead store elimination + // Print a backtrace. This should include diagnostics for the // bad return PC and a hex dump. panic("backtrace") diff --git a/test/codegen/stack.go b/test/codegen/stack.go index 4e45d68f381..59284ae8886 100644 --- a/test/codegen/stack.go +++ b/test/codegen/stack.go @@ -168,3 +168,9 @@ func getp1() *[4]int { func getp2() *[4]int { return nil } + +// Store to an argument without read can be removed. +func storeArg(a [2]int) { + // amd64:-`MOVQ\t\$123,.*\.a\+\d+\(SP\)` + a[1] = 123 +}