cmd/compile: update default ABI choices for calls and bodyless fn stack maps

After recent discussion about bodyless functions, their wrappers,
their stack maps, nosplit, and callbacks, I was inspired to go and
be sure that more defaults were sensible.  This may not be all --
currently rtcall is "ABIDefault" which I think is correct, but I
am not 100% certain.

Updates #40724.

Change-Id: I95b14ee0e5952fa53e7fea9f6f5192358aa24f23
Reviewed-on: https://go-review.googlesource.com/c/go/+/304549
Trust: David Chase <drchase@google.com>
Run-TryBot: David Chase <drchase@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>

diff --git a/src/cmd/compile/internal/gc/compile.go b/src/cmd/compile/internal/gc/compile.go
index e066d3345e9e44c941f37e85d718a0d3c4612c0a..6db37919fa92a52e70d6e7aedbb7e47ad12082d3 100644 (file)
--- a/src/cmd/compile/internal/gc/compile.go
+++ b/src/cmd/compile/internal/gc/compile.go
@@ -44,7 +44,7 @@ func enqueueFunc(fn *ir.Func) {
                // Initialize ABI wrappers if necessary.
                ssagen.InitLSym(fn, false)
                types.CalcSize(fn.Type()) // TODO register args; remove this once all is done by abiutils
-               a := ssagen.AbiForFunc(fn)
+               a := ssagen.AbiForBodylessFuncStackMap(fn)
                abiInfo := a.ABIAnalyze(fn.Type(), true) // will set parameter spill/home locations correctly
                liveness.WriteFuncMap(fn, abiInfo)
                return

diff --git a/src/cmd/compile/internal/ssagen/ssa.go b/src/cmd/compile/internal/ssagen/ssa.go
index 0062cc5fc7a150fbe1f976ce8659a7ceb42637c3..57099371e66191eb318c060b70db2ecee7c9fa0f 100644 (file)
--- a/src/cmd/compile/internal/ssagen/ssa.go
+++ b/src/cmd/compile/internal/ssagen/ssa.go
@@ -209,12 +209,15 @@ func InitConfig() {
        ir.Syms.SigPanic = typecheck.LookupRuntimeFunc("sigpanic")
 }
 
-// AbiForFunc returns the ABI for a function, used to figure out arg/result mapping for rtcall and bodyless functions.
-// This follows policy for GOEXPERIMENT=regabi, //go:registerparams, and currently defined ABIInternal.
-// Policy is subject to change....
+// AbiForBodylessFuncStackMap returns the ABI for a bodyless function's stack map.
+// This is not necessarily the ABI used to call it.
+// Currently (1.17 dev) such a stack map is always ABI0;
+// any ABI wrapper that is present is nosplit, hence a precise
+// stack map is not needed there (the parameters survive only long
+// enough to call the wrapped assembly function).
 // This always returns a freshly copied ABI.
-func AbiForFunc(fn *ir.Func) *abi.ABIConfig {
-       return abiForFunc(fn, ssaConfig.ABI0, ssaConfig.ABI1).Copy() // No idea what races will result, be safe
+func AbiForBodylessFuncStackMap(fn *ir.Func) *abi.ABIConfig {
+       return ssaConfig.ABI0.Copy() // No idea what races will result, be safe
 }
 
 // TODO (NLT 2021-04-15) This must be changed to a name that cannot match; it may be helpful to other register ABI work to keep the trigger-logic
@@ -4839,24 +4842,24 @@ func (s *state) call(n *ir.CallExpr, k callKind, returnResultAddr bool) *ssa.Val
        var codeptr *ssa.Value // ptr to target code (if dynamic)
        var rcvr *ssa.Value    // receiver to set
        fn := n.X
-       var ACArgs []*types.Type    // AuxCall args
-       var ACResults []*types.Type // AuxCall results
-       var callArgs []*ssa.Value   // For late-expansion, the args themselves (not stored, args to the call instead).
-       inRegisters := false
+       var ACArgs []*types.Type       // AuxCall args
+       var ACResults []*types.Type    // AuxCall results
+       var callArgs []*ssa.Value      // For late-expansion, the args themselves (not stored, args to the call instead).
+       inRegistersForTesting := false // If a call uses register ABI for one of the testing reasons, pragma, magic types, magic names
 
        var magicFnNameSym *types.Sym
        if fn.Name() != nil {
                magicFnNameSym = fn.Name().Sym()
                ss := magicFnNameSym.Name
                if strings.HasSuffix(ss, magicNameDotSuffix) {
-                       inRegisters = true
+                       inRegistersForTesting = true
                }
        }
        if magicFnNameSym == nil && n.Op() == ir.OCALLINTER {
                magicFnNameSym = fn.(*ir.SelectorExpr).Sym()
                ss := magicFnNameSym.Name
                if strings.HasSuffix(ss, magicNameDotSuffix[1:]) {
-                       inRegisters = true
+                       inRegistersForTesting = true
                }
        }
 
@@ -4872,7 +4875,7 @@ func (s *state) call(n *ir.CallExpr, k callKind, returnResultAddr bool) *ssa.Val
                        // TODO(register args) remove after register abi is working
                        inRegistersImported := fn.Pragma()&ir.RegisterParams != 0
                        inRegistersSamePackage := fn.Func != nil && fn.Func.Pragma&ir.RegisterParams != 0
-                       inRegisters = inRegisters || inRegistersImported || inRegistersSamePackage
+                       inRegistersForTesting = inRegistersForTesting || inRegistersImported || inRegistersSamePackage
                        break
                }
                closure = s.expr(fn)
@@ -4898,13 +4901,13 @@ func (s *state) call(n *ir.CallExpr, k callKind, returnResultAddr bool) *ssa.Val
        }
 
        if regAbiForFuncType(n.X.Type().FuncType()) {
-               // fmt.Printf("Saw magic last type in call %v\n", n)
-               inRegisters = true
+               // Magic last type in input args to call
+               inRegistersForTesting = true
        }
 
-       callABI := s.f.ABI1
-       if !inRegisters {
-               callABI = s.f.ABI0
+       callABI := s.f.ABIDefault
+       if inRegistersForTesting {
+               callABI = s.f.ABI1
        }
 
        params := callABI.ABIAnalyze(n.X.Type(), false /* Do not set (register) nNames from caller side -- can cause races. */)