cmd/compile: test register ABI for method, interface, closure calls

This is enabled with a ridiculous magic name for method,
or for last input type passed, that needs to be changed
to something inutterable before actual release.

Ridiculous method name: MagicMethodNameForTestingRegisterABI
Ridiculous last (input) type name: MagicLastTypeNameForTestingRegisterABI

RLTN is tested with strings.Contains, so you can have
MagicLastTypeNameForTestingRegisterABI1
and
MagicLastTypeNameForTestingRegisterABI2
if that is helpful

Includes test test/abi/fibish2.go

Updates #44816.

Change-Id: I592a6edc71ca9bebdd1d00e24edee1ceebb3e43f
Reviewed-on: https://go-review.googlesource.com/c/go/+/299410
Trust: David Chase <drchase@google.com>
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

2 files changed, 27 insertions, 8 deletions

diff --git a/src/cmd/compile/internal/ssa/gen/AMD64Ops.go b/src/cmd/compile/internal/ssa/gen/AMD64Ops.go
index 6bf5be9e47..6c3fe1d192 100644
--- a/src/cmd/compile/internal/ssa/gen/AMD64Ops.go
+++ b/src/cmd/compile/internal/ssa/gen/AMD64Ops.go
@@ -775,10 +775,10 @@ func init() {
 			faultOnNilArg0: true,
 		},
 
-		// With a register ABI, the actual register info for these instructions (i.e., what is used in regalloc) is augmented with per-call-site bindings of additional arguments to specific registers.
-		{name: "CALLstatic", argLength: -1, reg: regInfo{clobbers: callerSave}, aux: "CallOff", clobberFlags: true, call: true},                                             // call static function aux.(*obj.LSym).  arg0=mem, auxint=argsize, returns mem
-		{name: "CALLclosure", argLength: 3, reg: regInfo{inputs: []regMask{gpsp, buildReg("DX"), 0}, clobbers: callerSave}, aux: "CallOff", clobberFlags: true, call: true}, // call function via closure.  arg0=codeptr, arg1=closure, arg2=mem, auxint=argsize, returns mem
-		{name: "CALLinter", argLength: 2, reg: regInfo{inputs: []regMask{gp}, clobbers: callerSave}, aux: "CallOff", clobberFlags: true, call: true},                        // call fn by pointer.  arg0=codeptr, arg1=mem, auxint=argsize, returns mem
+		// With a register ABI, the actual register info for these instructions (i.e., what is used in regalloc) is augmented with per-call-site bindings of additional arguments to specific in and out registers.
+		{name: "CALLstatic", argLength: -1, reg: regInfo{clobbers: callerSave}, aux: "CallOff", clobberFlags: true, call: true},                                              // call static function aux.(*obj.LSym).  last arg=mem, auxint=argsize, returns mem
+		{name: "CALLclosure", argLength: -1, reg: regInfo{inputs: []regMask{gpsp, buildReg("DX"), 0}, clobbers: callerSave}, aux: "CallOff", clobberFlags: true, call: true}, // call function via closure.  arg0=codeptr, arg1=closure, last arg=mem, auxint=argsize, returns mem
+		{name: "CALLinter", argLength: -1, reg: regInfo{inputs: []regMask{gp}, clobbers: callerSave}, aux: "CallOff", clobberFlags: true, call: true},                        // call fn by pointer.  arg0=codeptr, last arg=mem, auxint=argsize, returns mem
 
 		// arg0 = destination pointer
 		// arg1 = source pointer
diff --git a/src/cmd/compile/internal/ssa/gen/genericOps.go b/src/cmd/compile/internal/ssa/gen/genericOps.go
index ee85156a42..2a5b77bad0 100644
--- a/src/cmd/compile/internal/ssa/gen/genericOps.go
+++ b/src/cmd/compile/internal/ssa/gen/genericOps.go
@@ -264,7 +264,7 @@ var genericOps = []opData{
 	//   ±0  → ±0 (sign preserved)
 	//   x<0 → NaN
 	//   NaN → NaN
-	{name: "Sqrt", argLength: 1}, // √arg0   (floating point, double precision)
+	{name: "Sqrt", argLength: 1},   // √arg0   (floating point, double precision)
 	{name: "Sqrt32", argLength: 1}, // √arg0 (floating point, single precision)
 
 	// Round to integer, float64 only.
@@ -396,9 +396,28 @@ var genericOps = []opData{
 	// TODO(josharian): ClosureCall and InterCall should have Int32 aux
 	// to match StaticCall's 32 bit arg size limit.
 	// TODO(drchase,josharian): could the arg size limit be bundled into the rules for CallOff?
-	{name: "ClosureCall", argLength: 3, aux: "CallOff", call: true},    // arg0=code pointer, arg1=context ptr, arg2=memory.  auxint=arg size.  Returns memory.
-	{name: "StaticCall", argLength: -1, aux: "CallOff", call: true},    // call function aux.(*obj.LSym), arg0..argN-1 are register inputs, argN=memory.  auxint=arg size.  Returns Result of register results, plus memory.
-	{name: "InterCall", argLength: 2, aux: "CallOff", call: true},      // interface call.  arg0=code pointer, arg1=memory, auxint=arg size.  Returns memory.
+
+	// Before lowering, LECalls receive their fixed inputs (first), memory (last),
+	// and a variable number of input values in the middle.
+	// They produce a variable number of result values.
+	// These values are not necessarily "SSA-able"; they can be too large,
+	// but in that case inputs are loaded immediately before with OpDereference,
+	// and outputs are stored immediately with OpStore.
+	//
+	// After call expansion, Calls have the same fixed-middle-memory arrangement of inputs,
+	// with the difference that the "middle" is only the register-resident inputs,
+	// and the non-register inputs are instead stored at ABI-defined offsets from SP
+	// (and the stores thread through the memory that is ultimately an input to the call).
+	// Outputs follow a similar pattern; register-resident outputs are the leading elements
+	// of a Result-typed output, with memory last, and any memory-resident outputs have been
+	// stored to ABI-defined locations.  Each non-memory input or output fits in a register.
+	//
+	// Subsequent architecture-specific lowering only changes the opcode.
+
+	{name: "ClosureCall", argLength: -1, aux: "CallOff", call: true}, // arg0=code pointer, arg1=context ptr, arg2..argN-1 are register inputs, argN=memory.  auxint=arg size.  Returns Result of register results, plus memory.
+	{name: "StaticCall", argLength: -1, aux: "CallOff", call: true},  // call function aux.(*obj.LSym), arg0..argN-1 are register inputs, argN=memory.  auxint=arg size.  Returns Result of register results, plus memory.
+	{name: "InterCall", argLength: -1, aux: "CallOff", call: true},   // interface call.  arg0=code pointer, arg1..argN-1 are register inputs, argN=memory, auxint=arg size.  Returns Result of register results, plus memory.
+
 	{name: "ClosureLECall", argLength: -1, aux: "CallOff", call: true}, // late-expanded closure call. arg0=code pointer, arg1=context ptr,  arg2..argN-1 are inputs, argN is mem. auxint = arg size. Result is tuple of result(s), plus mem.
 	{name: "StaticLECall", argLength: -1, aux: "CallOff", call: true},  // late-expanded static call function aux.(*ssa.AuxCall.Fn). arg0..argN-1 are inputs, argN is mem. auxint = arg size. Result is tuple of result(s), plus mem.
 	{name: "InterLECall", argLength: -1, aux: "CallOff", call: true},   // late-expanded interface call. arg0=code pointer, arg1..argN-1 are inputs, argN is mem. auxint = arg size. Result is tuple of result(s), plus mem.