internal/sys: add LR and fixed frame size to sys.Arch

Storing this information in the Arch eliminates some code duplication
between the compiler and linker. This information is entirely
determined by the Arch, so the current approach of attaching it to an
entire Ctxt is a little silly. This will also make it easier to use
this information from tests.

The next CL will be a rote refactoring to eliminate the
Ctxt.FixedFrameSize methods.

Change-Id: I315c524fa66a0ea99f63ae5a2a6fdc367d843bad
Reviewed-on: https://go-review.googlesource.com/c/go/+/400818
Run-TryBot: Austin Clements <austin@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

1 files changed, 147 insertions, 105 deletions

diff --git a/src/cmd/internal/sys/arch.go b/src/cmd/internal/sys/arch.go
index 84ed35ba8d..5886b42e51 100644
--- a/src/cmd/internal/sys/arch.go
+++ b/src/cmd/internal/sys/arch.go
@@ -56,6 +56,18 @@ type Arch struct {
 	// CanJumpTable reports whether the backend can handle
 	// compiling a jump table.
 	CanJumpTable bool
+
+	// HasLR indicates that this architecture uses a link register
+	// for calls.
+	HasLR bool
+
+	// FixedFrameSize is the smallest possible offset from the
+	// hardware stack pointer to a local variable on the stack.
+	// Architectures that use a link register save its value on
+	// the stack in the function prologue and so always have a
+	// pointer between the hardware stack pointer and the local
+	// variable area.
+	FixedFrameSize int64
 }
 
 // InFamily reports whether a is a member of any of the specified
@@ -70,103 +82,121 @@ func (a *Arch) InFamily(xs ...ArchFamily) bool {
 }
 
 var Arch386 = &Arch{
-	Name:          "386",
-	Family:        I386,
-	ByteOrder:     binary.LittleEndian,
-	PtrSize:       4,
-	RegSize:       4,
-	MinLC:         1,
-	Alignment:     1,
-	CanMergeLoads: true,
+	Name:           "386",
+	Family:         I386,
+	ByteOrder:      binary.LittleEndian,
+	PtrSize:        4,
+	RegSize:        4,
+	MinLC:          1,
+	Alignment:      1,
+	CanMergeLoads:  true,
+	HasLR:          false,
+	FixedFrameSize: 0,
 }
 
 var ArchAMD64 = &Arch{
-	Name:          "amd64",
-	Family:        AMD64,
-	ByteOrder:     binary.LittleEndian,
-	PtrSize:       8,
-	RegSize:       8,
-	MinLC:         1,
-	Alignment:     1,
-	CanMergeLoads: true,
-	CanJumpTable:  true,
+	Name:           "amd64",
+	Family:         AMD64,
+	ByteOrder:      binary.LittleEndian,
+	PtrSize:        8,
+	RegSize:        8,
+	MinLC:          1,
+	Alignment:      1,
+	CanMergeLoads:  true,
+	CanJumpTable:   true,
+	HasLR:          false,
+	FixedFrameSize: 0,
 }
 
 var ArchARM = &Arch{
-	Name:          "arm",
-	Family:        ARM,
-	ByteOrder:     binary.LittleEndian,
-	PtrSize:       4,
-	RegSize:       4,
-	MinLC:         4,
-	Alignment:     4, // TODO: just for arm5?
-	CanMergeLoads: false,
+	Name:           "arm",
+	Family:         ARM,
+	ByteOrder:      binary.LittleEndian,
+	PtrSize:        4,
+	RegSize:        4,
+	MinLC:          4,
+	Alignment:      4, // TODO: just for arm5?
+	CanMergeLoads:  false,
+	HasLR:          true,
+	FixedFrameSize: 4, // LR
 }
 
 var ArchARM64 = &Arch{
-	Name:          "arm64",
-	Family:        ARM64,
-	ByteOrder:     binary.LittleEndian,
-	PtrSize:       8,
-	RegSize:       8,
-	MinLC:         4,
-	Alignment:     1,
-	CanMergeLoads: true,
+	Name:           "arm64",
+	Family:         ARM64,
+	ByteOrder:      binary.LittleEndian,
+	PtrSize:        8,
+	RegSize:        8,
+	MinLC:          4,
+	Alignment:      1,
+	CanMergeLoads:  true,
+	HasLR:          true,
+	FixedFrameSize: 8, // LR
 }
 
 var ArchLoong64 = &Arch{
-	Name:          "loong64",
-	Family:        Loong64,
-	ByteOrder:     binary.LittleEndian,
-	PtrSize:       8,
-	RegSize:       8,
-	MinLC:         4,
-	Alignment:     8, // Unaligned accesses are not guaranteed to be fast
-	CanMergeLoads: false,
+	Name:           "loong64",
+	Family:         Loong64,
+	ByteOrder:      binary.LittleEndian,
+	PtrSize:        8,
+	RegSize:        8,
+	MinLC:          4,
+	Alignment:      8, // Unaligned accesses are not guaranteed to be fast
+	CanMergeLoads:  false,
+	HasLR:          true,
+	FixedFrameSize: 8, // LR
 }
 
 var ArchMIPS = &Arch{
-	Name:          "mips",
-	Family:        MIPS,
-	ByteOrder:     binary.BigEndian,
-	PtrSize:       4,
-	RegSize:       4,
-	MinLC:         4,
-	Alignment:     4,
-	CanMergeLoads: false,
+	Name:           "mips",
+	Family:         MIPS,
+	ByteOrder:      binary.BigEndian,
+	PtrSize:        4,
+	RegSize:        4,
+	MinLC:          4,
+	Alignment:      4,
+	CanMergeLoads:  false,
+	HasLR:          true,
+	FixedFrameSize: 4, // LR
 }
 
 var ArchMIPSLE = &Arch{
-	Name:          "mipsle",
-	Family:        MIPS,
-	ByteOrder:     binary.LittleEndian,
-	PtrSize:       4,
-	RegSize:       4,
-	MinLC:         4,
-	Alignment:     4,
-	CanMergeLoads: false,
+	Name:           "mipsle",
+	Family:         MIPS,
+	ByteOrder:      binary.LittleEndian,
+	PtrSize:        4,
+	RegSize:        4,
+	MinLC:          4,
+	Alignment:      4,
+	CanMergeLoads:  false,
+	HasLR:          true,
+	FixedFrameSize: 4, // LR
 }
 
 var ArchMIPS64 = &Arch{
-	Name:          "mips64",
-	Family:        MIPS64,
-	ByteOrder:     binary.BigEndian,
-	PtrSize:       8,
-	RegSize:       8,
-	MinLC:         4,
-	Alignment:     8,
-	CanMergeLoads: false,
+	Name:           "mips64",
+	Family:         MIPS64,
+	ByteOrder:      binary.BigEndian,
+	PtrSize:        8,
+	RegSize:        8,
+	MinLC:          4,
+	Alignment:      8,
+	CanMergeLoads:  false,
+	HasLR:          true,
+	FixedFrameSize: 8, // LR
 }
 
 var ArchMIPS64LE = &Arch{
-	Name:          "mips64le",
-	Family:        MIPS64,
-	ByteOrder:     binary.LittleEndian,
-	PtrSize:       8,
-	RegSize:       8,
-	MinLC:         4,
-	Alignment:     8,
-	CanMergeLoads: false,
+	Name:           "mips64le",
+	Family:         MIPS64,
+	ByteOrder:      binary.LittleEndian,
+	PtrSize:        8,
+	RegSize:        8,
+	MinLC:          4,
+	Alignment:      8,
+	CanMergeLoads:  false,
+	HasLR:          true,
+	FixedFrameSize: 8, // LR
 }
 
 var ArchPPC64 = &Arch{
@@ -178,50 +208,62 @@ var ArchPPC64 = &Arch{
 	MinLC:         4,
 	Alignment:     1,
 	CanMergeLoads: false,
+	HasLR:         true,
+	// PIC code on ppc64le requires 32 bytes of stack, and it's
+	// easier to just use that much stack always.
+	FixedFrameSize: 4 * 8,
 }
 
 var ArchPPC64LE = &Arch{
-	Name:          "ppc64le",
-	Family:        PPC64,
-	ByteOrder:     binary.LittleEndian,
-	PtrSize:       8,
-	RegSize:       8,
-	MinLC:         4,
-	Alignment:     1,
-	CanMergeLoads: true,
+	Name:           "ppc64le",
+	Family:         PPC64,
+	ByteOrder:      binary.LittleEndian,
+	PtrSize:        8,
+	RegSize:        8,
+	MinLC:          4,
+	Alignment:      1,
+	CanMergeLoads:  true,
+	HasLR:          true,
+	FixedFrameSize: 4 * 8,
 }
 
 var ArchRISCV64 = &Arch{
-	Name:          "riscv64",
-	Family:        RISCV64,
-	ByteOrder:     binary.LittleEndian,
-	PtrSize:       8,
-	RegSize:       8,
-	MinLC:         4,
-	Alignment:     8, // riscv unaligned loads work, but are really slow (trap + simulated by OS)
-	CanMergeLoads: false,
+	Name:           "riscv64",
+	Family:         RISCV64,
+	ByteOrder:      binary.LittleEndian,
+	PtrSize:        8,
+	RegSize:        8,
+	MinLC:          4,
+	Alignment:      8, // riscv unaligned loads work, but are really slow (trap + simulated by OS)
+	CanMergeLoads:  false,
+	HasLR:          true,
+	FixedFrameSize: 8, // LR
 }
 
 var ArchS390X = &Arch{
-	Name:          "s390x",
-	Family:        S390X,
-	ByteOrder:     binary.BigEndian,
-	PtrSize:       8,
-	RegSize:       8,
-	MinLC:         2,
-	Alignment:     1,
-	CanMergeLoads: true,
+	Name:           "s390x",
+	Family:         S390X,
+	ByteOrder:      binary.BigEndian,
+	PtrSize:        8,
+	RegSize:        8,
+	MinLC:          2,
+	Alignment:      1,
+	CanMergeLoads:  true,
+	HasLR:          true,
+	FixedFrameSize: 8, // LR
 }
 
 var ArchWasm = &Arch{
-	Name:          "wasm",
-	Family:        Wasm,
-	ByteOrder:     binary.LittleEndian,
-	PtrSize:       8,
-	RegSize:       8,
-	MinLC:         1,
-	Alignment:     1,
-	CanMergeLoads: false,
+	Name:           "wasm",
+	Family:         Wasm,
+	ByteOrder:      binary.LittleEndian,
+	PtrSize:        8,
+	RegSize:        8,
+	MinLC:          1,
+	Alignment:      1,
+	CanMergeLoads:  false,
+	HasLR:          false,
+	FixedFrameSize: 0,
 }
 
 var Archs = [...]*Arch{