reflect,runtime: add reflect support for regabi on PPC64

This adds the regabi support needed for reflect including:
- implementation of the makeFuncSub and methodValueCall for
reflect
- implementations of archFloat32FromReg and archFloat32ToReg
needed for PPC64 due to differences in the way float32 are
represented in registers as compared to other platforms
- change needed to stack.go due to the functions that are
changed above

Change-Id: Ida40d831370e39b91711ccb9616492b7fad3debf
Reviewed-on: https://go-review.googlesource.com/c/go/+/352429
Run-TryBot: Lynn Boger <laboger@linux.vnet.ibm.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Lynn Boger <laboger@linux.vnet.ibm.com>

5 files changed, 104 insertions, 17 deletions

diff --git a/src/reflect/asm_ppc64x.s b/src/reflect/asm_ppc64x.s
index d955e4110f..1ccfb25b94 100644
--- a/src/reflect/asm_ppc64x.s
+++ b/src/reflect/asm_ppc64x.s
@@ -9,34 +9,76 @@
 #include "funcdata.h"
 #include "asm_ppc64x.h"
 
+// The frames of each of the two functions below contain two locals, at offsets
+// that are known to the runtime.
+//
+// The first local is a bool called retValid with a whole pointer-word reserved
+// for it on the stack. The purpose of this word is so that the runtime knows
+// whether the stack-allocated return space contains valid values for stack
+// scanning.
+//
+// The second local is an abi.RegArgs value whose offset is also known to the
+// runtime, so that a stack map for it can be constructed, since it contains
+// pointers visible to the GC.
+
+#define LOCAL_RETVALID 32+FIXED_FRAME
+#define LOCAL_REGARGS 40+FIXED_FRAME
+
+// The frame size of the functions below is
+// 32 (args of callReflect) + 8 (bool + padding) + 296 (abi.RegArgs) = 336.
+
 // makeFuncStub is the code half of the function returned by MakeFunc.
 // See the comment on the declaration of makeFuncStub in makefunc.go
 // for more details.
 // No arg size here, runtime pulls arg map out of the func value.
-TEXT ·makeFuncStub(SB),(NOSPLIT|WRAPPER),$40
+TEXT ·makeFuncStub(SB),(NOSPLIT|WRAPPER),$336
 	NO_LOCAL_POINTERS
-	MOVD	R11, FIXED_FRAME+0(R1)
-	MOVD	$argframe+0(FP), R3
-	MOVD	R3, FIXED_FRAME+8(R1)
-	MOVB	R0, FIXED_FRAME+32(R1)
-	ADD	$FIXED_FRAME+32, R1, R3
-	MOVD	R3, FIXED_FRAME+16(R1)
-	MOVD	R0, FIXED_FRAME+24(R1)
+	// NO_LOCAL_POINTERS is a lie. The stack map for the two locals in this
+	// frame is specially handled in the runtime. See the comment above LOCAL_RETVALID.
+	ADD	$LOCAL_REGARGS, R1, R20
+	CALL	runtime·spillArgs(SB)
+	MOVD	R11, FIXED_FRAME+32(R1)	// save R11
+	MOVD	R11, FIXED_FRAME+0(R1)	// arg for moveMakeFuncArgPtrs
+	MOVD	R20, FIXED_FRAME+8(R1)	// arg for local args
+	CALL	·moveMakeFuncArgPtrs(SB)
+	MOVD	FIXED_FRAME+32(R1), R11	// restore R11 ctxt
+	MOVD	R11, FIXED_FRAME+0(R1)	// ctxt (arg0)
+	MOVD	$argframe+0(FP), R3	// save arg to callArg
+	MOVD	R3, FIXED_FRAME+8(R1)	// frame (arg1)
+	ADD	$LOCAL_RETVALID, R1, R3 // addr of return flag
+	MOVB	R0, (R3)		// clear flag
+	MOVD	R3, FIXED_FRAME+16(R1)	// addr retvalid (arg2)
+	ADD     $LOCAL_REGARGS, R1, R3
+	MOVD	R3, FIXED_FRAME+24(R1)	// abiregargs (arg3)
 	BL	·callReflect(SB)
+	ADD	$LOCAL_REGARGS, R1, R20	// set address of spill area
+	CALL	runtime·unspillArgs(SB)
 	RET
 
 // methodValueCall is the code half of the function returned by makeMethodValue.
 // See the comment on the declaration of methodValueCall in makefunc.go
 // for more details.
 // No arg size here; runtime pulls arg map out of the func value.
-TEXT ·methodValueCall(SB),(NOSPLIT|WRAPPER),$40
+TEXT ·methodValueCall(SB),(NOSPLIT|WRAPPER),$336
 	NO_LOCAL_POINTERS
-	MOVD	R11, FIXED_FRAME+0(R1)
-	MOVD	$argframe+0(FP), R3
-	MOVD	R3, FIXED_FRAME+8(R1)
-	MOVB	R0, FIXED_FRAME+32(R1)
-	ADD	$FIXED_FRAME+32, R1, R3
-	MOVD	R3, FIXED_FRAME+16(R1)
-	MOVD	R0, FIXED_FRAME+24(R1)
+	// NO_LOCAL_POINTERS is a lie. The stack map for the two locals in this
+	// frame is specially handled in the runtime. See the comment above LOCAL_RETVALID.
+	ADD	$LOCAL_REGARGS, R1, R20
+	CALL	runtime·spillArgs(SB)
+	MOVD	R11, FIXED_FRAME+0(R1) // arg0 ctxt
+	MOVD	R11, FIXED_FRAME+32(R1) // save for later
+	MOVD	R20, FIXED_FRAME+8(R1) // arg1 abiregargs
+	CALL	·moveMakeFuncArgPtrs(SB)
+	MOVD	FIXED_FRAME+32(R1), R11 // restore ctxt
+	MOVD	R11, FIXED_FRAME+0(R1) // set as arg0
+	MOVD	$argframe+0(FP), R3	// frame pointer
+	MOVD	R3, FIXED_FRAME+8(R1)	// set as arg1
+	ADD	$LOCAL_RETVALID, R1, R3
+	MOVB	$0, (R3)		// clear ret flag
+	MOVD	R3, FIXED_FRAME+16(R1)	// addr of return flag
+	ADD	$LOCAL_REGARGS, R1, R3	// addr of abiregargs
+	MOVD	R3, FIXED_FRAME+24(R1)	// set as arg3
 	BL	·callMethod(SB)
+	ADD     $LOCAL_REGARGS, R1, R20
+	CALL	runtime·unspillArgs(SB)
 	RET
diff --git a/src/reflect/float32reg_generic.go b/src/reflect/float32reg_generic.go
index 381d458057..bfceb9ecaa 100644
--- a/src/reflect/float32reg_generic.go
+++ b/src/reflect/float32reg_generic.go
@@ -2,6 +2,9 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build !ppc64 && !ppc64le
+// +build !ppc64,!ppc64le
+
 package reflect
 
 import "unsafe"
diff --git a/src/reflect/float32reg_ppc64x.s b/src/reflect/float32reg_ppc64x.s
new file mode 100644
index 0000000000..391edfa7ce
--- /dev/null
+++ b/src/reflect/float32reg_ppc64x.s
@@ -0,0 +1,31 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build ppc64 || ppc64le
+// +build ppc64 ppc64le
+
+#include "textflag.h"
+
+// On PPC64, the float32 becomes a float64
+// when loaded in a register, different from
+// other platforms. These functions are
+// needed to ensure correct conversions on PPC64.
+
+// Convert float32->uint64
+TEXT ·archFloat32ToReg(SB),NOSPLIT,$0-16
+	FMOVS	val+0(FP), F1
+	FMOVD	F1, ret+8(FP)
+	RET
+
+// Convert uint64->float32
+TEXT ·archFloat32FromReg(SB),NOSPLIT,$0-12
+	FMOVD	reg+0(FP), F1
+	// Normally a float64->float32 conversion
+	// would need rounding, but that is not needed
+	// here since the uint64 was originally converted
+	// from float32, and should be avoided to
+	// preserve SNaN values.
+	FMOVS	F1, ret+8(FP)
+	RET
+
diff --git a/src/reflect/stubs_ppc64x.go b/src/reflect/stubs_ppc64x.go
new file mode 100644
index 0000000000..dbd3f9e748
--- /dev/null
+++ b/src/reflect/stubs_ppc64x.go
@@ -0,0 +1,11 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build ppc64le || ppc64
+// +build ppc64le ppc64
+
+package reflect
+
+func archFloat32FromReg(reg uint64) float32
+func archFloat32ToReg(val float32) uint64
diff --git a/src/runtime/stack.go b/src/runtime/stack.go
index cccec49f8e..22fff73947 100644
--- a/src/runtime/stack.go
+++ b/src/runtime/stack.go
@@ -1316,7 +1316,7 @@ func getStackMap(frame *stkframe, cache *pcvalueCache, debug bool) (locals, args
 	}
 
 	// stack objects.
-	if (GOARCH == "amd64" || GOARCH == "arm64") && unsafe.Sizeof(abi.RegArgs{}) > 0 && frame.argmap != nil {
+	if (GOARCH == "amd64" || GOARCH == "arm64" || GOARCH == "ppc64" || GOARCH == "ppc64le") && unsafe.Sizeof(abi.RegArgs{}) > 0 && frame.argmap != nil {
 		// argmap is set when the function is reflect.makeFuncStub or reflect.methodValueCall.
 		// We don't actually use argmap in this case, but we need to fake the stack object
 		// record for these frames which contain an internal/abi.RegArgs at a hard-coded offset.