reflect: preserve ctxt across moveMakeFuncArgPtrs

In makeFuncStub and methodValueCall, it stores ctxt (DX) as an
argument of moveMakeFuncArgPtrs, and assumes it does not change
by the call. This is not guaranteed, and it does happen if
-clobberdead compiler flag is used. Store it somewhere else and
reload after the call.

Change-Id: I9307e3cf94db4b38305ab35494088386dfcbaae8
Reviewed-on: https://go-review.googlesource.com/c/go/+/310409
Trust: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>

diff --git a/src/reflect/asm_amd64.s b/src/reflect/asm_amd64.s
index 22d95f2a7e1ada44adcf9623138a2713d1026dc0..facf07516d8c2441058c7c032db482bd5a4d2c6b 100644 (file)
--- a/src/reflect/asm_amd64.s
+++ b/src/reflect/asm_amd64.s
@@ -33,9 +33,12 @@ TEXT ·makeFuncStub<ABIInternal>(SB),(NOSPLIT|WRAPPER),$312
        // frame is specially handled in the runtime. See the comment above LOCAL_RETVALID.
        LEAQ    LOCAL_REGARGS(SP), R12
        CALL    runtime·spillArgs<ABIInternal>(SB)
+       MOVQ    DX, 24(SP) // outside of moveMakeFuncArgPtrs's arg area
        MOVQ    DX, 0(SP)
        MOVQ    R12, 8(SP)
        CALL    ·moveMakeFuncArgPtrs(SB)
+       MOVQ    24(SP), DX
+       MOVQ    DX, 0(SP)
        LEAQ    argframe+0(FP), CX
        MOVQ    CX, 8(SP)
        MOVB    $0, LOCAL_RETVALID(SP)
@@ -61,9 +64,12 @@ TEXT ·methodValueCall<ABIInternal>(SB),(NOSPLIT|WRAPPER),$312
        // frame is specially handled in the runtime. See the comment above LOCAL_RETVALID.
        LEAQ    LOCAL_REGARGS(SP), R12
        CALL    runtime·spillArgs<ABIInternal>(SB)
+       MOVQ    DX, 24(SP) // outside of moveMakeFuncArgPtrs's arg area
        MOVQ    DX, 0(SP)
        MOVQ    R12, 8(SP)
        CALL    ·moveMakeFuncArgPtrs(SB)
+       MOVQ    24(SP), DX
+       MOVQ    DX, 0(SP)
        LEAQ    argframe+0(FP), CX
        MOVQ    CX, 8(SP)
        MOVB    $0, LOCAL_RETVALID(SP)