runtime: fix nacl/amd64p32 build

Update #8675
Fixes nacl/amd64p32 build.

TBR=khr
CC=golang-codereviews
https://golang.org/cl/141140045

src/liblink/obj6.c

@@ -483,11 +483,19 @@ addstacksplit(Link *ctxt, LSym *cursym)
 		p->from.type = D_INDIR+D_CX;
 		p->from.offset = 2*ctxt->arch->ptrsize; // G.panic
 		p->to.type = D_BX;
+		if(ctxt->headtype == Hnacl) {
+			p->as = AMOVL;
+			p->from.type = D_INDIR+D_R15;
+			p->from.scale = 1;
+			p->from.index = D_CX;
+		}
 
 		p = appendp(ctxt, p);
 		p->as = ATESTQ;
 		p->from.type = D_BX;
 		p->to.type = D_BX;
+		if(ctxt->headtype == Hnacl)
+			p->as = ATESTL;
 
 		p = appendp(ctxt, p);
 		p->as = AJEQ;
@@ -499,12 +507,20 @@ addstacksplit(Link *ctxt, LSym *cursym)
 		p->from.type = D_INDIR+D_SP;
 		p->from.offset = autoffset+8;
 		p->to.type = D_DI;
+		if(ctxt->headtype == Hnacl)
+			p->as = ALEAL;
 
 		p = appendp(ctxt, p);
 		p->as = ACMPQ;
 		p->from.type = D_INDIR+D_BX;
 		p->from.offset = 0; // Panic.argp
 		p->to.type = D_DI;
+		if(ctxt->headtype == Hnacl) {
+			p->as = ACMPL;
+			p->from.type = D_INDIR+D_R15;
+			p->from.scale = 1;
+			p->from.index = D_BX;
+		}
 
 		p = appendp(ctxt, p);
 		p->as = AJNE;
@@ -516,6 +532,12 @@ addstacksplit(Link *ctxt, LSym *cursym)
 		p->from.type = D_SP;
 		p->to.type = D_INDIR+D_BX;
 		p->to.offset = 0; // Panic.argp
+		if(ctxt->headtype == Hnacl) {
+			p->as = AMOVL;
+			p->to.type = D_INDIR+D_R15;
+			p->to.scale = 1;
+			p->to.index = D_BX;
+		}
 
 		p = appendp(ctxt, p);
 		p->as = ANOP;

src/pkg/runtime/asm_amd64p32.s

@@ -281,7 +281,7 @@ TEXT runtime·morestack(SB),NOSPLIT,$0-0
 	RET
 
 // reflect·call: call a function with the given argument list
-// func call(f *FuncVal, arg *byte, argsize, retoffset uint32, p *Panic).
+// func call(f *FuncVal, arg *byte, argsize, retoffset uint32).
 // we don't have variable-sized frames, so we use a small number
 // of constant-sized-frame functions to encode a few bits of size in the pc.
 // Caution: ugly multiline assembly macros in your future!
@@ -293,7 +293,7 @@ TEXT runtime·morestack(SB),NOSPLIT,$0-0
 	JMP	AX
 // Note: can't just "JMP NAME(SB)" - bad inlining results.
 
-TEXT reflect·call(SB), NOSPLIT, $0-20
+TEXT reflect·call(SB), NOSPLIT, $0-16
 	MOVLQZX argsize+8(FP), CX
 	DISPATCH(runtime·call16, 16)
 	DISPATCH(runtime·call32, 32)
@@ -338,7 +338,7 @@ DATA gclocals_reflectcall<>+0x04(SB)/4, $0  // 0 locals
 GLOBL gclocals_reflectcall<>(SB),RODATA,$8
 
 #define CALLFN(NAME,MAXSIZE)			\
-TEXT NAME(SB), WRAPPER, $MAXSIZE-20;		\
+TEXT NAME(SB), WRAPPER, $MAXSIZE-16;		\
 	FUNCDATA $FUNCDATA_ArgsPointerMaps,gcargs_reflectcall<>(SB);	\
 	FUNCDATA $FUNCDATA_LocalsPointerMaps,gclocals_reflectcall<>(SB);\
 	/* copy arguments to stack */		\
@@ -346,20 +346,10 @@ TEXT NAME(SB), WRAPPER, $MAXSIZE-20;		\
 	MOVL	argsize+8(FP), CX;		\
 	MOVL	SP, DI;				\
 	REP;MOVSB;				\
-	/* initialize panic argp */		\
-	MOVL	panic+16(FP), CX;		\
-	CMPL	CX, $0;				\
-	JEQ	2(PC);				\
-	MOVL	SP, panic_argp(CX);		\
 	/* call function */			\
 	MOVL	f+0(FP), DX;			\
 	MOVL	(DX), AX;				\
 	CALL	AX; \
-	/* clear panic argp */			\
-	MOVL	panic+16(FP), CX;		\
-	CMPL	CX, $0;				\
-	JEQ	2(PC);				\
-	MOVL	$0, panic_argp(CX);		\
 	/* copy return values back */		\
 	MOVL	argptr+4(FP), DI;		\
 	MOVL	argsize+8(FP), CX;		\