Tweak xptc so that it works on Irix with gcc.

Thanks to John Vandenberg <zeroJ@null.net> for the patches.
Bug #79362 r=cls a=asa for 0.9.1

xpcom/reflect/xptcall/src/md/unix/Makefile.in

@@ -169,6 +169,9 @@ ifeq ($(OS_ARCH),IRIX)
 ifneq ($(basename $(OS_RELEASE)),5)
 CPPSRCS		:= xptcinvoke_irix.cpp xptcstubs_irix.cpp
 ASFILES		:= xptcinvoke_asm_irix.s xptcstubs_asm_irix.s
+ifdef GNU_CC
+ASFLAGS		+= -Wa,-D__GNUC__
+endif
 endif
 endif
 

xpcom/reflect/xptcall/src/md/unix/xptcinvoke_asm_irix.s

@@ -73,25 +73,40 @@ NESTED(_XPTC_InvokeByIndex, FRAMESZ, ra)
 	REG_L	a0, A0OFF(sp)	# a0 - that
 	REG_L	a1, A1OFF(sp)	# a1 - methodIndex
 
+#ifdef __GNUC__
+	# t1 = methodIndex * 8
+	# (use shift instead of mult)
+	sll	t1, a1, 3
+#else
 	# t1 = methodIndex * 12
 	# (use shift and subtract trick instead of mult)
  	sll	t1, a1, 2
 	subu	t1, t1, a1
 	sll	t1, t1, 2
+#endif
 
 	# calculate the function we need to jump to,
 	# which must then be saved in t9
 	lw	t9, 0(a0)
 	addu	t9, t9, t1
+#ifdef __GNUC__
+	lw      t9, 12(t9)      # t9 = *(that+t1+12)
+#else
 	li	t2, 20
 	addu	t9, t9, t2
 	lw	t9, 0(t9)	# t9 = *(that+t1+20)	
+#endif
 
 	# calculate the proper "this" pointer for the
 	# function that they asked for
 	lw	t0, 0(a0)
 	addu	t0, t1
+#ifdef __GNUC__
+	lh      t0, 8(t0)
+#else
 	lw	t0, 12(t0)
+#endif
+	
 	addu	a0, a0, t0
 
 	# get register save area from invoke_copy_to_stack

xpcom/reflect/xptcall/src/md/unix/xptcstubs_asm_irix.s

@@ -28,7 +28,11 @@ F19OFF=FRAMESZ-(10*SZREG)
 
 #define SENTINEL_ENTRY(nn)         /* defined in cpp file, not here */
 
+#ifdef __GNUC__
+#define STUB_ENTRY(nn)    MAKE_STUB(nn, Stub/**/nn/**/__14nsXPTCStubBase)
+#else
 #define STUB_ENTRY(nn)    MAKE_STUB(nn, Stub/**/nn/**/__14nsXPTCStubBaseGv)
+#endif
 
 #define MAKE_STUB(nn, name)					\
 NESTED(name, FRAMESZ, ra);					\