/* -----------------------------------------------------------------------------
- * $Id: StgCRun.c,v 1.12 2000/02/24 14:05:55 sewardj Exp $
+ * $Id: StgCRun.c,v 1.14 2000/03/08 10:58:38 simonmar Exp $
*
- * (c) The GHC Team, 1998-1999
+ * (c) The GHC Team, 1998-2000
*
- * STG-to-C glue. Some architectures have this code written in
- * straight assembler (see StgRun.S), some in C.
+ * STG-to-C glue.
+ *
+ * To run an STG function from C land, call
+ *
+ * rv = StgRun(f,BaseReg);
+ *
+ * where "f" is the STG function to call, and BaseReg is the address of the
+ * RegTable for this run (we might have separate RegTables if we're running
+ * multiple threads on an SMP machine).
+ *
+ * In the end, "f" must JMP to StgReturn (defined below),
+ * passing the return-value "rv" in R1,
+ * to return to the caller of StgRun returning "rv" in
+ * the whatever way C returns a value.
+ *
+ * NOTE: StgRun/StgReturn do *NOT* load or store Hp or any
+ * other registers (other than saving the C callee-saves
+ * registers). Instead, the called function "f" must do that
+ * in STG land.
+ *
+ * GCC will have assumed that pushing/popping of C-stack frames is
+ * going on when it generated its code, and used stack space
+ * accordingly. However, we actually {\em post-process away} all
+ * such stack-framery (see \tr{ghc/driver/ghc-asm.lprl}). Things will
+ * be OK however, if we initially make sure there are
+ * @RESERVED_C_STACK_BYTES@ on the C-stack to begin with, for local
+ * variables.
*
* -------------------------------------------------------------------------- */
#endif
/* -----------------------------------------------------------------------------
- sparc architecture
+ x86 architecture
+ -------------------------------------------------------------------------- */
+
+#ifdef i386_TARGET_ARCH
+
+StgThreadReturnCode
+StgRun(StgFunPtr f, StgRegTable *basereg) {
+
+ StgChar space[ RESERVED_C_STACK_BYTES + 4*sizeof(void *) ];
+ StgThreadReturnCode r;
+
+ __asm__ volatile (
+ /*
+ * save callee-saves registers on behalf of the STG code.
+ */
+ "movl %%esp, %%eax\n\t"
+ "addl %4, %%eax\n\t"
+ "movl %%ebx,0(%%eax)\n\t"
+ "movl %%esi,4(%%eax)\n\t"
+ "movl %%edi,8(%%eax)\n\t"
+ "movl %%ebp,12(%%eax)\n\t"
+ /*
+ * Set BaseReg
+ */
+ "movl %3,%%ebx\n\t"
+ /*
+ * grab the function argument from the stack, and jump to it.
+ */
+ "movl %2,%%eax\n\t"
+ "jmp *%%eax\n\t"
+
+ ".global " STG_RETURN "\n"
+ STG_RETURN ":\n\t"
+
+ "movl %%esi, %%eax\n\t" /* Return value in R1 */
+
+ /*
+ * restore callee-saves registers. (Don't stomp on %%eax!)
+ */
+ "movl %%esp, %%edx\n\t"
+ "addl %4, %%edx\n\t"
+ "movl 0(%%edx),%%ebx\n\t" /* restore the registers saved above */
+ "movl 4(%%edx),%%esi\n\t"
+ "movl 8(%%edx),%%edi\n\t"
+ "movl 12(%%edx),%%ebp\n\t"
+
+ : "=&a" (r), "=m" (space)
+ : "m" (f), "m" (basereg), "i" (RESERVED_C_STACK_BYTES)
+ : "edx" /* stomps on %edx */
+ );
+
+ return r;
+}
+
+#endif
+
+/* -----------------------------------------------------------------------------
+ Sparc architecture
+
+ --
+ OLD COMMENT from GHC-3.02:
+
+ We want tailjumps to be calls, because `call xxx' is the only Sparc
+ branch that allows an arbitrary label as a target. (Gcc's ``goto
+ *target'' construct ends up loading the label into a register and
+ then jumping, at the cost of two extra instructions for the 32-bit
+ load.)
+
+ When entering the threaded world, we stash our return address in a
+ known location so that \tr{%i7} is available as an extra
+ callee-saves register. Of course, we have to restore this when
+ coming out of the threaded world.
+
+ I hate this god-forsaken architecture. Since the top of the
+ reserved stack space is used for globals and the bottom is reserved
+ for outgoing arguments, we have to stick our return address
+ somewhere in the middle. Currently, I'm allowing 100 extra
+ outgoing arguments beyond the first 6. --JSM
+
+ Updated info (GHC 4.06): we don't appear to use %i7 any more, so
+ I'm not sure whether we still need to save it. Incedentally, what
+ does the last paragraph above mean when it says "the top of the
+ stack is used for globals"? What globals? --SDM
+
-------------------------------------------------------------------------- */
#ifdef sparc_TARGET_ARCH
register void *i7 __asm__("%i7");
((void **)(space))[100] = i7;
f();
- __asm__ volatile (".align 4\n"
+ __asm__ volatile (
+ ".align 4\n"
".global " STG_RETURN "\n"
- STG_RETURN ":\n"
- "\tld %1,%0" : "=r" (i7) : "m" (((void **)(space))[100]));
+ STG_RETURN ":"
+ : : : "l0","l1","l2","l3","l4","l5","l6","l7");
+ /* we tell the C compiler that l0-l7 are clobbered on return to
+ * StgReturn, otherwise it tries to use these to save eg. the
+ * address of space[100] across the call. The correct thing
+ * to do would be to save all the callee-saves regs, but we
+ * can't be bothered to do that.
+ *
+ * The code that gcc generates for this little fragment is now
+ * terrible. We could do much better by coding it directly in
+ * assembler.
+ */
+ __asm__ volatile ("ld %1,%0"
+ : "=r" (i7) : "m" (((void **)(space))[100]));
return (StgThreadReturnCode)R1.i;
}
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