From 28cb5723b82b6c2989565451a9672c5b3a5ab61c Mon Sep 17 00:00:00 2001 From: Peter Bex Date: Sun, 28 Feb 2016 14:57:56 +0100 Subject: [PATCH 1/2] Simplify code generation by only using C_demand() This obsoletes C_stack_probe(), which was a bit broken in general, because it was passed the base pointer. This would only work reliably on architectures where the stack grows downward; on architectures where the stack grows upward, we would have to add the allocated amount to the base pointer to find out how much stack was used. In many cases this didn't break because often we statically allocate using the "C_word *ab[DEMAND]; C_word *a = ab;" idiom. In this case, "a" would be allocated at the end of the stack, before/after the entire buffer. But in situations where we dynamically allocated using the "C_word *a; a = C_alloc(DEMAND);" idiom, "a" might still fall within range of the stack, while a+DEMAND might push it just over the stack reserve. Besides simplifying and removing a potential bug on platforms where the stack grows upwards, this change makes it possible to add argvector allocation to the C_demand() call. --- c-backend.scm | 40 +++++++++++++++++----------------------- chicken.h | 2 ++ 2 files changed, 19 insertions(+), 23 deletions(-) diff --git a/c-backend.scm b/c-backend.scm index 3f9846f..55c5ae9 100644 --- a/c-backend.scm +++ b/c-backend.scm @@ -824,46 +824,40 @@ (when insert-timer-checks (gen #t "C_check_for_interrupt;")) (gen #t "if(!C_demand((c-" n ")*C_SIZEOF_PAIR +" demand ")){") ) (else - (cond [(and (not direct) (> demand 0)) - (if looping - (gen #t "C_word *a;" - #t "loop:" - #t "a=C_alloc(" demand ");") - (gen #t "C_word ab[" demand "],*a=ab;") ) ] - [else - (unless direct (gen #t "C_word *a;")) - (when (and direct (not unsafe) (not disable-stack-overflow-checking)) - (gen #t "C_stack_overflow_check;") ) - (when looping (gen #t "loop:"))]) + (unless direct (gen #t "C_word *a;")) + (when (and direct (not unsafe) (not disable-stack-overflow-checking)) + (gen #t "C_stack_overflow_check;") ) + (when looping (gen #t "loop:")) (when (and external (not unsafe) (not no-argc-checks) (not customizable)) ;; (not customizable) implies empty-closure (if (eq? rest-mode 'none) (when (> n 2) (gen #t "if(c<" n ") C_bad_min_argc_2(c," n ",t0);")) (gen #t "if(c!=" n ") C_bad_argc_2(c," n ",t0);") ) ) - (cond ((and (not direct) (or external (> demand 0))) - (when insert-timer-checks (gen #t "C_check_for_interrupt;")) - (if (and looping (> demand 0)) - (gen #t "if(!C_stack_probe(a)){") - (gen #t "if(!C_stack_probe(&a)){") ) ) + + (cond ((not direct) + ;; This fills up the stack if there was an + ;; interrupt, so only check when restartable + (when insert-timer-checks + (gen #t "C_check_for_interrupt;")) + (gen #t "if(!C_demand(" demand ")){")) (else (gen #\{))))) - (cond ((and (not (eq? 'toplevel id)) - (not direct) - (or rest external (> demand 0)) ) - (cond [rest + (cond ((and (not (eq? 'toplevel id)) (not direct)) + (cond (rest (gen #t "C_save_and_reclaim((void*)" id ",c,av);}" #t "a=C_alloc((c-" n ")*C_SIZEOF_PAIR+" demand ");") (gen #t "t" n "=C_build_rest(&a,c," n ",av);") (do ([i (+ n 1) (+ i 1)] [j temps (- j 1)] ) ((zero? j)) - (gen #t "C_word t" i #\;) )] - [else + (gen #t "C_word t" i #\;) )) + (else (cond ((and customizable (> nec 0)) (gen #t "C_save_and_reclaim_args((void *)tr" id #\, nec #\,) (apply gen arglist) (gen ");}")) (else - (gen "C_save_and_reclaim((void *)" id #\, n ",av);}")))])) + (gen "C_save_and_reclaim((void *)" id #\, n ",av);}"))) + (when (> demand 0) (gen #t "a=C_alloc(" demand ");"))))) (else (gen #\}))) (set! non-av-proc customizable) (expression diff --git a/chicken.h b/chicken.h index 3694cd6..ab36598 100644 --- a/chicken.h +++ b/chicken.h @@ -1078,6 +1078,7 @@ typedef void (C_ccall *C_proc)(C_word, C_word *) C_noret; #if C_STACK_GROWS_DOWNWARD # define C_demand(n) (C_stress && ((C_word)(C_stack_pointer - C_stack_limit) > (n))) +/* OBSOLETE: */ # define C_stack_probe(p) (C_stress && ((C_word *)(p) >= C_stack_limit)) # define C_stack_check1(err) if(!C_disable_overflow_check) { \ @@ -1089,6 +1090,7 @@ typedef void (C_ccall *C_proc)(C_word, C_word *) C_noret; #else # define C_demand(n) (C_stress && ((C_word)(C_stack_limit - C_stack_pointer) > (n))) +/* OBSOLETE: */ # define C_stack_probe(p) (C_stress && ((C_word *)(p) < C_stack_limit)) # define C_stack_check1(err) if(!C_disable_overflow_check) { \ -- 2.1.4