On Wed, May 21, 2025 at 05:38:27PM +0800, Yang Yujie wrote:
> The current master branch does not seem to have _BitInt support for s390x,
> is the patch on this list?
>
> Also, I cannot find the relevant psABI definition or discussions at
> https://github.com/IBM/s390x-abi
They were mailed to me privately, I'm waiting for IBM to post them publicly
now that the big-endian support is in and so it can work mostly out of the
box.
> So I am not sure if the info->extended really affects parameter passing for
> s390x,
> or the exact definition of its psABI.
>
> If you have a s390x targeted build with _BitInt enabled, you can perhaps try
> gcc.target/aarch64/bitint-args.c on s390x to see if the parameters are
> actually
> assumed to be extended by not emitting extraneous extension instruction(s),
> which is one of the key reason to have them extended in psABI in the first
> place.
With the following patch instead the test finally FAILs on s390x with -O1
and higher, which shows that left shifts really need special casing for
info->extended.
I don't have proof of anything else though.
In gimple-lower-bitint.cc I'd strongly prefer to differentiate between
changes required to get info->extended working correctly (that is what
should be committed first, and right now should include the LSHIFT_EXPR in
lower_shift_stmt) from just optimizations where you want to avoid some
extensions that might not be strictly necessary and where those
optimizations can cause further needs to extend at some other places.
2025-05-21 Jakub Jelinek <ja...@redhat.com>
* gcc.dg/bitintext.h: New file.
* gcc.dg/torture/bitint-82.c: New test.
--- gcc/testsuite/gcc.dg/bitintext.h.jj 2025-05-20 22:39:28.647171638 +0200
+++ gcc/testsuite/gcc.dg/bitintext.h 2025-05-21 11:35:50.642636439 +0200
@@ -0,0 +1,29 @@
+[[gnu::noipa]] void
+do_copy (void *p, const void *q, __SIZE_TYPE__ r)
+{
+ __builtin_memcpy (p, q, r);
+}
+
+/* Macro to test whether (on targets where psABI requires it) _BitInt
+ with padding bits have those filled with sign or zero extension. */
+#if defined(__s390x__) || defined(__arm__) || defined(__loongarch__)
+#define BEXTC(x) \
+ do { \
+ if ((typeof (x)) -1 < 0) \
+ { \
+ _BitInt(sizeof (x) * __CHAR_BIT__) __x; \
+ do_copy (&__x, &(x), sizeof (__x)); \
+ if (__x != (x)) \
+ __builtin_abort (); \
+ } \
+ else \
+ { \
+ unsigned _BitInt(sizeof (x) * __CHAR_BIT__) __x; \
+ do_copy (&__x, &(x), sizeof (__x)); \
+ if (__x != (x)) \
+ __builtin_abort (); \
+ } \
+ } while (0)
+#else
+#define BEXTC(x) do { (void) (x); } while (0)
+#endif
--- gcc/testsuite/gcc.dg/torture/bitint-82.c.jj 2025-05-20 22:39:28.647171638
+0200
+++ gcc/testsuite/gcc.dg/torture/bitint-82.c 2025-05-21 11:28:06.483905700
+0200
@@ -0,0 +1,94 @@
+/* { dg-do run { target bitint } } */
+/* { dg-options "-std=c23 -pedantic-errors" } */
+/* { dg-skip-if "" { ! run_expensive_tests } { "*" } { "-O0" "-O2" } } */
+/* { dg-skip-if "" { ! run_expensive_tests } { "-flto" } { "" } } */
+
+#if __BITINT_MAXWIDTH__ >= 532
+_BitInt(5) a = 2, b = -2;
+_BitInt(38) c = 12345, d = -12345;
+_BitInt(129) e = 147090211948845388976606115811401318743wb, f =
-147090211948845388976606115811401318743wb;
+_BitInt(532) g = 34476769918317100226195145251004381172591594205376273814wb, h
= -102116935649428556311918486808926113041433456371844211259677321wb;
+unsigned _BitInt(1) i = 1;
+unsigned _BitInt(17) j = 49127uwb;
+unsigned _BitInt(60) k = 588141367522129848uwb;
+unsigned _BitInt(205) l =
33991671979236490040668305838261113909013362173682935296620088uwb;
+unsigned _BitInt(475) z =
14834685124553929878903720794923785539321715423294864257448721201977655202426343038777008759878862591302200019811097993772912691139803983786083uwb;
+#endif
+
+#include "../bitintext.h"
+
+#if __BITINT_MAXWIDTH__ >= 532
+[[gnu::noipa]] _BitInt(217)
+f1 (_BitInt(9) a, unsigned _BitInt(12) b, _BitInt(36) c, unsigned _BitInt(105)
d,
+ _BitInt(135) e, unsigned _BitInt(168) f, _BitInt(207) g, _BitInt(207) h,
+ unsigned _BitInt(531) i, _BitInt(36) j)
+{
+ BEXTC (a); BEXTC (b); BEXTC (c); BEXTC (d);
+ BEXTC (e); BEXTC (f); BEXTC (g); BEXTC (h);
+ BEXTC (i); BEXTC (j);
+ _BitInt(9) k = a + 1;
+ unsigned _BitInt(12) l = b - a;
+ _BitInt(36) m = c * j;
+ unsigned _BitInt(105) n = d >> (-2 * j);
+ _BitInt(135) o = e | -j;
+ unsigned _BitInt(168) p = f & 101010101010101010101010uwb;
+ _BitInt(207) q = g * j;
+ _BitInt(207) r = g + h;
+ unsigned _BitInt(531) s = i / j;
+ BEXTC (k); BEXTC (l); BEXTC (m); BEXTC (n);
+ BEXTC (o); BEXTC (p); BEXTC (q); BEXTC (r);
+ BEXTC (s);
+ unsigned _BitInt(105) t = d << (38 - j);
+ BEXTC (t);
+ _Atomic _BitInt(5) u = 15;
+ u += 8U;
+ BEXTC (u);
+ _BitInt(135) v = e << 28;
+ BEXTC (v);
+ unsigned _BitInt(475) w = z << (29 + j);
+ BEXTC (w);
+ return a + 4;
+}
+#endif
+
+int
+main ()
+{
+#if __BITINT_MAXWIDTH__ >= 532
+ BEXTC (a); BEXTC (b);
+ BEXTC (c); BEXTC (d);
+ BEXTC (e); BEXTC (f);
+ BEXTC (g); BEXTC (h);
+ BEXTC (i);
+ BEXTC (j);
+ BEXTC (k);
+ BEXTC (l);
+ BEXTC (z);
+ {
+ _BitInt(5) a = 2, b = -2;
+ _BitInt(38) c = 12345, d = -12345;
+ _BitInt(129) e = 147090211948845388976606115811401318743wb, f =
-147090211948845388976606115811401318743wb;
+ _BitInt(532) g =
34476769918317100226195145251004381172591594205376273814wb, h =
-102116935649428556311918486808926113041433456371844211259677321wb;
+ unsigned _BitInt(1) i = 1;
+ unsigned _BitInt(17) j = 49127uwb;
+ unsigned _BitInt(60) k = 588141367522129848uwb;
+ unsigned _BitInt(205) l =
33991671979236490040668305838261113909013362173682935296620088uwb;
+ BEXTC (a); BEXTC (b);
+ BEXTC (c); BEXTC (d);
+ BEXTC (e); BEXTC (f);
+ BEXTC (g); BEXTC (h);
+ BEXTC (i);
+ BEXTC (j);
+ BEXTC (k);
+ BEXTC (l);
+ }
+ _BitInt(217) m = f1 (57wb, 3927uwb, 10625699364wb,
23030359755638571619326514462579uwb,
+ 20797625176303404170317957140841712396356wb,
+ 111831871006433449872067089878311637796827405335256uwb,
+
64853652491049541618437564623858346454131583900201311683495230wb,
+
25108562626494976011700565632680191924545340440636663075662700wb,
+
6366583146545926097709747296452085257498446783797668089081516596003270602920229800152065594152964557479773813310423759077951305431130758723519892452009351743676uwb,
+ -1);
+ BEXTC (m);
+#endif
+}
Jakub
