diff options
| author | Cheng Shao <astrohavoc@gmail.com> | 2022-09-12 13:55:05 +0000 |
|---|---|---|
| committer | Marge Bot <ben+marge-bot@smart-cactus.org> | 2022-10-11 12:49:59 -0400 |
| commit | 66af1399963a1872e520d1dbd1c94fd43e65082d (patch) | |
| tree | d9b2ab22c705a238ad7497a26a53a6b9a083dc28 | |
| parent | 284cf387537110ce9139bf6ed0841c8f4f41db2a (diff) | |
| download | haskell-66af1399963a1872e520d1dbd1c94fd43e65082d.tar.gz | |
CmmToC: emit explicit tail calls when the C compiler supports it
Clang 13+ supports annotating a return statement using the musttail
attribute, which guarantees that it lowers to a tail call if compilation
succeeds.
This patch takes advantage of that feature for the unregisterised code
generator. The configure script tests availability of the musttail
attribute, if it's available, the Cmm tail calls will become C tail
calls that avoids the mini interpreter trampoline overhead. Nothing is
affected if the musttail attribute is not supported.
Clang documentation:
https://clang.llvm.org/docs/AttributeReference.html#musttail
| -rw-r--r-- | configure.ac | 2 | ||||
| -rw-r--r-- | m4/fp_musttail.m4 | 16 | ||||
| -rw-r--r-- | rts/include/Stg.h | 7 |
3 files changed, 23 insertions, 2 deletions
diff --git a/configure.ac b/configure.ac index f4c66de811..28f954a9a3 100644 --- a/configure.ac +++ b/configure.ac @@ -996,6 +996,8 @@ fi FP_VISIBILITY_HIDDEN +FP_MUSTTAIL + dnl ** check for librt AC_CHECK_LIB([rt], [clock_gettime]) AC_CHECK_LIB([rt], [clock_gettime], [AC_SUBST([CabalHaveLibrt], [True])], [AC_SUBST([CabalHaveLibrt], [False])]) diff --git a/m4/fp_musttail.m4 b/m4/fp_musttail.m4 new file mode 100644 index 0000000000..e309f44c7b --- /dev/null +++ b/m4/fp_musttail.m4 @@ -0,0 +1,16 @@ +# FP_MUSTTAIL +# ---------------------------------- +# Is the musttail attribute supported? +AC_DEFUN([FP_MUSTTAIL], +[ + AC_MSG_CHECKING([whether __attribute__((musttail)) is supported]) + echo 'extern int foo(void); int bar(void) { __attribute__((musttail)) return foo(); }' > conftest.c + if $CC -c conftest.c -o conftest.o + then + AC_MSG_RESULT([yes]) + AC_DEFINE(HAS_MUSTTAIL, 1, [Has musttail]) + else + AC_MSG_RESULT([no]) + fi + rm -f conftest.c conftest.o +]) diff --git a/rts/include/Stg.h b/rts/include/Stg.h index 5849de32c1..31a7a55e9c 100644 --- a/rts/include/Stg.h +++ b/rts/include/Stg.h @@ -325,7 +325,11 @@ external prototype return neither of these types to workaround #11395. Tail calls -------------------------------------------------------------------------- */ -#define JMP_(cont) return((StgFunPtr)(cont)) +#if defined(HAS_MUSTTAIL) +#define JMP_(cont) { StgFunPtr (*_f)(void) = (StgFunPtr (*)(void))(cont); __attribute__((musttail)) return _f(); } +#else +#define JMP_(cont) return (StgFunPtr)(cont) +#endif /* ----------------------------------------------------------------------------- Other Stg stuff... @@ -591,4 +595,3 @@ typedef union { c; \ }) #endif - |