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| 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 /m4 | |
| 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
Diffstat (limited to 'm4')
| -rw-r--r-- | m4/fp_musttail.m4 | 16 |
1 files changed, 16 insertions, 0 deletions
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 +]) |