Commit 7aede9b1 authored by Simon Marlow's avatar Simon Marlow
Browse files

gcc is getting smarter, so we need to hit it with a bigger stick

On x86_64 we are using C argument registers for global registers in
the STG machine.  This is always going to be problematic when it comes
to making C calls from STG and compiling via C.  Prior to GCC 4.1.0
(approx) it was possible to just assign the argument expressions to
temporaries to avoid a clash.  Now, we need to add an extra dummy
function call as a barrier between the temporary assignments and the
actual call.  The dummy call is removed by the mangler.
parent 851154f0
......@@ -702,6 +702,15 @@ pprCall ppr_fn cconv results args vols
| otherwise
= save vols $$
#if x86_64_TARGET_ARCH
-- HACK around gcc optimisations.
-- x86_64 needs a __DISCARD__() here, to create a barrier between
-- putting the arguments into temporaries and passing the arguments
-- to the callee, because the argument expressions may refer to
-- machine registers that are also used for passing arguments in the
-- C calling convention.
ptext SLIT("__DISCARD__();") $$
ppr_assign results (ppr_fn <> parens (commafy (map pprArg args))) <> semi $$
restore vols
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