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x86_64: Fix calls to __morestack under the large code model.

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Under the large code model, we cannot assume that __morestack lives within
2^31 bytes of the call site, so we cannot use pc-relative addressing. We
cannot perform the call via a temporary register, as the rax register may
be used to store the static chain, and all other suitable registers may be
either callee-save or used for parameter passing. We cannot use the stack
at this point either because __morestack manipulates the stack directly.

To avoid these issues, perform an indirect call via a read-only memory
location containing the address.

This solution is not perfect, as it assumes that the .rodata section
is laid out within 2^31 bytes of each function body, but this seems to
be sufficient for JIT.

Differential Revision: http://reviews.llvm.org/D6787

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225003 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Peter Collingbourne
2014-12-30 20:05:19 +00:00
parent dd890d5c5e
commit d8ae3e1fee
5 changed files with 78 additions and 7 deletions
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2
lib/CodeGen/MachineModuleInfo.cpp
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@ -273,7 +273,7 @@ bool MachineModuleInfo::doInitialization(Module &M) {
CurCallSite = 0;
CallsEHReturn = 0;
CallsUnwindInit = 0;
DbgInfoAvailable = UsesVAFloatArgument = false;
DbgInfoAvailable = UsesVAFloatArgument = UsesMorestackAddr = false;
// Always emit some info, by default "no personality" info.
Personalities.push_back(nullptr);
AddrLabelSymbols = nullptr;