Commit 1bda00ba authored by Simon Marlow's avatar Simon Marlow
Browse files

x86-64: fix a problem exposed by negative offsets in vector tables

static relative offsets (eg .long l1-l2) are restricted to 32 bits on
x86-64 due to lack of support in the linker.  The codegen, NCG and
runtime work around this, using 32-bit offsets instead of 64.
However, we were missing a workaround for vector tables, and it
happened to work by accident because the offsets were always positive
and resolved by the assembler.  The bug was exposed by using the NCG
to compile the RTS, where the offsets became negative, again by
accident.
parent 27db51b3
......@@ -51,7 +51,7 @@ import CgMonad
import CmmUtils ( mkIntCLit, zeroCLit )
import Cmm ( CmmStmt(..), CmmExpr(..), CmmLit(..), LocalReg,
CmmBasicBlock, nodeReg )
import MachOp ( MachOp(..), wordRep, halfWordRep )
import MachOp
import CLabel
import StgSyn ( SRT(..) )
import Name ( Name )
......@@ -217,7 +217,14 @@ retVec :: CmmExpr -> CmmExpr -> CmmExpr
-- Get a return vector from the info pointer
retVec info_amode zero_indexed_tag
= let slot = vectorSlot info_amode zero_indexed_tag
#ifdef x86_64_TARGET_ARCH
tableEntry = CmmMachOp (MO_S_Conv I32 I64) [CmmLoad slot I32]
-- offsets are 32-bits on x86-64, due to the inability of
-- the tools to handle 64-bit PC-relative relocations. See also
-- PprMach.pprDataItem, and InfoTables.h:OFFSET_FIELD().
#else
tableEntry = CmmLoad slot wordRep
#endif
in if tablesNextToCode
then CmmMachOp (MO_Add wordRep) [tableEntry, info_amode]
else tableEntry
......
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