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commit a93ab43ab5f40cadbedea2f6342b93c245e91434
Author: Sergei Trofimovich <slyfox@gentoo.org>
Date: Wed Aug 27 22:19:52 2014 +0300
driver: pass '-fPIC' option to assembler as well
Summary:
Before the patch '-fPIC' was passed only to C compiler,
but not to assembler itself.
It led to runtime crash in GHC_DYNAMIC_PROGRAMS=YES mode
on sparc32.
Technical details are in 'Note [-fPIC for assembler]'.
Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
Test Plan: validate on sparc
Reviewers: simonmar, austin, kgardas
Reviewed By: austin
Subscribers: simonmar, ezyang, carter
Differential Revision: https://phabricator.haskell.org/D177
diff --git a/compiler/main/DriverPipeline.hs b/compiler/main/DriverPipeline.hs
index 183f435..5a18e6e 100644
--- a/compiler/main/DriverPipeline.hs
+++ b/compiler/main/DriverPipeline.hs
@@ -1199,6 +1199,7 @@ runPhase (RealPhase (As with_cpp)) input_fn dflags
as_prog <- whichAsProg
let cmdline_include_paths = includePaths dflags
+ let pic_c_flags = picCCOpts dflags
next_phase <- maybeMergeStub
output_fn <- phaseOutputFilename next_phase
@@ -1212,6 +1213,9 @@ runPhase (RealPhase (As with_cpp)) input_fn dflags
= liftIO $ as_prog dflags
([ SysTools.Option ("-I" ++ p) | p <- cmdline_include_paths ]
+ -- See Note [-fPIC for assembler]
+ ++ map SysTools.Option pic_c_flags
+
-- We only support SparcV9 and better because V8 lacks an atomic CAS
-- instruction so we have to make sure that the assembler accepts the
-- instruction set. Note that the user can still override this
@@ -1253,6 +1257,8 @@ runPhase (RealPhase SplitAs) _input_fn dflags
osuf = objectSuf dflags
split_odir = base_o ++ "_" ++ osuf ++ "_split"
+ let pic_c_flags = picCCOpts dflags
+
-- this also creates the hierarchy
liftIO $ createDirectoryIfMissing True split_odir
@@ -1286,6 +1292,9 @@ runPhase (RealPhase SplitAs) _input_fn dflags
then [SysTools.Option "-mcpu=v9"]
else []) ++
+ -- See Note [-fPIC for assembler]
+ map SysTools.Option pic_c_flags ++
+
[ SysTools.Option "-c"
, SysTools.Option "-o"
, SysTools.FileOption "" (split_obj n)
@@ -2203,3 +2212,38 @@ haveRtsOptsFlags dflags =
isJust (rtsOpts dflags) || case rtsOptsEnabled dflags of
RtsOptsSafeOnly -> False
_ -> True
+
+-- Note [-fPIC for assembler]
+-- When compiling .c source file GHC's driver pipeline basically
+-- does the following two things:
+-- 1. ${CC} -S 'PIC_CFLAGS' source.c
+-- 2. ${CC} -x assembler -c 'PIC_CFLAGS' source.S
+--
+-- Why do we need to pass 'PIC_CFLAGS' both to C compiler and assembler?
+-- Because on some architectures (at least sparc32) assembler also choses
+-- relocation type!
+-- Consider the following C module:
+--
+-- /* pic-sample.c */
+-- int v;
+-- void set_v (int n) { v = n; }
+-- int get_v (void) { return v; }
+--
+-- $ gcc -S -fPIC pic-sample.c
+-- $ gcc -c pic-sample.s -o pic-sample.no-pic.o # incorrect binary
+-- $ gcc -c -fPIC pic-sample.s -o pic-sample.pic.o # correct binary
+--
+-- $ objdump -r -d pic-sample.pic.o > pic-sample.pic.o.od
+-- $ objdump -r -d pic-sample.no-pic.o > pic-sample.no-pic.o.od
+-- $ diff -u pic-sample.pic.o.od pic-sample.no-pic.o.od
+--
+-- Most of architectures won't show any difference in this test, but on sparc32
+-- the following assembly snippet:
+--
+-- sethi %hi(_GLOBAL_OFFSET_TABLE_-8), %l7
+--
+-- generates two kinds or relocations, only 'R_SPARC_PC22' is correct:
+--
+-- 3c: 2f 00 00 00 sethi %hi(0), %l7
+-- - 3c: R_SPARC_PC22 _GLOBAL_OFFSET_TABLE_-0x8
+-- + 3c: R_SPARC_HI22 _GLOBAL_OFFSET_TABLE_-0x8
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