Build the IRT with nacl-clang for x86

SConstruct

Index: SConstruct
diff --git a/SConstruct b/SConstruct
index aaeec3804bbe9309c726fe815d21ab8a85169cd2..fe355db761b0f6aecd114cf700821012ad7e989b 100755
--- a/SConstruct
+++ b/SConstruct
@@ -3468,17 +3468,24 @@ nacl_env.AddMethod(RawSyscallObjects)
 nacl_irt_env.ClearBits('nacl_glibc')
 nacl_irt_env.ClearBits('nacl_pic')
 nacl_irt_env.ClearBits('nacl_clang')
+
 # The choice of toolchain used to build the IRT does not depend on the toolchain
-# used to build user/test code. The PNaCl toolchain is used on x86, except on
-# Windows (because pnacl-clang doesn't run on Windows XP. If we stop supporting
-# building on XP, we can remove this exception).  See
-# https://code.google.com/p/nativeclient/issues/detail?id=3936
-if (nacl_irt_env.Bit('build_mips32') or nacl_irt_env.Bit('build_x86_64') or
-    (nacl_irt_env.Bit('build_x86_32') and
-     not nacl_irt_env.Bit('host_windows'))):
+# used to build user/test code. PNaCl is used on mips because that's currently
+# the only compiler for mips. nacl-clang is used on x86.
+if nacl_irt_env.Bit('build_mips32'):
   nacl_irt_env.SetBits('bitcode')
 else:
   nacl_irt_env.ClearBits('bitcode')
+if nacl_irt_env.Bit('build_x86_64') or nacl_irt_env.Bit('build_x86_32'):
+  nacl_irt_env.SetBits('nacl_clang')
+  # The IRT must be built using LLVM's assembler on x86-64 to preserve sandbox
+  # base address hiding. It's also use on x86-32 for consistency.

[jvoung (off chromium), 2015/03/19 17:36:25]

"It's also use on" -> "It's also used on"
or something

[Derek Schuff, 2015/03/19 18:36:16]

Done.

+  nacl_irt_env.Append(CCFLAGS=['-integrated-as'])

[jvoung (off chromium), 2015/03/19 17:36:25]

Might want to check with Nick about the GN build.

I see a "nacl_toolchain("irt_x64")", but I don't know if it's using the
integrated-as.

Also not sure if it's doing the appropriate mstackrealign, etc. for
nacl_toolchain("irt_x86")

[Derek Schuff, 2015/03/19 18:36:16]

Yeah, my plan was to get this landed for gyp and ensure it works before circling
back to GN, since they've always been doing their own thing anyway.

+  if nacl_irt_env.Bit('build_x86_32'):
+    # The x86-32 IRT needs to be callable with an under-aligned stack.
+    # See  https://code.google.com/p/nativeclient/issues/detail?id=3935
+    nacl_irt_env.Append(CCFLAGS=['-mstackrealign', '-mno-sse'])
+
 nacl_irt_env.ClearBits('pnacl_generate_pexe')

[jvoung (off chromium), 2015/03/19 17:36:25]

Maybe these last couple of ClearBits('...') should be moved up to be with the
rest of the ClearBits.

[Derek Schuff, 2015/03/19 18:36:16]

Done.

 nacl_irt_env.ClearBits('use_sandboxed_translator')
 nacl_irt_env.Tool('naclsdk')
@@ -3519,6 +3526,8 @@ if nacl_irt_env.Bit('bitcode'):
 # libc++) pthread.
 nacl_irt_env.Replace(LINK=(nacl_irt_env['LINK'].
                            replace('pnacl-clang++', 'pnacl-clang')))
+nacl_irt_env.Replace(LINK=(nacl_irt_env['LINK'].
+                           replace('nacl-clang++', 'nacl-clang')))
 
 if nacl_irt_env.Bit('bitcode'):
   nacl_irt_env.Append(LINKFLAGS=['--pnacl-allow-native'])

[jvoung (off chromium), 2015/03/19 17:36:24]

Could put this under the "3504 if nacl_irt_env.Bit('bitcode'):" to consolidate.

[Derek Schuff, 2015/03/19 18:36:16]

Done.