[MC] Ensure that pending labels are flushed when -mc-relax-all flag is used

Summary:
The current implementation doesn't always flush all pending labels
beforeemitting data which can result in an incorrectly placed labels in
case when when instruction bundling is enabled and -mc-relax-all flag is
being used. To address this issue, we always flush pending labels before
emitting data.

The change was tested by running PNaCl toolchain trybots with
-mc-relax-all flag set.

Fixes https://code.google.com/p/nativeclient/issues/detail?id=4063

Test Plan: Regression test attached

Reviewers: mseaborn

Subscribers: jfb, llvm-commits

Differential Revision: http://reviews.llvm.org/D10325

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@240870 91177308-0d34-0410-b5e6-96231b3b80d8

test/MC/X86/AlignedBundling/rodata-section.s

@@ -0,0 +1,30 @@
+# RUN: llvm-mc -triple=i686-nacl -filetype=obj %s -o - \
+# RUN:    | llvm-objdump -disassemble -no-show-raw-insn - | FileCheck %s
+# RUN: llvm-mc -triple=i686-nacl -filetype=obj -mc-relax-all %s -o - \
+# RUN:    | llvm-objdump -disassemble -no-show-raw-insn - | FileCheck %s
+
+  .bundle_align_mode 5
+  .text
+  .align	32, 0x90
+# CHECK: 0: movl $14, 8(%esp)
+  movl	$.str2, 8(%esp)
+# CHECK: 8: movl $7, 4(%esp)
+  movl	$.str1, 4(%esp)
+# CHECK: 10: movl $0, (%esp)
+  movl	$.str, (%esp)
+
+  .type	.str,@object
+  .section	.rodata,"a",@progbits
+.str:
+  .asciz	"hello1"
+  .size	.str, 7
+
+  .type	.str1,@object
+.str1:
+  .asciz	"hello2"
+  .size	.str1, 7
+
+  .type	.str2,@object
+.str2:
+  .asciz	"hello3"
+  .size	.str2, 7