[MC] Align fragments when -mc-relax-all flag is used
Summary:
Ensure that fragments are bundle aligned when instruction bundling
is enabled and the -mc-relax-all flag is set. This is implicitly
assumed by the bundle padding implementation but this assumption
does not hold when custom alignment is being used.
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/D10044
llvm-svn: 240869
diff --git a/llvm/lib/MC/MCAssembler.cpp b/llvm/lib/MC/MCAssembler.cpp
index 76be67c..da6516a 100644
--- a/llvm/lib/MC/MCAssembler.cpp
+++ b/llvm/lib/MC/MCAssembler.cpp
@@ -254,7 +254,7 @@
else { // EndOfFragment > BundleSize
return 2 * BundleSize - EndOfFragment;
}
- } else if (EndOfFragment > BundleSize)
+ } else if (OffsetInBundle > 0 && EndOfFragment > BundleSize)
return BundleSize - OffsetInBundle;
else
return 0;
@@ -581,16 +581,22 @@
// size won't include the padding.
//
// When the -mc-relax-all flag is used, we optimize bundling by writting the
- // bundle padding directly into fragments when the instructions are emitted
- // inside the streamer.
+ // padding directly into fragments when the instructions are emitted inside
+ // the streamer. When the fragment is larger than the bundle size, we need to
+ // ensure that it's bundle aligned. This means that if we end up with
+ // multiple fragments, we must emit bundle padding between fragments.
//
- if (Assembler.isBundlingEnabled() && !Assembler.getRelaxAll() &&
- F->hasInstructions()) {
+ // ".align N" is an example of a directive that introduces multiple
+ // fragments. We could add a special case to handle ".align N" by emitting
+ // within-fragment padding (which would produce less padding when N is less
+ // than the bundle size), but for now we don't.
+ //
+ if (Assembler.isBundlingEnabled() && F->hasInstructions()) {
assert(isa<MCEncodedFragment>(F) &&
"Only MCEncodedFragment implementations have instructions");
uint64_t FSize = Assembler.computeFragmentSize(*this, *F);
- if (FSize > Assembler.getBundleAlignSize())
+ if (!Assembler.getRelaxAll() && FSize > Assembler.getBundleAlignSize())
report_fatal_error("Fragment can't be larger than a bundle size");
uint64_t RequiredBundlePadding = computeBundlePadding(Assembler, F,