[MC] Make bundle alignment mode setting idempotent and support nested bundles

Summary:
Currently an error is thrown if bundle alignment mode is set more than once
per module (either via the API or the .bundle_align_mode directive). This
change allows setting it multiple times as long as the alignment doesn't
change.

Also nested bundle_lock groups are currently not allowed. This change allows
them, with the effect that the group stays open until all nests are exited,
and if any of the bundle_lock directives has the align_to_end flag, the
group becomes align_to_end.

These changes make the bundle aligment simpler to use in the compiler, and
also better match the corresponding support in GNU as.

Reviewers: jvoung, eliben

Differential Revision: http://reviews.llvm.org/D5801

llvm-svn: 219811

1 files changed, 67 insertions, 0 deletions

diff --git a/llvm/test/MC/X86/AlignedBundling/nesting.s b/llvm/test/MC/X86/AlignedBundling/nesting.s
new file mode 100644
index 00000000000..8996170a1d1
--- /dev/null
+++ b/llvm/test/MC/X86/AlignedBundling/nesting.s
@@ -0,0 +1,67 @@
+# RUN: llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu %s -o - \
+# RUN:   | llvm-objdump -disassemble -no-show-raw-insn - | FileCheck %s
+
+# Will be bundle-aligning to 16 byte boundaries
+  .bundle_align_mode 4
+  .text
+# CHECK-LABEL: foo
+foo:
+# Test that bundle alignment mode can be set more than once.
+  .bundle_align_mode 4
+# Each of these callq instructions is 5 bytes long
+  callq bar
+  callq bar
+  .bundle_lock
+  .bundle_lock
+  callq bar
+  callq bar     
+  .bundle_unlock
+  .bundle_unlock
+# CHECK:      10: callq
+# CHECK-NEXT: 15: callq
+
+  .p2align 4
+# CHECK-LABEL: bar
+bar:
+  callq foo
+  callq foo
+# Check that the callqs get bundled together, and that the whole group is
+# align_to_end
+  .bundle_lock 
+  callq bar
+  .bundle_lock align_to_end
+  callq bar
+  .bundle_unlock
+  .bundle_unlock
+# CHECK:      36: callq
+# CHECK-NEXT: 3b: callq
+
+# CHECK-LABEL: baz
+baz:
+  callq foo
+  callq foo
+# Check that the callqs get bundled together, and that the whole group is
+# align_to_end (with the outer directive marked align_to_end)
+  .bundle_lock align_to_end
+  callq bar
+  .bundle_lock
+  callq bar
+  .bundle_unlock
+  .bundle_unlock
+# CHECK:      56: callq
+# CHECK-NEXT: 5b: callq
+
+# CHECK-LABEL: quux
+quux:
+  callq bar
+  callq bar
+  .bundle_lock
+  .bundle_lock
+  callq bar
+  .bundle_unlock
+  callq bar     
+  .bundle_unlock
+# Check that the calls are bundled together when the second one is after the
+# inner nest is closed.
+# CHECK:      70: callq
+# CHECK-NEXT: 75: callq