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[MC] Align fragments when -mc-relax-all flag is used

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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

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@240869 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Petr Hosek 2015-06-27 01:49:53 +00:00
parent 1f0cde9fd7
commit 0aaf3287e3
3 changed files with 66 additions and 6 deletions
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18
lib/MC/MCAssembler.cpp
View File

@ -254,7 +254,7 @@ uint64_t llvm::computeBundlePadding(const MCAssembler &Assembler,
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 @@ void MCAsmLayout::layoutFragment(MCFragment *F) {
// 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,

23
test/MC/X86/AlignedBundling/misaligned-bundle-group.s Normal file
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@ -0,0 +1,23 @@
# RUN: llvm-mc -filetype=obj -triple i686-pc-linux-gnu %s -o - \
# RUN: | llvm-objdump -disassemble -no-show-raw-insn - \
# RUN: | FileCheck -check-prefix=CHECK -check-prefix=CHECK-OPT %s
# RUN: llvm-mc -filetype=obj -triple i686-pc-linux-gnu -mc-relax-all %s -o - \
# RUN: | llvm-objdump -disassemble -no-show-raw-insn - \
# RUN: | FileCheck -check-prefix=CHECK -check-prefix=CHECK-RELAX %s
.text
foo:
.bundle_align_mode 5
push %ebp # 1 byte
.align 16
.bundle_lock align_to_end
# CHECK: 1: nopw %cs:(%eax,%eax)
# CHECK: 10: nopw %cs:(%eax,%eax)
# CHECK-RELAX: 1f: nop
# CHECK-RELAX: 20: nopw %cs:(%eax,%eax)
# CHECK-RELAX: 2f: nopw %cs:(%eax,%eax)
# CHECK-OPT: 1b: calll -4
# CHECK-RELAX: 3b: calll -4
calll bar # 5 bytes
.bundle_unlock
ret # 1 byte

31
test/MC/X86/AlignedBundling/misaligned-bundle.s Normal file
View File

@ -0,0 +1,31 @@
# RUN: llvm-mc -filetype=obj -triple i686-pc-linux-gnu %s -o - \
# RUN: | llvm-objdump -disassemble -no-show-raw-insn - \
# RUN: | FileCheck -check-prefix=CHECK -check-prefix=CHECK-OPT %s
# RUN: llvm-mc -filetype=obj -triple i686-pc-linux-gnu -mc-relax-all %s -o - \
# RUN: | llvm-objdump -disassemble -no-show-raw-insn - \
# RUN: | FileCheck -check-prefix=CHECK -check-prefix=CHECK-RELAX %s
.text
foo:
.bundle_align_mode 5
push %ebp # 1 byte
.align 16
# CHECK: 1: nopw %cs:(%eax,%eax)
# CHECK-RELAX: 10: nopw %cs:(%eax,%eax)
# CHECK-RELAX: 1f: nop
# CHECK-OPT: 10: movl $1, (%esp)
# CHECK-RELAX: 20: movl $1, (%esp)
movl $0x1, (%esp) # 7 bytes
movl $0x1, (%esp) # 7 bytes
# CHECK-OPT: 1e: nop
movl $0x2, 0x1(%esp) # 8 bytes
movl $0x2, 0x1(%esp) # 8 bytes
# CHECK-RELAX: 3e: nop
# CHECK-RELAX: 40: movl $2, 1(%esp)
movl $0x2, 0x1(%esp) # 8 bytes
movl $0x2, (%esp) # 7 bytes
# CHECK-OPT: 3f: nop
# CHECK-OPT: 40: movl $3, (%esp)
movl $0x3, (%esp) # 7 bytes
movl $0x3, (%esp) # 7 bytes
ret