[llvm] [MC] Move some bool members to MCFragment. NFC (PR #100976)
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Sun Jul 28 23:25:24 PDT 2024
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-mc
Author: Fangrui Song (MaskRay)
<details>
<summary>Changes</summary>
Move `AllowAutoPadding` to MCFragment, which reduce the
MCRelaxableFragment size by 8 bytes. While here, also move
`AlignToBundleEnd` next to `HasInstructions`. Functions that create
fragments are slightly shorter due to fewer byte zeroing instructions.
Although fewer in number than MCDataFragments, MCRelaxableFragment
objects still constitute a significant proportion warranting
optimization.
```
% clang -c sqlite3.i -w -g -Xclang -print-stats
...
2206 assembler - Number of emitted assembler fragments - align
83980 assembler - Number of emitted assembler fragments - data
84 assembler - Number of emitted assembler fragments - fill
169462 assembler - Number of emitted assembler fragments - total
11396 assembler - Number of emitted assembler fragments - relaxable
```
---
Full diff: https://github.com/llvm/llvm-project/pull/100976.diff
2 Files Affected:
- (modified) llvm/include/llvm/MC/MCFragment.h (+7-6)
- (modified) llvm/lib/MC/MCFragment.cpp (+2-1)
``````````diff
diff --git a/llvm/include/llvm/MC/MCFragment.h b/llvm/include/llvm/MC/MCFragment.h
index 84f8e060320a1..bfd349e8b8e7e 100644
--- a/llvm/include/llvm/MC/MCFragment.h
+++ b/llvm/include/llvm/MC/MCFragment.h
@@ -69,8 +69,15 @@ class MCFragment {
FragmentType Kind;
protected:
+ /// Used by subclasses for better packing.
+ ///
+ /// MCEncodedFragment
bool HasInstructions : 1;
+ bool AlignToBundleEnd : 1;
+ /// MCDataFragment
bool LinkerRelaxable : 1;
+ /// MCRelaxableFragment: x86-specific
+ bool AllowAutoPadding : 1;
MCFragment(FragmentType Kind, bool HasInstructions);
@@ -115,9 +122,6 @@ class MCDummyFragment : public MCFragment {
/// data.
///
class MCEncodedFragment : public MCFragment {
- /// Should this fragment be aligned to the end of a bundle?
- bool AlignToBundleEnd = false;
-
uint8_t BundlePadding = 0;
protected:
@@ -228,11 +232,8 @@ class MCDataFragment : public MCEncodedFragmentWithFixups<32, 4> {
/// relaxed during the assembler layout and relaxation stage.
///
class MCRelaxableFragment : public MCEncodedFragmentWithFixups<8, 1> {
-
/// The instruction this is a fragment for.
MCInst Inst;
- /// Can we auto pad the instruction?
- bool AllowAutoPadding = false;
public:
MCRelaxableFragment(const MCInst &Inst, const MCSubtargetInfo &STI)
diff --git a/llvm/lib/MC/MCFragment.cpp b/llvm/lib/MC/MCFragment.cpp
index 3086730b1be8a..ac1b5a8fb8274 100644
--- a/llvm/lib/MC/MCFragment.cpp
+++ b/llvm/lib/MC/MCFragment.cpp
@@ -27,7 +27,8 @@
using namespace llvm;
MCFragment::MCFragment(FragmentType Kind, bool HasInstructions)
- : Kind(Kind), HasInstructions(HasInstructions), LinkerRelaxable(false) {}
+ : Kind(Kind), HasInstructions(HasInstructions), AlignToBundleEnd(false),
+ LinkerRelaxable(false), AllowAutoPadding(false) {}
void MCFragment::destroy() {
switch (Kind) {
``````````
</details>
https://github.com/llvm/llvm-project/pull/100976
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