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Implement global merge optimization for global variables.

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This commit implements two command line switches -global-merge-on-external
and -global-merge-aligned, and both of them are false by default, so this
optimization is disabled by default for all targets.

For ARM64, some back-end behaviors need to be tuned to get this optimization
further enabled.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@208934 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jiangning Liu
2014-05-15 23:45:42 +00:00
parent 01a02d91dc
commit d5db8765d6
20 changed files with 448 additions and 68 deletions
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14
lib/Target/AArch64/AArch64ISelLowering.cpp
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@@ -5560,3 +5560,17 @@ unsigned AArch64TargetLowering::getMaximalGlobalOffset() const {
return 4095;
}
/// getGlobalMergeAlignment - Set alignment to be the max size of merged
/// global variable data structure, and make it aligned up to power of 2.
/// This way, we could guarantee the merged global variable data structure
/// doesn't cross page boundary, because usually OS always allocates page at
/// 4096-byte aligned boundary.
unsigned AArch64TargetLowering::getGlobalMergeAlignment(
StructType *MergedTy) const {
unsigned Align = getDataLayout()->getTypeAllocSize(MergedTy);
if (Align & (Align - 1))
Align = llvm::NextPowerOf2(Align);
return Align;
}