BranchRelaxation: Account for function alignment
llvm-svn: 283462
diff --git a/llvm/lib/CodeGen/BranchRelaxation.cpp b/llvm/lib/CodeGen/BranchRelaxation.cpp
index f138306..4f0dfaf 100644
--- a/llvm/lib/CodeGen/BranchRelaxation.cpp
+++ b/llvm/lib/CodeGen/BranchRelaxation.cpp
@@ -46,13 +46,22 @@
BasicBlockInfo() : Offset(0), Size(0) {}
- /// Compute the offset immediately following this block. If LogAlign is
- /// specified, return the offset the successor block will get if it has
- /// this alignment.
- unsigned postOffset(unsigned LogAlign = 0) const {
+ /// Compute the offset immediately following this block. \p MBB is the next
+ /// block.
+ unsigned postOffset(const MachineBasicBlock &MBB) const {
unsigned PO = Offset + Size;
- unsigned Align = 1 << LogAlign;
- return (PO + Align - 1) / Align * Align;
+ unsigned Align = MBB.getAlignment();
+ if (Align == 0)
+ return PO;
+
+ unsigned AlignAmt = 1 << Align;
+ unsigned ParentAlign = MBB.getParent()->getAlignment();
+ if (Align <= ParentAlign)
+ return PO + OffsetToAlignment(PO, AlignAmt);
+
+ // The alignment of this MBB is larger than the function's alignment, so we
+ // can't tell whether or not it will insert nops. Assume that it will.
+ return PO + AlignAmt + OffsetToAlignment(PO, AlignAmt);
}
};
@@ -99,7 +108,7 @@
unsigned Align = MBB.getAlignment();
unsigned Num = MBB.getNumber();
assert(BlockInfo[Num].Offset % (1u << Align) == 0);
- assert(!Num || BlockInfo[PrevNum].postOffset() <= BlockInfo[Num].Offset);
+ assert(!Num || BlockInfo[PrevNum].postOffset(MBB) <= BlockInfo[Num].Offset);
PrevNum = Num;
}
#endif
@@ -167,8 +176,8 @@
continue;
// Get the offset and known bits at the end of the layout predecessor.
// Include the alignment of the current block.
- unsigned LogAlign = MBB.getAlignment();
- BlockInfo[Num].Offset = BlockInfo[PrevNum].postOffset(LogAlign);
+ BlockInfo[Num].Offset = BlockInfo[PrevNum].postOffset(MBB);
+
PrevNum = Num;
}
}