Fix constant island pass's handling of tBR_JTr. The offset of the instruction does not have to be 4-byte aligned. Rather, it's the offset + 2 that must be aligned since the instruction expands into:
mov pc, r1
.align 2
LJTI0_0_0:
.long LBB0_14
This fixes rdar://8213383. No test case since it's not possible to come up with a suitable small one.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@109076 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/ARM/ARMConstantIslandPass.cpp b/lib/Target/ARM/ARMConstantIslandPass.cpp
index 65a3da6..50ba0d1 100644
--- a/lib/Target/ARM/ARMConstantIslandPass.cpp
+++ b/lib/Target/ARM/ARMConstantIslandPass.cpp
@@ -366,6 +366,8 @@
if (isThumb && !HasFarJump && AFI->isLRSpilledForFarJump())
MadeChange |= UndoLRSpillRestore();
+ DEBUG(errs() << '\n'; dumpBBs());
+
BBSizes.clear();
BBOffsets.clear();
WaterList.clear();
@@ -509,8 +511,11 @@
case ARM::tBR_JTr:
// A Thumb1 table jump may involve padding; for the offsets to
// be right, functions containing these must be 4-byte aligned.
+ // tBR_JTr expands to a mov pc followed by .align 2 and then the jump
+ // table entries. So this code checks whether offset of tBR_JTr + 2
+ // is aligned.
MF.EnsureAlignment(2U);
- if ((Offset+MBBSize)%4 != 0 || HasInlineAsm)
+ if ((Offset+MBBSize+2)%4 != 0 || HasInlineAsm)
// FIXME: Add a pseudo ALIGN instruction instead.
MBBSize += 2; // padding
continue; // Does not get an entry in ImmBranches
@@ -915,9 +920,12 @@
}
// Thumb1 jump tables require padding. They should be at the end;
// following unconditional branches are removed by AnalyzeBranch.
+ // tBR_JTr expands to a mov pc followed by .align 2 and then the jump
+ // table entries. So this code checks whether offset of tBR_JTr + 2
+ // is aligned.
MachineInstr *ThumbJTMI = prior(MBB->end());
if (ThumbJTMI->getOpcode() == ARM::tBR_JTr) {
- unsigned NewMIOffset = GetOffsetOf(ThumbJTMI);
+ unsigned NewMIOffset = GetOffsetOf(ThumbJTMI) + 2;
unsigned OldMIOffset = NewMIOffset - delta;
if ((OldMIOffset%4) == 0 && (NewMIOffset%4) != 0) {
// remove existing padding