Change the INLINEASM_BR MachineInstr to be a non-terminating instruction.
Before this instruction supported output values, it fit fairly
naturally as a terminator. However, being a terminator while also
supporting outputs causes some trouble, as the physreg->vreg COPY
operations cannot be in the same block.
Modeling it as a non-terminator allows it to be handled the same way
as invoke is handled already.
Most of the changes here were created by auditing all the existing
users of MachineBasicBlock::isEHPad() and
MachineBasicBlock::hasEHPadSuccessor(), and adding calls to
isInlineAsmBrIndirectTarget or mayHaveInlineAsmBr, as appropriate.
Reviewed By: nickdesaulniers, void
Differential Revision: https://reviews.llvm.org/D79794
diff --git a/llvm/lib/CodeGen/BranchFolding.cpp b/llvm/lib/CodeGen/BranchFolding.cpp
index 022689c..c6d5aa3 100644
--- a/llvm/lib/CodeGen/BranchFolding.cpp
+++ b/llvm/lib/CodeGen/BranchFolding.cpp
@@ -1083,8 +1083,9 @@
if (!UniquePreds.insert(PBB).second)
continue;
- // Skip blocks which may jump to a landing pad. Can't tail merge these.
- if (PBB->hasEHPadSuccessor())
+ // Skip blocks which may jump to a landing pad or jump from an asm blob.
+ // Can't tail merge these.
+ if (PBB->hasEHPadSuccessor() || PBB->mayHaveInlineAsmBr())
continue;
// After block placement, only consider predecessors that belong to the
@@ -1665,13 +1666,15 @@
if (!MBB->isEHPad()) {
// Check all the predecessors of this block. If one of them has no fall
- // throughs, move this block right after it.
+ // throughs, and analyzeBranch thinks it _could_ fallthrough to this
+ // block, move this block right after it.
for (MachineBasicBlock *PredBB : MBB->predecessors()) {
// Analyze the branch at the end of the pred.
MachineBasicBlock *PredTBB = nullptr, *PredFBB = nullptr;
SmallVector<MachineOperand, 4> PredCond;
if (PredBB != MBB && !PredBB->canFallThrough() &&
!TII->analyzeBranch(*PredBB, PredTBB, PredFBB, PredCond, true) &&
+ (PredTBB == MBB || PredFBB == MBB) &&
(!CurFallsThru || !CurTBB || !CurFBB) &&
(!CurFallsThru || MBB->getNumber() >= PredBB->getNumber())) {
// If the current block doesn't fall through, just move it.
@@ -1697,21 +1700,24 @@
}
if (!CurFallsThru) {
- // Check all successors to see if we can move this block before it.
- for (MachineBasicBlock *SuccBB : MBB->successors()) {
- // Analyze the branch at the end of the block before the succ.
- MachineFunction::iterator SuccPrev = --SuccBB->getIterator();
+ // Check analyzable branch-successors to see if we can move this block
+ // before one.
+ if (!CurUnAnalyzable) {
+ for (MachineBasicBlock *SuccBB : {CurFBB, CurTBB}) {
+ if (!SuccBB)
+ continue;
+ // Analyze the branch at the end of the block before the succ.
+ MachineFunction::iterator SuccPrev = --SuccBB->getIterator();
- // If this block doesn't already fall-through to that successor, and if
- // the succ doesn't already have a block that can fall through into it,
- // and if the successor isn't an EH destination, we can arrange for the
- // fallthrough to happen.
- if (SuccBB != MBB && &*SuccPrev != MBB &&
- !SuccPrev->canFallThrough() && !CurUnAnalyzable &&
- !SuccBB->isEHPad()) {
- MBB->moveBefore(SuccBB);
- MadeChange = true;
- goto ReoptimizeBlock;
+ // If this block doesn't already fall-through to that successor, and
+ // if the succ doesn't already have a block that can fall through into
+ // it, we can arrange for the fallthrough to happen.
+ if (SuccBB != MBB && &*SuccPrev != MBB &&
+ !SuccPrev->canFallThrough()) {
+ MBB->moveBefore(SuccBB);
+ MadeChange = true;
+ goto ReoptimizeBlock;
+ }
}
}