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[WebAssembly] Remove loop's bottom label.

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Per spec changes, loop constructs no longer have a bottom label.

https://reviews.llvm.org/D25118


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@283502 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman
2016-10-06 22:10:23 +00:00
parent a5e77a0215
commit d8d953ef76
3 changed files with 47 additions and 43 deletions
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lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp
+14 -19
View File
@@ -306,12 +306,14 @@ static bool IsChild(const MachineInstr &MI,
}
/// Insert a BLOCK marker for branches to MBB (if needed).
static void PlaceBlockMarker(MachineBasicBlock &MBB, MachineFunction &MF,
SmallVectorImpl<MachineBasicBlock *> &ScopeTops,
const WebAssemblyInstrInfo &TII,
const MachineLoopInfo &MLI,
MachineDominatorTree &MDT,
WebAssemblyFunctionInfo &MFI) {
static void PlaceBlockMarker(
MachineBasicBlock &MBB, MachineFunction &MF,
SmallVectorImpl<MachineBasicBlock *> &ScopeTops,
DenseMap<const MachineInstr *, const MachineBasicBlock *> &LoopTops,
const WebAssemblyInstrInfo &TII,
const MachineLoopInfo &MLI,
MachineDominatorTree &MDT,
WebAssemblyFunctionInfo &MFI) {
// First compute the nearest common dominator of all forward non-fallthrough
// predecessors so that we minimize the time that the BLOCK is on the stack,
// which reduces overall stack height.
@@ -347,13 +349,6 @@ static void PlaceBlockMarker(MachineBasicBlock &MBB, MachineFunction &MF,
}
}
// If there's a loop which ends just before MBB which contains Header, we can
// reuse its label instead of inserting a new BLOCK.
for (MachineLoop *Loop = MLI.getLoopFor(LayoutPred);
Loop && Loop->contains(LayoutPred); Loop = Loop->getParentLoop())
if (Loop && LoopBottom(Loop) == LayoutPred && Loop->contains(Header))
return;
// Decide where in Header to put the BLOCK.
MachineBasicBlock::iterator InsertPos;
MachineLoop *HeaderLoop = MLI.getLoopFor(Header);
@@ -361,7 +356,8 @@ static void PlaceBlockMarker(MachineBasicBlock &MBB, MachineFunction &MF,
// Header is the header of a loop that does not lexically contain MBB, so
// the BLOCK needs to be above the LOOP, after any END constructs.
InsertPos = Header->begin();
while (InsertPos->getOpcode() != WebAssembly::LOOP)
while (InsertPos->getOpcode() == WebAssembly::END_BLOCK ||
InsertPos->getOpcode() == WebAssembly::END_LOOP)
++InsertPos;
} else {
// Otherwise, insert the BLOCK as late in Header as we can, but before the
@@ -381,7 +377,8 @@ static void PlaceBlockMarker(MachineBasicBlock &MBB, MachineFunction &MF,
// Mark the end of the block.
InsertPos = MBB.begin();
while (InsertPos != MBB.end() &&
InsertPos->getOpcode() == WebAssembly::END_LOOP)
InsertPos->getOpcode() == WebAssembly::END_LOOP &&
LoopTops[&*InsertPos]->getNumber() >= Header->getNumber())
++InsertPos;
BuildMI(MBB, InsertPos, DebugLoc(), TII.get(WebAssembly::END_BLOCK));
@@ -468,7 +465,7 @@ static void PlaceMarkers(MachineFunction &MF, const MachineLoopInfo &MLI,
PlaceLoopMarker(MBB, MF, ScopeTops, LoopTops, TII, MLI);
// Place the BLOCK for MBB if MBB is branched to from above.
PlaceBlockMarker(MBB, MF, ScopeTops, TII, MLI, MDT, MFI);
PlaceBlockMarker(MBB, MF, ScopeTops, LoopTops, TII, MLI, MDT, MFI);
}
// Now rewrite references to basic blocks to be depth immediates.
@@ -477,20 +474,18 @@ static void PlaceMarkers(MachineFunction &MF, const MachineLoopInfo &MLI,
for (auto &MI : reverse(MBB)) {
switch (MI.getOpcode()) {
case WebAssembly::BLOCK:
assert(ScopeTops[Stack.back()->getNumber()] == &MBB &&
assert(ScopeTops[Stack.back()->getNumber()]->getNumber() <= MBB.getNumber() &&
"Block should be balanced");
Stack.pop_back();
break;
case WebAssembly::LOOP:
assert(Stack.back() == &MBB && "Loop top should be balanced");
Stack.pop_back();
Stack.pop_back();
break;
case WebAssembly::END_BLOCK:
Stack.push_back(&MBB);
break;
case WebAssembly::END_LOOP:
Stack.push_back(&MBB);
Stack.push_back(LoopTops[&MI]);
break;
default: