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[LoopInfo] Fix Loop::getLoopID() for loops with multiple latches

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The previous implementation traversed all loop blocks and bailed if one
was not a latch block. Since we are only interested in latch blocks, we
should only traverse those.

llvm-svn: 341926
This commit is contained in:
Johannes Doerfert 2018-09-11 11:44:17 +00:00
parent d6ccc95cfd
commit 218cfa8be2
2 changed files with 61 additions and 12 deletions
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17
lib/Analysis/LoopInfo.cpp
View File

@ -218,20 +218,13 @@ MDNode *Loop::getLoopID() const {
} else {
assert(!getLoopLatch() &&
"The loop should have no single latch at this point");
// Go through each predecessor of the loop header and check the
// terminator for the metadata.
BasicBlock *H = getHeader();
for (BasicBlock *BB : this->blocks()) {
// Go through the latch blocks and check the terminator for the metadata.
SmallVector<BasicBlock *, 4> LatchesBlocks;
getLoopLatches(LatchesBlocks);
for (BasicBlock *BB : LatchesBlocks) {
TerminatorInst *TI = BB->getTerminator();
MDNode *MD = nullptr;
MDNode *MD = TI->getMetadata(LLVMContext::MD_loop);
// Check if this terminator branches to the loop header.
for (BasicBlock *Successor : successors(TI)) {
if (Successor == H) {
MD = TI->getMetadata(LLVMContext::MD_loop);
break;
}
}
if (!MD)
return nullptr;

56
unittests/Analysis/LoopInfoTest.cpp
View File

@ -82,6 +82,62 @@ TEST(LoopInfoTest, LoopWithSingleLatch) {
});
}
// Test loop id handling for a loop with multiple latches.
TEST(LoopInfoTest, LoopWithMultipleLatches) {
const char *ModuleStr =
"target datalayout = \"e-m:o-i64:64-f80:128-n8:16:32:64-S128\"\n"
"define void @foo(i32 %n) {\n"
"entry:\n"
" br i1 undef, label %for.cond, label %for.end\n"
"for.cond:\n"
" %i.0 = phi i32 [ 0, %entry ], [ %inc, %latch.1 ], [ %inc, %latch.2 ]\n"
" %inc = add nsw i32 %i.0, 1\n"
" %cmp = icmp slt i32 %i.0, %n\n"
" br i1 %cmp, label %latch.1, label %for.end\n"
"latch.1:\n"
" br i1 undef, label %for.cond, label %latch.2, !llvm.loop !0\n"
"latch.2:\n"
" br label %for.cond, !llvm.loop !0\n"
"for.end:\n"
" ret void\n"
"}\n"
"!0 = distinct !{!0, !1}\n"
"!1 = !{!\"llvm.loop.distribute.enable\", i1 true}\n";
// Parse the module.
LLVMContext Context;
std::unique_ptr<Module> M = makeLLVMModule(Context, ModuleStr);
runWithLoopInfo(*M, "foo", [&](Function &F, LoopInfo &LI) {
Function::iterator FI = F.begin();
F.dump();
// First basic block is entry - skip it.
BasicBlock *Header = &*(++FI);
assert(Header->getName() == "for.cond");
Loop *L = LI.getLoopFor(Header);
EXPECT_NE(L, nullptr);
// This loop is not in simplified form.
EXPECT_FALSE(L->isLoopSimplifyForm());
// Try to get and set the metadata id for the loop.
MDNode *OldLoopID = L->getLoopID();
EXPECT_NE(OldLoopID, nullptr);
MDNode *NewLoopID = MDNode::get(Context, {nullptr});
// Set operand 0 to refer to the loop id itself.
NewLoopID->replaceOperandWith(0, NewLoopID);
L->setLoopID(NewLoopID);
EXPECT_EQ(L->getLoopID(), NewLoopID);
EXPECT_NE(L->getLoopID(), OldLoopID);
L->setLoopID(OldLoopID);
EXPECT_EQ(L->getLoopID(), OldLoopID);
EXPECT_NE(L->getLoopID(), NewLoopID);
});
}
TEST(LoopInfoTest, PreorderTraversals) {
const char *ModuleStr = "define void @f() {\n"
"entry:\n"