[llvm] r249187 - [WebAssembly] Fix CFG stackification of nested loops.

[Dan Gohman via llvm-commits]

Author: djg
Date: Fri Oct  2 16:11:36 2015
New Revision: 249187

URL: http://llvm.org/viewvc/llvm-project?rev=249187&view=rev
Log:
[WebAssembly] Fix CFG stackification of nested loops.

Modified:
    llvm/trunk/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp
    llvm/trunk/test/CodeGen/WebAssembly/cfg-stackify.ll

Modified: llvm/trunk/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp?rev=249187&r1=249186&r2=249187&view=diff
==============================================================================
--- llvm/trunk/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp (original)
+++ llvm/trunk/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp Fri Oct  2 16:11:36 2015
@@ -194,8 +194,10 @@ static void SortBlocks(MachineFunction &
     if (MachineLoop *Loop = MLI.getLoopFor(&MBB)) {
       // Assert that loops are contiguous.
       assert(Loop->getHeader() == Loop->getTopBlock());
-      assert(Loop->getHeader() == &MBB ||
-             MLI.getLoopFor(prev(MachineFunction::iterator(&MBB))) == Loop);
+      assert((Loop->getHeader() == &MBB ||
+              Loop->contains(
+                  MLI.getLoopFor(prev(MachineFunction::iterator(&MBB))))) &&
+             "Loop isn't contiguous");
     } else {
       // Assert that non-loops have no backedge predecessors.
       for (auto Pred : MBB.predecessors())
@@ -245,9 +247,18 @@ static void PlaceMarkers(MachineFunction
   for (auto &MBB : MF) {
     // Place the LOOP for loops.
     if (MachineLoop *Loop = MLI.getLoopFor(&MBB))
-      if (Loop->getHeader() == &MBB)
+      if (Loop->getHeader() == &MBB) {
+        // The operand of a LOOP is the first block after the loop. If the loop
+        // is the bottom of the function, insert a dummy block at the end.
+        MachineBasicBlock *Bottom = Loop->getBottomBlock();
+        auto Iter = next(MachineFunction::iterator(Bottom));
+        if (Iter == MF.end()) {
+          MF.push_back(MF.CreateMachineBasicBlock());
+          Iter = next(MachineFunction::iterator(Bottom));
+        }
         BuildMI(MBB, MBB.begin(), DebugLoc(), TII.get(WebAssembly::LOOP))
-            .addMBB(Loop->getBottomBlock());
+            .addMBB(Iter);
+      }
 
     // Check for forward branches and switches that need BLOCKS placed.
     for (auto &Term : MBB.terminators())

Modified: llvm/trunk/test/CodeGen/WebAssembly/cfg-stackify.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/WebAssembly/cfg-stackify.ll?rev=249187&r1=249186&r2=249187&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/WebAssembly/cfg-stackify.ll (original)
+++ llvm/trunk/test/CodeGen/WebAssembly/cfg-stackify.ll Fri Oct  2 16:11:36 2015
@@ -272,3 +272,33 @@ exit:
   store volatile i32 4, i32* %p
   ret i32 0
 }
+
+; Test that nested loops are handled.
+
+declare void @bar()
+
+define void @test3(i32 %w)  {
+entry:
+  br i1 undef, label %outer.ph, label %exit
+
+outer.ph:
+  br label %outer
+
+outer:
+  %tobool = icmp eq i32 undef, 0
+  br i1 %tobool, label %inner, label %unreachable
+
+unreachable:
+  unreachable
+
+inner:
+  %c = icmp eq i32 undef, %w
+  br i1 %c, label %if.end, label %inner
+
+exit:
+  ret void
+
+if.end:
+  call void @bar()
+  br label %outer
+}