[llvm] r259294 - [WebAssembly] Refine block placement to insert blocks between trees.

[Dan Gohman via llvm-commits]

Author: djg
Date: Fri Jan 29 23:01:06 2016
New Revision: 259294

URL: http://llvm.org/viewvc/llvm-project?rev=259294&view=rev
Log:
[WebAssembly] Refine block placement to insert blocks between trees.

Refine the test for whether an instruction is in an expression tree so that
it detects when one tree ends and another begins, so we can place a block
at that point, rather than continuing to find the first instruction not in
a tree at all.

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=259294&r1=259293&r2=259294&view=diff
==============================================================================
--- llvm/trunk/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp (original)
+++ llvm/trunk/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp Fri Jan 29 23:01:06 2016
@@ -27,6 +27,7 @@
 
 #include "WebAssembly.h"
 #include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
+#include "WebAssemblyMachineFunctionInfo.h"
 #include "WebAssemblySubtarget.h"
 #include "llvm/ADT/SCCIterator.h"
 #include "llvm/ADT/SetVector.h"
@@ -266,12 +267,26 @@ static bool ExplicitlyBranchesTo(Machine
   return false;
 }
 
+/// Test whether MI is a child of some other node in an expression tree.
+static bool IsChild(const MachineInstr *MI,
+                    const WebAssemblyFunctionInfo &MFI) {
+  if (MI->getNumOperands() == 0)
+    return false;
+  const MachineOperand &MO = MI->getOperand(0);
+  if (!MO.isReg() || MO.isImplicit() || !MO.isDef())
+    return false;
+  unsigned Reg = MO.getReg();
+  return TargetRegisterInfo::isVirtualRegister(Reg) &&
+         MFI.isVRegStackified(Reg);
+}
+
 /// 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) {
+                             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.
@@ -326,7 +341,7 @@ static void PlaceBlockMarker(MachineBasi
     // beginning of the local expression tree and any nested BLOCKs.
     InsertPos = Header->getFirstTerminator();
     while (InsertPos != Header->begin() &&
-           prev(InsertPos)->definesRegister(WebAssembly::EXPR_STACK) &&
+           IsChild(prev(InsertPos), MFI) &&
            prev(InsertPos)->getOpcode() != WebAssembly::LOOP &&
            prev(InsertPos)->getOpcode() != WebAssembly::END_BLOCK &&
            prev(InsertPos)->getOpcode() != WebAssembly::END_LOOP)
@@ -409,7 +424,8 @@ GetDepth(const SmallVectorImpl<const Mac
 /// Insert LOOP and BLOCK markers at appropriate places.
 static void PlaceMarkers(MachineFunction &MF, const MachineLoopInfo &MLI,
                          const WebAssemblyInstrInfo &TII,
-                         MachineDominatorTree &MDT) {
+                         MachineDominatorTree &MDT,
+                         WebAssemblyFunctionInfo &MFI) {
   // For each block whose label represents the end of a scope, record the block
   // which holds the beginning of the scope. This will allow us to quickly skip
   // over scoped regions when walking blocks. We allocate one more than the
@@ -425,7 +441,7 @@ static void PlaceMarkers(MachineFunction
     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);
+    PlaceBlockMarker(MBB, MF, ScopeTops, TII, MLI, MDT, MFI);
   }
 
   // Now rewrite references to basic blocks to be depth immediates.
@@ -478,6 +494,7 @@ bool WebAssemblyCFGStackify::runOnMachin
   auto &MDT = getAnalysis<MachineDominatorTree>();
   // Liveness is not tracked for EXPR_STACK physreg.
   const auto &TII = *MF.getSubtarget<WebAssemblySubtarget>().getInstrInfo();
+  WebAssemblyFunctionInfo &MFI = *MF.getInfo<WebAssemblyFunctionInfo>();
   MF.getRegInfo().invalidateLiveness();
 
   // RPO sorting needs all loops to be single-entry.
@@ -487,7 +504,7 @@ bool WebAssemblyCFGStackify::runOnMachin
   SortBlocks(MF, MLI);
 
   // Place the BLOCK and LOOP markers to indicate the beginnings of scopes.
-  PlaceMarkers(MF, MLI, TII, MDT);
+  PlaceMarkers(MF, MLI, TII, MDT, MFI);
 
   return true;
 }

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=259294&r1=259293&r2=259294&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/WebAssembly/cfg-stackify.ll (original)
+++ llvm/trunk/test/CodeGen/WebAssembly/cfg-stackify.ll Fri Jan 29 23:01:06 2016
@@ -949,9 +949,9 @@ bb6:
 ; CHECK-NEXT:  block{{$}}
 ; CHECK-NEXT:  block{{$}}
 ; CHECK:       br_if        {{[^,]+}}, 0{{$}}
-; CHECK-NEXT:  block{{$}}
 ; CHECK-NOT:   block
-; CHECK:       br_if        {{[^,]+}}, 0{{$}}
+; CHECK:       block{{$}}
+; CHECK-NEXT:  br_if        {{[^,]+}}, 0{{$}}
 ; CHECK-NOT:   block
 ; CHECK:       br_if        {{[^,]+}}, 2{{$}}
 ; CHECK-NEXT:  .LBB20_3:
@@ -980,9 +980,9 @@ bb6:
 ; OPT:       block{{$}}
 ; OPT-NEXT:  block{{$}}
 ; OPT:       br_if        $pop{{[0-9]+}}, 0{{$}}
-; OPT-NEXT:  block{{$}}
 ; OPT-NOT:   block
-; OPT:       br_if        $0, 0{{$}}
+; OPT:       block{{$}}
+; OPT-NEXT:  br_if        $0, 0{{$}}
 ; OPT-NOT:   block
 ; OPT:       br_if        {{[^,]+}}, 2{{$}}
 ; OPT-NEXT:  .LBB20_3: