[regalloc][WinEH] Do not mark intervals as not spillable if they contain a regmask

Differential Revision: http://reviews.llvm.org/D16831



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@260164 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/CodeGen/LiveInterval.h

@@ -544,6 +544,11 @@ namespace llvm {
       return true;
     }
 
+    // Returns true if any segment in the live range contains any of the
+    // provided slot indexes.  Slots which occur in holes between
+    // segments will not cause the function to return true.
+    bool isLiveAtIndexes(ArrayRef<SlotIndex> Slots) const;
+
     bool operator<(const LiveRange& other) const {
       const SlotIndex &thisIndex = beginIndex();
       const SlotIndex &otherIndex = other.beginIndex();

lib/CodeGen/CalcSpillWeights.cpp

@@ -213,8 +213,11 @@ VirtRegAuxInfo::calculateSpillWeightAndHint(LiveInterval &li) {
   if (!Spillable)
     return;
 
-  // Mark li as unspillable if all live ranges are tiny.
-  if (li.isZeroLength(LIS.getSlotIndexes())) {
+  // Mark li as unspillable if all live ranges are tiny and the interval
+  // is not live at any reg mask.  If the interval is live at a reg mask
+  // spilling may be required.
+  if (li.isZeroLength(LIS.getSlotIndexes()) &&
+      !li.isLiveAtIndexes(LIS.getRegMaskSlots())) {
     li.markNotSpillable();
     return;
   }

lib/CodeGen/LiveInterval.cpp

@@ -748,6 +748,40 @@ void LiveRange::flushSegmentSet() {
   verify();
 }
 
+bool LiveRange::isLiveAtIndexes(ArrayRef<SlotIndex> Slots) const {
+  ArrayRef<SlotIndex>::iterator SlotI = Slots.begin();
+  ArrayRef<SlotIndex>::iterator SlotE = Slots.end();
+
+  // If there are no regmask slots, we have nothing to search.
+  if (SlotI == SlotE)
+    return false;
+
+  // Start our search at the first segment that ends after the first slot.
+  const_iterator SegmentI = find(*SlotI);
+  const_iterator SegmentE = end();
+
+  // If there are no segments that end after the first slot, we're done.
+  if (SegmentI == SegmentE)
+    return false;
+
+  // Look for each slot in the live range.
+  for ( ; SlotI != SlotE; ++SlotI) {
+    // Go to the next segment that ends after the current slot.
+    // The slot may be within a hole in the range.
+    SegmentI = advanceTo(SegmentI, *SlotI);
+    if (SegmentI == SegmentE)
+      return false;
+
+    // If this segment contains the slot, we're done.
+    if (SegmentI->contains(*SlotI))
+      return true;
+    // Otherwise, look for the next slot.
+  }
+
+  // We didn't find a segment containing any of the slots.
+  return false;
+}
+
 void LiveInterval::freeSubRange(SubRange *S) {
   S->~SubRange();
   // Memory was allocated with BumpPtr allocator and is not freed here.

test/CodeGen/X86/regalloc-spill-at-ehpad.ll

@@ -0,0 +1,75 @@
+; RUN: llc -regalloc=greedy -mtriple=x86_64-pc-windows-msvc  < %s -o - | FileCheck %s
+
+; This test checks for proper handling of a condition where the greedy register
+; allocator encounters a very short interval that contains no uses but does
+; contain an EH pad unwind edge, which requires spilling.  Previously the
+; register allocator marked a interval like this as unspillable, resulting in
+; a compilation failure.
+
+
+; The following checks that the value %p is reloaded within the catch handler.
+; CHECK-LABEL: "?catch$8@?0?test@4HA":
+; CHECK:           .seh_endprologue
+; CHECK:           movq    -16(%rbp), %rax
+; CHECK:           movb    $0, (%rax)
+
+define i32* @test(i32* %a) personality i8* bitcast (i32 (...)* @__CxxFrameHandler3 to i8*) {
+entry:
+  %call = call i32 @f()
+  %p = bitcast i32* %a to i8*
+  br i1 undef, label %if.end, label %if.else
+
+if.else:                                          ; preds = %entry
+  br i1 undef, label %cond.false.i, label %if.else.else
+
+if.else.else:                                     ; preds = %if.else
+  br i1 undef, label %cond.true.i, label %cond.false.i
+
+cond.true.i:                                      ; preds = %if.else.else
+  br label %invoke.cont
+
+cond.false.i:                                     ; preds = %if.else.else, %if.else
+  %call.i = invoke i32 @f()
+          to label %invoke.cont unwind label %catch.dispatch
+
+catch.dispatch:                                   ; preds = %cond.false.i
+  %tmp0 = catchswitch within none [label %catch] unwind label %ehcleanup
+
+catch:                                            ; preds = %catch.dispatch
+  %tmp1 = catchpad within %tmp0 [i8* null, i32 64, i8* null]
+  %p.0 = getelementptr inbounds i8, i8* %p, i64 0
+  store i8 0, i8* %p.0, align 8
+  invoke void @_CxxThrowException(i8* null, %eh.ThrowInfo* null) [ "funclet"(token %tmp1) ]
+          to label %noexc unwind label %ehcleanup
+
+noexc:                                            ; preds = %catch
+  unreachable
+
+invoke.cont:                                      ; preds = %cond.false.i, %cond.true.i
+  %cond.i = phi i32 [ %call, %cond.true.i ], [ %call.i, %cond.false.i ]
+  %cmp = icmp eq i32 %cond.i, -1
+  %tmp3 = select i1 %cmp, i32 4, i32 0
+  br label %if.end
+
+if.end:                                           ; preds = %invoke.cont, %entry
+  %state.0 = phi i32 [ %tmp3, %invoke.cont ], [ 4, %entry ]
+  %p.1 = getelementptr inbounds i8, i8* %p, i64 0
+  invoke void @g(i8* %p.1, i32 %state.0)
+          to label %invoke.cont.1 unwind label %ehcleanup
+
+invoke.cont.1:                                    ; preds = %if.end
+  ret i32* %a
+
+ehcleanup:                                        ; preds = %if.end, %catch, %catch.dispatch
+  %tmp4 = cleanuppad within none []
+  cleanupret from %tmp4 unwind to caller
+}
+
+%eh.ThrowInfo = type { i32, i32, i32, i32 }
+
+declare i32 @__CxxFrameHandler3(...)
+
+declare void @_CxxThrowException(i8*, %eh.ThrowInfo*)
+
+declare i32 @f()
+declare void @g(i8*, i32)