[RegAllocGreedy] Fix crash in tryLocalSplit

[waltl]

Summary

tryLocalSplit only handles a single use block, but an interval may have multiple use blocks. So don't crash in that case. This fixes PR38795.

[waltl]

Simplify fix; bugpoint test case.

[niravd]

LGTM

[waltl]

Typo.

llvm/lib/CodeGen/RegAllocGreedy.cpp

 /// @return Physreg when VirtReg may be assigned and/or new NewVRegs.
 unsigned RAGreedy::trySplit(LiveInterval &VirtReg, AllocationOrder &Order,
                             SmallVectorImpl<unsigned>&NewVRegs) {
   // Ranges must be Split2 or less.
   if (getStage(VirtReg) >= RS_Spill)
     return 0;
 
   // Local intervals are handled separately.
-  if (LIS->intervalIsInOneMBB(VirtReg)) {
+  bool TryLocal = LIS->intervalIsInOneMBB(VirtReg)
+  if (TryLocal) {
     NamedRegionTimer T("local_split", "Local Splitting", TimerGroupName,
                        TimerGroupDescription, TimePassesIsEnabled);
     SA->analyze(&VirtReg);
+    // We may have two disjoint uses in a single block.
+    if (SA->getUseBlocks().size() == 1) {
       unsigned PhysReg = tryLocalSplit(VirtReg, Order, NewVRegs);
       if (PhysReg || !NewVRegs.empty())
         return PhysReg;
+    }
     return tryInstructionSplit(VirtReg, Order, NewVRegs);
   }
 
   NamedRegionTimer T("global_split", "Global Splitting", TimerGroupName,
                      TimerGroupDescription, TimePassesIsEnabled);
 
+  // Don't reanalyze if local_split failed.
+  if (!TryLocal)
     SA->analyze(&VirtReg);
 
   // FIXME: SplitAnalysis may repair broken live ranges coming from the
   // coalescer. That may cause the range to become allocatable which means that
   // tryRegionSplit won't be making progress. This check should be replaced with
   // an assertion when the coalescer is fixed.
   if (SA->didRepairRange()) {
     // VirtReg has changed, so all cached queries are invalid.
     Matrix->invalidateVirtRegs();

llvm/test/CodeGen/X86/pr38795.ll

+; ModuleID = '/usr/local/google/home/niravd/pr38795.c'
+source_filename = "/usr/local/google/home/niravd/pr38795.c"
+target datalayout = "e-m:e-p:32:32-f64:32:64-f80:32-n8:16:32-S128"
+target triple = "i386-unknown-linux-gnu"
+
+@c = common dso_local local_unnamed_addr global i8 0, align 1
+@.str = private unnamed_addr constant [6 x i8] c"%lld\0A\00", align 1
+@f = common dso_local local_unnamed_addr global i64 0, align 8
+@a = common dso_local local_unnamed_addr global i32 0, align 4
+@h = common dso_local local_unnamed_addr global i32 0, align 4
+@d = common dso_local local_unnamed_addr global i16 0, align 2
+@b = common dso_local local_unnamed_addr global i32 0, align 4
+@g = common dso_local local_unnamed_addr global i8 0, align 1
+@e = common dso_local local_unnamed_addr global i32 0, align 4
+
+; Function Attrs: noreturn nounwind
+define dso_local void @fn() #0 {
+entry:
+  br label %for.cond
+
+for.cond:                                         ; preds = %for.inc, %entry
+  %l.0 = phi i16 [ undef, %entry ], [ %l.3, %for.inc ]
+  %m.0 = phi i32 [ undef, %entry ], [ %m.2, %for.inc ]
+  %n.0 = phi i32 [ 1, %entry ], [ %n.2, %for.inc ]
+  %i.0 = phi i32 [ undef, %entry ], [ %i.2, %for.inc ]
+  %o.0 = phi i32 [ undef, %entry ], [ %o.1, %for.inc ]
+  %p.0 = phi i8 [ undef, %entry ], [ %p.2, %for.inc ]
+  %k.0 = phi i8 [ undef, %entry ], [ %k.2, %for.inc ]
+  %q.0 = phi i32 [ undef, %entry ], [ %q.2, %for.inc ]
+  %0 = load i8, i8* @c, align 1, !tbaa !3
+  %tobool = icmp ne i8 %0, 0
+  %cmp = icmp ugt i8 %k.0, 8
+  %or.cond61 = or i1 %cmp, %tobool
+  br i1 %or.cond61, label %if.then, label %if.end
+
+if.then:                                          ; preds = %for.cond
+  %1 = load i64, i64* @f, align 8, !tbaa !6
+  %call = tail call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([6 x i8], [6 x i8]* @.str, i32 0, i32 0), i64 %1)
+  br label %for.cond35
+
+if.end:                                           ; preds = %for.cond
+  %2 = load i32, i32* @a, align 4, !tbaa !8
+  %div = sdiv i32 %m.0, %2
+  %conv4 = trunc i32 %div to i16
+  %tobool7 = icmp eq i16 %conv4, 0
+  br label %ac
+
+ac:                                               ; preds = %ac, %if.end
+  br i1 %tobool7, label %if.end9, label %ac
+
+if.end9:                                          ; preds = %ac
+  %conv3 = trunc i32 %m.0 to i8
+  %conv5 = sext i16 %l.0 to i32
+  store i32 %conv5, i32* @h, align 4, !tbaa !8
+  %conv6.le = trunc i32 %2 to i16
+  %cmp11 = icmp slt i8 %k.0, 9
+  br i1 %cmp11, label %if.then13, label %if.end21
+
+if.then13:                                        ; preds = %if.end9
+  %3 = load i16, i16* @d, align 2, !tbaa !10
+  %conv14 = sext i16 %3 to i64
+  %call15 = tail call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([6 x i8], [6 x i8]* @.str, i32 0, i32 0), i64 %conv14)
+  %4 = load i32, i32* @a, align 4, !tbaa !8
+  %tobool16 = icmp eq i32 %4, 0
+  br i1 %tobool16, label %for.inc, label %for.cond35
+
+if.end21:                                         ; preds = %if.end9
+  %5 = load i8, i8* @g, align 1, !tbaa !3
+  %conv22 = sext i8 %5 to i32
+  br label %ae
+
+ae:                                               ; preds = %for.cond47, %if.end21
+  %l.2 = phi i16 [ %conv6.le, %if.end21 ], [ %l.7, %for.cond47 ]
+  %m.1 = phi i32 [ %div, %if.end21 ], [ %m.6, %for.cond47 ]
+  %n.1 = phi i32 [ %n.0, %if.end21 ], [ %n.7, %for.cond47 ]
+  %i.1 = phi i32 [ %i.0, %if.end21 ], [ %i.5, %for.cond47 ]
+  %p.1 = phi i8 [ %k.0, %if.end21 ], [ %p.6, %for.cond47 ]
+  %k.1 = phi i8 [ %conv3, %if.end21 ], [ %k.6, %for.cond47 ]
+  %q.1 = phi i32 [ %conv22, %if.end21 ], [ %q.5, %for.cond47 ]
+  %6 = load i8, i8* @c, align 1, !tbaa !3
+  %conv23 = sext i8 %6 to i32
+  %7 = load i32, i32* @b, align 4, !tbaa !8
+  %tobool24 = icmp eq i32 %7, 0
+  br i1 %tobool24, label %if.end26, label %af
+
+if.end26:                                         ; preds = %ae
+  %tobool27 = icmp eq i32 %q.1, 0
+  %tobool30 = icmp ne i8 %p.1, 0
+  %or.cond = and i1 %tobool30, %tobool27
+  br i1 %or.cond, label %if.then31, label %for.inc
+
+if.then31:                                        ; preds = %if.end26
+  %8 = load i32, i32* @e, align 4, !tbaa !8
+  %conv32 = sext i32 %8 to i64
+  %call33 = tail call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([6 x i8], [6 x i8]* @.str, i32 0, i32 0), i64 %conv32)
+  br label %for.inc
+
+for.inc:                                          ; preds = %if.then13, %if.end26, %if.then31
+  %l.3 = phi i16 [ %l.2, %if.then31 ], [ %l.2, %if.end26 ], [ %conv6.le, %if.then13 ]
+  %m.2 = phi i32 [ %m.1, %if.then31 ], [ %m.1, %if.end26 ], [ %div, %if.then13 ]
+  %n.2 = phi i32 [ %n.1, %if.then31 ], [ %n.1, %if.end26 ], [ %n.0, %if.then13 ]
+  %i.2 = phi i32 [ %i.1, %if.then31 ], [ %i.1, %if.end26 ], [ %i.0, %if.then13 ]
+  %o.1 = phi i32 [ %conv23, %if.then31 ], [ %conv23, %if.end26 ], [ %o.0, %if.then13 ]
+  %p.2 = phi i8 [ %p.1, %if.then31 ], [ %p.1, %if.end26 ], [ undef, %if.then13 ]
+  %k.2 = phi i8 [ %k.1, %if.then31 ], [ %k.1, %if.end26 ], [ %conv3, %if.then13 ]
+  %q.2 = phi i32 [ 0, %if.then31 ], [ %q.1, %if.end26 ], [ %q.0, %if.then13 ]
+  %9 = load i32, i32* @h, align 4, !tbaa !8
+  %inc = add nsw i32 %9, 1
+  store i32 %inc, i32* @h, align 4, !tbaa !8
+  br label %for.cond
+
+for.cond35:                                       ; preds = %if.then, %if.then13, %for.inc44
+  %l.5 = phi i16 [ %l.6, %for.inc44 ], [ %l.0, %if.then ], [ %conv6.le, %if.then13 ]
+  %m.4 = phi i32 [ %m.5, %for.inc44 ], [ %m.0, %if.then ], [ %div, %if.then13 ]
+  %n.3 = phi i32 [ %n.4, %for.inc44 ], [ %n.0, %if.then ], [ %n.0, %if.then13 ]
+  %i.3 = phi i32 [ %inc45, %for.inc44 ], [ %i.0, %if.then ], [ %i.0, %if.then13 ]
+  %o.2 = phi i32 [ %o.3, %for.inc44 ], [ %o.0, %if.then ], [ %o.0, %if.then13 ]
+  %p.4 = phi i8 [ %p.5, %for.inc44 ], [ %p.0, %if.then ], [ %k.0, %if.then13 ]
+  %k.4 = phi i8 [ %k.5, %for.inc44 ], [ %k.0, %if.then ], [ %conv3, %if.then13 ]
+  %q.3 = phi i32 [ %q.4, %for.inc44 ], [ %q.0, %if.then ], [ %q.0, %if.then13 ]
+  %tobool36 = icmp eq i32 %i.3, 0
+  br i1 %tobool36, label %for.end46, label %af
+
+af:                                               ; preds = %for.cond35, %ae
+  %l.6 = phi i16 [ %l.5, %for.cond35 ], [ %l.2, %ae ]
+  %m.5 = phi i32 [ %m.4, %for.cond35 ], [ %m.1, %ae ]
+  %n.4 = phi i32 [ %n.3, %for.cond35 ], [ %n.1, %ae ]
+  %i.4 = phi i32 [ %i.3, %for.cond35 ], [ %i.1, %ae ]
+  %o.3 = phi i32 [ %o.2, %for.cond35 ], [ %conv23, %ae ]
+  %p.5 = phi i8 [ %p.4, %for.cond35 ], [ %p.1, %ae ]
+  %k.5 = phi i8 [ %k.4, %for.cond35 ], [ %k.1, %ae ]
+  %q.4 = phi i32 [ %q.3, %for.cond35 ], [ %q.1, %ae ]
+  %10 = load i8, i8* @c, align 1, !tbaa !3
+  %tobool37 = icmp eq i8 %10, 0
+  br i1 %tobool37, label %if.end39, label %for.inc44
+
+if.end39:                                         ; preds = %af
+  %tobool40 = icmp eq i32 %o.3, 0
+  br i1 %tobool40, label %for.end46, label %if.then41
+
+if.then41:                                        ; preds = %if.end39
+  %call42 = tail call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([6 x i8], [6 x i8]* @.str, i32 0, i32 0), i64 ptrtoint (void ()* @fn to i64))
+  br label %for.end46
+
+for.inc44:                                        ; preds = %af
+  %inc45 = add nsw i32 %i.4, 1
+  br label %for.cond35
+
+for.end46:                                        ; preds = %for.cond35, %if.end39, %if.then41
+  %l.7 = phi i16 [ %l.6, %if.then41 ], [ %l.6, %if.end39 ], [ %l.5, %for.cond35 ]
+  %m.6 = phi i32 [ %m.5, %if.then41 ], [ %m.5, %if.end39 ], [ %m.4, %for.cond35 ]
+  %n.5 = phi i32 [ %n.4, %if.then41 ], [ %n.4, %if.end39 ], [ %n.3, %for.cond35 ]
+  %i.5 = phi i32 [ %i.4, %if.then41 ], [ %i.4, %if.end39 ], [ 0, %for.cond35 ]
+  %p.6 = phi i8 [ %p.5, %if.then41 ], [ %p.5, %if.end39 ], [ %p.4, %for.cond35 ]
+  %k.6 = phi i8 [ %k.5, %if.then41 ], [ %k.5, %if.end39 ], [ %k.4, %for.cond35 ]
+  %q.5 = phi i32 [ %q.4, %if.then41 ], [ %q.4, %if.end39 ], [ %q.3, %for.cond35 ]
+  %tobool50 = icmp eq i32 %m.6, 0
+  br label %for.cond47
+
+for.cond47:                                       ; preds = %for.cond47, %for.end46
+  %n.7 = phi i32 [ %n.5, %for.end46 ], [ %.mux, %for.cond47 ]
+  %tobool48 = icmp eq i32 %n.7, 0
+  %brmerge = or i1 %tobool48, %tobool50
+  %.mux = select i1 %tobool48, i32 0, i32 9
+  br i1 %brmerge, label %for.cond47, label %ae
+}
+
+; Function Attrs: nounwind
+declare dso_local i32 @printf(i8* nocapture readonly, ...) local_unnamed_addr #1
+
+attributes #0 = { noreturn nounwind "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="pentium4" "target-features"="+fxsr,+mmx,+sse,+sse2,+x87" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #1 = { nounwind "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="pentium4" "target-features"="+fxsr,+mmx,+sse,+sse2,+x87" "unsafe-fp-math"="false" "use-soft-float"="false" }
+
+!llvm.module.flags = !{!0, !1}
+!llvm.ident = !{!2}
+
+!0 = !{i32 1, !"NumRegisterParameters", i32 0}
+!1 = !{i32 1, !"wchar_size", i32 4}
+!2 = !{!"clang version 8.0.0 "}
+!3 = !{!4, !4, i64 0}
+!4 = !{!"omnipotent char", !5, i64 0}
+!5 = !{!"Simple C/C++ TBAA"}
+!6 = !{!7, !7, i64 0}
+!7 = !{!"long long", !4, i64 0}
+!8 = !{!9, !9, i64 0}
+!9 = !{!"int", !4, i64 0}
+!10 = !{!11, !11, i64 0}
+!11 = !{!"short", !4, i64 0}