[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

void RAGreedy::calcGapWeights(unsigned PhysReg,
   }
 }
 
 /// tryLocalSplit - Try to split VirtReg into smaller intervals inside its only
 /// basic block.
 ///
 unsigned RAGreedy::tryLocalSplit(LiveInterval &VirtReg, AllocationOrder &Order,
                                  SmallVectorImpl<unsigned> &NewVRegs) {
-  assert(SA->getUseBlocks().size() == 1 && "Not a local interval");
+  // TODO: the function currently only handle a single UseBlock; it should be
+  // possible to generalize.
+  if (SA->getUseBlocks().size() != 1)
+    return 0;
+
   const SplitAnalysis::BlockInfo &BI = SA->getUseBlocks().front();
 
   // Note that it is possible to have an interval that is live-in or live-out
   // while only covering a single block - A phi-def can use undef values from
   // predecessors, and the block could be a single-block loop.
   // We don't bother doing anything clever about such a case, we simply assume
   // that the interval is continuous from FirstInstr to LastInstr. We should
   // make sure that we don't do anything illegal to such an interval, though.

llvm/test/CodeGen/X86/pr38795.ll

+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc %s -O2 -mtriple=i386-unknown-linux-gnu -o - | FileCheck %s
+@.str = external dso_local unnamed_addr constant [6 x i8], align 1
+@a = external dso_local local_unnamed_addr global i32, align 4
+@h = external dso_local local_unnamed_addr global i32, align 4
+@g = external dso_local local_unnamed_addr global i8, align 1
+
+define dso_local void @fn() {
+; CHECK-LABEL: fn:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    pushl %ebp
+; CHECK-NEXT:    .cfi_def_cfa_offset 8
+; CHECK-NEXT:    pushl %ebx
+; CHECK-NEXT:    .cfi_def_cfa_offset 12
+; CHECK-NEXT:    pushl %edi
+; CHECK-NEXT:    .cfi_def_cfa_offset 16
+; CHECK-NEXT:    pushl %esi
+; CHECK-NEXT:    .cfi_def_cfa_offset 20
+; CHECK-NEXT:    subl $28, %esp
+; CHECK-NEXT:    .cfi_def_cfa_offset 48
+; CHECK-NEXT:    .cfi_offset %esi, -20
+; CHECK-NEXT:    .cfi_offset %edi, -16
+; CHECK-NEXT:    .cfi_offset %ebx, -12
+; CHECK-NEXT:    .cfi_offset %ebp, -8
+; CHECK-NEXT:    xorl %ebx, %ebx
+; CHECK-NEXT:    # implicit-def: $esi
+; CHECK-NEXT:    # implicit-def: $edi
+; CHECK-NEXT:    # implicit-def: $ah
+; CHECK-NEXT:    # implicit-def: $al
+; CHECK-NEXT:    # implicit-def: $edx
+; CHECK-NEXT:    jmp .LBB0_1
+; CHECK-NEXT:    .p2align 4, 0x90
+; CHECK-NEXT:  .LBB0_16: # %for.inc
+; CHECK-NEXT:    # in Loop: Header=BB0_1 Depth=1
+; CHECK-NEXT:    movb {{[-0-9]+}}(%e{{[sb]}}p), %ah # 1-byte Reload
+; CHECK-NEXT:    movb %cl, %al
+; CHECK-NEXT:  .LBB0_1: # %for.cond
+; CHECK-NEXT:    # =>This Loop Header: Depth=1
+; CHECK-NEXT:    # Child Loop BB0_20 Depth 2
+; CHECK-NEXT:    cmpb $8, %al
+; CHECK-NEXT:    movb %al, {{[-0-9]+}}(%e{{[sb]}}p) # 1-byte Spill
+; CHECK-NEXT:    ja .LBB0_3
+; CHECK-NEXT:  # %bb.2: # %for.cond
+; CHECK-NEXT:    # in Loop: Header=BB0_1 Depth=1
+; CHECK-NEXT:    testb %bl, %bl
+; CHECK-NEXT:    je .LBB0_3
+; CHECK-NEXT:  # %bb.4: # %if.end
+; CHECK-NEXT:    # in Loop: Header=BB0_1 Depth=1
+; CHECK-NEXT:    movl %edx, %ebp
+; CHECK-NEXT:    movl %esi, %ecx
+; CHECK-NEXT:    movl %esi, %eax
+; CHECK-NEXT:    cltd
+; CHECK-NEXT:    idivl a
+; CHECK-NEXT:    movl %eax, %esi
+; CHECK-NEXT:    movb {{[-0-9]+}}(%e{{[sb]}}p), %al # 1-byte Reload
+; CHECK-NEXT:    # kill: def $cl killed $cl killed $ecx
+; CHECK-NEXT:    movl $0, h
+; CHECK-NEXT:    cmpb $8, %al
+; CHECK-NEXT:    jg .LBB0_8
+; CHECK-NEXT:  # %bb.5: # %if.then13
+; CHECK-NEXT:    # in Loop: Header=BB0_1 Depth=1
+; CHECK-NEXT:    movl $.str, (%esp)
+; CHECK-NEXT:    movb %cl, {{[-0-9]+}}(%e{{[sb]}}p) # 1-byte Spill
+; CHECK-NEXT:    calll printf
+; CHECK-NEXT:    movb {{[-0-9]+}}(%e{{[sb]}}p), %cl # 1-byte Reload
+; CHECK-NEXT:    testb %bl, %bl
+; CHECK-NEXT:    # implicit-def: $eax
+; CHECK-NEXT:    movb {{[-0-9]+}}(%e{{[sb]}}p), %ch # 1-byte Reload
+; CHECK-NEXT:    movb %cl, {{[-0-9]+}}(%e{{[sb]}}p) # 1-byte Spill
+; CHECK-NEXT:    movl %ebp, %edx
+; CHECK-NEXT:    jne .LBB0_16
+; CHECK-NEXT:    .p2align 4, 0x90
+; CHECK-NEXT:  # %bb.6: # %for.cond35
+; CHECK-NEXT:    # in Loop: Header=BB0_1 Depth=1
+; CHECK-NEXT:    testl %edi, %edi
+; CHECK-NEXT:    je .LBB0_7
+; CHECK-NEXT:  .LBB0_11: # %af
+; CHECK-NEXT:    # in Loop: Header=BB0_1 Depth=1
+; CHECK-NEXT:    testb %bl, %bl
+; CHECK-NEXT:    jne .LBB0_12
+; CHECK-NEXT:  .LBB0_17: # %if.end39
+; CHECK-NEXT:    # in Loop: Header=BB0_1 Depth=1
+; CHECK-NEXT:    testl %eax, %eax
+; CHECK-NEXT:    je .LBB0_19
+; CHECK-NEXT:  # %bb.18: # %if.then41
+; CHECK-NEXT:    # in Loop: Header=BB0_1 Depth=1
+; CHECK-NEXT:    movl $0, {{[0-9]+}}(%esp)
+; CHECK-NEXT:    movl $fn, {{[0-9]+}}(%esp)
+; CHECK-NEXT:    movl $.str, (%esp)
+; CHECK-NEXT:    calll printf
+; CHECK-NEXT:  .LBB0_19: # %for.end46
+; CHECK-NEXT:    # in Loop: Header=BB0_1 Depth=1
+; CHECK-NEXT:    # implicit-def: $ch
+; CHECK-NEXT:    # implicit-def: $cl
+; CHECK-NEXT:    # implicit-def: $edx
+; CHECK-NEXT:    jmp .LBB0_20
+; CHECK-NEXT:    .p2align 4, 0x90
+; CHECK-NEXT:  .LBB0_3: # %if.then
+; CHECK-NEXT:    # in Loop: Header=BB0_1 Depth=1
+; CHECK-NEXT:    movl $.str, (%esp)
+; CHECK-NEXT:    movl %edx, %esi
+; CHECK-NEXT:    movb %ah, {{[-0-9]+}}(%e{{[sb]}}p) # 1-byte Spill
+; CHECK-NEXT:    calll printf
+; CHECK-NEXT:    movb {{[-0-9]+}}(%e{{[sb]}}p), %ch # 1-byte Reload
+; CHECK-NEXT:    movl %esi, %edx
+; CHECK-NEXT:    # implicit-def: $eax
+; CHECK-NEXT:    testl %edi, %edi
+; CHECK-NEXT:    jne .LBB0_11
+; CHECK-NEXT:    jmp .LBB0_7
+; CHECK-NEXT:    .p2align 4, 0x90
+; CHECK-NEXT:  .LBB0_8: # %if.end21
+; CHECK-NEXT:    # in Loop: Header=BB0_1 Depth=1
+; CHECK-NEXT:    # implicit-def: $edx
+; CHECK-NEXT:    testb %bl, %bl
+; CHECK-NEXT:    je .LBB0_13
+; CHECK-NEXT:    .p2align 4, 0x90
+; CHECK-NEXT:  .LBB0_10: # in Loop: Header=BB0_1 Depth=1
+; CHECK-NEXT:    # implicit-def: $eax
+; CHECK-NEXT:    testb %bl, %bl
+; CHECK-NEXT:    je .LBB0_17
+; CHECK-NEXT:  .LBB0_12: # in Loop: Header=BB0_1 Depth=1
+; CHECK-NEXT:    # implicit-def: $edi
+; CHECK-NEXT:    # implicit-def: $ch
+; CHECK-NEXT:    # implicit-def: $cl
+; CHECK-NEXT:    # kill: killed $cl
+; CHECK-NEXT:    # implicit-def: $edx
+; CHECK-NEXT:    testl %edi, %edi
+; CHECK-NEXT:    jne .LBB0_11
+; CHECK-NEXT:  .LBB0_7: # in Loop: Header=BB0_1 Depth=1
+; CHECK-NEXT:    xorl %edi, %edi
+; CHECK-NEXT:    movb {{[-0-9]+}}(%e{{[sb]}}p), %cl # 1-byte Reload
+; CHECK-NEXT:    .p2align 4, 0x90
+; CHECK-NEXT:  .LBB0_20: # %for.cond47
+; CHECK-NEXT:    # Parent Loop BB0_1 Depth=1
+; CHECK-NEXT:    # => This Inner Loop Header: Depth=2
+; CHECK-NEXT:    testb %bl, %bl
+; CHECK-NEXT:    jne .LBB0_20
+; CHECK-NEXT:  # %bb.21: # %for.cond47
+; CHECK-NEXT:    # in Loop: Header=BB0_20 Depth=2
+; CHECK-NEXT:    testb %bl, %bl
+; CHECK-NEXT:    jne .LBB0_20
+; CHECK-NEXT:  # %bb.22: # in Loop: Header=BB0_1 Depth=1
+; CHECK-NEXT:    movb %ch, %al
+; CHECK-NEXT:    testb %bl, %bl
+; CHECK-NEXT:    jne .LBB0_10
+; CHECK-NEXT:  .LBB0_13: # %if.end26
+; CHECK-NEXT:    # in Loop: Header=BB0_1 Depth=1
+; CHECK-NEXT:    xorl %esi, %esi
+; CHECK-NEXT:    testb %al, %al
+; CHECK-NEXT:    movb %al, {{[-0-9]+}}(%e{{[sb]}}p) # 1-byte Spill
+; CHECK-NEXT:    je .LBB0_16
+; CHECK-NEXT:  # %bb.14: # %if.end26
+; CHECK-NEXT:    # in Loop: Header=BB0_1 Depth=1
+; CHECK-NEXT:    testl %edx, %edx
+; CHECK-NEXT:    jne .LBB0_16
+; CHECK-NEXT:  # %bb.15: # %if.then31
+; CHECK-NEXT:    # in Loop: Header=BB0_1 Depth=1
+; CHECK-NEXT:    xorl %esi, %esi
+; CHECK-NEXT:    xorl %edx, %edx
+; CHECK-NEXT:    jmp .LBB0_16
+entry:
+  br label %for.cond
+
+for.cond:                                         ; preds = %for.inc, %entry
+  %l.0 = phi i16 [ undef, %entry ], [ 0, %for.inc ]
+  %m.0 = phi i32 [ undef, %entry ], [ %m.2, %for.inc ]
+  %i.0 = phi i32 [ undef, %entry ], [ %i.2, %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 ]
+  %cmp = icmp ugt i8 %k.0, 8
+  %or.cond61 = or i1 %cmp, undef
+  br i1 %or.cond61, label %if.then, label %if.end
+
+if.then:                                          ; preds = %for.cond
+  tail call void (i8*, ...) @printf(i8* getelementptr inbounds ([6 x i8], [6 x i8]* @.str, i32 0, i32 0), i64 undef)
+  br label %for.cond35
+
+if.end:                                           ; preds = %for.cond
+  %0 = load i32, i32* @a, align 4
+  %div = sdiv i32 %m.0, %0
+  br label %ac
+
+ac:                                               ; preds = %ac, %if.end
+  br i1 undef, 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
+  %cmp11 = icmp slt i8 %k.0, 9
+  br i1 %cmp11, label %if.then13, label %if.end21
+
+if.then13:                                        ; preds = %if.end9
+  tail call void (i8*, ...) @printf(i8* getelementptr inbounds ([6 x i8], [6 x i8]* @.str, i32 0, i32 0), i64 undef)
+  br i1 undef, label %for.inc, label %for.cond35
+
+if.end21:                                         ; preds = %if.end9
+  %1 = load i8, i8* @g, align 1
+  br label %ae
+
+ae:                                               ; preds = %for.cond47, %if.end21
+  %l.2 = phi i16 [ undef, %if.end21 ], [ 0, %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 [ undef, %if.end21 ], [ %q.5, %for.cond47 ]
+  br i1 undef, 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
+  br label %for.inc
+
+for.inc:                                          ; preds = %if.then31, %if.end26, %if.then13
+  %m.2 = phi i32 [ 0, %if.then31 ], [ 0, %if.end26 ], [ %div, %if.then13 ]
+  %i.2 = phi i32 [ %i.1, %if.then31 ], [ %i.1, %if.end26 ], [ %i.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 ]
+  %2 = load i32, i32* @h, align 4
+  br label %for.cond
+
+for.cond35:                                       ; preds = %for.inc44, %if.then13, %if.then
+  %i.3 = phi i32 [ undef, %for.inc44 ], [ %i.0, %if.then ], [ %i.0, %if.then13 ]
+  %o.2 = phi i32 [ %o.3, %for.inc44 ], [ undef, %if.then ], [ undef, %if.then13 ]
+  %p.4 = phi i8 [ undef, %for.inc44 ], [ %p.0, %if.then ], [ %k.0, %if.then13 ]
+  %k.4 = phi i8 [ undef, %for.inc44 ], [ %k.0, %if.then ], [ %conv3, %if.then13 ]
+  %q.3 = phi i32 [ undef, %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
+  %i.4 = phi i32 [ %i.3, %for.cond35 ], [ %i.1, %ae ]
+  %o.3 = phi i32 [ %o.2, %for.cond35 ], [ undef, %ae ]
+  br i1 undef, 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
+  tail call void (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
+  br label %for.cond35
+
+for.end46:                                        ; preds = %if.then41, %if.end39, %for.cond35
+  %i.5 = phi i32 [ %i.4, %if.then41 ], [ %i.4, %if.end39 ], [ 0, %for.cond35 ]
+  %p.6 = phi i8 [ undef, %if.then41 ], [ undef, %if.end39 ], [ %p.4, %for.cond35 ]
+  %k.6 = phi i8 [ undef, %if.then41 ], [ undef, %if.end39 ], [ %k.4, %for.cond35 ]
+  %q.5 = phi i32 [ undef, %if.then41 ], [ undef, %if.end39 ], [ %q.3, %for.cond35 ]
+  br label %for.cond47
+
+for.cond47:                                       ; preds = %for.cond47, %for.end46
+  %brmerge = or i1 false, undef
+  br i1 %brmerge, label %for.cond47, label %ae
+}
+
+declare dso_local void @printf(i8* nocapture readonly, ...) local_unnamed_addr