Index: llvm/trunk/test/Transforms/LoopVectorize/pr43166-fold-tail-by-masking.ll
===================================================================
--- llvm/trunk/test/Transforms/LoopVectorize/pr43166-fold-tail-by-masking.ll
+++ llvm/trunk/test/Transforms/LoopVectorize/pr43166-fold-tail-by-masking.ll
@@ -0,0 +1,235 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -loop-vectorize -force-vector-width=4 -S | FileCheck %s
+
+
+; Test cases below are reduced (and slightly modified) reproducers based on a
+; problem seen when compiling a C program like this:
+;
+;    #include <stdint.h>
+;    #include <stdio.h>
+;
+;    int y = 0;
+;    int b = 1;
+;    int d = 1;
+;
+;    int main() {
+;      #pragma clang loop vectorize_width(4)
+;      for (int i = 0; i < 3; ++i) {
+;        b = (y == 0) ? d : (d / y);
+;      }
+;
+;      if (b == 1)
+;        printf("GOOD!\n");
+;      else
+;        printf("BAD!\n");
+;    }
+;
+; When compiled+executed using
+;    build-all/bin/clang -O1 lv-bug.c && ./a.out
+; the result is "GOOD!"
+;
+; When compiled+executed using
+;    build-all/bin/clang -O1 lv-bug.c -fvectorize && ./a.out
+; the result is "BAD!"
+
+
+; FIXME: The result here is incorrect! See https://bugs.llvm.org/show_bug.cgi?id=43166
+define i64 @test1(i64 %y) {
+; CHECK-LABEL: @test1(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br i1 false, label [[SCALAR_PH:%.*]], label [[VECTOR_PH:%.*]]
+; CHECK:       vector.ph:
+; CHECK-NEXT:    [[BROADCAST_SPLATINSERT1:%.*]] = insertelement <4 x i64> undef, i64 [[Y:%.*]], i32 0
+; CHECK-NEXT:    [[BROADCAST_SPLAT2:%.*]] = shufflevector <4 x i64> [[BROADCAST_SPLATINSERT1]], <4 x i64> undef, <4 x i32> zeroinitializer
+; CHECK-NEXT:    br label [[VECTOR_BODY:%.*]]
+; CHECK:       vector.body:
+; CHECK-NEXT:    [[INDEX:%.*]] = phi i32 [ 0, [[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], [[VECTOR_BODY]] ]
+; CHECK-NEXT:    [[BROADCAST_SPLATINSERT:%.*]] = insertelement <4 x i32> undef, i32 [[INDEX]], i32 0
+; CHECK-NEXT:    [[BROADCAST_SPLAT:%.*]] = shufflevector <4 x i32> [[BROADCAST_SPLATINSERT]], <4 x i32> undef, <4 x i32> zeroinitializer
+; CHECK-NEXT:    [[INDUCTION:%.*]] = add <4 x i32> [[BROADCAST_SPLAT]], <i32 0, i32 1, i32 2, i32 3>
+; CHECK-NEXT:    [[TMP0:%.*]] = add i32 [[INDEX]], 0
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp eq <4 x i64> [[BROADCAST_SPLAT2]], zeroinitializer
+; CHECK-NEXT:    [[TMP2:%.*]] = xor <4 x i64> <i64 3, i64 3, i64 3, i64 3>, [[BROADCAST_SPLAT2]]
+; CHECK-NEXT:    [[TMP3:%.*]] = icmp ule <4 x i32> [[INDUCTION]], <i32 2, i32 2, i32 2, i32 2>
+; CHECK-NEXT:    [[TMP4:%.*]] = xor <4 x i1> [[TMP1]], <i1 true, i1 true, i1 true, i1 true>
+; CHECK-NEXT:    [[TMP5:%.*]] = and <4 x i1> [[TMP4]], [[TMP3]]
+; CHECK-NEXT:    [[TMP6:%.*]] = and <4 x i1> [[TMP1]], [[TMP3]]
+; CHECK-NEXT:    [[PREDPHI:%.*]] = select <4 x i1> [[TMP6]], <4 x i64> <i64 77, i64 77, i64 77, i64 77>, <4 x i64> [[TMP2]]
+; CHECK-NEXT:    [[INDEX_NEXT]] = add i32 [[INDEX]], 4
+; CHECK-NEXT:    [[TMP7:%.*]] = icmp eq i32 [[INDEX_NEXT]], 4
+; CHECK-NEXT:    br i1 [[TMP7]], label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], !llvm.loop !0
+; CHECK:       middle.block:
+; CHECK-NEXT:    [[TMP8:%.*]] = extractelement <4 x i64> [[PREDPHI]], i32 3
+; CHECK-NEXT:    br i1 true, label [[FOR_COND_CLEANUP:%.*]], label [[SCALAR_PH]]
+; CHECK:       scalar.ph:
+; CHECK-NEXT:    [[BC_RESUME_VAL:%.*]] = phi i32 [ 4, [[MIDDLE_BLOCK]] ], [ 0, [[ENTRY:%.*]] ]
+; CHECK-NEXT:    br label [[FOR_BODY:%.*]]
+; CHECK:       for.body:
+; CHECK-NEXT:    [[I:%.*]] = phi i32 [ [[BC_RESUME_VAL]], [[SCALAR_PH]] ], [ [[INC:%.*]], [[COND_END:%.*]] ]
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i64 [[Y]], 0
+; CHECK-NEXT:    br i1 [[CMP]], label [[COND_END]], label [[COND_FALSE:%.*]]
+; CHECK:       cond.false:
+; CHECK-NEXT:    [[DIV:%.*]] = xor i64 3, [[Y]]
+; CHECK-NEXT:    br label [[COND_END]]
+; CHECK:       cond.end:
+; CHECK-NEXT:    [[COND:%.*]] = phi i64 [ [[DIV]], [[COND_FALSE]] ], [ 77, [[FOR_BODY]] ]
+; CHECK-NEXT:    [[INC]] = add nuw nsw i32 [[I]], 1
+; CHECK-NEXT:    [[EXITCOND:%.*]] = icmp eq i32 [[INC]], 3
+; CHECK-NEXT:    br i1 [[EXITCOND]], label [[FOR_COND_CLEANUP]], label [[FOR_BODY]], !llvm.loop !2
+; CHECK:       for.cond.cleanup:
+; CHECK-NEXT:    [[COND_LCSSA:%.*]] = phi i64 [ [[COND]], [[COND_END]] ], [ [[TMP8]], [[MIDDLE_BLOCK]] ]
+; CHECK-NEXT:    ret i64 [[COND_LCSSA]]
+;
+entry:
+  br label %for.body
+
+for.body:
+  %i = phi i32 [ 0, %entry ], [ %inc, %cond.end ]
+  %cmp = icmp eq i64 %y, 0
+  br i1 %cmp, label %cond.end, label %cond.false
+
+cond.false:
+  %div = xor i64 3, %y
+  br label %cond.end
+
+cond.end:
+  %cond = phi i64 [ %div, %cond.false ], [ 77, %for.body ]
+  %inc = add nuw nsw i32 %i, 1
+  %exitcond = icmp eq i32 %inc, 3
+  br i1 %exitcond, label %for.cond.cleanup, label %for.body
+
+for.cond.cleanup:
+  ret i64 %cond
+}
+
+
+; FIXME: The result here is incorrect! See https://bugs.llvm.org/show_bug.cgi?id=43166
+define i64 @test2(i64 %y) {
+; CHECK-LABEL: @test2(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br i1 false, label [[SCALAR_PH:%.*]], label [[VECTOR_PH:%.*]]
+; CHECK:       vector.ph:
+; CHECK-NEXT:    [[BROADCAST_SPLATINSERT1:%.*]] = insertelement <4 x i64> undef, i64 [[Y:%.*]], i32 0
+; CHECK-NEXT:    [[BROADCAST_SPLAT2:%.*]] = shufflevector <4 x i64> [[BROADCAST_SPLATINSERT1]], <4 x i64> undef, <4 x i32> zeroinitializer
+; CHECK-NEXT:    br label [[VECTOR_BODY:%.*]]
+; CHECK:       vector.body:
+; CHECK-NEXT:    [[INDEX:%.*]] = phi i32 [ 0, [[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], [[VECTOR_BODY]] ]
+; CHECK-NEXT:    [[BROADCAST_SPLATINSERT:%.*]] = insertelement <4 x i32> undef, i32 [[INDEX]], i32 0
+; CHECK-NEXT:    [[BROADCAST_SPLAT:%.*]] = shufflevector <4 x i32> [[BROADCAST_SPLATINSERT]], <4 x i32> undef, <4 x i32> zeroinitializer
+; CHECK-NEXT:    [[INDUCTION:%.*]] = add <4 x i32> [[BROADCAST_SPLAT]], <i32 0, i32 1, i32 2, i32 3>
+; CHECK-NEXT:    [[TMP0:%.*]] = add i32 [[INDEX]], 0
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp eq <4 x i64> [[BROADCAST_SPLAT2]], zeroinitializer
+; CHECK-NEXT:    [[TMP2:%.*]] = icmp ule <4 x i32> [[INDUCTION]], <i32 2, i32 2, i32 2, i32 2>
+; CHECK-NEXT:    [[TMP3:%.*]] = xor <4 x i1> [[TMP1]], <i1 true, i1 true, i1 true, i1 true>
+; CHECK-NEXT:    [[TMP4:%.*]] = and <4 x i1> [[TMP3]], [[TMP2]]
+; CHECK-NEXT:    [[TMP5:%.*]] = and <4 x i1> [[TMP1]], [[TMP2]]
+; CHECK-NEXT:    [[PREDPHI:%.*]] = select <4 x i1> [[TMP5]], <4 x i64> <i64 77, i64 77, i64 77, i64 77>, <4 x i64> <i64 55, i64 55, i64 55, i64 55>
+; CHECK-NEXT:    [[INDEX_NEXT]] = add i32 [[INDEX]], 4
+; CHECK-NEXT:    [[TMP6:%.*]] = icmp eq i32 [[INDEX_NEXT]], 4
+; CHECK-NEXT:    br i1 [[TMP6]], label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], !llvm.loop !4
+; CHECK:       middle.block:
+; CHECK-NEXT:    [[TMP7:%.*]] = extractelement <4 x i64> [[PREDPHI]], i32 3
+; CHECK-NEXT:    br i1 true, label [[FOR_COND_CLEANUP:%.*]], label [[SCALAR_PH]]
+; CHECK:       scalar.ph:
+; CHECK-NEXT:    [[BC_RESUME_VAL:%.*]] = phi i32 [ 4, [[MIDDLE_BLOCK]] ], [ 0, [[ENTRY:%.*]] ]
+; CHECK-NEXT:    br label [[FOR_BODY:%.*]]
+; CHECK:       for.body:
+; CHECK-NEXT:    [[I:%.*]] = phi i32 [ [[BC_RESUME_VAL]], [[SCALAR_PH]] ], [ [[INC:%.*]], [[COND_END:%.*]] ]
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i64 [[Y]], 0
+; CHECK-NEXT:    br i1 [[CMP]], label [[COND_END]], label [[COND_FALSE:%.*]]
+; CHECK:       cond.false:
+; CHECK-NEXT:    br label [[COND_END]]
+; CHECK:       cond.end:
+; CHECK-NEXT:    [[COND:%.*]] = phi i64 [ 55, [[COND_FALSE]] ], [ 77, [[FOR_BODY]] ]
+; CHECK-NEXT:    [[INC]] = add nuw nsw i32 [[I]], 1
+; CHECK-NEXT:    [[EXITCOND:%.*]] = icmp eq i32 [[INC]], 3
+; CHECK-NEXT:    br i1 [[EXITCOND]], label [[FOR_COND_CLEANUP]], label [[FOR_BODY]], !llvm.loop !5
+; CHECK:       for.cond.cleanup:
+; CHECK-NEXT:    [[COND_LCSSA:%.*]] = phi i64 [ [[COND]], [[COND_END]] ], [ [[TMP7]], [[MIDDLE_BLOCK]] ]
+; CHECK-NEXT:    ret i64 [[COND_LCSSA]]
+;
+entry:
+  br label %for.body
+
+for.body:
+  %i = phi i32 [ 0, %entry ], [ %inc, %cond.end ]
+  %cmp = icmp eq i64 %y, 0
+  br i1 %cmp, label %cond.end, label %cond.false
+
+cond.false:
+  br label %cond.end
+
+cond.end:
+  %cond = phi i64 [ 55, %cond.false ], [ 77, %for.body ]
+  %inc = add nuw nsw i32 %i, 1
+  %exitcond = icmp eq i32 %inc, 3
+  br i1 %exitcond, label %for.cond.cleanup, label %for.body
+
+for.cond.cleanup:
+  ret i64 %cond
+}
+
+
+; FIXME: The result here is incorrect! See https://bugs.llvm.org/show_bug.cgi?id=43166
+define i32 @test3(i64 %y) {
+; CHECK-LABEL: @test3(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br i1 false, label [[SCALAR_PH:%.*]], label [[VECTOR_PH:%.*]]
+; CHECK:       vector.ph:
+; CHECK-NEXT:    [[BROADCAST_SPLATINSERT:%.*]] = insertelement <4 x i64> undef, i64 [[Y:%.*]], i32 0
+; CHECK-NEXT:    [[BROADCAST_SPLAT:%.*]] = shufflevector <4 x i64> [[BROADCAST_SPLATINSERT]], <4 x i64> undef, <4 x i32> zeroinitializer
+; CHECK-NEXT:    br label [[VECTOR_BODY:%.*]]
+; CHECK:       vector.body:
+; CHECK-NEXT:    [[INDEX:%.*]] = phi i32 [ 0, [[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], [[VECTOR_BODY]] ]
+; CHECK-NEXT:    [[VEC_IND:%.*]] = phi <4 x i32> [ <i32 0, i32 1, i32 2, i32 3>, [[VECTOR_PH]] ], [ [[VEC_IND_NEXT:%.*]], [[VECTOR_BODY]] ]
+; CHECK-NEXT:    [[TMP0:%.*]] = icmp eq <4 x i64> [[BROADCAST_SPLAT]], zeroinitializer
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp ule <4 x i32> [[VEC_IND]], <i32 2, i32 2, i32 2, i32 2>
+; CHECK-NEXT:    [[TMP2:%.*]] = xor <4 x i1> [[TMP0]], <i1 true, i1 true, i1 true, i1 true>
+; CHECK-NEXT:    [[TMP3:%.*]] = and <4 x i1> [[TMP2]], [[TMP1]]
+; CHECK-NEXT:    [[TMP4:%.*]] = and <4 x i1> [[TMP0]], [[TMP1]]
+; CHECK-NEXT:    [[PREDPHI:%.*]] = select <4 x i1> [[TMP4]], <4 x i32> [[VEC_IND]], <4 x i32> <i32 55, i32 55, i32 55, i32 55>
+; CHECK-NEXT:    [[INDEX_NEXT]] = add i32 [[INDEX]], 4
+; CHECK-NEXT:    [[VEC_IND_NEXT]] = add <4 x i32> [[VEC_IND]], <i32 4, i32 4, i32 4, i32 4>
+; CHECK-NEXT:    [[TMP5:%.*]] = icmp eq i32 [[INDEX_NEXT]], 4
+; CHECK-NEXT:    br i1 [[TMP5]], label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], !llvm.loop !6
+; CHECK:       middle.block:
+; CHECK-NEXT:    [[TMP6:%.*]] = extractelement <4 x i32> [[PREDPHI]], i32 3
+; CHECK-NEXT:    br i1 true, label [[FOR_COND_CLEANUP:%.*]], label [[SCALAR_PH]]
+; CHECK:       scalar.ph:
+; CHECK-NEXT:    [[BC_RESUME_VAL:%.*]] = phi i32 [ 4, [[MIDDLE_BLOCK]] ], [ 0, [[ENTRY:%.*]] ]
+; CHECK-NEXT:    br label [[FOR_BODY:%.*]]
+; CHECK:       for.body:
+; CHECK-NEXT:    [[I:%.*]] = phi i32 [ [[BC_RESUME_VAL]], [[SCALAR_PH]] ], [ [[INC:%.*]], [[COND_END:%.*]] ]
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i64 [[Y]], 0
+; CHECK-NEXT:    br i1 [[CMP]], label [[COND_END]], label [[COND_FALSE:%.*]]
+; CHECK:       cond.false:
+; CHECK-NEXT:    br label [[COND_END]]
+; CHECK:       cond.end:
+; CHECK-NEXT:    [[COND:%.*]] = phi i32 [ 55, [[COND_FALSE]] ], [ [[I]], [[FOR_BODY]] ]
+; CHECK-NEXT:    [[INC]] = add nuw nsw i32 [[I]], 1
+; CHECK-NEXT:    [[EXITCOND:%.*]] = icmp eq i32 [[INC]], 3
+; CHECK-NEXT:    br i1 [[EXITCOND]], label [[FOR_COND_CLEANUP]], label [[FOR_BODY]], !llvm.loop !7
+; CHECK:       for.cond.cleanup:
+; CHECK-NEXT:    [[COND_LCSSA:%.*]] = phi i32 [ [[COND]], [[COND_END]] ], [ [[TMP6]], [[MIDDLE_BLOCK]] ]
+; CHECK-NEXT:    ret i32 [[COND_LCSSA]]
+;
+entry:
+  br label %for.body
+
+for.body:
+  %i = phi i32 [ 0, %entry ], [ %inc, %cond.end ]
+  %cmp = icmp eq i64 %y, 0
+  br i1 %cmp, label %cond.end, label %cond.false
+
+cond.false:
+  br label %cond.end
+
+cond.end:
+  %cond = phi i32 [ 55, %cond.false ], [ %i, %for.body ]
+  %inc = add nuw nsw i32 %i, 1
+  %exitcond = icmp eq i32 %inc, 3
+  br i1 %exitcond, label %for.cond.cleanup, label %for.body
+
+for.cond.cleanup:
+  ret i32 %cond
+}