diff --git a/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp b/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
--- a/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
@@ -5579,16 +5579,23 @@
                         << "\n");
       return;
     }
-    // Bail out if we have a PHI on an EHPad that gets a value from a
-    // CatchSwitchInst.  Because the CatchSwitchInst cannot be split, there is
-    // no good place to stick any instructions.
+
     if (auto *PN = dyn_cast<PHINode>(U.getUser())) {
        auto *FirstNonPHI = PN->getParent()->getFirstNonPHI();
        if (isa<FuncletPadInst>(FirstNonPHI) ||
            isa<CatchSwitchInst>(FirstNonPHI))
+         // Bail out if we have a PHI on an EHPad that gets a value from a
+         // CatchSwitchInst. Because the CatchSwitchInst cannot be split, there
+         // is no good place to stick any instructions.
          for (BasicBlock *PredBB : PN->blocks())
            if (isa<CatchSwitchInst>(PredBB->getFirstNonPHI()))
              return;
+
+       // Also bail out if we have a PHI with a value from a block ending in a
+       // CallBrInst, because those also can't be split for similar reasons.
+       for (BasicBlock *PredBB : PN->blocks())
+         if (isa<CallBrInst>(PredBB->getTerminator()))
+           return;
     }
   }
 
diff --git a/llvm/test/CodeGen/Generic/callbr-critical-edge-splitting.ll b/llvm/test/CodeGen/Generic/callbr-critical-edge-splitting.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/CodeGen/Generic/callbr-critical-edge-splitting.ll
@@ -0,0 +1,231 @@
+; RUN: llc < %s -o /dev/null
+
+; Test that we don't try to break a critical edge to a block ending in a callbr
+; instruction. See https://github.com/ClangBuiltLinux/linux/issues/1252
+
+source_filename = "test.c"
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+$__llvm_profile_raw_version = comdat any
+
+$__llvm_profile_filename = comdat any
+
+@rdrand_int_ok = dso_local local_unnamed_addr global i32 0, align 4
+@random_ioctl_cmd = dso_local local_unnamed_addr global i32 0, align 4
+@random_ioctl_b = dso_local local_unnamed_addr global i32 0, align 4
+@random_ioctl_bytes = dso_local local_unnamed_addr global i32 0, align 4
+@write_pool_count = dso_local local_unnamed_addr global i32 0, align 4
+@__llvm_profile_raw_version = local_unnamed_addr constant i64 72057594037927941, comdat
+@__profc__static_cpu_has = private global [3 x i64] zeroinitializer, section "__llvm_prf_cnts", align 8
+@__profd__static_cpu_has = private global { i64, i64, i64*, i8*, i8*, i32, [2 x i16] } { i64 1706648762473371179, i64 1063705160746808702, i64* getelementptr inbounds ([3 x i64], [3 x i64]* @__profc__static_cpu_has, i32 0, i32 0), i8* bitcast (i1 ()* @_static_cpu_has to i8*), i8* null, i32 3, [2 x i16] zeroinitializer }, section "__llvm_prf_data", align 8
+@__profc_rdrand_int = private global [3 x i64] zeroinitializer, section "__llvm_prf_cnts", align 8
+@__profd_rdrand_int = private global { i64, i64, i64*, i8*, i8*, i32, [2 x i16] } { i64 -6327555252135034333, i64 1063705159444028162, i64* getelementptr inbounds ([3 x i64], [3 x i64]* @__profc_rdrand_int, i32 0, i32 0), i8* bitcast (i32 ()* @rdrand_int to i8*), i8* null, i32 3, [2 x i16] zeroinitializer }, section "__llvm_prf_data", align 8
+@__profc_arch_get_random_int = private global [5 x i64] zeroinitializer, section "__llvm_prf_cnts", align 8
+@__profd_arch_get_random_int = private global { i64, i64, i64*, i8*, i8*, i32, [2 x i16] } { i64 -8914602053785216465, i64 798733566790625302, i64* getelementptr inbounds ([5 x i64], [5 x i64]* @__profc_arch_get_random_int, i32 0, i32 0), i8* bitcast (i1 ()* @arch_get_random_int to i8*), i8* null, i32 5, [2 x i16] zeroinitializer }, section "__llvm_prf_data", align 8
+@__profc_random_ioctl = private global [6 x i64] zeroinitializer, section "__llvm_prf_cnts", align 8
+@__profd_random_ioctl = private global { i64, i64, i64*, i8*, i8*, i32, [2 x i16] } { i64 -1609339618991391358, i64 694937220162189167, i64* getelementptr inbounds ([6 x i64], [6 x i64]* @__profc_random_ioctl, i32 0, i32 0), i8* bitcast (i32 ()* @random_ioctl to i8*), i8* null, i32 6, [2 x i16] zeroinitializer }, section "__llvm_prf_data", align 8
+@__llvm_prf_nm = private constant [56 x i8] c";6x\DA5\C8\C9\09\00 \0C\04@\ACt\09Q\8C\E0E\\\FB\17\05\7F\C3`QX\14:7LV\F0\E8\D2#Jg\10WCN\C4\9D\D1\DE}\0Ee=\B2\EC\17\14", section "__llvm_prf_names", align 1
+@__llvm_profile_filename = local_unnamed_addr constant [19 x i8] c"default_%m.profraw\00", comdat
+@llvm.used = appending global [5 x i8*] [i8* getelementptr inbounds ([56 x i8], [56 x i8]* @__llvm_prf_nm, i32 0, i32 0), i8* bitcast ({ i64, i64, i64*, i8*, i8*, i32, [2 x i16] }* @__profd__static_cpu_has to i8*), i8* bitcast ({ i64, i64, i64*, i8*, i8*, i32, [2 x i16] }* @__profd_arch_get_random_int to i8*), i8* bitcast ({ i64, i64, i64*, i8*, i8*, i32, [2 x i16] }* @__profd_random_ioctl to i8*), i8* bitcast ({ i64, i64, i64*, i8*, i8*, i32, [2 x i16] }* @__profd_rdrand_int to i8*)], section "llvm.metadata"
+
+define dso_local zeroext i1 @_static_cpu_has() {
+entry:
+  %pgocount = load i64, i64* getelementptr inbounds ([3 x i64], [3 x i64]* @__profc__static_cpu_has, i64 0, i64 0), align 8
+  %0 = add i64 %pgocount, 1
+  store i64 %0, i64* getelementptr inbounds ([3 x i64], [3 x i64]* @__profc__static_cpu_has, i64 0, i64 0), align 8
+  callbr void asm sideeffect "", "X,X,~{dirflag},~{fpsr},~{flags}"(i8* blockaddress(@_static_cpu_has, %return), i8* blockaddress(@_static_cpu_has, %t_no))
+          to label %asm.fallthrough [label %return, label %t_no]
+
+asm.fallthrough:                                  ; preds = %entry
+  %pgocount1 = load i64, i64* getelementptr inbounds ([3 x i64], [3 x i64]* @__profc__static_cpu_has, i64 0, i64 2), align 8
+  %1 = add i64 %pgocount1, 1
+  store i64 %1, i64* getelementptr inbounds ([3 x i64], [3 x i64]* @__profc__static_cpu_has, i64 0, i64 2), align 8
+  br label %return
+
+t_no:                                             ; preds = %entry
+  %pgocount2 = load i64, i64* getelementptr inbounds ([3 x i64], [3 x i64]* @__profc__static_cpu_has, i64 0, i64 1), align 8
+  %2 = add i64 %pgocount2, 1
+  store i64 %2, i64* getelementptr inbounds ([3 x i64], [3 x i64]* @__profc__static_cpu_has, i64 0, i64 1), align 8
+  br label %return
+
+return:                                           ; preds = %entry, %asm.fallthrough, %t_no
+  %retval.0 = phi i1 [ false, %t_no ], [ true, %asm.fallthrough ], [ true, %entry ]
+  ret i1 %retval.0
+}
+
+define dso_local i32 @rdrand_int() local_unnamed_addr {
+entry:
+  %pgocount = load i64, i64* getelementptr inbounds ([3 x i64], [3 x i64]* @__profc_rdrand_int, i64 0, i64 2), align 8
+  %0 = add i64 %pgocount, 1
+  store i64 %0, i64* getelementptr inbounds ([3 x i64], [3 x i64]* @__profc_rdrand_int, i64 0, i64 2), align 8
+  br label %do.body
+
+do.body:                                          ; preds = %do.cond, %entry
+  %pgocount24 = phi i64 [ 0, %entry ], [ %2, %do.cond ]
+  %retry.0 = phi i32 [ 0, %entry ], [ %dec, %do.cond ]
+  tail call void asm sideeffect "", "~{dirflag},~{fpsr},~{flags}"()
+  %1 = load i32, i32* @rdrand_int_ok, align 4
+  %tobool.not = icmp eq i32 %1, 0
+  br i1 %tobool.not, label %do.cond, label %cleanup
+
+do.cond:                                          ; preds = %do.body
+  %2 = add nuw nsw i64 %pgocount24, 1
+  %dec = add i32 %retry.0, -1
+  %tobool1.not = icmp eq i32 %dec, 0
+  br i1 %tobool1.not, label %do.cond.cleanup_crit_edge, label %do.body
+
+do.cond.cleanup_crit_edge:                        ; preds = %do.cond
+  %pgocount.promoted5 = load i64, i64* getelementptr inbounds ([3 x i64], [3 x i64]* @__profc_rdrand_int, i64 0, i64 1), align 8
+  %3 = add i64 %pgocount.promoted5, 4294967296
+  store i64 %3, i64* getelementptr inbounds ([3 x i64], [3 x i64]* @__profc_rdrand_int, i64 0, i64 1), align 8
+  br label %cleanup
+
+cleanup:                                          ; preds = %do.body, %do.cond.cleanup_crit_edge
+  %.sink = phi i64* [ getelementptr inbounds ([3 x i64], [3 x i64]* @__profc_rdrand_int, i64 0, i64 0), %do.cond.cleanup_crit_edge ], [ getelementptr inbounds ([3 x i64], [3 x i64]* @__profc_rdrand_int, i64 0, i64 1), %do.body ]
+  %pgocount24.sink = phi i64 [ 1, %do.cond.cleanup_crit_edge ], [ %pgocount24, %do.body ]
+  %retval.0 = phi i32 [ 0, %do.cond.cleanup_crit_edge ], [ 1, %do.body ]
+  %pgocount.promoted = load i64, i64* %.sink, align 8
+  %4 = add i64 %pgocount.promoted, %pgocount24.sink
+  store i64 %4, i64* %.sink, align 8
+  ret i32 %retval.0
+}
+
+define dso_local zeroext i1 @arch_get_random_int() local_unnamed_addr {
+entry:
+  %pgocount = load i64, i64* getelementptr inbounds ([5 x i64], [5 x i64]* @__profc_arch_get_random_int, i64 0, i64 2), align 8
+  %0 = add i64 %pgocount, 1
+  store i64 %0, i64* getelementptr inbounds ([5 x i64], [5 x i64]* @__profc_arch_get_random_int, i64 0, i64 2), align 8
+  callbr void asm sideeffect "", "X,X,~{dirflag},~{fpsr},~{flags}"(i8* blockaddress(@arch_get_random_int, %do.body.i), i8* blockaddress(@arch_get_random_int, %cond.end))
+          to label %asm.fallthrough.i [label %do.body.i, label %cond.end]
+
+asm.fallthrough.i:                                ; preds = %entry
+  %pgocount4 = load i64, i64* getelementptr inbounds ([5 x i64], [5 x i64]* @__profc_arch_get_random_int, i64 0, i64 4), align 8
+  %1 = add i64 %pgocount4, 1
+  store i64 %1, i64* getelementptr inbounds ([5 x i64], [5 x i64]* @__profc_arch_get_random_int, i64 0, i64 4), align 8
+  br label %do.body.i
+
+do.body.i:                                        ; preds = %entry, %asm.fallthrough.i, %do.cond.i
+  %pgocount58 = phi i64 [ %3, %do.cond.i ], [ 0, %asm.fallthrough.i ], [ 0, %entry ]
+  %retry.0.i = phi i32 [ %dec.i, %do.cond.i ], [ 0, %asm.fallthrough.i ], [ 0, %entry ]
+  tail call void asm sideeffect "", "~{dirflag},~{fpsr},~{flags}"()
+  %2 = load i32, i32* @rdrand_int_ok, align 4
+  %tobool.not.i = icmp eq i32 %2, 0
+  br i1 %tobool.not.i, label %do.cond.i, label %rdrand_int.exit
+
+do.cond.i:                                        ; preds = %do.body.i
+  %3 = add nuw nsw i64 %pgocount58, 1
+  %dec.i = add i32 %retry.0.i, -1
+  %tobool1.not.i = icmp eq i32 %dec.i, 0
+  br i1 %tobool1.not.i, label %do.cond.i.rdrand_int.exit_crit_edge, label %do.body.i
+
+do.cond.i.rdrand_int.exit_crit_edge:              ; preds = %do.cond.i
+  %pgocount.promoted9 = load i64, i64* getelementptr inbounds ([5 x i64], [5 x i64]* @__profc_arch_get_random_int, i64 0, i64 1), align 8
+  %4 = add i64 %pgocount.promoted9, 4294967296
+  store i64 %4, i64* getelementptr inbounds ([5 x i64], [5 x i64]* @__profc_arch_get_random_int, i64 0, i64 1), align 8
+  br label %rdrand_int.exit
+
+rdrand_int.exit:                                  ; preds = %do.body.i, %do.cond.i.rdrand_int.exit_crit_edge
+  %.sink = phi i64* [ getelementptr inbounds ([5 x i64], [5 x i64]* @__profc_arch_get_random_int, i64 0, i64 0), %do.cond.i.rdrand_int.exit_crit_edge ], [ getelementptr inbounds ([5 x i64], [5 x i64]* @__profc_arch_get_random_int, i64 0, i64 1), %do.body.i ]
+  %pgocount58.sink = phi i64 [ 1, %do.cond.i.rdrand_int.exit_crit_edge ], [ %pgocount58, %do.body.i ]
+  %pgocount.promoted = load i64, i64* %.sink, align 8
+  %5 = add i64 %pgocount.promoted, %pgocount58.sink
+  store i64 %5, i64* %.sink, align 8
+  %pgocount7 = load i64, i64* getelementptr inbounds ([5 x i64], [5 x i64]* @__profc_arch_get_random_int, i64 0, i64 3), align 8
+  %6 = add i64 %pgocount7, 1
+  store i64 %6, i64* getelementptr inbounds ([5 x i64], [5 x i64]* @__profc_arch_get_random_int, i64 0, i64 3), align 8
+  %7 = xor i1 %tobool.not.i, true
+  br label %cond.end
+
+cond.end:                                         ; preds = %entry, %rdrand_int.exit
+  %cond = phi i1 [ %7, %rdrand_int.exit ], [ false, %entry ]
+  ret i1 %cond
+}
+
+define dso_local i32 @random_ioctl() local_unnamed_addr {
+entry:
+  %pgocount = load i64, i64* getelementptr inbounds ([6 x i64], [6 x i64]* @__profc_random_ioctl, i64 0, i64 4), align 8
+  %0 = add i64 %pgocount, 1
+  store i64 %0, i64* getelementptr inbounds ([6 x i64], [6 x i64]* @__profc_random_ioctl, i64 0, i64 4), align 8
+  %1 = load i32, i32* @random_ioctl_cmd, align 4
+  %cond = icmp eq i32 %1, 0
+  br i1 %cond, label %for.cond, label %sw.epilog
+
+for.cond:                                         ; preds = %entry, %for.inc
+  %pgocount.promoted23 = phi i64 [ %pgocount.promoted2226, %for.inc ], [ 0, %entry ]
+  %pgocount919 = phi i64 [ %10, %for.inc ], [ 0, %entry ]
+  %pgocount816 = phi i64 [ %9, %for.inc ], [ 0, %entry ]
+  %pgocount613 = phi i64 [ %pgocount612, %for.inc ], [ 0, %entry ]
+  callbr void asm sideeffect "", "X,X,~{dirflag},~{fpsr},~{flags}"(i8* blockaddress(@random_ioctl, %cond.true.i), i8* blockaddress(@random_ioctl, %for.end))
+          to label %asm.fallthrough.i.i [label %cond.true.i, label %for.end]
+
+asm.fallthrough.i.i:                              ; preds = %for.cond
+  %2 = add i64 %pgocount613, 1
+  br label %cond.true.i
+
+cond.true.i:                                      ; preds = %asm.fallthrough.i.i, %for.cond
+  %pgocount612 = phi i64 [ %2, %asm.fallthrough.i.i ], [ %pgocount613, %for.cond ]
+  tail call void asm sideeffect "", "~{dirflag},~{fpsr},~{flags}"()
+  %3 = load i32, i32* @rdrand_int_ok, align 4
+  %tobool.not.i.i2 = icmp eq i32 %3, 0
+  br i1 %tobool.not.i.i2, label %do.body.i.i.do.body.i.i_crit_edge, label %arch_get_random_int.exit
+
+do.body.i.i.do.body.i.i_crit_edge:                ; preds = %cond.true.i, %do.body.i.i.do.body.i.i_crit_edge
+  %pgocount711 = phi i64 [ %4, %do.body.i.i.do.body.i.i_crit_edge ], [ 0, %cond.true.i ]
+  %dec.i.i5 = phi i32 [ %dec.i.i, %do.body.i.i.do.body.i.i_crit_edge ], [ -1, %cond.true.i ]
+  %4 = add nuw nsw i64 %pgocount711, 1
+  tail call void asm sideeffect "", "~{dirflag},~{fpsr},~{flags}"()
+  %5 = load i32, i32* @rdrand_int_ok, align 4
+  %tobool.not.i.i = icmp eq i32 %5, 0
+  %tobool.not.i.i.not = xor i1 %tobool.not.i.i, true
+  %dec.i.i = add i32 %dec.i.i5, -1
+  %tobool1.not.i.i = icmp eq i32 %dec.i.i, 0
+  %or.cond = or i1 %tobool1.not.i.i, %tobool.not.i.i.not
+  br i1 %or.cond, label %do.body.i.i.rdrand_int.exit.i_crit_edge, label %do.body.i.i.do.body.i.i_crit_edge
+
+do.body.i.i.rdrand_int.exit.i_crit_edge:          ; preds = %do.body.i.i.do.body.i.i_crit_edge
+  %6 = add i64 %4, %pgocount.promoted23
+  %7 = add i64 %pgocount816, 1
+  br i1 %tobool.not.i.i, label %for.end, label %for.inc
+
+arch_get_random_int.exit:                         ; preds = %cond.true.i
+  %8 = add i64 %pgocount816, 1
+  br label %for.inc
+
+for.inc:                                          ; preds = %arch_get_random_int.exit, %do.body.i.i.rdrand_int.exit.i_crit_edge
+  %9 = phi i64 [ %7, %do.body.i.i.rdrand_int.exit.i_crit_edge ], [ %8, %arch_get_random_int.exit ]
+  %pgocount.promoted2226 = phi i64 [ %6, %do.body.i.i.rdrand_int.exit.i_crit_edge ], [ %pgocount.promoted23, %arch_get_random_int.exit ]
+  %10 = add i64 %pgocount919, 1
+  %11 = load i32, i32* @random_ioctl_b, align 4
+  %sub = add i32 %11, -4
+  store i32 %sub, i32* @random_ioctl_b, align 4
+  br label %for.cond
+
+for.end:                                          ; preds = %do.body.i.i.rdrand_int.exit.i_crit_edge, %for.cond
+  %pgocount.promoted24 = phi i64 [ %pgocount.promoted23, %for.cond ], [ %6, %do.body.i.i.rdrand_int.exit.i_crit_edge ]
+  %pgocount817 = phi i64 [ %pgocount816, %for.cond ], [ %7, %do.body.i.i.rdrand_int.exit.i_crit_edge ]
+  %pgocount614 = phi i64 [ %pgocount613, %for.cond ], [ %pgocount612, %do.body.i.i.rdrand_int.exit.i_crit_edge ]
+  %pgocount.promoted15 = load i64, i64* getelementptr inbounds ([6 x i64], [6 x i64]* @__profc_random_ioctl, i64 0, i64 3), align 8
+  %12 = add i64 %pgocount.promoted15, %pgocount614
+  store i64 %12, i64* getelementptr inbounds ([6 x i64], [6 x i64]* @__profc_random_ioctl, i64 0, i64 3), align 8
+  %pgocount.promoted18 = load i64, i64* getelementptr inbounds ([6 x i64], [6 x i64]* @__profc_random_ioctl, i64 0, i64 1), align 8
+  %13 = add i64 %pgocount.promoted18, %pgocount817
+  store i64 %13, i64* getelementptr inbounds ([6 x i64], [6 x i64]* @__profc_random_ioctl, i64 0, i64 1), align 8
+  %pgocount.promoted21 = load i64, i64* getelementptr inbounds ([6 x i64], [6 x i64]* @__profc_random_ioctl, i64 0, i64 2), align 8
+  %14 = add i64 %pgocount.promoted21, %pgocount919
+  store i64 %14, i64* getelementptr inbounds ([6 x i64], [6 x i64]* @__profc_random_ioctl, i64 0, i64 2), align 8
+  %pgocount.promoted25 = load i64, i64* getelementptr inbounds ([6 x i64], [6 x i64]* @__profc_random_ioctl, i64 0, i64 0), align 8
+  %15 = add i64 %pgocount.promoted25, %pgocount.promoted24
+  store i64 %15, i64* getelementptr inbounds ([6 x i64], [6 x i64]* @__profc_random_ioctl, i64 0, i64 0), align 8
+  %pgocount10 = load i64, i64* getelementptr inbounds ([6 x i64], [6 x i64]* @__profc_random_ioctl, i64 0, i64 5), align 8
+  %16 = add i64 %pgocount10, 1
+  store i64 %16, i64* getelementptr inbounds ([6 x i64], [6 x i64]* @__profc_random_ioctl, i64 0, i64 5), align 8
+  %17 = load i32, i32* @random_ioctl_bytes, align 4
+  %18 = load i32, i32* @write_pool_count, align 4
+  %sub2 = sub i32 %18, %17
+  store i32 %sub2, i32* @write_pool_count, align 4
+  br label %sw.epilog
+
+sw.epilog:                                        ; preds = %entry, %for.end
+  ret i32 undef
+}