Index: llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp
===================================================================
--- llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp
+++ llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp
@@ -3967,9 +3967,27 @@
     if (SrcTy != DstTy && TTI.isTruncateFree(SrcTy, DstTy)) {
       Formula F = Base;
 
-      if (F.ScaledReg) F.ScaledReg = SE.getAnyExtendExpr(F.ScaledReg, SrcTy);
-      for (const SCEV *&BaseReg : F.BaseRegs)
-        BaseReg = SE.getAnyExtendExpr(BaseReg, SrcTy);
+      // Sometimes SCEV is able to prove zero during ext transform. It may
+      // happen if SCEV did not do all possible transforms while creating the
+      // initial node (maybe due to depth limitations), but it can do them while
+      // taking ext.
+      if (F.ScaledReg) {
+        const SCEV *NewScaledReg = SE.getAnyExtendExpr(F.ScaledReg, SrcTy);
+        if (NewScaledReg->isZero())
+         continue;
+        F.ScaledReg = NewScaledReg;
+      }
+      bool HasZeroBaseReg = false;
+      for (const SCEV *&BaseReg : F.BaseRegs) {
+        const SCEV *NewBaseReg = SE.getAnyExtendExpr(BaseReg, SrcTy);
+        if (NewBaseReg->isZero()) {
+          HasZeroBaseReg = true;
+          break;
+        }
+        BaseReg = NewBaseReg;
+      }
+      if (HasZeroBaseReg)
+        continue;
 
       // TODO: This assumes we've done basic processing on all uses and
       // have an idea what the register usage is.
Index: llvm/trunk/test/Transforms/LoopStrengthReduce/X86/pr40514.ll
===================================================================
--- llvm/trunk/test/Transforms/LoopStrengthReduce/X86/pr40514.ll
+++ llvm/trunk/test/Transforms/LoopStrengthReduce/X86/pr40514.ll
@@ -0,0 +1,57 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -loop-reduce -S | FileCheck %s
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128-ni:1"
+target triple = "x86_64-unknown-linux-gnu"
+
+define i32 @pluto(i32 %arg) #0 {
+; CHECK-LABEL: @pluto(
+; CHECK-NEXT:  bb:
+; CHECK-NEXT:    br label [[BB10:%.*]]
+; CHECK:       bb1:
+; CHECK-NEXT:    store i64 [[LSR_IV_NEXT2:%.*]], i64 addrspace(1)* undef, align 8
+; CHECK-NEXT:    ret i32 [[LSR_IV_NEXT:%.*]]
+; CHECK:       bb10:
+; CHECK-NEXT:    [[LSR_IV1:%.*]] = phi i64 [ [[LSR_IV_NEXT2]], [[BB10]] ], [ 9, [[BB:%.*]] ]
+; CHECK-NEXT:    [[LSR_IV:%.*]] = phi i32 [ [[LSR_IV_NEXT]], [[BB10]] ], [ undef, [[BB]] ]
+; CHECK-NEXT:    [[LSR_IV_NEXT]] = add i32 [[LSR_IV]], 1
+; CHECK-NEXT:    [[LSR_IV_NEXT2]] = add nuw nsw i64 [[LSR_IV1]], 1
+; CHECK-NEXT:    br i1 true, label [[BB1:%.*]], label [[BB10]]
+;
+
+bb:
+  br label %bb10
+
+bb1:                                              ; preds = %bb10
+  %tmp = and i64 %tmp24, 4294967295
+  %tmp2 = shl i64 %tmp23, 33
+  %tmp3 = ashr exact i64 %tmp2, 32
+  %tmp4 = add i64 undef, %tmp
+  %tmp5 = add i64 %tmp4, %tmp3
+  %tmp6 = add i64 %tmp5, undef
+  %tmp7 = add i64 %tmp6, undef
+  %tmp8 = add i64 undef, %tmp7
+  store i64 %tmp8, i64 addrspace(1)* undef, align 8
+  %tmp9 = trunc i64 %tmp7 to i32
+  ret i32 %tmp9
+
+bb10:                                             ; preds = %bb10, %bb
+  %tmp11 = phi i64 [ 9, %bb ], [ %tmp24, %bb10 ]
+  %tmp12 = shl i64 undef, 1
+  %tmp13 = mul i64 %tmp12, %tmp12
+  %tmp14 = shl i64 %tmp13, 1
+  %tmp15 = mul i64 %tmp14, %tmp14
+  %tmp16 = shl i64 %tmp15, 1
+  %tmp17 = mul i64 %tmp16, %tmp16
+  %tmp18 = shl i64 %tmp17, 1
+  %tmp19 = mul i64 %tmp18, %tmp18
+  %tmp20 = shl i64 %tmp19, 1
+  %tmp21 = mul i64 %tmp20, %tmp20
+  %tmp22 = shl i64 %tmp21, 1
+  %tmp23 = mul i64 %tmp22, %tmp22
+  %tmp24 = add nuw nsw i64 %tmp11, 1
+  br i1 undef, label %bb1, label %bb10
+}
+
+
+attributes #0 = { "target-cpu"="broadwell" "target-features"="+sse2,+cx16,+sahf,-tbm,-avx512ifma,-sha,-gfni,-fma4,-vpclmulqdq,+prfchw,+bmi2,-cldemote,+fsgsbase,-ptwrite,-xsavec,+popcnt,+aes,-avx512bitalg,-movdiri,-xsaves,-avx512er,-avx512vnni,-avx512vpopcntdq,-pconfig,-clwb,-avx512f,-clzero,-pku,+mmx,-lwp,-rdpid,-xop,+rdseed,-waitpkg,-movdir64b,-sse4a,-avx512bw,-clflushopt,+xsave,-avx512vbmi2,+64bit,-avx512vl,+invpcid,-avx512cd,+avx,-vaes,+rtm,+fma,+bmi,+rdrnd,-mwaitx,+sse4.1,+sse4.2,+avx2,-wbnoinvd,+sse,+lzcnt,+pclmul,-prefetchwt1,+f16c,+ssse3,-sgx,-shstk,+cmov,-avx512vbmi,+movbe,+xsaveopt,-avx512dq,+adx,-avx512pf,+sse3" }