Index: lib/Transforms/Vectorize/LoopVectorizationLegality.cpp
===================================================================
--- lib/Transforms/Vectorize/LoopVectorizationLegality.cpp
+++ lib/Transforms/Vectorize/LoopVectorizationLegality.cpp
@@ -789,6 +789,10 @@
       ORE->emit(createMissedAnalysis("NoInductionVariable")
                 << "loop induction variable could not be identified");
       return false;
+    } else if (!WidestIndTy) {
+      ORE->emit(createMissedAnalysis("NoIntegerInductionVariable")
+                << "integer loop induction variable could not be identified");
+      return false;
     }
   }
 
Index: test/Transforms/LoopVectorize/pr38800.ll
===================================================================
--- test/Transforms/LoopVectorize/pr38800.ll
+++ test/Transforms/LoopVectorize/pr38800.ll
@@ -0,0 +1,34 @@
+; RUN: opt -loop-vectorize -force-vector-width=2 -pass-remarks-missed='loop-vectorize' -S < %s 2>&1 | FileCheck %s
+
+; CHECK: remark: <unknown>:0:0: loop not vectorized: integer loop induction variable could not be identified
+
+; Test-case ('-O2 -ffast-math') from PR38800.
+; (Set '-force-vector-width=2' to enable vector code generation.)
+;
+; No integral induction variable in the source-code caused a compiler-crash
+; when attempting to vectorize.  With the fix, a remark indicating why it
+; wasn't vectorized is produced
+;
+;void foo(float *ptr, float val) {
+;  float f;
+;  for (f = 0.1f; f < 1.0f; f += 0.01f)
+;    *ptr += val;
+;}
+
+define void @foo(float* nocapture %ptr, float %val) local_unnamed_addr {
+entry:
+  %ptr.promoted = load float, float* %ptr, align 4
+  br label %for.body
+
+for.body:                                         ; preds = %entry, %for.body
+  %add5 = phi float [ %ptr.promoted, %entry ], [ %add, %for.body ]
+  %f.04 = phi float [ 0x3FB99999A0000000, %entry ], [ %add1, %for.body ]
+  %add = fadd fast float %add5, %val
+  %add1 = fadd fast float %f.04, 0x3F847AE140000000
+  %cmp = fcmp fast olt float %add1, 1.000000e+00
+  br i1 %cmp, label %for.body, label %for.end
+
+for.end:                                          ; preds = %for.body
+  store float %add, float* %ptr, align 4
+  ret void
+}