Precommit test for pr77798

Test shows assertion failure through SCEV's usage of multiplicative
inverse.

Author: annamthomas

llvm/test/Transforms/IndVarSimplify/pr87798.ll

@@ -0,0 +1,37 @@
+; RUN: opt -S -passes='indvars' -verify-scev < %s | FileCheck %s
+
+; REQUIRES: asserts
+; XFAIL: *
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128-ni:1-p2:32:8:8:32-ni:2"
+target triple = "x86_64-unknown-linux-gnu"
+
+; We should not crash on multiplicative inverse called within SCEV's binomial
+; coefficient function.
+define i32 @pr87798() {
+; CHECK-LABEL: pr87798 
+bb:
+  br label %bb1
+
+bb1:                                              ; preds = %bb1, %bb
+  %phi = phi i32 [ 0, %bb ], [ %add4, %bb1 ]
+  %phi2 = phi i32 [ 0, %bb ], [ %add, %bb1 ]
+  %phi3 = phi i32 [ 0, %bb ], [ %add5, %bb1 ]
+  %add = add i32 %phi2, %phi3
+  %mul = mul i32 %phi2, %phi3
+  %add4 = add i32 %mul, %phi
+  %and = and i32 %phi, 1
+  %add5 = add i32 %phi3, 1
+  br i1 true, label %preheader, label %bb1
+
+preheader:                                              ; preds = %bb1
+  %phi9 = phi i32 [ %and, %bb1 ]
+  br label %loop
+
+loop:                                              ; preds = %preheader, %loop
+  br label %loop
+
+bb7:                                              ; No predecessors!
+  %zext = zext i32 %phi9 to i64
+  ret i32 0
+}