[IndVars] Smart hard uses detection

When rewriting loop exit values, IndVars considers this transform not profitable if
the loop instruction has a loop user which it believes cannot be optimized away.
In current implementation only calls that immediately use the instruction are considered
as such.

This patch extends the definition of "hard" users to any side-effecting instructions
(which usually cannot be optimized away from the loop) and also allows handling
of not just immediate users, but use chains.

Differentlai Revision: https://reviews.llvm.org/D51584
Reviewed By: etherzhhb

llvm-svn: 345814

1 files changed, 3 insertions, 3 deletions

diff --git a/llvm/test/Analysis/ScalarEvolution/pr28705.ll b/llvm/test/Analysis/ScalarEvolution/pr28705.ll
index 8fbc08e3ca6..9a8487a6c66 100644
--- a/llvm/test/Analysis/ScalarEvolution/pr28705.ll
+++ b/llvm/test/Analysis/ScalarEvolution/pr28705.ll
@@ -1,11 +1,11 @@
 ; PR28705
 ; RUN: opt < %s -indvars -S | FileCheck %s
 
-; Check IndVarSimplify replaces the exitval use of the induction var "%inc.i.i"
-; with "%.sroa.speculated + 1".
+; Check IndVarSimplify doesn't replace external use of the induction var
+; "%inc.i.i" with "%.sroa.speculated + 1" because it is not profitable.
 ;
 ; CHECK-LABEL: @foo(
-; CHECK: %[[EXIT:.+]] = sub i32 %.sroa.speculated, -1
+; CHECK: %[[EXIT:.+]] = phi i32 [ %inc.i.i, %for.body650 ]
 ; CHECK: %DB.sroa.9.0.lcssa = phi i32 [ 1, %entry ], [ %[[EXIT]], %loopexit ]
 ;
 define void @foo(i32 %sub.ptr.div.i, i8* %ref.i1174) local_unnamed_addr {