[LSR] If no Use is interesting, early return.

Summary:
By looking at the callers of getUse(), we can see that even though
IVUsers may offer uses, but they may not be interesting to
LSR. It's possible that none of them is interesting.

Reviewers: sanjoy

Subscribers: jlebar, hiraditya, bixia, llvm-commits

Differential Revision: https://reviews.llvm.org/D49049

llvm-svn: 337072

2 files changed, 44 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp b/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
index 03429e9698a..fa83b48210b 100644
--- a/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
@@ -5400,7 +5400,9 @@ LSRInstance::LSRInstance(Loop *L, IVUsers &IU, ScalarEvolution &SE,
   CollectFixupsAndInitialFormulae();
   CollectLoopInvariantFixupsAndFormulae();
 
-  assert(!Uses.empty() && "IVUsers reported at least one use");
+  if (Uses.empty())
+    return;
+
   LLVM_DEBUG(dbgs() << "LSR found " << Uses.size() << " uses:\n";
              print_uses(dbgs()));
 
diff --git a/llvm/test/CodeGen/X86/lsr-crash-empty-uses.ll b/llvm/test/CodeGen/X86/lsr-crash-empty-uses.ll
new file mode 100644
index 00000000000..ef72f87cce4
--- /dev/null
+++ b/llvm/test/CodeGen/X86/lsr-crash-empty-uses.ll
@@ -0,0 +1,41 @@
+; RUN: llc --start-before loop-reduce --stop-after loop-reduce %s -o - | FileCheck %s
+target datalayout = "e-m:e-p:32:32-i64:64-n32-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define void @hoge() {
+bb:
+  %tmp = sext i32 undef to i64
+  %tmp3 = sub nsw i64 0, %tmp
+  br label %bb4
+
+bb4:                                              ; preds = %bb20, %bb
+  %tmp5 = getelementptr inbounds double, double* undef, i64 undef
+  %tmp6 = getelementptr inbounds double, double* %tmp5, i64 %tmp3
+  br label %bb7
+
+bb7:                                              ; preds = %bb7, %bb4
+  %tmp8 = phi double* [ %tmp10, %bb7 ], [ %tmp6, %bb4 ]
+  %tmp9 = load double, double* %tmp8
+  %tmp10 = getelementptr inbounds double, double* %tmp8, i64 1
+  br i1 true, label %bb11, label %bb7
+
+bb11:                                             ; preds = %bb7
+  br i1 undef, label %bb20, label %bb12
+
+bb12:                                             ; preds = %bb11
+  br label %bb13
+
+bb13:                                             ; preds = %bb13, %bb12
+  %tmp14 = phi double* [ %tmp18, %bb13 ], [ %tmp10, %bb12 ]
+  %tmp15 = load double, double* %tmp14, align 8
+  %tmp16 = getelementptr inbounds double, double* %tmp14, i64 1
+  %tmp17 = load double, double* %tmp16, align 8
+  %tmp18 = getelementptr inbounds double, double* %tmp14, i64 8
+  br i1 true, label %bb19, label %bb13
+
+bb19:                                             ; preds = %bb13
+  br label %bb20
+
+bb20:                                             ; preds = %bb19, %bb11
+  br label %bb4
+}