[LoopLoadElim] Add test showing that LoopLoadElim doesn't work correc…

…tly with new PM
llvm · Apr 8, 2020 · 7adb9e0 · 7adb9e0
1 parent c839324
commit 7adb9e0
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diff --git a/llvm/lib/Transforms/Scalar/LoopLoadElimination.cpp b/llvm/lib/Transforms/Scalar/LoopLoadElimination.cpp
@@ -432,6 +432,7 @@ class LoadEliminationForLoop {
     Value *Ptr = Cand.Load->getPointerOperand();
     auto *PtrSCEV = cast<SCEVAddRecExpr>(PSE.getSCEV(Ptr));
     auto *PH = L->getLoopPreheader();
+    assert(PH && "Preheader should exist!");
     Value *InitialPtr = SEE.expandCodeFor(PtrSCEV->getStart(), Ptr->getType(),
                                           PH->getTerminator());
     Value *Initial = new LoadInst(

diff --git a/llvm/test/Transforms/LoopLoadElim/new-pm-preheader-problem.ll b/llvm/test/Transforms/LoopLoadElim/new-pm-preheader-problem.ll
@@ -0,0 +1,27 @@
+; XFAIL: *
+; RUN: opt -passes=loop-load-elim -S < %s | FileCheck %s
+; This test demonstrates an assertion failure due to missing preheader in new PM.
+; REQUIRES: asserts
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+
+define void @test(i32* noalias nocapture %A, i32* noalias nocapture readonly %B, i64 %N, i1 %C) {
+entry:
+  br i1 %C, label %for.body, label %for.end
+
+; CHECK: test
+for.body:
+  %indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ]
+  %arrayidx = getelementptr inbounds i32, i32* %A, i64 %indvars.iv
+  %load = load i32, i32* %arrayidx, align 4
+  %arrayidx2 = getelementptr inbounds i32, i32* %B, i64 %indvars.iv
+  %load_1 = load i32, i32* %arrayidx2, align 4
+  %add = add i32 %load_1, %load
+  %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+  %arrayidx_next = getelementptr inbounds i32, i32* %A, i64 %indvars.iv.next
+  store i32 %add, i32* %arrayidx_next, align 4
+  %exitcond = icmp eq i64 %indvars.iv.next, %N
+  br i1 %exitcond, label %for.end, label %for.body
+
+for.end:
+  ret void
+}