[PATCH] D16986: [LICM] Don't assert on volatile accesses

[Matthew Simpson via llvm-commits]

mssimpso created this revision.
mssimpso added reviewers: reames, majnemer, sanjoy.
mssimpso added subscribers: llvm-commits, mcrosier.

A constant pointer in a non-volatile alias set (e.g., null) may be used by volatile accesses. For such cases, we might should bail out instead of asserting. This should fix PR25628.

Contributed-by: Ed Baunton

http://reviews.llvm.org/D16986

Files:
  lib/Transforms/Scalar/LICM.cpp
  test/Transforms/LICM/PR25628.ll

Index: test/Transforms/LICM/PR25628.ll
===================================================================
--- /dev/null
+++ test/Transforms/LICM/PR25628.ll
@@ -0,0 +1,29 @@
+; RUN: opt -S -tbaa -licm < %s | FileCheck %s
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+; CHECK-NOT: %load2 = load i32*, i32** @b
+
+ at b = external global i32*, align 8
+
+define void @f(i1 %B, i1 %D) {
+entry:
+  br i1 %B, label %for.body, label %for.end4
+
+for.body:
+  store i32* null, i32** @b, align 8, !tbaa !0
+  store i32 1, i32* null, align 8
+  %load2 = load i32*, i32** @b, align 8, !tbaa !0
+  %load3 = load volatile i32, i32* %load2, align 8, !tbaa !4
+  br i1 %D, label %for.body, label %for.end4
+
+for.end4:
+  ret void
+}
+
+!0 = !{!1, !1, i64 0}
+!1 = !{!"any pointer", !2, i64 0}
+!2 = !{!"omnipotent char", !3, i64 0}
+!3 = !{!"Simple C/C++ TBAA"}
+!4 = !{!5, !5, i64 0}
+!5 = !{!"int", !2, i64 0}
Index: lib/Transforms/Scalar/LICM.cpp
===================================================================
--- lib/Transforms/Scalar/LICM.cpp
+++ lib/Transforms/Scalar/LICM.cpp
@@ -954,16 +954,14 @@
       // If there is an non-load/store instruction in the loop, we can't promote
       // it.
       if (const LoadInst *Load = dyn_cast<LoadInst>(UI)) {
-        assert(!Load->isVolatile() && "AST broken");
-        if (!Load->isSimple())
+        if (!Load->isSimple() || !Load->isUnordered())
           return Changed;
       } else if (const StoreInst *Store = dyn_cast<StoreInst>(UI)) {
         // Stores *of* the pointer are not interesting, only stores *to* the
         // pointer.
         if (UI->getOperand(1) != ASIV)
           continue;
-        assert(!Store->isVolatile() && "AST broken");
-        if (!Store->isSimple())
+        if (!Store->isSimple() || !Store->isUnordered())
           return Changed;
         // Don't sink stores from loops without dedicated block exits. Exits
         // containing indirect branches are not transformed by loop simplify,


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