[llvm] r321075 - [InlineCost] Skip volatile loads when looking for repeated loads

[Haicheng Wu via llvm-commits]

Author: haicheng
Date: Tue Dec 19 05:42:58 2017
New Revision: 321075

URL: http://llvm.org/viewvc/llvm-project?rev=321075&view=rev
Log:
[InlineCost] Skip volatile loads when looking for repeated loads

This is a follow-up fix of r320814.  A test case is also added.

Modified:
    llvm/trunk/lib/Analysis/InlineCost.cpp
    llvm/trunk/test/Transforms/Inline/redundant-loads.ll

Modified: llvm/trunk/lib/Analysis/InlineCost.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/InlineCost.cpp?rev=321075&r1=321074&r2=321075&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/InlineCost.cpp (original)
+++ llvm/trunk/lib/Analysis/InlineCost.cpp Tue Dec 19 05:42:58 2017
@@ -363,6 +363,7 @@ void CallAnalyzer::accumulateSROACost(De
 void CallAnalyzer::disableLoadElimination() {
   if (EnableLoadElimination) {
     Cost += LoadEliminationCost;
+    LoadEliminationCost = 0;
     EnableLoadElimination = false;
   }
 }
@@ -1097,7 +1098,7 @@ bool CallAnalyzer::visitLoad(LoadInst &I
   // by any stores or calls, this load is likely to be redundant and can be
   // eliminated.
   if (EnableLoadElimination &&
-      !LoadAddrSet.insert(I.getPointerOperand()).second) {
+      !LoadAddrSet.insert(I.getPointerOperand()).second && I.isUnordered()) {
     LoadEliminationCost += InlineConstants::InstrCost;
     return true;
   }

Modified: llvm/trunk/test/Transforms/Inline/redundant-loads.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/Inline/redundant-loads.ll?rev=321075&r1=321074&r2=321075&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/Inline/redundant-loads.ll (original)
+++ llvm/trunk/test/Transforms/Inline/redundant-loads.ll Tue Dec 19 05:42:58 2017
@@ -184,3 +184,21 @@ define void @inner9(i32* %a, void ()* %f
   call void @pad()
   ret void
 }
+
+
+define void @outer10(i32* %a) {
+; CHECK-LABEL: @outer10(
+; CHECK: call void @inner10
+  %b = alloca i32
+  call void @inner10(i32* %a, i32* %b)
+  ret void
+}
+
+define void @inner10(i32* %a, i32* %b) {
+  %1 = load i32, i32* %a
+  store i32 %1, i32 * %b
+  %2 = load volatile i32, i32* %a ; volatile load should be kept.
+  call void @pad()
+  %3 = load volatile i32, i32* %a ; Same as the above.
+  ret void
+}