[llvm] r267023 - [instcombine][unordered] Extend load(select) transform to handle unordered loads

[Philip Reames via llvm-commits]

Author: reames
Date: Thu Apr 21 12:59:40 2016
New Revision: 267023

URL: http://llvm.org/viewvc/llvm-project?rev=267023&view=rev
Log:
[instcombine][unordered] Extend load(select) transform to handle unordered loads


Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
    llvm/trunk/test/Transforms/InstCombine/atomic.ll

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp?rev=267023&r1=267022&r2=267023&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp Thu Apr 21 12:59:40 2016
@@ -867,10 +867,6 @@ Instruction *InstCombiner::visitLoadInst
     return replaceInstUsesWith(LI, UndefValue::get(LI.getType()));
   }
 
-  // TODO: The transform below needs updated for unordered loads
-  if (!LI.isSimple())
-    return nullptr;
-
   if (Op->hasOneUse()) {
     // Change select and PHI nodes to select values instead of addresses: this
     // helps alias analysis out a lot, allows many others simplifications, and
@@ -891,8 +887,11 @@ Instruction *InstCombiner::visitLoadInst
                                            SI->getOperand(1)->getName()+".val");
         LoadInst *V2 = Builder->CreateLoad(SI->getOperand(2),
                                            SI->getOperand(2)->getName()+".val");
+        assert(LI.isUnordered() && "implied by above");
         V1->setAlignment(Align);
+        V1->setAtomic(LI.getOrdering(), LI.getSynchScope());
         V2->setAlignment(Align);
+        V2->setAtomic(LI.getOrdering(), LI.getSynchScope());
         return SelectInst::Create(SI->getCondition(), V1, V2);
       }
 

Modified: llvm/trunk/test/Transforms/InstCombine/atomic.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/atomic.ll?rev=267023&r1=267022&r2=267023&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/atomic.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/atomic.ll Thu Apr 21 12:59:40 2016
@@ -143,4 +143,32 @@ define i32 @test14() {
   ret i32 0
 }
 
+ at a = external global i32
+ at b = external global i32
 
+define i32 @test15(i1 %cnd) {
+; CHECK-LABEL: define i32 @test15(
+; CHECK: load atomic i32, i32* @a unordered, align 4
+; CHECK: load atomic i32, i32* @b unordered, align 4
+  %addr = select i1 %cnd, i32* @a, i32* @b
+  %x = load atomic i32, i32* %addr unordered, align 4
+  ret i32 %x
+}
+
+; FIXME: This would be legal to transform
+define i32 @test16(i1 %cnd) {
+; CHECK-LABEL: define i32 @test16(
+; CHECK: load atomic i32, i32* %addr monotonic, align 4
+  %addr = select i1 %cnd, i32* @a, i32* @b
+  %x = load atomic i32, i32* %addr monotonic, align 4
+  ret i32 %x
+}
+
+; FIXME: This would be legal to transform
+define i32 @test17(i1 %cnd) {
+; CHECK-LABEL: define i32 @test17(
+; CHECK: load atomic i32, i32* %addr seq_cst, align 4
+  %addr = select i1 %cnd, i32* @a, i32* @b
+  %x = load atomic i32, i32* %addr seq_cst, align 4
+  ret i32 %x
+}