[llvm] r332855 - [InstCombine] Fix PR37526: MinMax patterns produce an infinite loop.

[Alexey Bataev via llvm-commits]

Author: abataev
Date: Mon May 21 10:46:34 2018
New Revision: 332855

URL: http://llvm.org/viewvc/llvm-project?rev=332855&view=rev
Log:
[InstCombine] Fix PR37526: MinMax patterns produce an infinite loop.

Summary:
This patch fixes PR37526 by simplifying the newly generated LoadInst
instructions. If the pointer address is a bitcast from the pointer to
the NewType, we can just remove this extra bitcast instead of creating
the new one. This fixes the PR37526 + may speed up the whole compilation
process.

Reviewers: spatel, RKSimon, hfinkel

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D47144

Added:
    llvm/trunk/test/Transforms/InstCombine/PR37526.ll
Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp?rev=332855&r1=332854&r2=332855&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp Mon May 21 10:46:34 2018
@@ -453,15 +453,20 @@ static LoadInst *combineLoadToNewType(In
                                       const Twine &Suffix = "") {
   assert((!LI.isAtomic() || isSupportedAtomicType(NewTy)) &&
          "can't fold an atomic load to requested type");
-  
+
   Value *Ptr = LI.getPointerOperand();
   unsigned AS = LI.getPointerAddressSpace();
   SmallVector<std::pair<unsigned, MDNode *>, 8> MD;
   LI.getAllMetadata(MD);
 
+  Value *NewPtr = nullptr;
+  if (!(match(Ptr, m_BitCast(m_Value(NewPtr))) &&
+        NewPtr->getType()->getPointerElementType() == NewTy &&
+        NewPtr->getType()->getPointerAddressSpace() == AS))
+    NewPtr = IC.Builder.CreateBitCast(Ptr, NewTy->getPointerTo(AS));
+
   LoadInst *NewLoad = IC.Builder.CreateAlignedLoad(
-      IC.Builder.CreateBitCast(Ptr, NewTy->getPointerTo(AS)),
-      LI.getAlignment(), LI.isVolatile(), LI.getName() + Suffix);
+      NewPtr, LI.getAlignment(), LI.isVolatile(), LI.getName() + Suffix);
   NewLoad->setAtomic(LI.getOrdering(), LI.getSyncScopeID());
   MDBuilder MDB(NewLoad->getContext());
   for (const auto &MDPair : MD) {

Added: llvm/trunk/test/Transforms/InstCombine/PR37526.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/PR37526.ll?rev=332855&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/PR37526.ll (added)
+++ llvm/trunk/test/Transforms/InstCombine/PR37526.ll Mon May 21 10:46:34 2018
@@ -0,0 +1,22 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -instcombine -S < %s | FileCheck %s
+
+define void @PR37526(i32* %pz, i32* %px, i32* %py) {
+; CHECK-LABEL: @PR37526(
+; CHECK-NEXT:    [[T2:%.*]] = load i32, i32* [[PY:%.*]], align 4
+; CHECK-NEXT:    [[T3:%.*]] = load i32, i32* [[PX:%.*]], align 4
+; CHECK-NEXT:    [[CMP:%.*]] = icmp slt i32 [[T2]], [[T3]]
+; CHECK-NEXT:    [[R1:%.*]] = select i1 [[CMP]], i32 [[T3]], i32 [[T2]]
+; CHECK-NEXT:    store i32 [[R1]], i32* [[PZ:%.*]], align 4
+; CHECK-NEXT:    ret void
+;
+  %t1 = bitcast i32* %pz to i64*
+  %t2 = load i32, i32* %py
+  %t3 = load i32, i32* %px
+  %cmp = icmp slt i32 %t2, %t3
+  %select = select i1 %cmp, i32* %px, i32* %py
+  %bc = bitcast i32* %select to i64*
+  %r = load i64, i64* %bc
+  store i64 %r, i64* %t1
+  ret void
+}