[llvm] r332786 - Constant fold launder of null and undef

[Piotr Padlewski via llvm-commits]

Author: prazek
Date: Fri May 18 16:52:57 2018
New Revision: 332786

URL: http://llvm.org/viewvc/llvm-project?rev=332786&view=rev
Log:
Constant fold launder of null and undef

Summary:
This might be useful because clang will add
some barriers for pointer comparisons.

Reviewers: majnemer, dberlin, hfinkel, nlewycky, davide, rsmith, amharc,
kuhar

Subscribers: davide, amharc, llvm-commits

Differential Revision: https://reviews.llvm.org/D32423

Added:
    llvm/trunk/test/Transforms/InstCombine/invariant.group.ll
Modified:
    llvm/trunk/lib/Analysis/ConstantFolding.cpp
    llvm/trunk/lib/Transforms/Utils/Local.cpp

Modified: llvm/trunk/lib/Analysis/ConstantFolding.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ConstantFolding.cpp?rev=332786&r1=332785&r2=332786&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/ConstantFolding.cpp (original)
+++ llvm/trunk/lib/Analysis/ConstantFolding.cpp Fri May 18 16:52:57 2018
@@ -1392,6 +1392,7 @@ bool llvm::canConstantFoldCallTo(Immutab
   case Intrinsic::fma:
   case Intrinsic::fmuladd:
   case Intrinsic::copysign:
+  case Intrinsic::launder_invariant_group:
   case Intrinsic::round:
   case Intrinsic::masked_load:
   case Intrinsic::sadd_with_overflow:
@@ -1594,9 +1595,19 @@ Constant *ConstantFoldScalarCall(StringR
       if (IntrinsicID == Intrinsic::cos)
         return Constant::getNullValue(Ty);
       if (IntrinsicID == Intrinsic::bswap ||
-          IntrinsicID == Intrinsic::bitreverse)
+          IntrinsicID == Intrinsic::bitreverse ||
+          IntrinsicID == Intrinsic::launder_invariant_group)
         return Operands[0];
     }
+
+    if (isa<ConstantPointerNull>(Operands[0]) &&
+        Operands[0]->getType()->getPointerAddressSpace() == 0) {
+      // launder(null) == null iff in addrspace 0
+      if (IntrinsicID == Intrinsic::launder_invariant_group)
+        return Operands[0];
+      return nullptr;
+    }
+
     if (auto *Op = dyn_cast<ConstantFP>(Operands[0])) {
       if (IntrinsicID == Intrinsic::convert_to_fp16) {
         APFloat Val(Op->getValueAPF());

Modified: llvm/trunk/lib/Transforms/Utils/Local.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/Local.cpp?rev=332786&r1=332785&r2=332786&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/Local.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/Local.cpp Fri May 18 16:52:57 2018
@@ -384,8 +384,9 @@ bool llvm::wouldInstructionBeTriviallyDe
   // Special case intrinsics that "may have side effects" but can be deleted
   // when dead.
   if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
-    // Safe to delete llvm.stacksave if dead.
-    if (II->getIntrinsicID() == Intrinsic::stacksave)
+    // Safe to delete llvm.stacksave and launder.invariant.group if dead.
+    if (II->getIntrinsicID() == Intrinsic::stacksave ||
+        II->getIntrinsicID() == Intrinsic::launder_invariant_group)
       return true;
 
     // Lifetime intrinsics are dead when their right-hand is undef.

Added: llvm/trunk/test/Transforms/InstCombine/invariant.group.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/invariant.group.ll?rev=332786&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/invariant.group.ll (added)
+++ llvm/trunk/test/Transforms/InstCombine/invariant.group.ll Fri May 18 16:52:57 2018
@@ -0,0 +1,34 @@
+; RUN: opt -instcombine -S < %s | FileCheck %s
+
+; CHECK-LABEL: define i8* @simplifyNullLaunder()
+define i8* @simplifyNullLaunder() {
+; CHECK-NEXT: ret i8* null
+  %b2 = call i8* @llvm.launder.invariant.group.p0i8(i8* null)
+  ret i8* %b2
+}
+
+; CHECK-LABEL: define i8 addrspace(42)* @dontsimplifyNullLaunderForDifferentAddrspace()
+define i8 addrspace(42)* @dontsimplifyNullLaunderForDifferentAddrspace() {
+; CHECK: %b2 = call i8 addrspace(42)* @llvm.launder.invariant.group.p42i8(i8 addrspace(42)* null)
+; CHECK: ret i8 addrspace(42)* %b2
+  %b2 = call i8 addrspace(42)* @llvm.launder.invariant.group.p42i8(i8 addrspace(42)* null)
+  ret i8 addrspace(42)* %b2
+}
+
+; CHECK-LABEL: define i8* @simplifyUndefLaunder()
+define i8* @simplifyUndefLaunder() {
+; CHECK-NEXT: ret i8* undef
+  %b2 = call i8* @llvm.launder.invariant.group.p0i8(i8* undef)
+  ret i8* %b2
+}
+
+; CHECK-LABEL: define i8 addrspace(42)* @simplifyUndefLaunder2()
+define i8 addrspace(42)* @simplifyUndefLaunder2() {
+; CHECK-NEXT: ret i8 addrspace(42)* undef
+  %b2 = call i8 addrspace(42)* @llvm.launder.invariant.group.p42i8(i8 addrspace(42)* undef)
+  ret i8 addrspace(42)* %b2
+}
+
+
+declare i8* @llvm.launder.invariant.group.p0i8(i8*)
+declare i8 addrspace(42)* @llvm.launder.invariant.group.p42i8(i8 addrspace(42)*)