Add @llvm.assume, lowering, and some basic properties
This is the first commit in a series that add an @llvm.assume intrinsic which
can be used to provide the optimizer with a condition it may assume to be true
(when the control flow would hit the intrinsic call). Some basic properties are added here:
- llvm.invariant(true) is dead.
- llvm.invariant(false) is unreachable (this directly corresponds to the
documented behavior of MSVC's __assume(0)), so is llvm.invariant(undef).
The intrinsic is tagged as writing arbitrarily, in order to maintain control
dependencies. BasicAA has been updated, however, to return NoModRef for any
particular location-based query so that we don't unnecessarily block code
motion.
llvm-svn: 213973
diff --git a/llvm/lib/CodeGen/BasicTargetTransformInfo.cpp b/llvm/lib/CodeGen/BasicTargetTransformInfo.cpp
index b2737bf..d639101 100644
--- a/llvm/lib/CodeGen/BasicTargetTransformInfo.cpp
+++ b/llvm/lib/CodeGen/BasicTargetTransformInfo.cpp
@@ -572,6 +572,7 @@
case Intrinsic::pow: ISD = ISD::FPOW; break;
case Intrinsic::fma: ISD = ISD::FMA; break;
case Intrinsic::fmuladd: ISD = ISD::FMA; break;
+ // FIXME: We should return 0 whenever getIntrinsicCost == TCC_Free.
case Intrinsic::lifetime_start:
case Intrinsic::lifetime_end:
return 0;
diff --git a/llvm/lib/CodeGen/IntrinsicLowering.cpp b/llvm/lib/CodeGen/IntrinsicLowering.cpp
index a8b8600..9df8f3c 100644
--- a/llvm/lib/CodeGen/IntrinsicLowering.cpp
+++ b/llvm/lib/CodeGen/IntrinsicLowering.cpp
@@ -459,9 +459,10 @@
CI->replaceAllUsesWith(CI->getOperand(0));
break;
+ case Intrinsic::assume:
case Intrinsic::var_annotation:
- break; // Strip out annotate intrinsic
-
+ break; // Strip out these intrinsics
+
case Intrinsic::memcpy: {
Type *IntPtr = DL.getIntPtrType(Context);
Value *Size = Builder.CreateIntCast(CI->getArgOperand(2), IntPtr,
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index b3d6ab8..4ccdb1d 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -5304,8 +5304,9 @@
// Drop the intrinsic, but forward the value
setValue(&I, getValue(I.getOperand(0)));
return nullptr;
+ case Intrinsic::assume:
case Intrinsic::var_annotation:
- // Discard annotate attributes
+ // Discard annotate attributes and assumptions
return nullptr;
case Intrinsic::init_trampoline: {