[llvm] 90131e3 - [CostModel] Make target intrinsics cheap by default

[David Green via llvm-commits]

Author: David Green
Date: 2020-11-03T09:58:28Z
New Revision: 90131e3ecb753c38cc99e060aa69ca1766d96432

URL: https://github.com/llvm/llvm-project/commit/90131e3ecb753c38cc99e060aa69ca1766d96432
DIFF: https://github.com/llvm/llvm-project/commit/90131e3ecb753c38cc99e060aa69ca1766d96432.diff

LOG: [CostModel] Make target intrinsics cheap by default

This patch changes the intrinsics cost model to assume that by default
target intrinsics are cheap. This didn't seem to be the case for all
intrinsics, and is potentially an MVE problem due to our scalarization
overheads. Cheap seems to be a good default in general though.

Differential Revision: https://reviews.llvm.org/D90597

Added: 
    

Modified: 
    llvm/include/llvm/CodeGen/BasicTTIImpl.h
    llvm/include/llvm/IR/Function.h
    llvm/lib/IR/Function.cpp
    llvm/test/Analysis/CostModel/ARM/target-intrinsics.ll

Removed: 
    


################################################################################
diff  --git a/llvm/include/llvm/CodeGen/BasicTTIImpl.h b/llvm/include/llvm/CodeGen/BasicTTIImpl.h
index 67d088132316..ebf946d0fe2e 100644
--- a/llvm/include/llvm/CodeGen/BasicTTIImpl.h
+++ b/llvm/include/llvm/CodeGen/BasicTTIImpl.h
@@ -1135,6 +1135,11 @@ class BasicTTIImplBase : public TargetTransformInfoImplCRTPBase<T> {
     if (BaseT::getIntrinsicInstrCost(ICA, CostKind) == 0)
       return 0;
 
+    // Assume that target intrinsics are cheap.
+    Intrinsic::ID IID = ICA.getID();
+    if (Function::isTargetIntrinsic(IID))
+      return TargetTransformInfo::TCC_Basic;
+
     if (ICA.isTypeBasedOnly())
       return getTypeBasedIntrinsicInstrCost(ICA, CostKind);
 
@@ -1151,7 +1156,6 @@ class BasicTTIImplBase : public TargetTransformInfoImplCRTPBase<T> {
     const IntrinsicInst *I = ICA.getInst();
     const SmallVectorImpl<const Value *> &Args = ICA.getArgs();
     FastMathFlags FMF = ICA.getFlags();
-    Intrinsic::ID IID = ICA.getID();
     switch (IID) {
     default:
       // FIXME: all cost kinds should default to the same thing?

diff  --git a/llvm/include/llvm/IR/Function.h b/llvm/include/llvm/IR/Function.h
index 350d94ea09ed..061223d3bd78 100644
--- a/llvm/include/llvm/IR/Function.h
+++ b/llvm/include/llvm/IR/Function.h
@@ -199,6 +199,10 @@ class Function : public GlobalObject, public ilist_node<Function> {
   /// returns Intrinsic::not_intrinsic!
   bool isIntrinsic() const { return HasLLVMReservedName; }
 
+  /// isTargetIntrinsic - Returns true if IID is an intrinsic specific to a
+  /// certain target. If it is a generic intrinsic false is returned.
+  static bool isTargetIntrinsic(Intrinsic::ID IID);
+
   /// isTargetIntrinsic - Returns true if this function is an intrinsic and the
   /// intrinsic is specific to a certain target. If this is not an intrinsic
   /// or a generic intrinsic, false is returned.

diff  --git a/llvm/lib/IR/Function.cpp b/llvm/lib/IR/Function.cpp
index e228c3e0a4eb..8c360dd1841e 100644
--- a/llvm/lib/IR/Function.cpp
+++ b/llvm/lib/IR/Function.cpp
@@ -640,8 +640,12 @@ static const char * const IntrinsicNameTable[] = {
 #include "llvm/IR/IntrinsicImpl.inc"
 #undef GET_INTRINSIC_TARGET_DATA
 
+bool Function::isTargetIntrinsic(Intrinsic::ID IID) {
+  return IID > TargetInfos[0].Count;
+}
+
 bool Function::isTargetIntrinsic() const {
-  return IntID > TargetInfos[0].Count;
+  return isTargetIntrinsic(IntID);
 }
 
 /// Find the segment of \c IntrinsicNameTable for intrinsics with the same

diff  --git a/llvm/test/Analysis/CostModel/ARM/target-intrinsics.ll b/llvm/test/Analysis/CostModel/ARM/target-intrinsics.ll
index 269f3074aad9..bb2cdde7422f 100644
--- a/llvm/test/Analysis/CostModel/ARM/target-intrinsics.ll
+++ b/llvm/test/Analysis/CostModel/ARM/target-intrinsics.ll
@@ -9,7 +9,7 @@ define void @intrinsics() {
 ; CHECK-THUMB2-RECIP-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %t1 = call i32 @llvm.arm.ssat(i32 undef, i32 undef)
 ; CHECK-THUMB2-RECIP-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %t2 = tail call { <8 x half>, <8 x half> } @llvm.arm.mve.vld2q.v8f16.p0f16(half* undef)
 ; CHECK-THUMB2-RECIP-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %t3 = call { i32, i32 } @llvm.arm.mve.sqrshrl(i32 undef, i32 undef, i32 undef, i32 48)
-; CHECK-THUMB2-RECIP-NEXT:  Cost Model: Found an estimated cost of 135 for instruction: %t4 = tail call { i32, i32 } @llvm.arm.mve.vmlldava.v8i16(i32 0, i32 0, i32 0, i32 0, i32 0, <8 x i16> undef, <8 x i16> undef)
+; CHECK-THUMB2-RECIP-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %t4 = tail call { i32, i32 } @llvm.arm.mve.vmlldava.v8i16(i32 0, i32 0, i32 0, i32 0, i32 0, <8 x i16> undef, <8 x i16> undef)
 ; CHECK-THUMB2-RECIP-NEXT:  Cost Model: Found an estimated cost of 0 for instruction: ret void
 ;
 ; CHECK-THUMB2-LAT-LABEL: 'intrinsics'