[llvm] r303254 - [SystemZ] Modelling of costs of divisions with a constant power of 2.
Jonas Paulsson via llvm-commits
llvm-commits at lists.llvm.org
Wed May 17 05:46:26 PDT 2017
Author: jonpa
Date: Wed May 17 07:46:26 2017
New Revision: 303254
URL: http://llvm.org/viewvc/llvm-project?rev=303254&view=rev
Log:
[SystemZ] Modelling of costs of divisions with a constant power of 2.
Such divisions will eventually be implemented with shifts which should
be reflected in the cost function.
Review: Ulrich Weigand
Added:
llvm/trunk/test/Analysis/CostModel/SystemZ/div-pow2.ll
Modified:
llvm/trunk/lib/Target/SystemZ/SystemZTargetTransformInfo.cpp
Modified: llvm/trunk/lib/Target/SystemZ/SystemZTargetTransformInfo.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/SystemZ/SystemZTargetTransformInfo.cpp?rev=303254&r1=303253&r2=303254&view=diff
==============================================================================
--- llvm/trunk/lib/Target/SystemZ/SystemZTargetTransformInfo.cpp (original)
+++ llvm/trunk/lib/Target/SystemZ/SystemZTargetTransformInfo.cpp Wed May 17 07:46:26 2017
@@ -325,6 +325,30 @@ int SystemZTTIImpl::getArithmeticInstrCo
unsigned ScalarBits = Ty->getScalarSizeInBits();
+ // Div with a constant which is a power of 2 will be converted by
+ // DAGCombiner to use shifts. With vector shift-element instructions, a
+ // vector sdiv costs about as much as a scalar one.
+ const unsigned SDivCostEstimate = 4;
+ bool SDivPow2 = false;
+ bool UDivPow2 = false;
+ if ((Opcode == Instruction::SDiv || Opcode == Instruction::UDiv) &&
+ Args.size() == 2) {
+ const ConstantInt *CI = nullptr;
+ if (const Constant *C = dyn_cast<Constant>(Args[1])) {
+ if (C->getType()->isVectorTy())
+ CI = dyn_cast_or_null<const ConstantInt>(C->getSplatValue());
+ else
+ CI = dyn_cast<const ConstantInt>(C);
+ }
+ if (CI != nullptr &&
+ (CI->getValue().isPowerOf2() || (-CI->getValue()).isPowerOf2())) {
+ if (Opcode == Instruction::SDiv)
+ SDivPow2 = true;
+ else
+ UDivPow2 = true;
+ }
+ }
+
if (Ty->isVectorTy()) {
assert (ST->hasVector() && "getArithmeticInstrCost() called with vector type.");
unsigned VF = Ty->getVectorNumElements();
@@ -333,10 +357,13 @@ int SystemZTTIImpl::getArithmeticInstrCo
// These vector operations are custom handled, but are still supported
// with one instruction per vector, regardless of element size.
if (Opcode == Instruction::Shl || Opcode == Instruction::LShr ||
- Opcode == Instruction::AShr) {
+ Opcode == Instruction::AShr || UDivPow2) {
return NumVectors;
}
+ if (SDivPow2)
+ return (NumVectors * SDivCostEstimate);
+
// These FP operations are supported with a single vector instruction for
// double (base implementation assumes float generally costs 2). For
// FP128, the scalar cost is 1, and there is no overhead since the values
@@ -395,6 +422,11 @@ int SystemZTTIImpl::getArithmeticInstrCo
// 2 * ipm sequences ; xor ; shift ; compare
return 7;
+ if (UDivPow2)
+ return 1;
+ if (SDivPow2)
+ return SDivCostEstimate;
+
// An extra extension for narrow types is needed.
if ((Opcode == Instruction::SDiv || Opcode == Instruction::SRem))
// sext of op(s) for narrow types
Added: llvm/trunk/test/Analysis/CostModel/SystemZ/div-pow2.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Analysis/CostModel/SystemZ/div-pow2.ll?rev=303254&view=auto
==============================================================================
--- llvm/trunk/test/Analysis/CostModel/SystemZ/div-pow2.ll (added)
+++ llvm/trunk/test/Analysis/CostModel/SystemZ/div-pow2.ll Wed May 17 07:46:26 2017
@@ -0,0 +1,154 @@
+; RUN: opt < %s -cost-model -analyze -mtriple=systemz-unknown -mcpu=z13 | FileCheck %s
+
+; Scalar sdiv
+
+define i64 @fun0(i64 %a) {
+ %r = sdiv i64 %a, 2
+ ret i64 %r
+; CHECK: Cost Model: Found an estimated cost of 4 for instruction: %r = sdiv i64 %a, 2
+}
+
+define i64 @fun1(i64 %a) {
+ %r = sdiv i64 %a, -4
+ ret i64 %r
+; CHECK: Cost Model: Found an estimated cost of 4 for instruction: %r = sdiv i64 %a, -4
+}
+
+define i32 @fun2(i32 %a) {
+ %r = sdiv i32 %a, 8
+ ret i32 %r
+; CHECK: Cost Model: Found an estimated cost of 4 for instruction: %r = sdiv i32 %a, 8
+}
+
+define i32 @fun3(i32 %a) {
+ %r = sdiv i32 %a, -16
+ ret i32 %r
+; CHECK: Cost Model: Found an estimated cost of 4 for instruction: %r = sdiv i32 %a, -16
+}
+
+define i16 @fun4(i16 %a) {
+ %r = sdiv i16 %a, 32
+ ret i16 %r
+; CHECK: Cost Model: Found an estimated cost of 4 for instruction: %r = sdiv i16 %a, 32
+}
+
+define i16 @fun5(i16 %a) {
+ %r = sdiv i16 %a, -64
+ ret i16 %r
+; CHECK: Cost Model: Found an estimated cost of 4 for instruction: %r = sdiv i16 %a, -64
+}
+
+define i8 @fun6(i8 %a) {
+ %r = sdiv i8 %a, 64
+ ret i8 %r
+; CHECK: Cost Model: Found an estimated cost of 4 for instruction: %r = sdiv i8 %a, 64
+}
+
+define i8 @fun7(i8 %a) {
+ %r = sdiv i8 %a, -128
+ ret i8 %r
+; CHECK: Cost Model: Found an estimated cost of 4 for instruction: %r = sdiv i8 %a, -128
+}
+
+
+; Vector sdiv
+
+define <2 x i64> @fun8(<2 x i64> %a) {
+ %r = sdiv <2 x i64> %a, <i64 2, i64 2>
+ ret <2 x i64> %r
+; CHECK: Cost Model: Found an estimated cost of 4 for instruction: %r = sdiv <2 x i64> %a, <i64 2, i64 2>
+}
+
+define <2 x i64> @fun9(<2 x i64> %a) {
+ %r = sdiv <2 x i64> %a, <i64 -4, i64 -4>
+ ret <2 x i64> %r
+; CHECK: Cost Model: Found an estimated cost of 4 for instruction: %r = sdiv <2 x i64> %a, <i64 -4, i64 -4>
+}
+
+define <4 x i32> @fun10(<4 x i32> %a) {
+ %r = sdiv <4 x i32> %a, <i32 8, i32 8, i32 8, i32 8>
+ ret <4 x i32> %r
+; CHECK: Cost Model: Found an estimated cost of 4 for instruction: %r = sdiv <4 x i32> %a, <i32 8, i32 8, i32 8, i32 8>
+}
+
+define <4 x i32> @fun11(<4 x i32> %a) {
+ %r = sdiv <4 x i32> %a, <i32 -16, i32 -16, i32 -16, i32 -16>
+ ret <4 x i32> %r
+; CHECK: Cost Model: Found an estimated cost of 4 for instruction: %r = sdiv <4 x i32> %a, <i32 -16
+}
+
+define <8 x i16> @fun12(<8 x i16> %a) {
+ %r = sdiv <8 x i16> %a, <i16 32, i16 32, i16 32, i16 32, i16 32, i16 32, i16 32, i16 32>
+ ret <8 x i16> %r
+; CHECK: Cost Model: Found an estimated cost of 4 for instruction: %r = sdiv <8 x i16> %a, <i16 32
+}
+
+define <8 x i16> @fun13(<8 x i16> %a) {
+ %r = sdiv <8 x i16> %a, <i16 -64, i16 -64, i16 -64, i16 -64, i16 -64, i16 -64, i16 -64, i16 -64>
+ ret <8 x i16> %r
+; CHECK: Cost Model: Found an estimated cost of 4 for instruction: %r = sdiv <8 x i16> %a, <i16 -64
+}
+
+define <16 x i8> @fun14(<16 x i8> %a) {
+ %r = sdiv <16 x i8> %a, <i8 64, i8 64, i8 64, i8 64, i8 64, i8 64, i8 64, i8 64, i8 64, i8 64, i8 64, i8 64, i8 64, i8 64, i8 64, i8 64>
+ ret <16 x i8> %r
+; CHECK: Cost Model: Found an estimated cost of 4 for instruction: %r = sdiv <16 x i8> %a, <i8 64
+}
+
+define <16 x i8> @fun15(<16 x i8> %a) {
+ %r = sdiv <16 x i8> %a, <i8 -128, i8 -128, i8 -128, i8 -128, i8 -128, i8 -128, i8 -128, i8 -128, i8 -128, i8 -128, i8 -128, i8 -128, i8 -128, i8 -128, i8 -128, i8 -128>
+ ret <16 x i8> %r
+; CHECK: Cost Model: Found an estimated cost of 4 for instruction: %r = sdiv <16 x i8> %a, <i8 -128
+}
+
+; Scalar udiv
+
+define i64 @fun16(i64 %a) {
+ %r = udiv i64 %a, 2
+ ret i64 %r
+; CHECK: Cost Model: Found an estimated cost of 1 for instruction: %r = udiv i64 %a, 2
+}
+
+define i32 @fun17(i32 %a) {
+ %r = udiv i32 %a, 8
+ ret i32 %r
+; CHECK: Cost Model: Found an estimated cost of 1 for instruction: %r = udiv i32 %a, 8
+}
+
+define i16 @fun18(i16 %a) {
+ %r = udiv i16 %a, 32
+ ret i16 %r
+; CHECK: Cost Model: Found an estimated cost of 1 for instruction: %r = udiv i16 %a, 32
+}
+
+define i8 @fun19(i8 %a) {
+ %r = udiv i8 %a, 128
+ ret i8 %r
+; CHECK: Cost Model: Found an estimated cost of 1 for instruction: %r = udiv i8 %a, -128
+}
+
+; Vector udiv
+
+define <2 x i64> @fun20(<2 x i64> %a) {
+ %r = udiv <2 x i64> %a, <i64 2, i64 2>
+ ret <2 x i64> %r
+; CHECK: Cost Model: Found an estimated cost of 1 for instruction: %r = udiv <2 x i64> %a, <i64 2
+}
+
+define <4 x i32> @fun21(<4 x i32> %a) {
+ %r = udiv <4 x i32> %a, <i32 8, i32 8, i32 8, i32 8>
+ ret <4 x i32> %r
+; CHECK: Cost Model: Found an estimated cost of 1 for instruction: %r = udiv <4 x i32> %a, <i32 8
+}
+
+define <8 x i16> @fun22(<8 x i16> %a) {
+ %r = udiv <8 x i16> %a, <i16 32, i16 32, i16 32, i16 32, i16 32, i16 32, i16 32, i16 32>
+ ret <8 x i16> %r
+; CHECK: Cost Model: Found an estimated cost of 1 for instruction: %r = udiv <8 x i16> %a, <i16 32
+}
+
+define <16 x i8> @fun23(<16 x i8> %a) {
+ %r = udiv <16 x i8> %a, <i8 128, i8 128, i8 128, i8 128, i8 128, i8 128, i8 128, i8 128, i8 128, i8 128, i8 128, i8 128, i8 128, i8 128, i8 128, i8 128>
+ ret <16 x i8> %r
+; CHECK: Cost Model: Found an estimated cost of 1 for instruction: %r = udiv <16 x i8> %a, <i8 -128
+}
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