[llvm] [AArch64] Improve cost computations for odd vector mem ops. (PR #78181)
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Mon Jan 15 08:20:53 PST 2024
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-backend-aarch64
@llvm/pr-subscribers-llvm-analysis
Author: Florian Hahn (fhahn)
<details>
<summary>Changes</summary>
Improve cost computaton for odd vector mem ops by breaking them down into smaller power-of-2 parts and sum up the cost of those parts.
This fixes the current cost estimates, which for most parts underestimated the cos, due to using getTypeLegalizationCost, which widens to the next power-of-2 in a single step in most cases. This doesn't reflect the actual cost.
See https://llvm.godbolt.org/z/vMsnxMf1v for codegen for the tests.
Note that there is a special case for v3i8, for which current codegen is pretty bad, due to automatic widening to v4i8, which in turn requires the conversion to go through memory ops in the stack. I am planning on fixing that as a follow-up, but I am not yet sure where to best fix this.
At the moment, there are almost no cases in which such vector operations will be generated automatically. The motivating case is non-power-of-2 SLP vectorization: https://github.com/llvm/llvm-project/pull/77790
---
Full diff: https://github.com/llvm/llvm-project/pull/78181.diff
2 Files Affected:
- (modified) llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp (+41-8)
- (modified) llvm/test/Analysis/CostModel/AArch64/vec3-ops.ll (+32-32)
``````````diff
diff --git a/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp b/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
index 13b5e578391dee..fd389d70bb853b 100644
--- a/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
+++ b/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
@@ -3176,14 +3176,47 @@ InstructionCost AArch64TTIImpl::getMemoryOpCost(unsigned Opcode, Type *Ty,
if (Ty->isPtrOrPtrVectorTy())
return LT.first;
- // Check truncating stores and extending loads.
- if (useNeonVector(Ty) &&
- Ty->getScalarSizeInBits() != LT.second.getScalarSizeInBits()) {
- // v4i8 types are lowered to scalar a load/store and sshll/xtn.
- if (VT == MVT::v4i8)
- return 2;
- // Otherwise we need to scalarize.
- return cast<FixedVectorType>(Ty)->getNumElements() * 2;
+ if (useNeonVector(Ty)) {
+ // Check truncating stores and extending loads.
+ if (Ty->getScalarSizeInBits() != LT.second.getScalarSizeInBits()) {
+ // v4i8 types are lowered to scalar a load/store and sshll/xtn.
+ if (VT == MVT::v4i8)
+ return 2;
+ // Otherwise we need to scalarize.
+ return cast<FixedVectorType>(Ty)->getNumElements() * 2;
+ }
+ EVT EltVT = VT.getVectorElementType();
+ unsigned EltSize = EltVT.getScalarSizeInBits();
+ if (!isPowerOf2_32(EltSize) || EltSize < 8 || EltSize > 64 ||
+ VT.getVectorNumElements() >= 128 / EltSize || !Alignment ||
+ *Alignment != Align(1))
+ return LT.first;
+ // FIXME: v3i8 lowering currently is very inefficient, due to automatic
+ // widening to v4i8, which produces suboptimal results.
+ if (VT.getVectorNumElements() == 3 && EltVT == MVT::i8)
+ return LT.first;
+
+ // Check non-power-of-2 loads/stores for legal vector element types with
+ // NEON. Non-power-of-2 memory ops will get broken down to a set of
+ // operations on smaller power-of-2 ops, including ld1/st1.
+ LLVMContext &C = Ty->getContext();
+ InstructionCost Cost(0);
+ SmallVector<EVT> TypeWorklist;
+ TypeWorklist.push_back(VT);
+ while (!TypeWorklist.empty()) {
+ EVT CurrVT = TypeWorklist.pop_back_val();
+ unsigned CurrNumElements = CurrVT.getVectorNumElements();
+ if (isPowerOf2_32(CurrNumElements)) {
+ Cost += 1;
+ continue;
+ }
+
+ unsigned PrevPow2 = NextPowerOf2(CurrNumElements) / 2;
+ TypeWorklist.push_back(EVT::getVectorVT(C, EltVT, PrevPow2));
+ TypeWorklist.push_back(
+ EVT::getVectorVT(C, EltVT, CurrNumElements - PrevPow2));
+ }
+ return Cost;
}
return LT.first;
diff --git a/llvm/test/Analysis/CostModel/AArch64/vec3-ops.ll b/llvm/test/Analysis/CostModel/AArch64/vec3-ops.ll
index 3e439c2696683e..cf80bd677228ab 100644
--- a/llvm/test/Analysis/CostModel/AArch64/vec3-ops.ll
+++ b/llvm/test/Analysis/CostModel/AArch64/vec3-ops.ll
@@ -3,12 +3,12 @@
define void @vec3_i32(<3 x i32> %a, <3 x i32> %b, ptr %src, ptr %dst) {
; CHECK-LABEL: 'vec3_i32'
-; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %l = load <3 x i32>, ptr %src, align 1
+; CHECK-NEXT: Cost Model: Found an estimated cost of 2 for instruction: %l = load <3 x i32>, ptr %src, align 1
; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %add = add <3 x i32> %l, %b
; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %cmp = icmp uge <3 x i32> %add, %a
; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %sub = sub <3 x i32> %add, %a
; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %sel = select <3 x i1> %cmp, <3 x i32> %add, <3 x i32> %sub
-; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: store <3 x i32> %sel, ptr %dst, align 1
+; CHECK-NEXT: Cost Model: Found an estimated cost of 2 for instruction: store <3 x i32> %sel, ptr %dst, align 1
; CHECK-NEXT: Cost Model: Found an estimated cost of 0 for instruction: ret void
;
%l = load <3 x i32>, ptr %src, align 1
@@ -41,12 +41,12 @@ define void @vec3_i32_default_alignment(<3 x i32> %a, <3 x i32> %b, ptr %src, pt
define void @vec3_i16(<3 x i16> %a, <3 x i16> %b, ptr %src, ptr %dst) {
; CHECK-LABEL: 'vec3_i16'
-; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %l = load <3 x i16>, ptr %src, align 1
+; CHECK-NEXT: Cost Model: Found an estimated cost of 2 for instruction: %l = load <3 x i16>, ptr %src, align 1
; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %add = add <3 x i16> %l, %b
; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %cmp = icmp uge <3 x i16> %add, %a
; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %sub = sub <3 x i16> %add, %a
; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %sel = select <3 x i1> %cmp, <3 x i16> %add, <3 x i16> %sub
-; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: store <3 x i16> %sel, ptr %dst, align 1
+; CHECK-NEXT: Cost Model: Found an estimated cost of 2 for instruction: store <3 x i16> %sel, ptr %dst, align 1
; CHECK-NEXT: Cost Model: Found an estimated cost of 0 for instruction: ret void
;
%l = load <3 x i16>, ptr %src, align 1
@@ -60,9 +60,9 @@ define void @vec3_i16(<3 x i16> %a, <3 x i16> %b, ptr %src, ptr %dst) {
define void @vec7_i16(ptr %src, ptr %dst) {
; CHECK-LABEL: 'vec7_i16'
-; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %l = load <7 x i16>, ptr %src, align 1
+; CHECK-NEXT: Cost Model: Found an estimated cost of 3 for instruction: %l = load <7 x i16>, ptr %src, align 1
; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %add = add <7 x i16> %l, %l
-; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: store <7 x i16> %add, ptr %dst, align 1
+; CHECK-NEXT: Cost Model: Found an estimated cost of 3 for instruction: store <7 x i16> %add, ptr %dst, align 1
; CHECK-NEXT: Cost Model: Found an estimated cost of 0 for instruction: ret void
;
%l = load <7 x i16>, ptr %src, align 1
@@ -73,9 +73,9 @@ define void @vec7_i16(ptr %src, ptr %dst) {
define void @vec6_i16(ptr %src, ptr %dst) {
; CHECK-LABEL: 'vec6_i16'
-; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %l = load <6 x i16>, ptr %src, align 1
+; CHECK-NEXT: Cost Model: Found an estimated cost of 2 for instruction: %l = load <6 x i16>, ptr %src, align 1
; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %add = add <6 x i16> %l, %l
-; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: store <6 x i16> %add, ptr %dst, align 1
+; CHECK-NEXT: Cost Model: Found an estimated cost of 2 for instruction: store <6 x i16> %add, ptr %dst, align 1
; CHECK-NEXT: Cost Model: Found an estimated cost of 0 for instruction: ret void
;
%l = load <6 x i16>, ptr %src, align 1
@@ -86,9 +86,9 @@ define void @vec6_i16(ptr %src, ptr %dst) {
define void @vec5_i16(ptr %src, ptr %dst) {
; CHECK-LABEL: 'vec5_i16'
-; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %l = load <5 x i16>, ptr %src, align 1
+; CHECK-NEXT: Cost Model: Found an estimated cost of 2 for instruction: %l = load <5 x i16>, ptr %src, align 1
; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %add = add <5 x i16> %l, %l
-; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: store <5 x i16> %add, ptr %dst, align 1
+; CHECK-NEXT: Cost Model: Found an estimated cost of 2 for instruction: store <5 x i16> %add, ptr %dst, align 1
; CHECK-NEXT: Cost Model: Found an estimated cost of 0 for instruction: ret void
;
%l = load <5 x i16>, ptr %src, align 1
@@ -99,12 +99,12 @@ define void @vec5_i16(ptr %src, ptr %dst) {
define void @vec3_i16_zext_i32(<3 x i32> %a, <3 x i32> %b, ptr %src, ptr %dst) {
; CHECK-LABEL: 'vec3_i16_zext_i32'
-; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %l = load <3 x i16>, ptr %src, align 1
+; CHECK-NEXT: Cost Model: Found an estimated cost of 2 for instruction: %l = load <3 x i16>, ptr %src, align 1
; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %l.ext = zext <3 x i16> %l to <3 x i32>
; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %add = add <3 x i32> %l.ext, %b
; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %sub = sub <3 x i32> %add, %a
; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %sub.trunc = trunc <3 x i32> %sub to <3 x i16>
-; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: store <3 x i16> %sub.trunc, ptr %dst, align 1
+; CHECK-NEXT: Cost Model: Found an estimated cost of 2 for instruction: store <3 x i16> %sub.trunc, ptr %dst, align 1
; CHECK-NEXT: Cost Model: Found an estimated cost of 0 for instruction: ret void
;
%l = load <3 x i16>, ptr %src, align 1
@@ -190,10 +190,10 @@ define void @vec3_i30(<3 x i30> %a, <3 x i30> %b, ptr %src, ptr %dst) {
define void @vec3_float(<3 x float> %a, <3 x float> %b, ptr %src, ptr %dst) {
; CHECK-LABEL: 'vec3_float'
-; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %l = load <3 x float>, ptr %src, align 1
+; CHECK-NEXT: Cost Model: Found an estimated cost of 2 for instruction: %l = load <3 x float>, ptr %src, align 1
; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %add = fadd <3 x float> %l, %b
; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %sub = fsub <3 x float> %add, %a
-; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: store <3 x float> %sub, ptr %dst, align 1
+; CHECK-NEXT: Cost Model: Found an estimated cost of 2 for instruction: store <3 x float> %sub, ptr %dst, align 1
; CHECK-NEXT: Cost Model: Found an estimated cost of 0 for instruction: ret void
;
%l = load <3 x float>, ptr %src, align 1
@@ -205,10 +205,10 @@ define void @vec3_float(<3 x float> %a, <3 x float> %b, ptr %src, ptr %dst) {
define void @vec3_half(<3 x half> %a, <3 x half> %b, ptr %src, ptr %dst) {
; CHECK-LABEL: 'vec3_half'
-; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %l = load <3 x half>, ptr %src, align 1
+; CHECK-NEXT: Cost Model: Found an estimated cost of 2 for instruction: %l = load <3 x half>, ptr %src, align 1
; CHECK-NEXT: Cost Model: Found an estimated cost of 2 for instruction: %add = fadd <3 x half> %l, %b
; CHECK-NEXT: Cost Model: Found an estimated cost of 2 for instruction: %sub = fsub <3 x half> %add, %a
-; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: store <3 x half> %sub, ptr %dst, align 1
+; CHECK-NEXT: Cost Model: Found an estimated cost of 2 for instruction: store <3 x half> %sub, ptr %dst, align 1
; CHECK-NEXT: Cost Model: Found an estimated cost of 0 for instruction: ret void
;
%l = load <3 x half>, ptr %src, align 1
@@ -220,9 +220,9 @@ define void @vec3_half(<3 x half> %a, <3 x half> %b, ptr %src, ptr %dst) {
define void @vec15_i8(ptr %src, ptr %dst) {
; CHECK-LABEL: 'vec15_i8'
-; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %l = load <15 x i8>, ptr %src, align 1
+; CHECK-NEXT: Cost Model: Found an estimated cost of 4 for instruction: %l = load <15 x i8>, ptr %src, align 1
; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %add = add <15 x i8> %l, %l
-; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: store <15 x i8> %add, ptr %dst, align 1
+; CHECK-NEXT: Cost Model: Found an estimated cost of 4 for instruction: store <15 x i8> %add, ptr %dst, align 1
; CHECK-NEXT: Cost Model: Found an estimated cost of 0 for instruction: ret void
;
%l = load <15 x i8>, ptr %src, align 1
@@ -233,9 +233,9 @@ define void @vec15_i8(ptr %src, ptr %dst) {
define void @vec14_i8(ptr %src, ptr %dst) {
; CHECK-LABEL: 'vec14_i8'
-; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %l = load <14 x i8>, ptr %src, align 1
+; CHECK-NEXT: Cost Model: Found an estimated cost of 3 for instruction: %l = load <14 x i8>, ptr %src, align 1
; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %add = add <14 x i8> %l, %l
-; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: store <14 x i8> %add, ptr %dst, align 1
+; CHECK-NEXT: Cost Model: Found an estimated cost of 3 for instruction: store <14 x i8> %add, ptr %dst, align 1
; CHECK-NEXT: Cost Model: Found an estimated cost of 0 for instruction: ret void
;
%l = load <14 x i8>, ptr %src, align 1
@@ -246,9 +246,9 @@ define void @vec14_i8(ptr %src, ptr %dst) {
define void @vec13_i8(ptr %src, ptr %dst) {
; CHECK-LABEL: 'vec13_i8'
-; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %l = load <13 x i8>, ptr %src, align 1
+; CHECK-NEXT: Cost Model: Found an estimated cost of 3 for instruction: %l = load <13 x i8>, ptr %src, align 1
; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %add = add <13 x i8> %l, %l
-; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: store <13 x i8> %add, ptr %dst, align 1
+; CHECK-NEXT: Cost Model: Found an estimated cost of 3 for instruction: store <13 x i8> %add, ptr %dst, align 1
; CHECK-NEXT: Cost Model: Found an estimated cost of 0 for instruction: ret void
;
%l = load <13 x i8>, ptr %src, align 1
@@ -259,9 +259,9 @@ define void @vec13_i8(ptr %src, ptr %dst) {
define void @vec12_i8(ptr %src, ptr %dst) {
; CHECK-LABEL: 'vec12_i8'
-; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %l = load <12 x i8>, ptr %src, align 1
+; CHECK-NEXT: Cost Model: Found an estimated cost of 2 for instruction: %l = load <12 x i8>, ptr %src, align 1
; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %add = add <12 x i8> %l, %l
-; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: store <12 x i8> %add, ptr %dst, align 1
+; CHECK-NEXT: Cost Model: Found an estimated cost of 2 for instruction: store <12 x i8> %add, ptr %dst, align 1
; CHECK-NEXT: Cost Model: Found an estimated cost of 0 for instruction: ret void
;
%l = load <12 x i8>, ptr %src, align 1
@@ -272,9 +272,9 @@ define void @vec12_i8(ptr %src, ptr %dst) {
define void @vec11_i8(ptr %src, ptr %dst) {
; CHECK-LABEL: 'vec11_i8'
-; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %l = load <11 x i8>, ptr %src, align 1
+; CHECK-NEXT: Cost Model: Found an estimated cost of 3 for instruction: %l = load <11 x i8>, ptr %src, align 1
; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %add = add <11 x i8> %l, %l
-; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: store <11 x i8> %add, ptr %dst, align 1
+; CHECK-NEXT: Cost Model: Found an estimated cost of 3 for instruction: store <11 x i8> %add, ptr %dst, align 1
; CHECK-NEXT: Cost Model: Found an estimated cost of 0 for instruction: ret void
;
%l = load <11 x i8>, ptr %src, align 1
@@ -285,10 +285,10 @@ define void @vec11_i8(ptr %src, ptr %dst) {
define void @vec7_i8(<7 x i8> %a, <7 x i8> %b, ptr %src, ptr %dst) {
; CHECK-LABEL: 'vec7_i8'
-; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %l = load <7 x i8>, ptr %src, align 1
+; CHECK-NEXT: Cost Model: Found an estimated cost of 3 for instruction: %l = load <7 x i8>, ptr %src, align 1
; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %add = add <7 x i8> %l, %b
; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %sub = sub <7 x i8> %add, %a
-; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: store <7 x i8> %sub, ptr %dst, align 1
+; CHECK-NEXT: Cost Model: Found an estimated cost of 3 for instruction: store <7 x i8> %sub, ptr %dst, align 1
; CHECK-NEXT: Cost Model: Found an estimated cost of 0 for instruction: ret void
;
%l = load <7 x i8>, ptr %src, align 1
@@ -300,9 +300,9 @@ define void @vec7_i8(<7 x i8> %a, <7 x i8> %b, ptr %src, ptr %dst) {
define void @vec6_i8(ptr %src, ptr %dst) {
; CHECK-LABEL: 'vec6_i8'
-; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %l = load <6 x i8>, ptr %src, align 1
+; CHECK-NEXT: Cost Model: Found an estimated cost of 2 for instruction: %l = load <6 x i8>, ptr %src, align 1
; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %add = add <6 x i8> %l, %l
-; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: store <6 x i8> %add, ptr %dst, align 1
+; CHECK-NEXT: Cost Model: Found an estimated cost of 2 for instruction: store <6 x i8> %add, ptr %dst, align 1
; CHECK-NEXT: Cost Model: Found an estimated cost of 0 for instruction: ret void
;
%l = load <6 x i8>, ptr %src, align 1
@@ -313,9 +313,9 @@ define void @vec6_i8(ptr %src, ptr %dst) {
define void @vec5_i8(ptr %src, ptr %dst) {
; CHECK-LABEL: 'vec5_i8'
-; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %l = load <5 x i8>, ptr %src, align 1
+; CHECK-NEXT: Cost Model: Found an estimated cost of 2 for instruction: %l = load <5 x i8>, ptr %src, align 1
; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %add = add <5 x i8> %l, %l
-; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: store <5 x i8> %add, ptr %dst, align 1
+; CHECK-NEXT: Cost Model: Found an estimated cost of 2 for instruction: store <5 x i8> %add, ptr %dst, align 1
; CHECK-NEXT: Cost Model: Found an estimated cost of 0 for instruction: ret void
;
%l = load <5 x i8>, ptr %src, align 1
``````````
</details>
https://github.com/llvm/llvm-project/pull/78181
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