[llvm] [LV][AArch64] LoopVectorizer allows scalable frem instructions (PR #76247)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-llvm-analysis

@llvm/pr-subscribers-backend-aarch64

Author: Paschalis Mpeis (paschalis-mpeis)

<details>
<summary>Changes</summary>

In AArch64, when an 'frem' instruction uses scalable vectors, it will be replaced with a vector library call. LoopVectorize is now aware of that so it no longer returns invalid costs.

When it is not scalable, it returns the default costs, which are delegated to the BaseT TTI Implementation.

---

# Dependencies:
- merged after: #<!-- -->76166
- (not a stacked PR)

---
Full diff: https://github.com/llvm/llvm-project/pull/76247.diff


4 Files Affected:

- (modified) llvm/lib/Analysis/TargetTransformInfo.cpp (-1) 
- (modified) llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp (+15) 
- (modified) llvm/test/Analysis/CostModel/AArch64/arith-fp-sve.ll (+12-11) 
- (modified) llvm/test/Analysis/CostModel/AArch64/arith-fp.ll (+1-1) 


``````````diff
diff --git a/llvm/lib/Analysis/TargetTransformInfo.cpp b/llvm/lib/Analysis/TargetTransformInfo.cpp
index 3f76dfdaac317c..a50176d3ad7f7c 100644
--- a/llvm/lib/Analysis/TargetTransformInfo.cpp
+++ b/llvm/lib/Analysis/TargetTransformInfo.cpp
@@ -17,7 +17,6 @@
 #include "llvm/IR/IntrinsicInst.h"
 #include "llvm/IR/Module.h"
 #include "llvm/IR/Operator.h"
-#include "llvm/IR/PatternMatch.h"
 #include "llvm/InitializePasses.h"
 #include "llvm/Support/CommandLine.h"
 #include <optional>
diff --git a/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp b/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
index b5b8b68291786d..0a76c670c68a8b 100644
--- a/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
+++ b/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
@@ -2902,6 +2902,21 @@ InstructionCost AArch64TTIImpl::getArithmeticInstrCost(
     if (!Ty->getScalarType()->isFP128Ty())
       return LT.first;
     [[fallthrough]];
+  case ISD::FREM: {
+    // Scalable frem instructions will be replaced with Vector library calls.
+    if (Ty->isScalableTy()) {
+      SmallVector<Type *, 4> OpTypes;
+      for (auto &Op : CxtI->operands())
+        OpTypes.push_back(Op->getType());
+
+      InstructionCost ScalableCost =
+          getCallInstrCost(nullptr, Ty, OpTypes, CostKind);
+      return ScalableCost;
+    } else {
+      return BaseT::getArithmeticInstrCost(Opcode, Ty, CostKind, Op1Info,
+                                           Op2Info);
+    }
+  }
   case ISD::FMUL:
   case ISD::FDIV:
     // These nodes are marked as 'custom' just to lower them to SVE.
diff --git a/llvm/test/Analysis/CostModel/AArch64/arith-fp-sve.ll b/llvm/test/Analysis/CostModel/AArch64/arith-fp-sve.ll
index 18a1c31c03f748..682bb5a58a7846 100644
--- a/llvm/test/Analysis/CostModel/AArch64/arith-fp-sve.ll
+++ b/llvm/test/Analysis/CostModel/AArch64/arith-fp-sve.ll
@@ -1,7 +1,8 @@
-; NOTE: Assertions have been autogenerated by utils/update_analyze_test_checks.py
-; RUN: opt < %s -enable-no-nans-fp-math -passes="print<cost-model>" 2>&1 -disable-output -mtriple=aarch64 -mattr=+fullfp16 -mattr=+sve | FileCheck %s
+; NOTE: Assertions have been autogenerated by utils/update_analyze_test_checks.py UTC_ARGS: --version 4
+; RUN: opt -mattr=+sve -mattr=+fullfp16 -enable-no-nans-fp-math -disable-output -passes="print<cost-model>" %s 2>&1 | FileCheck %s
+
+target triple = "aarch64-unknown-linux-gnu"
 
-target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
 
 define void @fadd() {
 ; CHECK-LABEL: 'fadd'
@@ -137,14 +138,14 @@ define void @fdiv() {
 
 define void @frem() {
 ; CHECK-LABEL: 'frem'
-; CHECK-NEXT:  Cost Model: Invalid cost for instruction: %V4F16 = frem <vscale x 4 x half> undef, undef
-; CHECK-NEXT:  Cost Model: Invalid cost for instruction: %V8F16 = frem <vscale x 8 x half> undef, undef
-; CHECK-NEXT:  Cost Model: Invalid cost for instruction: %V16F16 = frem <vscale x 16 x half> undef, undef
-; CHECK-NEXT:  Cost Model: Invalid cost for instruction: %V2F32 = frem <vscale x 2 x float> undef, undef
-; CHECK-NEXT:  Cost Model: Invalid cost for instruction: %V4F32 = frem <vscale x 4 x float> undef, undef
-; CHECK-NEXT:  Cost Model: Invalid cost for instruction: %V8F32 = frem <vscale x 8 x float> undef, undef
-; CHECK-NEXT:  Cost Model: Invalid cost for instruction: %V2F64 = frem <vscale x 2 x double> undef, undef
-; CHECK-NEXT:  Cost Model: Invalid cost for instruction: %V4F64 = frem <vscale x 4 x double> undef, undef
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 10 for instruction: %V4F16 = frem <vscale x 4 x half> undef, undef
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 10 for instruction: %V8F16 = frem <vscale x 8 x half> undef, undef
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 10 for instruction: %V16F16 = frem <vscale x 16 x half> undef, undef
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 10 for instruction: %V2F32 = frem <vscale x 2 x float> undef, undef
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 10 for instruction: %V4F32 = frem <vscale x 4 x float> undef, undef
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 10 for instruction: %V8F32 = frem <vscale x 8 x float> undef, undef
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 10 for instruction: %V2F64 = frem <vscale x 2 x double> undef, undef
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 10 for instruction: %V4F64 = frem <vscale x 4 x double> undef, undef
 ; CHECK-NEXT:  Cost Model: Found an estimated cost of 0 for instruction: ret void
 ;
   %V4F16 = frem <vscale x 4 x half> undef, undef
diff --git a/llvm/test/Analysis/CostModel/AArch64/arith-fp.ll b/llvm/test/Analysis/CostModel/AArch64/arith-fp.ll
index c352892354fc24..403ee8e861387e 100644
--- a/llvm/test/Analysis/CostModel/AArch64/arith-fp.ll
+++ b/llvm/test/Analysis/CostModel/AArch64/arith-fp.ll
@@ -1,7 +1,7 @@
 ; NOTE: Assertions have been autogenerated by utils/update_analyze_test_checks.py
 ; RUN: opt < %s -enable-no-nans-fp-math  -passes="print<cost-model>" 2>&1 -disable-output -mtriple=aarch64 -mattr=+fullfp16 | FileCheck %s
 
-target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
+target triple = "aarch64-unknown-linux-gnu"
 
 define i32 @fadd(i32 %arg) {
 ; CHECK-LABEL: 'fadd'

``````````

</details>


https://github.com/llvm/llvm-project/pull/76247