[llvm] [CostModel][X86] Fix fpext conversion cost for 16 elements (PR #76278)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-backend-x86

@llvm/pr-subscribers-llvm-analysis

Author: None (HaohaiWen)

<details>
<summary>Changes</summary>

The fpext conversion cost for 16 elements should be 5.

---
Full diff: https://github.com/llvm/llvm-project/pull/76278.diff


2 Files Affected:

- (modified) llvm/lib/Target/X86/X86TargetTransformInfo.cpp (+1) 
- (modified) llvm/test/Analysis/CostModel/X86/cast.ll (+12-8) 


``````````diff
diff --git a/llvm/lib/Target/X86/X86TargetTransformInfo.cpp b/llvm/lib/Target/X86/X86TargetTransformInfo.cpp
index 8a04987e768a12..e7b7c9666ed43c 100644
--- a/llvm/lib/Target/X86/X86TargetTransformInfo.cpp
+++ b/llvm/lib/Target/X86/X86TargetTransformInfo.cpp
@@ -2223,6 +2223,7 @@ InstructionCost X86TTIImpl::getCastInstrCost(unsigned Opcode, Type *Dst,
   static const TypeConversionCostTblEntry AVX512FConversionTbl[] = {
     { ISD::FP_EXTEND, MVT::v8f64,   MVT::v8f32,  1 },
     { ISD::FP_EXTEND, MVT::v8f64,   MVT::v16f32, 3 },
+    { ISD::FP_EXTEND, MVT::v16f64,  MVT::v16f32, 5 }, // 2*vcvtps2pd+vextractf64x4
     { ISD::FP_ROUND,  MVT::v8f32,   MVT::v8f64,  1 },
 
     { ISD::TRUNCATE,  MVT::v2i1,    MVT::v2i8,   3 }, // sext+vpslld+vptestmd
diff --git a/llvm/test/Analysis/CostModel/X86/cast.ll b/llvm/test/Analysis/CostModel/X86/cast.ll
index 5a83d4e81fd38e..790f408b00609d 100644
--- a/llvm/test/Analysis/CostModel/X86/cast.ll
+++ b/llvm/test/Analysis/CostModel/X86/cast.ll
@@ -616,27 +616,31 @@ define void @fp_conv(<8 x float> %a, <16 x float>%b, <4 x float> %c) {
 ; SSE-LABEL: 'fp_conv'
 ; SSE-NEXT:  Cost Model: Found an estimated cost of 3 for instruction: %A1 = fpext <4 x float> %c to <4 x double>
 ; SSE-NEXT:  Cost Model: Found an estimated cost of 6 for instruction: %A2 = fpext <8 x float> %a to <8 x double>
-; SSE-NEXT:  Cost Model: Found an estimated cost of 3 for instruction: %A3 = fptrunc <4 x double> undef to <4 x float>
-; SSE-NEXT:  Cost Model: Found an estimated cost of 6 for instruction: %A4 = fptrunc <8 x double> undef to <8 x float>
+; SSE-NEXT:  Cost Model: Found an estimated cost of 12 for instruction: %A3 = fpext <16 x float> %b to <16 x double>
+; SSE-NEXT:  Cost Model: Found an estimated cost of 3 for instruction: %A4 = fptrunc <4 x double> undef to <4 x float>
+; SSE-NEXT:  Cost Model: Found an estimated cost of 6 for instruction: %A5 = fptrunc <8 x double> undef to <8 x float>
 ; SSE-NEXT:  Cost Model: Found an estimated cost of 0 for instruction: ret void
 ;
 ; AVX-LABEL: 'fp_conv'
 ; AVX-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %A1 = fpext <4 x float> %c to <4 x double>
 ; AVX-NEXT:  Cost Model: Found an estimated cost of 3 for instruction: %A2 = fpext <8 x float> %a to <8 x double>
-; AVX-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %A3 = fptrunc <4 x double> undef to <4 x float>
-; AVX-NEXT:  Cost Model: Found an estimated cost of 3 for instruction: %A4 = fptrunc <8 x double> undef to <8 x float>
+; AVX-NEXT:  Cost Model: Found an estimated cost of 6 for instruction: %A3 = fpext <16 x float> %b to <16 x double>
+; AVX-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %A4 = fptrunc <4 x double> undef to <4 x float>
+; AVX-NEXT:  Cost Model: Found an estimated cost of 3 for instruction: %A5 = fptrunc <8 x double> undef to <8 x float>
 ; AVX-NEXT:  Cost Model: Found an estimated cost of 0 for instruction: ret void
 ;
 ; AVX512-LABEL: 'fp_conv'
 ; AVX512-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %A1 = fpext <4 x float> %c to <4 x double>
 ; AVX512-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %A2 = fpext <8 x float> %a to <8 x double>
-; AVX512-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %A3 = fptrunc <4 x double> undef to <4 x float>
-; AVX512-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %A4 = fptrunc <8 x double> undef to <8 x float>
+; AVX512-NEXT:  Cost Model: Found an estimated cost of 5 for instruction: %A3 = fpext <16 x float> %b to <16 x double>
+; AVX512-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %A4 = fptrunc <4 x double> undef to <4 x float>
+; AVX512-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %A5 = fptrunc <8 x double> undef to <8 x float>
 ; AVX512-NEXT:  Cost Model: Found an estimated cost of 0 for instruction: ret void
 ;
   %A1 = fpext <4 x float> %c to <4 x double>
   %A2 = fpext <8 x float> %a to <8 x double>
-  %A3 = fptrunc <4 x double> undef to <4 x float>
-  %A4 = fptrunc <8 x double> undef to <8 x float>
+  %A3 = fpext <16 x float> %b to <16 x double>
+  %A4 = fptrunc <4 x double> undef to <4 x float>
+  %A5 = fptrunc <8 x double> undef to <8 x float>
   ret void
 }

``````````

</details>


https://github.com/llvm/llvm-project/pull/76278