[CostModel][X86] Fix expanded CTPOP i8 costs

Updated to match #79989 / 9410019

Author: RKSimon

llvm/lib/Target/X86/X86TargetTransformInfo.cpp

@@ -4000,7 +4000,7 @@ X86TTIImpl::getIntrinsicInstrCost(const IntrinsicCostAttributes &ICA,
     { ISD::CTTZ_ZERO_UNDEF, MVT::i8, {  2,  2,  1,  1 } }, // BSF
     { ISD::CTPOP,      MVT::i32,     {  8,  7, 15, 15 } },
     { ISD::CTPOP,      MVT::i16,     {  9,  8, 17, 17 } },
-    { ISD::CTPOP,      MVT::i8,      {  7,  6, 13, 13 } },
+    { ISD::CTPOP,      MVT::i8,      {  7,  6,  6,  6 } },
     { ISD::ROTL,       MVT::i32,     {  2,  3,  1,  3 } },
     { ISD::ROTL,       MVT::i16,     {  2,  3,  1,  3 } },
     { ISD::ROTL,       MVT::i8,      {  2,  3,  1,  3 } },

llvm/test/Analysis/CostModel/X86/ctpop-codesize.ll

@@ -57,7 +57,7 @@ define i16 @var_ctpop_i16(i16 %a) {
 
 define i8 @var_ctpop_i8(i8 %a) {
 ; NOPOPCNT-LABEL: 'var_ctpop_i8'
-; NOPOPCNT-NEXT:  Cost Model: Found an estimated cost of 13 for instruction: %ctpop = call i8 @llvm.ctpop.i8(i8 %a)
+; NOPOPCNT-NEXT:  Cost Model: Found an estimated cost of 6 for instruction: %ctpop = call i8 @llvm.ctpop.i8(i8 %a)
 ; NOPOPCNT-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: ret i8 %ctpop
 ;
 ; POPCNT-LABEL: 'var_ctpop_i8'

llvm/test/Analysis/CostModel/X86/ctpop-sizelatency.ll

@@ -57,7 +57,7 @@ define i16 @var_ctpop_i16(i16 %a) {
 
 define i8 @var_ctpop_i8(i8 %a) {
 ; NOPOPCNT-LABEL: 'var_ctpop_i8'
-; NOPOPCNT-NEXT:  Cost Model: Found an estimated cost of 13 for instruction: %ctpop = call i8 @llvm.ctpop.i8(i8 %a)
+; NOPOPCNT-NEXT:  Cost Model: Found an estimated cost of 6 for instruction: %ctpop = call i8 @llvm.ctpop.i8(i8 %a)
 ; NOPOPCNT-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: ret i8 %ctpop
 ;
 ; POPCNT-LABEL: 'var_ctpop_i8'