[llvm] r253349 - [ARM] Don't pessimize i32 vselect.

[Charlie Turner via llvm-commits]

Author: chatur01
Date: Tue Nov 17 11:25:15 2015
New Revision: 253349

URL: http://llvm.org/viewvc/llvm-project?rev=253349&view=rev
Log:
[ARM] Don't pessimize i32 vselect.

The underlying issues surrounding codegen for 32-bit vselects have been resolved. The pessimistic costs for 64-bit vselects remain due to the bad
scalarization that is still happening there.

I tested this on A57 in T32, A32 and A64 modes. I saw no regressions, and some improvements.

>From my benchmarks, I saw these improvements in A57 (T32)
spec.cpu2000.ref.177_mesa 5.95%
lnt.SingleSource/Benchmarks/Shootout/strcat 12.93%
lnt.MultiSource/Benchmarks/MiBench/telecomm-CRC32/telecomm-CRC32 11.89%

I also measured A57 A32, A53 T32 and A9 T32 and found no performance regressions. I see much bigger wins in third-party benchmarks with this change

Differential Revision: http://reviews.llvm.org/D14743


Modified:
    llvm/trunk/lib/Target/ARM/ARMTargetTransformInfo.cpp
    llvm/trunk/test/Analysis/CostModel/ARM/select.ll
    llvm/trunk/test/CodeGen/ARM/vselect_imax.ll

Modified: llvm/trunk/lib/Target/ARM/ARMTargetTransformInfo.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/ARM/ARMTargetTransformInfo.cpp?rev=253349&r1=253348&r2=253349&view=diff
==============================================================================
--- llvm/trunk/lib/Target/ARM/ARMTargetTransformInfo.cpp (original)
+++ llvm/trunk/lib/Target/ARM/ARMTargetTransformInfo.cpp Tue Nov 17 11:25:15 2015
@@ -274,9 +274,6 @@ int ARMTTIImpl::getCmpSelInstrCost(unsig
   if (ST->hasNEON() && ValTy->isVectorTy() && ISD == ISD::SELECT) {
     // Lowering of some vector selects is currently far from perfect.
     static const TypeConversionCostTblEntry NEONVectorSelectTbl[] = {
-      { ISD::SELECT, MVT::v16i1, MVT::v16i16, 2*16 + 1 + 3*1 + 4*1 },
-      { ISD::SELECT, MVT::v8i1, MVT::v8i32, 4*8 + 1*3 + 1*4 + 1*2 },
-      { ISD::SELECT, MVT::v16i1, MVT::v16i32, 4*16 + 1*6 + 1*8 + 1*4 },
       { ISD::SELECT, MVT::v4i1, MVT::v4i64, 4*4 + 1*2 + 1 },
       { ISD::SELECT, MVT::v8i1, MVT::v8i64, 50 },
       { ISD::SELECT, MVT::v16i1, MVT::v16i64, 100 }

Modified: llvm/trunk/test/Analysis/CostModel/ARM/select.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Analysis/CostModel/ARM/select.ll?rev=253349&r1=253348&r2=253349&view=diff
==============================================================================
--- llvm/trunk/test/Analysis/CostModel/ARM/select.ll (original)
+++ llvm/trunk/test/Analysis/CostModel/ARM/select.ll Tue Nov 17 11:25:15 2015
@@ -34,16 +34,16 @@ define void @casts() {
   %v12 = select <4 x i1>  undef, <4 x i16> undef, <4 x i16> undef
   ; CHECK: cost of 1 {{.*}} select
   %v13 = select <8 x i1>  undef, <8 x i16> undef, <8 x i16> undef
-  ; CHECK: cost of 40 {{.*}} select
+  ; CHECK: cost of 2 {{.*}} select
   %v13b = select <16 x i1>  undef, <16 x i16> undef, <16 x i16> undef
 
   ; CHECK: cost of 1 {{.*}} select
   %v14 = select <2 x i1> undef, <2 x i32> undef, <2 x i32> undef
   ; CHECK: cost of 1 {{.*}} select
   %v15 = select <4 x i1>  undef, <4 x i32> undef, <4 x i32> undef
-  ; CHECK: cost of 41 {{.*}} select
+  ; CHECK: cost of 2 {{.*}} select
   %v15b = select <8 x i1>  undef, <8 x i32> undef, <8 x i32> undef
-  ; CHECK: cost of 82 {{.*}} select
+  ; CHECK: cost of 4 {{.*}} select
   %v15c = select <16 x i1>  undef, <16 x i32> undef, <16 x i32> undef
 
   ; CHECK: cost of 1 {{.*}} select

Modified: llvm/trunk/test/CodeGen/ARM/vselect_imax.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/ARM/vselect_imax.ll?rev=253349&r1=253348&r2=253349&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/ARM/vselect_imax.ll (original)
+++ llvm/trunk/test/CodeGen/ARM/vselect_imax.ll Tue Nov 17 11:25:15 2015
@@ -10,8 +10,6 @@ define void @vmax_v4i32(<4 x i32>* %m, <
     ret void
 }
 
-; We adjusted the cost model of the following selects. When we improve code
-; lowering we also need to adjust the cost.
 %T0_10 = type <16 x i16>
 %T1_10 = type <16 x i1>
 ; CHECK-LABEL: func_blend10:
@@ -23,7 +21,7 @@ define void @func_blend10(%T0_10* %loada
 ; CHECK: vmin.s16
 ; CHECK: vmin.s16
 ; COST: func_blend10
-; COST: cost of 40 {{.*}} select
+; COST: cost of 2 {{.*}} select
   %r = select %T1_10 %c, %T0_10 %v0, %T0_10 %v1
   store %T0_10 %r, %T0_10* %storeaddr
   ret void
@@ -39,7 +37,7 @@ define void @func_blend14(%T0_14* %loada
 ; CHECK: vmin.s32
 ; CHECK: vmin.s32
 ; COST: func_blend14
-; COST: cost of 41 {{.*}} select
+; COST: cost of 2 {{.*}} select
   %r = select %T1_14 %c, %T0_14 %v0, %T0_14 %v1
   store %T0_14 %r, %T0_14* %storeaddr
   ret void
@@ -55,11 +53,14 @@ define void @func_blend15(%T0_15* %loada
   %v1 = load %T0_15, %T0_15* %loadaddr2
   %c = icmp slt %T0_15 %v0, %v1
 ; COST: func_blend15
-; COST: cost of 82 {{.*}} select
+; COST: cost of 4 {{.*}} select
   %r = select %T1_15 %c, %T0_15 %v0, %T0_15 %v1
   store %T0_15 %r, %T0_15* %storeaddr
   ret void
 }
+
+; We adjusted the cost model of the following selects. When we improve code
+; lowering we also need to adjust the cost.
 %T0_18 = type <4 x i64>
 %T1_18 = type <4 x i1>
 ; CHECK-LABEL: func_blend18: