[llvm] r176898 - ARM cost model: Increase the cost for vector casts that use the stack

[Arnold Schwaighofer]

Author: arnolds
Date: Tue Mar 12 16:19:22 2013
New Revision: 176898

URL: http://llvm.org/viewvc/llvm-project?rev=176898&view=rev
Log:
ARM cost model: Increase the cost for vector casts that use the stack

Increase the cost of v8/v16-i8 to v8/v16-i32 casts and truncates as the backend
currently lowers those using stack accesses.

This was responsible for a significant degradation on
MultiSource/Benchmarks/Trimaran/enc-pc1/enc-pc1
where we vectorize one loop to a vector factor of 16. After this patch we select
a vector factor of 4 which will generate reasonable code.

unsigned char cle[32];

void test(short c) {
  unsigned short compte;
  for (compte = 0; compte <= 31; compte++) {
    cle[compte] = cle[compte] ^ c;
  }
}

radar://13220512

Modified:
    llvm/trunk/lib/Target/ARM/ARMTargetTransformInfo.cpp
    llvm/trunk/test/Analysis/CostModel/ARM/cast.ll

Modified: llvm/trunk/lib/Target/ARM/ARMTargetTransformInfo.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/ARM/ARMTargetTransformInfo.cpp?rev=176898&r1=176897&r2=176898&view=diff
==============================================================================
--- llvm/trunk/lib/Target/ARM/ARMTargetTransformInfo.cpp (original)
+++ llvm/trunk/lib/Target/ARM/ARMTargetTransformInfo.cpp Tue Mar 12 16:19:22 2013
@@ -194,6 +194,14 @@ unsigned ARMTTI::getCastInstrCost(unsign
     { ISD::TRUNCATE,    MVT::v4i32, MVT::v4i64, 0 },
     { ISD::TRUNCATE,    MVT::v4i16, MVT::v4i32, 1 },
 
+    // Operations that we legalize using load/stores to the stack.
+    { ISD::SIGN_EXTEND, MVT::v16i32, MVT::v16i8, 16*2 + 4*4 },
+    { ISD::ZERO_EXTEND, MVT::v16i32, MVT::v16i8, 16*2 + 4*3 },
+    { ISD::SIGN_EXTEND, MVT::v8i32, MVT::v8i8, 8*2 + 2*4 },
+    { ISD::ZERO_EXTEND, MVT::v8i32, MVT::v8i8, 8*2 + 2*3 },
+    { ISD::TRUNCATE,    MVT::v16i8, MVT::v16i32, 4*1 + 16*2 + 2*1 },
+    { ISD::TRUNCATE,    MVT::v8i8, MVT::v8i32, 2*1 + 8*2 + 1 },
+
     // Vector float <-> i32 conversions.
     { ISD::SINT_TO_FP,  MVT::v4f32, MVT::v4i32, 1 },
     { ISD::UINT_TO_FP,  MVT::v4f32, MVT::v4i32, 1 },

Modified: llvm/trunk/test/Analysis/CostModel/ARM/cast.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Analysis/CostModel/ARM/cast.ll?rev=176898&r1=176897&r2=176898&view=diff
==============================================================================
--- llvm/trunk/test/Analysis/CostModel/ARM/cast.ll (original)
+++ llvm/trunk/test/Analysis/CostModel/ARM/cast.ll Tue Mar 12 16:19:22 2013
@@ -152,6 +152,20 @@ define i32 @casts() {
   ; CHECK: cost of 10 {{.*}} uitofp
   %r69 = uitofp i64 undef to double
 
+  ; Vector cast cost of instructions lowering the cast to the stack.
+  ; CHECK: cost of 24 {{.*}} sext
+  %r70 = sext <8 x i8> undef to <8 x i32>
+  ; CHECK: cost of 48 {{.*}} sext
+  %r71 = sext <16 x i8> undef to <16 x i32>
+  ; CHECK: cost of 22 {{.*}} zext
+  %r72 = zext <8 x i8> undef to <8 x i32>
+  ; CHECK: cost of 44 {{.*}} zext
+  %r73 = zext <16 x i8> undef to <16 x i32>
+  ; CHECK: cost of 19 {{.*}} trunc
+  %r74 = trunc <8 x i32> undef to <8 x i8>
+  ; CHECK: cost of 38 {{.*}} trunc
+  %r75 = trunc <16 x i32> undef to <16 x i8>
+
   ;CHECK: cost of 0 {{.*}} ret
   ret i32 undef
 }