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

llvm-svn: 176898

1 files changed, 8 insertions, 0 deletions

diff --git a/llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp b/llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp
index 01c04b48cfc..eef282e7092 100644
--- a/llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp
+++ b/llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp
@@ -194,6 +194,14 @@ unsigned ARMTTI::getCastInstrCost(unsigned Opcode, Type *Dst,
     { 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 },