[PPC] Give unaligned memory access lower cost on processor that supports it

Newer ppc supports unaligned memory access, it reduces the cost of unaligned memory access significantly. This patch handles this case in PPCTTIImpl::getMemoryOpCost.

This patch fixes pr31492.

Differential Revision: https://reviews.llvm.org/D28630

This is resubmit of r292680, which was reverted by r293092. The internal application failures were actually caused by a source code bug.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@295506 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/PowerPC/PPCTargetTransformInfo.cpp b/lib/Target/PowerPC/PPCTargetTransformInfo.cpp
index f94d1ea..2f1bcea 100644 (file)
--- a/lib/Target/PowerPC/PPCTargetTransformInfo.cpp
+++ b/lib/Target/PowerPC/PPCTargetTransformInfo.cpp
@@ -401,6 +401,10 @@ int PPCTTIImpl::getMemoryOpCost(unsigned Opcode, Type *Src, unsigned Alignment,
   if (IsVSXType || (ST->hasVSX() && IsAltivecType))
     return Cost;
 
+  // Newer PPC supports unaligned memory access.
+  if (TLI->allowsMisalignedMemoryAccesses(LT.second, 0))
+    return Cost;
+
   // PPC in general does not support unaligned loads and stores. They'll need
   // to be decomposed based on the alignment factor.
 

diff --git a/test/Analysis/CostModel/PowerPC/load_store.ll b/test/Analysis/CostModel/PowerPC/load_store.ll
index d48be5b..b77dd44 100644 (file)
--- a/test/Analysis/CostModel/PowerPC/load_store.ll
+++ b/test/Analysis/CostModel/PowerPC/load_store.ll
@@ -1,4 +1,4 @@
-; RUN: opt < %s  -cost-model -analyze -mtriple=powerpc64-unknown-linux-gnu -mcpu=g5 | FileCheck %s
+; RUN: opt < %s  -cost-model -analyze -mtriple=powerpc64-unknown-linux-gnu -mcpu=g5 -disable-ppc-unaligned | FileCheck %s
 target datalayout = "E-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-f128:128:128-v128:128:128-n32:64"
 target triple = "powerpc64-unknown-linux-gnu"
 

diff --git a/test/Analysis/CostModel/PowerPC/unaligned_ld_st.ll b/test/Analysis/CostModel/PowerPC/unaligned_ld_st.ll
new file mode 100644 (file)
index 0000000..6addf25
--- /dev/null
+++ b/test/Analysis/CostModel/PowerPC/unaligned_ld_st.ll
@@ -0,0 +1,26 @@
+; RUN: opt < %s -cost-model -analyze -mtriple=powerpc64-unknown-linux-gnu -mcpu=pwr8 -mattr=+vsx | FileCheck %s
+target datalayout = "E-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-f128:128:128-v128:128:128-n32:64"
+target triple = "powerpc64-unknown-linux-gnu"
+
+define i32 @test(i32 %arg) {
+
+  ; CHECK: cost of 1 {{.*}} load
+  load i8, i8* undef, align 1
+  ; CHECK: cost of 1 {{.*}} load
+  load i16, i16* undef, align 1
+  ; CHECK: cost of 1 {{.*}} load
+  load i32, i32* undef, align 1
+  ; CHECK: cost of 1 {{.*}} load
+  load i64, i64* undef, align 1
+
+  ; CHECK: cost of 1 {{.*}} store
+  store i8 undef, i8* undef, align 1
+  ; CHECK: cost of 1 {{.*}} store
+  store i16 undef, i16* undef, align 1
+  ; CHECK: cost of 1 {{.*}} store
+  store i32 undef, i32* undef, align 1
+  ; CHECK: cost of 1 {{.*}} store
+  store i64 undef, i64* undef, align 1
+
+  ret i32 undef
+}