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

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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.

llvm-svn: 295506
This commit is contained in:
Guozhi Wei 2017-02-17 22:29:39 +00:00
parent 1e2948ea7e
commit ad2db4b935
3 changed files with 31 additions and 1 deletions
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4
lib/Target/PowerPC/PPCTargetTransformInfo.cpp
View File

@ -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.

2
test/Analysis/CostModel/PowerPC/load_store.ll
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@ -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"

26
test/Analysis/CostModel/PowerPC/unaligned_ld_st.ll Normal file
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@ -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
}