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Optimize alignment of loads and stores. 

llvm-svn: 40102
This commit is contained in:
Dan Gohman 2007-07-20 16:34:21 +00:00
parent 45863cc202
commit e31a61eeca
2 changed files with 76 additions and 0 deletions
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10
llvm/lib/Transforms/Scalar/InstructionCombining.cpp
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@ -8790,6 +8790,11 @@ static bool isSafeToLoadUnconditionally(Value *V, Instruction *ScanFrom) {
Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
Value *Op = LI.getOperand(0);
// Attempt to improve the alignment.
unsigned KnownAlign = GetKnownAlignment(Op, TD);
if (KnownAlign > LI.getAlignment())
LI.setAlignment(KnownAlign);
// load (cast X) --> cast (load X) iff safe
if (isa<CastInst>(Op))
if (Instruction *Res = InstCombineLoadCast(*this, LI))
@ -8985,6 +8990,11 @@ Instruction *InstCombiner::visitStoreInst(StoreInst &SI) {
}
}
// Attempt to improve the alignment.
unsigned KnownAlign = GetKnownAlignment(Ptr, TD);
if (KnownAlign > SI.getAlignment())
SI.setAlignment(KnownAlign);
// Do really simple DSE, to catch cases where there are several consequtive
// stores to the same location, separated by a few arithmetic operations. This
// situation often occurs with bitfield accesses.

66
llvm/test/Transforms/InstCombine/loadstore-alignment.ll Normal file
View File

@ -0,0 +1,66 @@
; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep {, align 16} | wc -l | grep 12
@x = external global <2 x i64>, align 16
@xx = external global [13 x <2 x i64>], align 16
define <2 x i64> @static_hem() {
%t = getelementptr <2 x i64>* @x, i32 7
%tmp1 = load <2 x i64>* %t, align 1
ret <2 x i64> %tmp1
}
define <2 x i64> @hem(i32 %i) {
%t = getelementptr <2 x i64>* @x, i32 %i
%tmp1 = load <2 x i64>* %t, align 1
ret <2 x i64> %tmp1
}
define <2 x i64> @hem_2d(i32 %i, i32 %j) {
%t = getelementptr [13 x <2 x i64>]* @xx, i32 %i, i32 %j
%tmp1 = load <2 x i64>* %t, align 1
ret <2 x i64> %tmp1
}
define <2 x i64> @foo() {
%tmp1 = load <2 x i64>* @x, align 1
ret <2 x i64> %tmp1
}
define <2 x i64> @bar() {
%t = alloca <2 x i64>
call void @kip(<2 x i64>* %t);
%tmp1 = load <2 x i64>* %t, align 1
ret <2 x i64> %tmp1
}
define void @static_hem_store(<2 x i64> %y) {
%t = getelementptr <2 x i64>* @x, i32 7
store <2 x i64> %y, <2 x i64>* %t, align 1
ret void
}
define void @hem_store(i32 %i, <2 x i64> %y) {
%t = getelementptr <2 x i64>* @x, i32 %i
store <2 x i64> %y, <2 x i64>* %t, align 1
ret void
}
define void @hem_2d_store(i32 %i, i32 %j, <2 x i64> %y) {
%t = getelementptr [13 x <2 x i64>]* @xx, i32 %i, i32 %j
store <2 x i64> %y, <2 x i64>* %t, align 1
ret void
}
define void @foo_store(<2 x i64> %y) {
store <2 x i64> %y, <2 x i64>* @x, align 1
ret void
}
define void @bar_store(<2 x i64> %y) {
%t = alloca <2 x i64>
call void @kip(<2 x i64>* %t);
store <2 x i64> %y, <2 x i64>* %t, align 1
ret void
}
declare void @kip(<2 x i64>* %t)