Author: lattner
Date: Thu Aug 9 14:05:49 2007
New Revision: 40971
URL: http://llvm.org/viewvc/llvm-project?rev=40971&view=rev
Log:
when we see a unaligned load from an insufficiently aligned global or
alloca, increase the alignment of the load, turning it into an aligned load.
This allows us to compile:
#include <xmmintrin.h>
__m128i foo(__m128i x){
static const unsigned int c_0[4] = { 0, 0, 0, 0 };
__m128i v_Zero = _mm_loadu_si128((__m128i*)c_0);
x = _mm_unpacklo_epi8(x, v_Zero);
return x;
}
into:
_foo:
punpcklbw _c_0.5944, %xmm0
ret
.data
.lcomm _c_0.5944,16,4 # c_0.5944
instead of:
_foo:
movdqu _c_0.5944, %xmm1
punpcklbw %xmm1, %xmm0
ret
.data
.lcomm _c_0.5944,16,2 # c_0.5944
Added:
llvm/trunk/test/Transforms/InstCombine/align-inc.ll
Modified:
llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp
Modified: llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp
URL:
http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp?rev=40971&r1=40970&r2=40971&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp Thu Aug 9
14:05:49 2007
@@ -7492,13 +7492,23 @@
return 0;
}
-/// GetKnownAlignment - If the specified pointer has an alignment that we can
-/// determine, return it, otherwise return 0.
-static unsigned GetKnownAlignment(Value *V, TargetData *TD) {
+/// GetOrEnforceKnownAlignment - If the specified pointer has an alignment that
+/// we can determine, return it, otherwise return 0. If PrefAlign is
specified,
+/// and it is more than the alignment of the ultimate object, see if we can
+/// increase the alignment of the ultimate object, making this check succeed.
+static unsigned GetOrEnforceKnownAlignment(Value *V, TargetData *TD,
+ unsigned PrefAlign = 0) {
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V)) {
unsigned Align = GV->getAlignment();
if (Align == 0 && TD)
Align = TD->getPrefTypeAlignment(GV->getType()->getElementType());
+
+ // If there is a large requested alignment and we can, bump up the
alignment
+ // of the global.
+ if (PrefAlign > Align && GV->hasInitializer()) {
+ GV->setAlignment(PrefAlign);
+ Align = PrefAlign;
+ }
return Align;
} else if (AllocationInst *AI = dyn_cast<AllocationInst>(V)) {
unsigned Align = AI->getAlignment();
@@ -7516,18 +7526,20 @@
(unsigned)TD->getABITypeAlignment(Type::Int64Ty));
}
}
+
+ // If there is a requested alignment and if this is an alloca, round up.
We
+ // don't do this for malloc, because some systems can't respect the
request.
+ if (PrefAlign > Align && isa<AllocaInst>(AI)) {
+ AI->setAlignment(PrefAlign);
+ Align = PrefAlign;
+ }
return Align;
} else if (isa<BitCastInst>(V) ||
(isa<ConstantExpr>(V) &&
cast<ConstantExpr>(V)->getOpcode() == Instruction::BitCast)) {
- User *CI = cast<User>(V);
- if (isa<PointerType>(CI->getOperand(0)->getType()))
- return GetKnownAlignment(CI->getOperand(0), TD);
- return 0;
+ return GetOrEnforceKnownAlignment(cast<User>(V)->getOperand(0),
+ TD, PrefAlign);
} else if (User *GEPI = dyn_castGetElementPtr(V)) {
- unsigned BaseAlignment = GetKnownAlignment(GEPI->getOperand(0), TD);
- if (BaseAlignment == 0) return 0;
-
// If all indexes are zero, it is just the alignment of the base pointer.
bool AllZeroOperands = true;
for (unsigned i = 1, e = GEPI->getNumOperands(); i != e; ++i)
@@ -7536,9 +7548,15 @@
AllZeroOperands = false;
break;
}
- if (AllZeroOperands)
- return BaseAlignment;
-
+
+ if (AllZeroOperands) {
+ // Treat this like a bitcast.
+ return GetOrEnforceKnownAlignment(GEPI->getOperand(0), TD, PrefAlign);
+ }
+
+ unsigned BaseAlignment =
GetOrEnforceKnownAlignment(GEPI->getOperand(0),TD);
+ if (BaseAlignment == 0) return 0;
+
// Otherwise, if the base alignment is >= the alignment we expect for the
// base pointer type, then we know that the resultant pointer is aligned at
// least as much as its type requires.
@@ -7608,15 +7626,15 @@
// If we can determine a pointer alignment that is bigger than currently
// set, update the alignment.
if (isa<MemCpyInst>(MI) || isa<MemMoveInst>(MI)) {
- unsigned Alignment1 = GetKnownAlignment(MI->getOperand(1), TD);
- unsigned Alignment2 = GetKnownAlignment(MI->getOperand(2), TD);
+ unsigned Alignment1 = GetOrEnforceKnownAlignment(MI->getOperand(1), TD);
+ unsigned Alignment2 = GetOrEnforceKnownAlignment(MI->getOperand(2), TD);
unsigned Align = std::min(Alignment1, Alignment2);
if (MI->getAlignment()->getZExtValue() < Align) {
MI->setAlignment(ConstantInt::get(Type::Int32Ty, Align));
Changed = true;
}
} else if (isa<MemSetInst>(MI)) {
- unsigned Alignment = GetKnownAlignment(MI->getDest(), TD);
+ unsigned Alignment = GetOrEnforceKnownAlignment(MI->getDest(), TD);
if (MI->getAlignment()->getZExtValue() < Alignment) {
MI->setAlignment(ConstantInt::get(Type::Int32Ty, Alignment));
Changed = true;
@@ -7634,7 +7652,7 @@
case Intrinsic::x86_sse2_loadu_dq:
// Turn PPC lvx -> load if the pointer is known aligned.
// Turn X86 loadups -> load if the pointer is known aligned.
- if (GetKnownAlignment(II->getOperand(1), TD) >= 16) {
+ if (GetOrEnforceKnownAlignment(II->getOperand(1), TD, 16) >= 16) {
Value *Ptr = InsertCastBefore(Instruction::BitCast, II->getOperand(1),
PointerType::get(II->getType()), CI);
return new LoadInst(Ptr);
@@ -7643,7 +7661,7 @@
case Intrinsic::ppc_altivec_stvx:
case Intrinsic::ppc_altivec_stvxl:
// Turn stvx -> store if the pointer is known aligned.
- if (GetKnownAlignment(II->getOperand(2), TD) >= 16) {
+ if (GetOrEnforceKnownAlignment(II->getOperand(2), TD, 16) >= 16) {
const Type *OpPtrTy = PointerType::get(II->getOperand(1)->getType());
Value *Ptr = InsertCastBefore(Instruction::BitCast, II->getOperand(2),
OpPtrTy, CI);
@@ -7655,7 +7673,7 @@
case Intrinsic::x86_sse2_storeu_dq:
case Intrinsic::x86_sse2_storel_dq:
// Turn X86 storeu -> store if the pointer is known aligned.
- if (GetKnownAlignment(II->getOperand(1), TD) >= 16) {
+ if (GetOrEnforceKnownAlignment(II->getOperand(1), TD, 16) >= 16) {
const Type *OpPtrTy = PointerType::get(II->getOperand(2)->getType());
Value *Ptr = InsertCastBefore(Instruction::BitCast, II->getOperand(1),
OpPtrTy, CI);
@@ -8768,7 +8786,7 @@
Value *Op = LI.getOperand(0);
// Attempt to improve the alignment.
- unsigned KnownAlign = GetKnownAlignment(Op, TD);
+ unsigned KnownAlign = GetOrEnforceKnownAlignment(Op, TD);
if (KnownAlign > LI.getAlignment())
LI.setAlignment(KnownAlign);
@@ -8968,7 +8986,7 @@
}
// Attempt to improve the alignment.
- unsigned KnownAlign = GetKnownAlignment(Ptr, TD);
+ unsigned KnownAlign = GetOrEnforceKnownAlignment(Ptr, TD);
if (KnownAlign > SI.getAlignment())
SI.setAlignment(KnownAlign);
Added: llvm/trunk/test/Transforms/InstCombine/align-inc.ll
URL:
http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/align-inc.ll?rev=40971&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/align-inc.ll (added)
+++ llvm/trunk/test/Transforms/InstCombine/align-inc.ll Thu Aug 9 14:05:49 2007
@@ -0,0 +1,14 @@
+; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep {GLOBAL.*align 16}
+; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep {tmp = load}
+
[EMAIL PROTECTED] = internal constant [4 x i32] zeroinitializer
+
+declare <16 x i8> @llvm.x86.sse2.loadu.dq(i8*)
+
+
+define <16 x i8> @foo(<2 x i64> %x) {
+entry:
+ %tmp = tail call <16 x i8> @llvm.x86.sse2.loadu.dq( i8* bitcast ([4 x
i32]* @GLOBAL to i8*) )
+ ret <16 x i8> %tmp
+}
+
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