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This test case:

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long test(long x) { return (x & 123124) | 3; }

Currently compiles to:

_test:
        orl     $3, %edi
        movq    %rdi, %rax
        andq    $123127, %rax
        ret

This is because instruction and DAG combiners canonicalize

  (or (and x, C), D) -> (and (or, D), (C | D))

However, this is only profitable if (C & D) != 0. It gets in the way of the
3-addressification because the input bits are known to be zero.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@97616 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Bill Wendling 2010-03-03 00:35:56 +00:00
parent a43398283d
commit 7d9f2b93a3
4 changed files with 35 additions and 19 deletions
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4
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
View File

@ -1786,7 +1786,7 @@ SDValue DAGCombiner::visitAND(SDNode *N) {
SDValue RAND = ReassociateOps(ISD::AND, N->getDebugLoc(), N0, N1);
if (RAND.getNode() != 0)
return RAND;
// fold (and (or x, 0xFFFF), 0xFF) -> 0xFF
// fold (and (or x, C), D) -> D if (C & D) == D
if (N1C && N0.getOpcode() == ISD::OR)
if (ConstantSDNode *ORI = dyn_cast<ConstantSDNode>(N0.getOperand(1)))
if ((ORI->getAPIntValue() & N1C->getAPIntValue()) == N1C->getAPIntValue())
@ -2025,9 +2025,11 @@ SDValue DAGCombiner::visitOR(SDNode *N) {
if (ROR.getNode() != 0)
return ROR;
// Canonicalize (or (and X, c1), c2) -> (and (or X, c2), c1|c2)
// iff (c1 & c2) == 0.
if (N1C && N0.getOpcode() == ISD::AND && N0.getNode()->hasOneUse() &&
isa<ConstantSDNode>(N0.getOperand(1))) {
ConstantSDNode *C1 = cast<ConstantSDNode>(N0.getOperand(1));
if ((C1->getZExtValue() & N1C->getZExtValue()) != 0)
return DAG.getNode(ISD::AND, N->getDebugLoc(), VT,
DAG.getNode(ISD::OR, N0.getDebugLoc(), VT,
N0.getOperand(0), N1),

4
lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
View File

@ -1465,7 +1465,6 @@ Instruction *InstCombiner::visitOr(BinaryOperator &I) {
if (Value *V = SimplifyOrInst(Op0, Op1, TD))
return ReplaceInstUsesWith(I, V);
// See if we can simplify any instructions used by the instruction whose sole
// purpose is to compute bits we don't care about.
if (SimplifyDemandedInstructionBits(I))
@ -1474,7 +1473,9 @@ Instruction *InstCombiner::visitOr(BinaryOperator &I) {
if (ConstantInt *RHS = dyn_cast<ConstantInt>(Op1)) {
ConstantInt *C1 = 0; Value *X = 0;
// (X & C1) | C2 --> (X | C2) & (C1|C2)
// iff (C1 & C2) == 0.
if (match(Op0, m_And(m_Value(X), m_ConstantInt(C1))) &&
(RHS->getValue() & C1->getValue()) != 0 &&
Op0->hasOneUse()) {
Value *Or = Builder->CreateOr(X, RHS);
Or->takeName(Op0);
@ -1497,6 +1498,7 @@ Instruction *InstCombiner::visitOr(BinaryOperator &I) {
if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
if (Instruction *R = FoldOpIntoSelect(I, SI))
return R;
if (isa<PHINode>(Op0))
if (Instruction *NV = FoldOpIntoPhi(I))
return NV;

26
test/CodeGen/X86/and-or-fold.ll
View File

@ -1,14 +1,26 @@
; RUN: llc < %s -march=x86 | grep and | count 1
; RUN: llc < %s -mtriple=i686-apple-darwin | FileCheck -check-prefix=DARWIN %s
; RUN: opt < %s -O2 | llc -mtriple=x86_64-apple-darwin | FileCheck -check-prefix=DARWIN-OPT %s
; The dag combiner should fold together (x&127)|(y&16711680) -> (x|y)&c1
; in this case.
define i32 @test6(i32 %x, i16 %y) {
%tmp1 = zext i16 %y to i32 ; <i32> [#uses=1]
%tmp2 = and i32 %tmp1, 127 ; <i32> [#uses=1]
%tmp4 = shl i32 %x, 16 ; <i32> [#uses=1]
%tmp5 = and i32 %tmp4, 16711680 ; <i32> [#uses=1]
%tmp6 = or i32 %tmp2, %tmp5 ; <i32> [#uses=1]
define i32 @test1(i32 %x, i16 %y) {
%tmp1 = zext i16 %y to i32
%tmp2 = and i32 %tmp1, 127
%tmp4 = shl i32 %x, 16
%tmp5 = and i32 %tmp4, 16711680
%tmp6 = or i32 %tmp2, %tmp5
ret i32 %tmp6
; DARWIN: andl $16711807, %eax
}
; <rdar://problem/7529774> The optimizer shouldn't fold this into (and (or, C), D)
; if (C & D) == 0
define i64 @test2(i64 %x) nounwind readnone ssp {
entry:
%tmp1 = and i64 %x, 123127
%tmp2 = or i64 %tmp1, 3
ret i64 %tmp2
; DARWIN-OPT: andq $123124
; DARWIN-OPT-NEXT: leaq 3
}

8
test/Transforms/InstCombine/xor2.ll
View File

@ -22,8 +22,8 @@ define i1 @test1(i32 %A) {
; PR1014
define i32 @test2(i32 %tmp1) {
; CHECK: @test2
; CHECK-NEXT: or i32 %tmp1, 8
; CHECK-NEXT: and i32
; CHECK-NEXT: and i32 %tmp1, 32
; CHECK-NEXT: or i32 %ovm, 8
; CHECK-NEXT: ret i32
%ovm = and i32 %tmp1, 32
%ov3 = add i32 %ovm, 145
@ -33,8 +33,8 @@ define i32 @test2(i32 %tmp1) {
define i32 @test3(i32 %tmp1) {
; CHECK: @test3
; CHECK-NEXT: or i32 %tmp1, 8
; CHECK-NEXT: and i32
; CHECK-NEXT: and i32 %tmp1, 32
; CHECK-NEXT: or i32 %tmp, 8
; CHECK-NEXT: ret i32
%ovm = or i32 %tmp1, 145
%ov31 = and i32 %ovm, 177