[AArch64] Generate tbz/tbnz when comparing against zero.

The tbz/tbnz checks the sign bit to convert

op w1, w1, w10
cmp w1, #0
b.lt .LBB0_0

to

op w1, w1, w10
tbnz w1, #31, .LBB0_0

Differential Revision: http://reviews.llvm.org/D4440

llvm-svn: 214518
This commit is contained in:
Chad Rosier 2014-08-01 14:48:56 +00:00
parent 087606898b
commit 579c02c9a5
2 changed files with 274 additions and 10 deletions

View File

@ -2916,11 +2916,6 @@ SDValue AArch64TargetLowering::LowerBR_CC(SDValue Op, SelectionDAG &DAG) const {
isPowerOf2_64(LHS.getConstantOperandVal(1))) {
SDValue Test = LHS.getOperand(0);
uint64_t Mask = LHS.getConstantOperandVal(1);
// TBZ only operates on i64's, but the ext should be free.
if (Test.getValueType() == MVT::i32)
Test = DAG.getAnyExtOrTrunc(Test, dl, MVT::i64);
return DAG.getNode(AArch64ISD::TBZ, dl, MVT::Other, Chain, Test,
DAG.getConstant(Log2_64(Mask), MVT::i64), Dest);
}
@ -2936,18 +2931,29 @@ SDValue AArch64TargetLowering::LowerBR_CC(SDValue Op, SelectionDAG &DAG) const {
isPowerOf2_64(LHS.getConstantOperandVal(1))) {
SDValue Test = LHS.getOperand(0);
uint64_t Mask = LHS.getConstantOperandVal(1);
// TBNZ only operates on i64's, but the ext should be free.
if (Test.getValueType() == MVT::i32)
Test = DAG.getAnyExtOrTrunc(Test, dl, MVT::i64);
return DAG.getNode(AArch64ISD::TBNZ, dl, MVT::Other, Chain, Test,
DAG.getConstant(Log2_64(Mask), MVT::i64), Dest);
}
return DAG.getNode(AArch64ISD::CBNZ, dl, MVT::Other, Chain, LHS, Dest);
} else if (CC == ISD::SETLT && LHS.getOpcode() != ISD::AND) {
// Don't combine AND since emitComparison converts the AND to an ANDS
// (a.k.a. TST) and the test in the test bit and branch instruction
// becomes redundant. This would also increase register pressure.
uint64_t Mask = LHS.getValueType().getSizeInBits() - 1;
return DAG.getNode(AArch64ISD::TBNZ, dl, MVT::Other, Chain, LHS,
DAG.getConstant(Mask, MVT::i64), Dest);
}
}
if (RHSC && RHSC->getSExtValue() == -1 && CC == ISD::SETGT &&
LHS.getOpcode() != ISD::AND) {
// Don't combine AND since emitComparison converts the AND to an ANDS
// (a.k.a. TST) and the test in the test bit and branch instruction
// becomes redundant. This would also increase register pressure.
uint64_t Mask = LHS.getValueType().getSizeInBits() - 1;
return DAG.getNode(AArch64ISD::TBZ, dl, MVT::Other, Chain, LHS,
DAG.getConstant(Mask, MVT::i64), Dest);
}
SDValue CCVal;
SDValue Cmp = getAArch64Cmp(LHS, RHS, CC, CCVal, DAG, dl);

View File

@ -0,0 +1,258 @@
; RUN: llc -O1 -march=aarch64 < %s | FileCheck %s
declare void @t()
define void @test1(i32 %a) {
; CHECK-LABEL: @test1
entry:
%sub = add nsw i32 %a, -12
%cmp = icmp slt i32 %sub, 0
br i1 %cmp, label %if.then, label %if.end
; CHECK: sub [[CMP:w[0-9]+]], w0, #12
; CHECK: tbz [[CMP]], #31
if.then:
call void @t()
br label %if.end
if.end:
ret void
}
define void @test2(i64 %a) {
; CHECK-LABEL: @test2
entry:
%sub = add nsw i64 %a, -12
%cmp = icmp slt i64 %sub, 0
br i1 %cmp, label %if.then, label %if.end
; CHECK: sub [[CMP:x[0-9]+]], x0, #12
; CHECK: tbz [[CMP]], #63
if.then:
call void @t()
br label %if.end
if.end:
ret void
}
define void @test3(i32 %a) {
; CHECK-LABEL: @test3
entry:
%sub = add nsw i32 %a, -12
%cmp = icmp sgt i32 %sub, -1
br i1 %cmp, label %if.then, label %if.end
; CHECK: sub [[CMP:w[0-9]+]], w0, #12
; CHECK: tbnz [[CMP]], #31
if.then:
call void @t()
br label %if.end
if.end:
ret void
}
define void @test4(i64 %a) {
; CHECK-LABEL: @test4
entry:
%sub = add nsw i64 %a, -12
%cmp = icmp sgt i64 %sub, -1
br i1 %cmp, label %if.then, label %if.end
; CHECK: sub [[CMP:x[0-9]+]], x0, #12
; CHECK: tbnz [[CMP]], #63
if.then:
call void @t()
br label %if.end
if.end:
ret void
}
define void @test5(i32 %a) {
; CHECK-LABEL: @test5
entry:
%sub = add nsw i32 %a, -12
%cmp = icmp sge i32 %sub, 0
br i1 %cmp, label %if.then, label %if.end
; CHECK: sub [[CMP:w[0-9]+]], w0, #12
; CHECK: tbnz [[CMP]], #31
if.then:
call void @t()
br label %if.end
if.end:
ret void
}
define void @test6(i64 %a) {
; CHECK-LABEL: @test6
entry:
%sub = add nsw i64 %a, -12
%cmp = icmp sge i64 %sub, 0
br i1 %cmp, label %if.then, label %if.end
; CHECK: sub [[CMP:x[0-9]+]], x0, #12
; CHECK: tbnz [[CMP]], #63
if.then:
call void @t()
br label %if.end
if.end:
ret void
}
define void @test7(i32 %a) {
; CHECK-LABEL: @test7
entry:
%sub = sub nsw i32 %a, 12
%cmp = icmp slt i32 %sub, 0
br i1 %cmp, label %if.then, label %if.end
; CHECK: sub [[CMP:w[0-9]+]], w0, #12
; CHECK: tbz [[CMP]], #31
if.then:
call void @t()
br label %if.end
if.end:
ret void
}
define void @test8(i64 %val1, i64 %val2, i64 %val3) {
; CHECK-LABEL: @test8
%and1 = and i64 %val1, %val2
%tst1 = icmp slt i64 %and1, 0
br i1 %tst1, label %if.then1, label %if.end
; CHECK: tst x0, x1
; CHECK-NEXT: b.ge .L
if.then1:
%and2 = and i64 %val2, %val3
%tst2 = icmp sge i64 %and2, 0
br i1 %tst2, label %if.then2, label %if.end
; CHECK: and [[CMP:x[0-9]+]], x1, x2
; CHECK-NOT: cmp
; CHECK: tbnz [[CMP]], #63, .LBB7_5
if.then2:
%shifted_op1 = shl i64 %val2, 63
%shifted_and1 = and i64 %val1, %shifted_op1
%tst3 = icmp slt i64 %shifted_and1, 0
br i1 %tst3, label %if.then3, label %if.end
; CHECK: tst x0, x1, lsl #63
; CHECK: b.ge .L
if.then3:
%shifted_op2 = shl i64 %val2, 62
%shifted_and2 = and i64 %val1, %shifted_op2
%tst4 = icmp sge i64 %shifted_and2, 0
br i1 %tst4, label %if.then4, label %if.end
; CHECK: tst x0, x1, lsl #62
; CHECK: b.lt .L
if.then4:
call void @t()
br label %if.end
if.end:
ret void
}
define void @test9(i64 %val1) {
; CHECK-LABEL: @test9
%tst = icmp slt i64 %val1, 0
br i1 %tst, label %if.then, label %if.end
; CHECK-NOT: cmp
; CHECK: tbz x0, #63, .L
if.then:
call void @t()
br label %if.end
if.end:
ret void
}
define void @test10(i64 %val1) {
; CHECK-LABEL: @test10
%tst = icmp slt i64 %val1, 0
br i1 %tst, label %if.then, label %if.end
; CHECK-NOT: cmp
; CHECK: tbz x0, #63, .L
if.then:
call void @t()
br label %if.end
if.end:
ret void
}
define void @test11(i64 %val1, i64* %ptr) {
; CHECK-LABEL: @test11
; CHECK: ldr [[CMP:x[0-9]+]], [x1]
; CHECK-NOT: cmp
; CHECK: tbz [[CMP]], #63, .L
%val = load i64* %ptr
%tst = icmp slt i64 %val, 0
br i1 %tst, label %if.then, label %if.end
if.then:
call void @t()
br label %if.end
if.end:
ret void
}
define void @test12(i64 %val1) {
; CHECK-LABEL: @test12
%tst = icmp slt i64 %val1, 0
br i1 %tst, label %if.then, label %if.end
; CHECK-NOT: cmp
; CHECK: tbz x0, #63, .L
if.then:
call void @t()
br label %if.end
if.end:
ret void
}
define void @test13(i64 %val1, i64 %val2) {
; CHECK-LABEL: @test13
%or = or i64 %val1, %val2
%tst = icmp slt i64 %or, 0
br i1 %tst, label %if.then, label %if.end
; CHECK: orr [[CMP:x[0-9]+]], x0, x1
; CHECK-NOT: cmp
; CHECK: tbz [[CMP]], #63, .L
if.then:
call void @t()
br label %if.end
if.end:
ret void
}