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mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2024-12-14 11:32:34 +00:00

Fix the "test" optimization to recognize "dec" as an add of

negative one, as subtracts of immediates are canonicalized
to adds.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@66180 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2009-03-05 19:32:48 +00:00
parent 8733db351a
commit 4bfcf2a2a6
3 changed files with 31 additions and 9 deletions

View File

@ -5382,13 +5382,19 @@ SDValue X86TargetLowering::EmitTest(SDValue Op, SelectionDAG &DAG) {
UE = Op.getNode()->use_end(); UI != UE; ++UI)
if (UI->getOpcode() == ISD::STORE)
goto default_case;
// An add of one will be selected as an INC.
if (ConstantSDNode *C =
dyn_cast<ConstantSDNode>(Op.getNode()->getOperand(1)))
dyn_cast<ConstantSDNode>(Op.getNode()->getOperand(1))) {
// An add of one will be selected as an INC.
if (C->getAPIntValue() == 1) {
Opcode = X86ISD::INC;
break;
}
// An add of negative one (subtract of one) will be selected as a DEC.
if (C->getAPIntValue().isAllOnesValue()) {
Opcode = X86ISD::DEC;
break;
}
}
// Otherwise use a regular EFLAGS-setting add.
Opcode = X86ISD::ADD;
break;
@ -5399,13 +5405,6 @@ SDValue X86TargetLowering::EmitTest(SDValue Op, SelectionDAG &DAG) {
UE = Op.getNode()->use_end(); UI != UE; ++UI)
if (UI->getOpcode() == ISD::STORE)
goto default_case;
// A subtract of one will be selected as a DEC.
if (ConstantSDNode *C =
dyn_cast<ConstantSDNode>(Op.getNode()->getOperand(1)))
if (C->getAPIntValue() == 1) {
Opcode = X86ISD::DEC;
break;
}
// Otherwise use a regular EFLAGS-setting sub.
Opcode = X86ISD::SUB;
break;

View File

@ -0,0 +1,23 @@
; RUN: llvm-as < %s | llc -march=x86 > %t
; RUN: grep dec %t | count 1
; RUN: not grep test %t
; RUN: not grep cmp %t
define void @foo(i32 %n, double* nocapture %p) nounwind {
br label %bb
bb:
%indvar = phi i32 [ 0, %0 ], [ %indvar.next, %bb ]
%i.03 = sub i32 %n, %indvar
%1 = getelementptr double* %p, i32 %i.03
%2 = load double* %1, align 4
%3 = mul double %2, 2.930000e+00
store double %3, double* %1, align 4
%4 = add i32 %i.03, -1
%phitmp = icmp slt i32 %4, 0
%indvar.next = add i32 %indvar, 1
br i1 %phitmp, label %bb, label %return
return:
ret void
}