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[X86] Enable BT to be used in place of TEST for single bit checks under optsize 

We already do this for 64-bit when it won't fit into a 64-bit AND/TEST's immediate field. This adds an additional qualifier to do it for any single bit constant larger than 8-bits under optsize

Differential Revision: https://reviews.llvm.org/D43346

llvm-svn: 325290
This commit is contained in:
Craig Topper 2018-02-15 20:27:30 +00:00
parent dac3c1f5c8
commit f3f35efe5c
2 changed files with 15 additions and 12 deletions
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15
llvm/lib/Target/X86/X86ISelLowering.cpp
View File

@ -17709,12 +17709,15 @@ static SDValue LowerAndToBT(SDValue And, ISD::CondCode CC,
if (AndRHSVal == 1 && AndLHS.getOpcode() == ISD::SRL) {
LHS = AndLHS.getOperand(0);
RHS = AndLHS.getOperand(1);
}
// Use BT if the immediate can't be encoded in a TEST instruction.
if (!isUInt<32>(AndRHSVal) && isPowerOf2_64(AndRHSVal)) {
LHS = AndLHS;
RHS = DAG.getConstant(Log2_64_Ceil(AndRHSVal), dl, LHS.getValueType());
} else {
// Use BT if the immediate can't be encoded in a TEST instruction or we
// are optimizing for size and the immedaite won't fit in a byte.
bool OptForSize = DAG.getMachineFunction().getFunction().optForSize();
if ((!isUInt<32>(AndRHSVal) || (OptForSize && !isUInt<8>(AndRHSVal))) &&
isPowerOf2_64(AndRHSVal)) {
LHS = AndLHS;
RHS = DAG.getConstant(Log2_64_Ceil(AndRHSVal), dl, LHS.getValueType());
}
}
}

12
llvm/test/CodeGen/X86/test-vs-bittest.ll
View File

@ -75,8 +75,8 @@ define void @test64_optsize_2(i64 inreg %x) optsize {
; CHECK: # %bb.0:
; CHECK-NEXT: pushq %rax
; CHECK-NEXT: .cfi_def_cfa_offset 16
; CHECK-NEXT: testl $2048, %edi # imm = 0x800
; CHECK-NEXT: je .LBB3_2
; CHECK-NEXT: btl $11, %edi
; CHECK-NEXT: jae .LBB3_2
; CHECK-NEXT: # %bb.1: # %yes
; CHECK-NEXT: callq bar
; CHECK-NEXT: .LBB3_2: # %no
@ -259,8 +259,8 @@ define void @test32_optsize_2(i32 inreg %x) optsize {
; CHECK: # %bb.0:
; CHECK-NEXT: pushq %rax
; CHECK-NEXT: .cfi_def_cfa_offset 16
; CHECK-NEXT: testl $2048, %edi # imm = 0x800
; CHECK-NEXT: je .LBB11_2
; CHECK-NEXT: btl $11, %edi
; CHECK-NEXT: jae .LBB11_2
; CHECK-NEXT: # %bb.1: # %yes
; CHECK-NEXT: callq bar
; CHECK-NEXT: .LBB11_2: # %no
@ -351,8 +351,8 @@ define void @test16_optsize_2(i16 inreg %x) optsize {
; CHECK: # %bb.0:
; CHECK-NEXT: pushq %rax
; CHECK-NEXT: .cfi_def_cfa_offset 16
; CHECK-NEXT: testl $2048, %edi # imm = 0x800
; CHECK-NEXT: je .LBB15_2
; CHECK-NEXT: btl $11, %edi
; CHECK-NEXT: jae .LBB15_2
; CHECK-NEXT: # %bb.1: # %yes
; CHECK-NEXT: callq bar
; CHECK-NEXT: .LBB15_2: # %no