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[SystemZ] Prefer comparisons with zero

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Convert >= 1 to > 0, etc.  Using comparison with zero isn't a win on its own,
but it exposes more opportunities for CC reuse (the next patch).


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@187571 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Richard Sandiford 2013-08-01 10:29:45 +00:00
parent a701de8d24
commit 3237f88882
6 changed files with 79 additions and 11 deletions
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26
lib/Target/SystemZ/SystemZISelLowering.cpp
View File

@ -910,6 +910,29 @@ static unsigned CCMaskForCondCode(ISD::CondCode CC) {
#undef CONV
}
// If a comparison described by IsUnsigned, CCMask, CmpOp0 and CmpOp1
// can be converted to a comparison against zero, adjust the operands
// as necessary.
static void adjustZeroCmp(SelectionDAG &DAG, bool &IsUnsigned,
SDValue &CmpOp0, SDValue &CmpOp1,
unsigned &CCMask) {
if (IsUnsigned)
return;
ConstantSDNode *ConstOp1 = dyn_cast<ConstantSDNode>(CmpOp1.getNode());
if (!ConstOp1)
return;
int64_t Value = ConstOp1->getSExtValue();
if ((Value == -1 && CCMask == SystemZ::CCMASK_CMP_GT) ||
(Value == -1 && CCMask == SystemZ::CCMASK_CMP_LE) ||
(Value == 1 && CCMask == SystemZ::CCMASK_CMP_LT) ||
(Value == 1 && CCMask == SystemZ::CCMASK_CMP_GE)) {
CCMask ^= SystemZ::CCMASK_CMP_EQ;
CmpOp1 = DAG.getConstant(0, CmpOp1.getValueType());
}
}
// If a comparison described by IsUnsigned, CCMask, CmpOp0 and CmpOp1
// is suitable for CLI(Y), CHHSI or CLHHSI, adjust the operands as necessary.
static void adjustSubwordCmp(SelectionDAG &DAG, bool &IsUnsigned,
@ -954,7 +977,7 @@ static void adjustSubwordCmp(SelectionDAG &DAG, bool &IsUnsigned,
if (Value == 0 && CCMask == SystemZ::CCMASK_CMP_LT)
// Test whether the high bit of the byte is set.
Value = 127, CCMask = SystemZ::CCMASK_CMP_GT, IsUnsigned = true;
else if (SignedValue == -1 && CCMask == SystemZ::CCMASK_CMP_GT)
else if (Value == 0 && CCMask == SystemZ::CCMASK_CMP_GE)
// Test whether the high bit of the byte is clear.
Value = 128, CCMask = SystemZ::CCMASK_CMP_LT, IsUnsigned = true;
else
@ -1045,6 +1068,7 @@ static SDValue emitCmp(SelectionDAG &DAG, SDValue CmpOp0, SDValue CmpOp1,
IsUnsigned = CCMask & SystemZ::CCMASK_CMP_UO;
CCValid = SystemZ::CCMASK_ICMP;
CCMask &= CCValid;
adjustZeroCmp(DAG, IsUnsigned, CmpOp0, CmpOp1, CCMask);
adjustSubwordCmp(DAG, IsUnsigned, CmpOp0, CmpOp1, CCMask);
if (preferUnsignedComparison(DAG, CmpOp0, CmpOp1, CCMask))
IsUnsigned = true;

50
test/CodeGen/SystemZ/int-cmp-09.ll
View File

@ -13,13 +13,13 @@ define double @f1(double %a, double %b, i32 %i1) {
ret double %res
}
; Check comparisons with 1.
; Check comparisons with 2.
define double @f2(double %a, double %b, i32 %i1) {
; CHECK-LABEL: f2:
; CHECK: cijl %r2, 1
; CHECK: cijl %r2, 2
; CHECK: ldr %f0, %f2
; CHECK: br %r14
%cond = icmp slt i32 %i1, 1
%cond = icmp slt i32 %i1, 2
%res = select i1 %cond, double %a, double %b
ret double %res
}
@ -176,3 +176,47 @@ define double @f15(double %a, double %b, i32 %i1) {
%res = select i1 %cond, double %a, double %b
ret double %res
}
; Check that < 1 becomes <= 0.
define double @f16(double %a, double %b, i32 %i1) {
; CHECK-LABEL: f16:
; CHECK: cijle %r2, 0
; CHECK: ldr %f0, %f2
; CHECK: br %r14
%cond = icmp slt i32 %i1, 1
%res = select i1 %cond, double %a, double %b
ret double %res
}
; Check that >= 1 becomes > 0.
define double @f17(double %a, double %b, i32 %i1) {
; CHECK-LABEL: f17:
; CHECK: cijh %r2, 0
; CHECK: ldr %f0, %f2
; CHECK: br %r14
%cond = icmp sge i32 %i1, 1
%res = select i1 %cond, double %a, double %b
ret double %res
}
; Check that > -1 becomes >= 0.
define double @f18(double %a, double %b, i32 %i1) {
; CHECK-LABEL: f18:
; CHECK: cijhe %r2, 0
; CHECK: ldr %f0, %f2
; CHECK: br %r14
%cond = icmp sgt i32 %i1, -1
%res = select i1 %cond, double %a, double %b
ret double %res
}
; Check that <= -1 becomes < 0.
define double @f19(double %a, double %b, i32 %i1) {
; CHECK-LABEL: f19:
; CHECK: cijl %r2, 0
; CHECK: ldr %f0, %f2
; CHECK: br %r14
%cond = icmp sle i32 %i1, -1
%res = select i1 %cond, double %a, double %b
ret double %res
}

2
test/CodeGen/SystemZ/int-cmp-11.ll
View File

@ -16,7 +16,7 @@ define double @f1(double %a, double %b, i64 %i1) {
; Check comparisons with 1.
define double @f2(double %a, double %b, i64 %i1) {
; CHECK-LABEL: f2:
; CHECK: cgijl %r2, 1
; CHECK: cgijle %r2, 0
; CHECK: ldr %f0, %f2
; CHECK: br %r14
%cond = icmp slt i64 %i1, 1

4
test/CodeGen/SystemZ/int-cmp-22.ll
View File

@ -18,8 +18,8 @@ define double @f1(double %a, double %b, i16 *%ptr) {
; Check comparisons with 1.
define double @f2(double %a, double %b, i16 *%ptr) {
; CHECK-LABEL: f2:
; CHECK: chhsi 0(%r2), 1
; CHECK-NEXT: jl
; CHECK: chhsi 0(%r2), 0
; CHECK-NEXT: jle
; CHECK: ldr %f0, %f2
; CHECK: br %r14
%val = load i16 *%ptr

4
test/CodeGen/SystemZ/int-cmp-32.ll
View File

@ -18,8 +18,8 @@ define double @f1(double %a, double %b, i32 *%ptr) {
; Check ordered comparisons with 1.
define double @f2(double %a, double %b, i32 *%ptr) {
; CHECK-LABEL: f2:
; CHECK: chsi 0(%r2), 1
; CHECK-NEXT: jl
; CHECK: chsi 0(%r2), 0
; CHECK-NEXT: jle
; CHECK: ldr %f0, %f2
; CHECK: br %r14
%val = load i32 *%ptr

4
test/CodeGen/SystemZ/int-cmp-34.ll
View File

@ -18,8 +18,8 @@ define double @f1(double %a, double %b, i64 *%ptr) {
; Check ordered comparisons with 1.
define double @f2(double %a, double %b, i64 *%ptr) {
; CHECK-LABEL: f2:
; CHECK: cghsi 0(%r2), 1
; CHECK-NEXT: jl
; CHECK: cghsi 0(%r2), 0
; CHECK-NEXT: jle
; CHECK: ldr %f0, %f2
; CHECK: br %r14
%val = load i64 *%ptr