[SystemZ] Prefer comparisons with zero

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

6 files changed, 79 insertions, 11 deletions

diff --git a/lib/Target/SystemZ/SystemZISelLowering.cpp b/lib/Target/SystemZ/SystemZISelLowering.cpp
index 6a34fec..ffd842d 100644
--- a/lib/Target/SystemZ/SystemZISelLowering.cpp
+++ b/lib/Target/SystemZ/SystemZISelLowering.cpp
@@ -911,6 +911,29 @@ static unsigned CCMaskForCondCode(ISD::CondCode CC) {
 }
 
 // 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,
                              SDValue &CmpOp0, SDValue &CmpOp1,
@@ -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;
diff --git a/test/CodeGen/SystemZ/int-cmp-09.ll b/test/CodeGen/SystemZ/int-cmp-09.ll
index 66c9d8d..0eb8c66 100644
--- a/test/CodeGen/SystemZ/int-cmp-09.ll
+++ b/test/CodeGen/SystemZ/int-cmp-09.ll
@@ -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
+}
diff --git a/test/CodeGen/SystemZ/int-cmp-11.ll b/test/CodeGen/SystemZ/int-cmp-11.ll
index 8dd2ebc..c74135a 100644
--- a/test/CodeGen/SystemZ/int-cmp-11.ll
+++ b/test/CodeGen/SystemZ/int-cmp-11.ll
@@ -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
diff --git a/test/CodeGen/SystemZ/int-cmp-22.ll b/test/CodeGen/SystemZ/int-cmp-22.ll
index ea16604..43daec9 100644
--- a/test/CodeGen/SystemZ/int-cmp-22.ll
+++ b/test/CodeGen/SystemZ/int-cmp-22.ll
@@ -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
diff --git a/test/CodeGen/SystemZ/int-cmp-32.ll b/test/CodeGen/SystemZ/int-cmp-32.ll
index 96398dd..6596f9f 100644
--- a/test/CodeGen/SystemZ/int-cmp-32.ll
+++ b/test/CodeGen/SystemZ/int-cmp-32.ll
@@ -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
diff --git a/test/CodeGen/SystemZ/int-cmp-34.ll b/test/CodeGen/SystemZ/int-cmp-34.ll
index 53a5c76..8a02197 100644
--- a/test/CodeGen/SystemZ/int-cmp-34.ll
+++ b/test/CodeGen/SystemZ/int-cmp-34.ll
@@ -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