2 files changed, 77 insertions, 6 deletions

diff --git a/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp b/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp
index 3afcec1248d..46f103141bc 100644
--- a/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp
+++ b/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp
@@ -1533,6 +1533,8 @@ bool PPCInstrInfo::analyzeCompare(const MachineInstr &MI, unsigned &SrcReg,
   case PPC::FCMPUD:
     SrcReg = MI.getOperand(1).getReg();
     SrcReg2 = MI.getOperand(2).getReg();
+    Value = 0;
+    Mask = 0;
     return true;
   }
 }
@@ -1591,9 +1593,12 @@ bool PPCInstrInfo::optimizeCompareInstr(MachineInstr &CmpInstr, unsigned SrcReg,
 
       // We can perform this optimization, equality only, if MI is
       // zero-extending.
+      // FIXME: Other possible target instructions include ANDISo and
+      //        RLWINM aliases, such as ROTRWI, EXTLWI, SLWI and SRWI.
       if (MIOpC == PPC::CNTLZW || MIOpC == PPC::CNTLZWo ||
           MIOpC == PPC::SLW    || MIOpC == PPC::SLWo ||
           MIOpC == PPC::SRW    || MIOpC == PPC::SRWo ||
+          MIOpC == PPC::ANDIo  ||
           isZeroExtendingRotate) {
         noSub = true;
         equalityOnly = true;
@@ -1641,6 +1646,9 @@ bool PPCInstrInfo::optimizeCompareInstr(MachineInstr &CmpInstr, unsigned SrcReg,
       break;
   }
 
+  SmallVector<std::pair<MachineOperand*, PPC::Predicate>, 4> PredsToUpdate;
+  SmallVector<std::pair<MachineOperand*, unsigned>, 4> SubRegsToUpdate;
+
   // There are two possible candidates which can be changed to set CR[01].
   // One is MI, the other is a SUB instruction.
   // For CMPrr(r1,r2), we are looking for SUB(r1,r2) or SUB(r2,r1).
@@ -1652,9 +1660,37 @@ bool PPCInstrInfo::optimizeCompareInstr(MachineInstr &CmpInstr, unsigned SrcReg,
   // same BB as the comparison. This is to allow the check below to avoid calls
   // (and other explicit clobbers); instead we should really check for these
   // more explicitly (in at least a few predecessors).
-  else if (MI->getParent() != CmpInstr.getParent() || Value != 0) {
-    // PPC does not have a record-form SUBri.
+  else if (MI->getParent() != CmpInstr.getParent())
     return false;
+  else if (Value != 0) {
+    // The record-form instructions set CR bit based on signed comparison against 0.
+    // We try to convert a compare against 1 or -1 into a compare against 0.
+    bool Success = false;
+    if (!equalityOnly && MRI->hasOneUse(CRReg)) {
+      MachineInstr *UseMI = &*MRI->use_instr_begin(CRReg);
+      if (UseMI->getOpcode() == PPC::BCC) {
+        PPC::Predicate Pred = (PPC::Predicate)UseMI->getOperand(0).getImm();
+        int16_t Immed = (int16_t)Value;
+
+        if (Immed == -1 && Pred == PPC::PRED_GT) {
+          // We convert "greater than -1" into "greater than or equal to 0",
+          // since we are assuming signed comparison by !equalityOnly
+          PredsToUpdate.push_back(std::make_pair(&(UseMI->getOperand(0)),
+                                  PPC::PRED_GE));
+          Success = true;
+        }
+        else if (Immed == 1 && Pred == PPC::PRED_LT) {
+          // We convert "less than 1" into "less than or equal to 0".
+          PredsToUpdate.push_back(std::make_pair(&(UseMI->getOperand(0)),
+                                  PPC::PRED_LE));
+          Success = true;
+        }
+      }
+    }
+
+    // PPC does not have a record-form SUBri.
+    if (!Success)
+      return false;
   }
 
   // Search for Sub.
@@ -1720,15 +1756,14 @@ bool PPCInstrInfo::optimizeCompareInstr(MachineInstr &CmpInstr, unsigned SrcReg,
   if (NewOpC == -1)
     return false;
 
-  SmallVector<std::pair<MachineOperand*, PPC::Predicate>, 4> PredsToUpdate;
-  SmallVector<std::pair<MachineOperand*, unsigned>, 4> SubRegsToUpdate;
-
   // If we have SUB(r1, r2) and CMP(r2, r1), the condition code based on CMP
   // needs to be updated to be based on SUB.  Push the condition code
   // operands to OperandsToUpdate.  If it is safe to remove CmpInstr, the
   // condition code of these operands will be modified.
+  // Here, Value == 0 means we haven't converted comparison against 1 or -1 to
+  // comparison against 0, which may modify predicate.
   bool ShouldSwap = false;
-  if (Sub) {
+  if (Sub && Value == 0) {
     ShouldSwap = SrcReg2 != 0 && Sub->getOperand(1).getReg() == SrcReg2 &&
       Sub->getOperand(2).getReg() == SrcReg;
 
@@ -1765,6 +1800,9 @@ bool PPCInstrInfo::optimizeCompareInstr(MachineInstr &CmpInstr, unsigned SrcReg,
       } else // We need to abort on a user we don't understand.
         return false;
     }
+  assert(!(Value != 0 && ShouldSwap) &&
+         "Non-zero immediate support and ShouldSwap"
+         "may conflict in updating predicate");
 
   // Create a new virtual register to hold the value of the CR set by the
   // record-form instruction. If the instruction was not previously in
diff --git a/llvm/test/CodeGen/PowerPC/opt-cmp-inst-cr0-live.ll b/llvm/test/CodeGen/PowerPC/opt-cmp-inst-cr0-live.ll
index 64d02c5b963..2aeb0e1f71f 100644
--- a/llvm/test/CodeGen/PowerPC/opt-cmp-inst-cr0-live.ll
+++ b/llvm/test/CodeGen/PowerPC/opt-cmp-inst-cr0-live.ll
@@ -1,5 +1,6 @@
 ; RUN: llc -verify-machineinstrs -print-before=peephole-opt -print-after=peephole-opt -mtriple=powerpc64-unknown-linux-gnu -o /dev/null 2>&1 < %s | FileCheck %s
 
+; CHECK-LABEL: fn1
 define signext i32 @fn1(i32 %baz) {
   %1 = mul nsw i32 %baz, 208
   %2 = zext i32 %1 to i64
@@ -21,3 +22,35 @@ foo:
 bar:
   ret i32 0
 }
+
+; CHECK-LABEL: fn2
+define signext i32 @fn2(i64 %a, i64 %b) {
+; CHECK: OR8o {{[^, ]+}}, {{[^, ]+}}, %CR0<imp-def>;
+; CHECK: [[CREG:[^, ]+]]<def> = COPY %CR0
+; CHECK: BCC 12, [[CREG]]<kill>
+  %1 = or i64 %b, %a
+  %2 = icmp sgt i64 %1, -1
+  br i1 %2, label %foo, label %bar
+
+foo:
+  ret i32 1
+
+bar:
+  ret i32 0
+}
+
+; CHECK-LABEL: fn3
+define signext i32 @fn3(i32 %a) {
+; CHECK: ANDIo {{[^, ]+}}, 10, %CR0<imp-def>;
+; CHECK: [[CREG:[^, ]+]]<def> = COPY %CR0
+; CHECK: BCC 76, [[CREG]]<kill>
+  %1 = and i32 %a, 10
+  %2 = icmp ne i32 %1, 0
+  br i1 %2, label %foo, label %bar
+
+foo:
+  ret i32 1
+
+bar:
+  ret i32 0
+}