[PATCH] D39078: [PowerPC] Relax the checking on AND/AND8 in isSignOrZeroExtended

[Sean Fertile via Phabricator via llvm-commits]

sfertile created this revision.

Separate the handling  of AND/AND8 out from PHI/OR/ISEL checking. The reasoning is the others need all their operands to be sign/zero extended  for their output to also be sign/zero extended. This is true for AND and sign-extension, but for zero-extension we only need at least one of the input operands to be sign extended for the result to also be zero extended.


Repository:
  rL LLVM

https://reviews.llvm.org/D39078

Files:
  lib/Target/PowerPC/PPCInstrInfo.cpp
  test/CodeGen/PowerPC/zext-and-cmp.ll


Index: test/CodeGen/PowerPC/zext-and-cmp.ll
===================================================================
--- /dev/null
+++ test/CodeGen/PowerPC/zext-and-cmp.ll
@@ -0,0 +1,33 @@
+; RUN: llc -verify-machineinstrs -mtriple=powerpc64le-unknown-linux-gnu  < %s | FileCheck %s
+
+; Test that we recognize that an 'and' instruction that feeds a comparison
+; to zero can be simplifed by using the record form when one of its operands
+; is known to be zero extended.
+
+ at k = common local_unnamed_addr global i32 0, align 4
+
+; Function Attrs: norecurse nounwind
+define signext i32 @cmplwi(i32* nocapture readonly %p, i32* nocapture readonly %q, i32 signext %j, i32 signext %r10) {
+entry:
+  %0 = load i32, i32* %q, align 4
+  %shl = shl i32 %0, %j
+  %1 = load i32, i32* %p, align 4
+  %and = and i32 %shl, %r10
+  %and1 = and i32 %and, %1
+  %tobool = icmp eq i32 %and1, 0
+  br i1 %tobool, label %cleanup, label %if.then
+
+if.then:
+  store i32 %j, i32* @k, align 4
+  br label %cleanup
+
+cleanup:
+  %retval.0 = phi i32 [ 0, %if.then ], [ 1, %entry ]
+  ret i32 %retval.0
+}
+
+; CHECK-LABEL: cmplwi:
+; CHECK:      lwz [[T1:[0-9]+]], 0(3)
+; CHECK:      and. {{[0-9]+}}, {{[0-9]+}}, [[T1]]
+; CHECK-NOT:  cmplwi
+; CHECK-NEXT: beq      0,
Index: lib/Target/PowerPC/PPCInstrInfo.cpp
===================================================================
--- lib/Target/PowerPC/PPCInstrInfo.cpp
+++ lib/Target/PowerPC/PPCInstrInfo.cpp
@@ -2294,9 +2294,7 @@
   }
 
   // If all incoming values are sign-/zero-extended,
-  // the output of AND, OR, ISEL or PHI is also sign-/zero-extended.
-  case PPC::AND:
-  case PPC::AND8:
+  // the output of OR, ISEL or PHI is also sign-/zero-extended.
   case PPC::OR:
   case PPC::OR8:
   case PPC::ISEL:
@@ -2327,6 +2325,37 @@
     return true;
   }
 
+  // If at least one of the incoming values of an AND is zero extended
+  // then the output is also zero-extended. If both of the incoming values
+  // are sign-extended then the output is also sign extended.
+  case PPC::AND:
+  case PPC::AND8: {
+    if (Depth >= MAX_DEPTH)
+       return false;
+
+    if (!MI.getOperand(1).isReg() || !MI.getOperand(2).isReg())
+      return false;
+
+    unsigned SrcReg1 = MI.getOperand(1).getReg();
+    unsigned SrcReg2 = MI.getOperand(2).getReg();
+
+    if (!TargetRegisterInfo::isVirtualRegister(SrcReg1) ||
+        !TargetRegisterInfo::isVirtualRegister(SrcReg2))
+       return false;
+
+    const MachineInstr *MISrc1 = MRI->getVRegDef(SrcReg1);
+    const MachineInstr *MISrc2 = MRI->getVRegDef(SrcReg2);
+    if (!MISrc1 || !MISrc2)
+        return false;
+
+    if(SignExt)
+        return isSignOrZeroExtended(*MISrc1, SignExt, Depth+1) &&
+               isSignOrZeroExtended(*MISrc2, SignExt, Depth+1);
+    else
+        return isSignOrZeroExtended(*MISrc1, SignExt, Depth+1) ||
+               isSignOrZeroExtended(*MISrc2, SignExt, Depth+1);
+  }
+
   default:
     break;
   }


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