[DAGCombiner] add and use TLI hook to convert and-of-seteq / or-of-setne to bitwise logic+setcc (PR32401)

This is a generic combine enabled via target hook to reduce icmp logic as discussed in:
https://bugs.llvm.org/show_bug.cgi?id=32401

It's likely that other targets will want to enable this hook for scalar transforms, 
and there are probably other patterns that can use bitwise logic to reduce comparisons.

Note that we are missing an IR canonicalization for these patterns, and we will probably
prefer the pair-of-compares form in IR (shorter, more likely to fold).

Differential Revision: https://reviews.llvm.org/D31483

llvm-svn: 299542

3 files changed, 12 insertions, 0 deletions

diff --git a/llvm/lib/Target/ARM/ARMISelLowering.h b/llvm/lib/Target/ARM/ARMISelLowering.h
index ad632427470..198000e5b5b 100644
--- a/llvm/lib/Target/ARM/ARMISelLowering.h
+++ b/llvm/lib/Target/ARM/ARMISelLowering.h
@@ -515,6 +515,10 @@ class InstrItineraryData;
     bool isCheapToSpeculateCttz() const override;
     bool isCheapToSpeculateCtlz() const override;
 
+    bool convertSetCCLogicToBitwiseLogic(EVT VT) const override {
+      return VT.isScalarInteger();
+    }
+
     bool supportSwiftError() const override {
       return true;
     }
diff --git a/llvm/lib/Target/PowerPC/PPCISelLowering.h b/llvm/lib/Target/PowerPC/PPCISelLowering.h
index 3dc9a9f184c..6113eb58f42 100644
--- a/llvm/lib/Target/PowerPC/PPCISelLowering.h
+++ b/llvm/lib/Target/PowerPC/PPCISelLowering.h
@@ -531,6 +531,10 @@ namespace llvm {
       return true;
     }
 
+    bool convertSetCCLogicToBitwiseLogic(EVT VT) const override {
+      return VT.isScalarInteger();
+    }
+
     bool supportSplitCSR(MachineFunction *MF) const override {
       return
         MF->getFunction()->getCallingConv() == CallingConv::CXX_FAST_TLS &&
diff --git a/llvm/lib/Target/X86/X86ISelLowering.h b/llvm/lib/Target/X86/X86ISelLowering.h
index 13642c219e8..ab4910daca0 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.h
+++ b/llvm/lib/Target/X86/X86ISelLowering.h
@@ -814,6 +814,10 @@ namespace llvm {
 
     bool hasAndNotCompare(SDValue Y) const override;
 
+    bool convertSetCCLogicToBitwiseLogic(EVT VT) const override {
+      return VT.isScalarInteger();
+    }
+
     /// Vector-sized comparisons are fast using PCMPEQ + PMOVMSK or PTEST.
     MVT hasFastEqualityCompare(unsigned NumBits) const override;