[llvm] 1ccebb1 - [GlobalISel] Micro-optimize the conditional branch optimization.

[Amara Emerson via llvm-commits]

Author: Amara Emerson
Date: 2021-05-07T00:03:09-07:00
New Revision: 1ccebb18ef9f4110e555209261d73dbec393e364

URL: https://github.com/llvm/llvm-project/commit/1ccebb18ef9f4110e555209261d73dbec393e364
DIFF: https://github.com/llvm/llvm-project/commit/1ccebb18ef9f4110e555209261d73dbec393e364.diff

LOG: [GlobalISel] Micro-optimize the conditional branch optimization.

Convert a check into an assert and pass an MI instead of recomputing in the
apply function.

Added: 
    

Modified: 
    llvm/include/llvm/CodeGen/GlobalISel/CombinerHelper.h
    llvm/include/llvm/Target/GlobalISel/Combine.td
    llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp

Removed: 
    


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diff  --git a/llvm/include/llvm/CodeGen/GlobalISel/CombinerHelper.h b/llvm/include/llvm/CodeGen/GlobalISel/CombinerHelper.h
index 06bbeeb88ec13..f93193093ae28 100644
--- a/llvm/include/llvm/CodeGen/GlobalISel/CombinerHelper.h
+++ b/llvm/include/llvm/CodeGen/GlobalISel/CombinerHelper.h
@@ -163,8 +163,8 @@ class CombinerHelper {
 
   /// If a brcond's true block is not the fallthrough, make it so by inverting
   /// the condition and swapping operands.
-  bool matchOptBrCondByInvertingCond(MachineInstr &MI);
-  void applyOptBrCondByInvertingCond(MachineInstr &MI);
+  bool matchOptBrCondByInvertingCond(MachineInstr &MI, MachineInstr *&BrCond);
+  void applyOptBrCondByInvertingCond(MachineInstr &MI, MachineInstr *&BrCond);
 
   /// If \p MI is G_CONCAT_VECTORS, try to combine it.
   /// Returns true if MI changed.

diff  --git a/llvm/include/llvm/Target/GlobalISel/Combine.td b/llvm/include/llvm/Target/GlobalISel/Combine.td
index a63b9b8548bfc..a8c64e0be6bd9 100644
--- a/llvm/include/llvm/Target/GlobalISel/Combine.td
+++ b/llvm/include/llvm/Target/GlobalISel/Combine.td
@@ -149,11 +149,12 @@ def combine_indexed_load_store : GICombineRule<
          [{ return Helper.matchCombineIndexedLoadStore(*${root}, ${matchinfo}); }]),
   (apply [{ Helper.applyCombineIndexedLoadStore(*${root}, ${matchinfo}); }])>;
 
+def opt_brcond_by_inverting_cond_matchdata : GIDefMatchData<"MachineInstr *">;
 def opt_brcond_by_inverting_cond : GICombineRule<
-  (defs root:$root),
+  (defs root:$root, opt_brcond_by_inverting_cond_matchdata:$matchinfo),
   (match (wip_match_opcode G_BR):$root,
-         [{ return Helper.matchOptBrCondByInvertingCond(*${root}); }]),
-  (apply [{ Helper.applyOptBrCondByInvertingCond(*${root}); }])>;
+         [{ return Helper.matchOptBrCondByInvertingCond(*${root}, ${matchinfo}); }]),
+  (apply [{ Helper.applyOptBrCondByInvertingCond(*${root}, ${matchinfo}); }])>;
 
 def ptr_add_immed_matchdata : GIDefMatchData<"PtrAddChain">;
 def ptr_add_immed_chain : GICombineRule<

diff  --git a/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp b/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
index e3af0c43bbcad..c4678f68a6096 100644
--- a/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
@@ -1033,9 +1033,9 @@ void CombinerHelper::applyCombineDivRem(MachineInstr &MI,
   OtherMI->eraseFromParent();
 }
 
-bool CombinerHelper::matchOptBrCondByInvertingCond(MachineInstr &MI) {
-  if (MI.getOpcode() != TargetOpcode::G_BR)
-    return false;
+bool CombinerHelper::matchOptBrCondByInvertingCond(MachineInstr &MI,
+                                                   MachineInstr *&BrCond) {
+  assert(MI.getOpcode() == TargetOpcode::G_BR);
 
   // Try to match the following:
   // bb1:
@@ -1056,7 +1056,7 @@ bool CombinerHelper::matchOptBrCondByInvertingCond(MachineInstr &MI) {
     return false;
   assert(std::next(BrIt) == MBB->end() && "expected G_BR to be a terminator");
 
-  MachineInstr *BrCond = &*std::prev(BrIt);
+  BrCond = &*std::prev(BrIt);
   if (BrCond->getOpcode() != TargetOpcode::G_BRCOND)
     return false;
 
@@ -1067,11 +1067,9 @@ bool CombinerHelper::matchOptBrCondByInvertingCond(MachineInstr &MI) {
          MBB->isLayoutSuccessor(BrCondTarget);
 }
 
-void CombinerHelper::applyOptBrCondByInvertingCond(MachineInstr &MI) {
+void CombinerHelper::applyOptBrCondByInvertingCond(MachineInstr &MI,
+                                                   MachineInstr *&BrCond) {
   MachineBasicBlock *BrTarget = MI.getOperand(0).getMBB();
-  MachineBasicBlock::iterator BrIt(MI);
-  MachineInstr *BrCond = &*std::prev(BrIt);
-
   Builder.setInstrAndDebugLoc(*BrCond);
   LLT Ty = MRI.getType(BrCond->getOperand(0).getReg());
   // FIXME: Does int/fp matter for this? If so, we might need to restrict