[llvm] 112f352 - [AArch64] Add A+B+1 and A-B-1 macro fusion for Ampere1A

[Philipp Tomsich via llvm-commits]

Author: Philipp Tomsich
Date: 2023-01-29T17:25:12+01:00
New Revision: 112f352bc0ad2f4b17569cc8ea339dc3940451cd

URL: https://github.com/llvm/llvm-project/commit/112f352bc0ad2f4b17569cc8ea339dc3940451cd
DIFF: https://github.com/llvm/llvm-project/commit/112f352bc0ad2f4b17569cc8ea339dc3940451cd.diff

LOG: [AArch64] Add A+B+1 and A-B-1 macro fusion for Ampere1A

The Ampere1A core supports a new fusion pattern that optimises the
case of A+B+1 and A-B-1.  Add support.

Depends on D142396

Differential Revision: https://reviews.llvm.org/D142502

Added: 
    llvm/test/CodeGen/AArch64/macro-fusion-addsub-2reg-const1.mir

Modified: 
    llvm/lib/Target/AArch64/AArch64.td
    llvm/lib/Target/AArch64/AArch64MacroFusion.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Target/AArch64/AArch64.td b/llvm/lib/Target/AArch64/AArch64.td
index 4bf53792d6777..cbe0b83f9e553 100644
--- a/llvm/lib/Target/AArch64/AArch64.td
+++ b/llvm/lib/Target/AArch64/AArch64.td
@@ -289,6 +289,10 @@ def FeatureFuseLiterals : SubtargetFeature<
     "fuse-literals", "HasFuseLiterals", "true",
     "CPU fuses literal generation operations">;
 
+def FeatureFuseAddSub2RegAndConstOne : SubtargetFeature<
+   "fuse-addsub-2reg-const1", "HasFuseAddSub2RegAndConstOne", "true",
+   "CPU fuses (a + b + 1) and (a - b - 1)">;
+
 def FeatureDisableLatencySchedHeuristic : SubtargetFeature<
     "disable-latency-sched-heuristic", "DisableLatencySchedHeuristic", "true",
     "Disable latency scheduling heuristic">;

diff  --git a/llvm/lib/Target/AArch64/AArch64MacroFusion.cpp b/llvm/lib/Target/AArch64/AArch64MacroFusion.cpp
index f51c27c62dfb7..05d60872bf51a 100644
--- a/llvm/lib/Target/AArch64/AArch64MacroFusion.cpp
+++ b/llvm/lib/Target/AArch64/AArch64MacroFusion.cpp
@@ -379,6 +379,64 @@ static bool isArithmeticLogicPair(const MachineInstr *FirstMI,
   return false;
 }
 
+// "(A + B) + 1" or "(A - B) - 1"
+static bool isAddSub2RegAndConstOnePair(const MachineInstr *FirstMI,
+                                        const MachineInstr &SecondMI) {
+  bool NeedsSubtract = false;
+
+  // The 2nd instr must be an add-immediate or subtract-immediate.
+  switch (SecondMI.getOpcode()) {
+  case AArch64::SUBWri:
+  case AArch64::SUBXri:
+    NeedsSubtract = true;
+    [[fallthrough]];
+  case AArch64::ADDWri:
+  case AArch64::ADDXri:
+    break;
+
+  default:
+    return false;
+  }
+
+  // The immediate in the 2nd instr must be "1".
+  if (!SecondMI.getOperand(2).isImm() || SecondMI.getOperand(2).getImm() != 1) {
+    return false;
+  }
+
+  // Assume the 1st instr to be a wildcard if it is unspecified.
+  if (FirstMI == nullptr) {
+    return true;
+  }
+
+  switch (FirstMI->getOpcode()) {
+  case AArch64::SUBWrs:
+  case AArch64::SUBXrs:
+    if (AArch64InstrInfo::hasShiftedReg(*FirstMI))
+      return false;
+    [[fallthrough]];
+  case AArch64::SUBWrr:
+  case AArch64::SUBXrr:
+    if (NeedsSubtract) {
+      return true;
+    }
+    break;
+
+  case AArch64::ADDWrs:
+  case AArch64::ADDXrs:
+    if (AArch64InstrInfo::hasShiftedReg(*FirstMI))
+      return false;
+    [[fallthrough]];
+  case AArch64::ADDWrr:
+  case AArch64::ADDXrr:
+    if (!NeedsSubtract) {
+      return true;
+    }
+    break;
+  }
+
+  return false;
+}
+
 /// \brief Check if the instr pair, FirstMI and SecondMI, should be fused
 /// together. Given SecondMI, when FirstMI is unspecified, then check if
 /// SecondMI may be part of a fused pair at all.
@@ -411,6 +469,9 @@ static bool shouldScheduleAdjacent(const TargetInstrInfo &TII,
     return true;
   if (ST.hasFuseArithmeticLogic() && isArithmeticLogicPair(FirstMI, SecondMI))
     return true;
+  if (ST.hasFuseAddSub2RegAndConstOne() &&
+      isAddSub2RegAndConstOnePair(FirstMI, SecondMI))
+    return true;
 
   return false;
 }

diff  --git a/llvm/test/CodeGen/AArch64/macro-fusion-addsub-2reg-const1.mir b/llvm/test/CodeGen/AArch64/macro-fusion-addsub-2reg-const1.mir
new file mode 100644
index 0000000000000..8c5a85a4e7a61
--- /dev/null
+++ b/llvm/test/CodeGen/AArch64/macro-fusion-addsub-2reg-const1.mir
@@ -0,0 +1,23 @@
+# RUN: llc -o - %s -mtriple=aarch64-- -mattr=+fuse-addsub-2reg-const1 -run-pass postmisched | FileCheck %s --check-prefixes=CHECK,FUSION
+# RUN: llc -o - %s -mtriple=aarch64-- -mattr=-fuse-addsub-2reg-const1 -run-pass postmisched | FileCheck %s --check-prefixes=CHECK,NOFUSION
+---
+# CHECK-LABEL: name: addsub2reg
+# CHECK: $w8 = ADDWrr killed renamable $w0, killed renamable $w1
+# FUSION: renamable $w0 = ADDWri killed renamable $w8, 1, 0
+# CHECK: $w9 = SUBWrr killed renamable $w2, killed renamable $w3
+# NOFUSION: renamable $w0 = ADDWri killed renamable $w8, 1, 0
+# CHECK: renamable $w1 = SUBWri killed renamable $w9, 1, 0
+name: addsub2reg
+tracksRegLiveness: true
+body: |
+  bb.0.entry:
+    liveins: $w0, $w1, $w2, $w3
+
+    $w8 = ADDWrr killed renamable $w0, killed renamable $w1
+    $w9 = SUBWrr killed renamable $w2, killed renamable $w3
+    renamable $w0 = ADDWri killed renamable $w8, 1, 0
+    renamable $w1 = SUBWri killed renamable $w9, 1, 0
+
+    $w0 = ORRWrs killed renamable $w0, killed renamable $w1, 0
+    RET undef $lr, implicit $w0
+...