[PATCH] D24857: [ARM] Assign cost of scaling used in addressing mode for ARM cores

[Javed Absar via llvm-commits]

javed.absar retitled this revision from "Assign cost of scaling used in addressing mode for ARM cores" to "[ARM] Assign cost of scaling used in addressing mode for ARM cores".
javed.absar updated this revision to Diff 72473.
javed.absar added a comment.

Hi James: 
Thanks for the review and feedback.
I have made changes based on your comments:

1. Have reduced the scope to Cortex-A53 and Cortex-A57 where I can confirm the performance gains currently based on benchmark runs (results shared previously).
2. Have adjusted the cost from '2' to '1' as this is sufficient to differentiate.

Thanks


https://reviews.llvm.org/D24857

Files:
  lib/Target/ARM/ARMISelLowering.cpp
  lib/Target/ARM/ARMISelLowering.h
  lib/Target/ARM/ARMSubtarget.h
  test/CodeGen/ARM/lsr-scale-addr-mode.ll

Index: test/CodeGen/ARM/lsr-scale-addr-mode.ll
===================================================================
--- test/CodeGen/ARM/lsr-scale-addr-mode.ll
+++ test/CodeGen/ARM/lsr-scale-addr-mode.ll
@@ -1,6 +1,10 @@
 ; RUN: llc -mtriple=arm-eabi %s -o - | FileCheck %s
 ; Should use scaled addressing mode.
 
+; RUN: llc -mtriple=arm-eabi -mcpu=cortex-a53 %s -o - | FileCheck %s -check-prefix CHECK-NONEGOFF-A53
+; RUN: llc -mtriple=arm-eabi -mcpu=cortex-a57 %s -o - | FileCheck %s -check-prefix CHECK-NONEGOFF-A57
+; Should not generate negated register offset
+
 define void @sintzero(i32* %a) nounwind {
 entry:
 	store i32 0, i32* %a
@@ -19,4 +23,6 @@
 }
 
 ; CHECK: lsl{{.*}}#2]
+; CHECK-NONEGOFF-A53: [{{r[0-9]+}}, {{r[0-9]+}}, lsl{{.*}}#2]
+; CHECK-NONEGOFF-A57: [{{r[0-9]+}}, {{r[0-9]+}}, lsl{{.*}}#2]
 
Index: lib/Target/ARM/ARMSubtarget.h
===================================================================
--- lib/Target/ARM/ARMSubtarget.h
+++ lib/Target/ARM/ARMSubtarget.h
@@ -412,6 +412,8 @@
   bool isCortexA8() const { return ARMProcFamily == CortexA8; }
   bool isCortexA9() const { return ARMProcFamily == CortexA9; }
   bool isCortexA15() const { return ARMProcFamily == CortexA15; }
+  bool isCortexA53() const { return ARMProcFamily == CortexA53; }
+  bool isCortexA57() const { return ARMProcFamily == CortexA57; }
   bool isSwift()    const { return ARMProcFamily == Swift; }
   bool isCortexM3() const { return ARMProcFamily == CortexM3; }
   bool isLikeA9() const { return isCortexA9() || isCortexA15() || isKrait(); }
Index: lib/Target/ARM/ARMISelLowering.h
===================================================================
--- lib/Target/ARM/ARMISelLowering.h
+++ lib/Target/ARM/ARMISelLowering.h
@@ -291,6 +291,14 @@
     /// by AM is legal for this target, for a load/store of the specified type.
     bool isLegalAddressingMode(const DataLayout &DL, const AddrMode &AM,
                                Type *Ty, unsigned AS) const override;
+
+    /// getScalingFactorCost - Return the cost of the scaling used in
+    /// addressing mode represented by AM.
+    /// If the AM is supported, the return value must be >= 0.
+    /// If the AM is not supported, the return value must be negative.
+    int getScalingFactorCost(const DataLayout &DL, const AddrMode &AM, Type *Ty,
+                             unsigned AS) const override;
+
     bool isLegalT2ScaledAddressingMode(const AddrMode &AM, EVT VT) const;
 
     /// isLegalICmpImmediate - Return true if the specified immediate is legal
Index: lib/Target/ARM/ARMISelLowering.cpp
===================================================================
--- lib/Target/ARM/ARMISelLowering.cpp
+++ lib/Target/ARM/ARMISelLowering.cpp
@@ -11597,6 +11597,17 @@
   return true;
 }
 
+int ARMTargetLowering::getScalingFactorCost(const DataLayout &DL,
+                                                const AddrMode &AM, Type *Ty,
+                                                unsigned AS) const {
+  if (isLegalAddressingMode(DL, AM, Ty, AS)) {
+    if (Subtarget->isCortexA53() || Subtarget->isCortexA57())
+      return AM.Scale < 0 ? 1 : 0; // negative scaling costs extra cycles
+    return 0;
+  }
+  return -1;
+}
+
 
 static bool isLegalT1AddressImmediate(int64_t V, EVT VT) {
   if (V < 0)


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