[PATCH] D80745: [DAGCombiner] Add a command line option to guard ReduceLoadOpStoreWidth

[Guozhi Wei via Phabricator via llvm-commits]

Carrot updated this revision to Diff 267066.
Carrot marked 2 inline comments as done.

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D80745/new/

https://reviews.llvm.org/D80745

Files:
  llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
  llvm/test/CodeGen/X86/clear-bitfield.ll
  llvm/test/CodeGen/X86/disable-shrink-store.ll


Index: llvm/test/CodeGen/X86/disable-shrink-store.ll
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/X86/disable-shrink-store.ll
@@ -0,0 +1,18 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc < %s -mtriple=x86_64-- -combiner-shrink-load-replace-store-with-store=false | FileCheck %s
+
+define void @shrink(i16* %ptr) {
+; CHECK-LABEL: shrink:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    movzbl (%rdi), %eax
+; CHECK-NEXT:    orl $25600, %eax # imm = 0x6400
+; CHECK-NEXT:    movw %ax, (%rdi)
+; CHECK-NEXT:    retq
+entry:
+  %val = load i16, i16* %ptr
+  %masked_val = and i16 %val, 255
+  %replaced_val = or i16 %masked_val, 25600
+  store i16 %replaced_val, i16* %ptr
+  ret void
+}
+
Index: llvm/test/CodeGen/X86/clear-bitfield.ll
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/X86/clear-bitfield.ll
@@ -0,0 +1,30 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc < %s -mtriple=x86_64-- -combiner-reduce-load-op-store-width=false | FileCheck %s
+
+%struct.bit_fields = type { i32 }
+
+define void @clear_b1(%struct.bit_fields* %ptr) {
+; CHECK-LABEL: clear_b1:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    andl $-2, (%rdi)
+; CHECK-NEXT:    retq
+entry:
+  %0 = bitcast %struct.bit_fields* %ptr to i32*
+  %bf.load = load i32, i32* %0
+  %bf.clear = and i32 %bf.load, -2
+  store i32 %bf.clear, i32* %0
+  ret void
+}
+
+define void @clear16(%struct.bit_fields* %ptr) {
+; CHECK-LABEL: clear16:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    andw $-2, (%rdi)
+; CHECK-NEXT:    retq
+entry:
+  %0 = bitcast %struct.bit_fields* %ptr to i16*
+  %bf.load = load i16, i16* %0
+  %bf.clear = and i16 %bf.load, -2
+  store i16 %bf.clear, i16* %0
+  ret void
+}
Index: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -125,6 +125,16 @@
     cl::desc("Limit the number of times for the same StoreNode and RootNode "
              "to bail out in store merging dependence check"));
 
+static cl::opt<bool> EnableReduceLoadOpStoreWidth(
+    "combiner-reduce-load-op-store-width", cl::Hidden, cl::init(true),
+    cl::desc("DAG cominber enable reducing the width of load/op/store "
+             "sequence"));
+
+static cl::opt<bool> EnableShrinkLoadReplaceStoreWithStore(
+    "combiner-shrink-load-replace-store-with-store", cl::Hidden, cl::init(true),
+    cl::desc("DAG cominber enable load/<replace bytes>/store with "
+             "a narrower store"));
+
 namespace {
 
   class DAGCombiner {
@@ -15424,7 +15434,7 @@
   // Y is known to provide just those bytes.  If so, we try to replace the
   // load + replace + store sequence with a single (narrower) store, which makes
   // the load dead.
-  if (Opc == ISD::OR) {
+  if (Opc == ISD::OR && EnableShrinkLoadReplaceStoreWithStore) {
     std::pair<unsigned, unsigned> MaskedLoad;
     MaskedLoad = CheckForMaskedLoad(Value.getOperand(0), Ptr, Chain);
     if (MaskedLoad.first)
@@ -15440,6 +15450,9 @@
         return NewST;
   }
 
+  if (!EnableReduceLoadOpStoreWidth)
+    return SDValue();
+
   if ((Opc != ISD::OR && Opc != ISD::XOR && Opc != ISD::AND) ||
       Value.getOperand(1).getOpcode() != ISD::Constant)
     return SDValue();


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