[PATCH] D30110: AArch64LoadStoreOptimizer: Correctly clear kill flags

[Matthias Braun via Phabricator via llvm-commits]

MatzeB created this revision.
Herald added subscribers: rengolin, aemerson.

When promoting the Load of a Store-Load pair to a COPY all kill flags
between the store and the load need to be cleared.


Repository:
  rL LLVM

https://reviews.llvm.org/D30110

Files:
  lib/Target/AArch64/AArch64LoadStoreOptimizer.cpp
  test/CodeGen/AArch64/ldst-opt.mir


Index: test/CodeGen/AArch64/ldst-opt.mir
===================================================================
--- test/CodeGen/AArch64/ldst-opt.mir
+++ test/CodeGen/AArch64/ldst-opt.mir
@@ -1,10 +1,4 @@
 # RUN: llc -mtriple=aarch64--linux-gnu -run-pass=aarch64-ldst-opt %s -verify-machineinstrs -o - 2>&1 | FileCheck %s
---- |
-  define void @promote-load-from-store() { ret void }
-  define void @store-pair() { ret void }
-  define void @store-pair-clearkill0() { ret void }
-  define void @store-pair-clearkill1() { ret void }
-...
 ---
 name: promote-load-from-store
 tracksRegLiveness: true
@@ -130,3 +124,23 @@
 # CHECK-NOT: %w2 = COPY killed %w1
 # CHECK: %w2 = COPY %w1
 # CHECK: STPWi %w1, killed %w2, killed %x0, 0
+---
+name: store-load-clearkill
+tracksRegLiveness: true
+body: |
+  bb.0:
+    liveins: %w1
+
+    STRWui %w1, %sp, 0 :: (store 4)
+    %wzr = COPY killed %w1 ; killing use of %w1
+    %w11 = LDRWui %sp, 0 :: (load 4)
+    HINT 0, implicit %w11 ; some use of %w11
+...
+# When replaceing the load of a store-load pair with a copy the kill flags
+# along the way need to be cleared.
+# CHECK-LABEL: name: store-load-clearkill
+# CHECK: STRWui %w1, %sp, 0 :: (store 4)
+# CHECK-NOT: COPY killed %w1
+# CHECK: %wzr = COPY %w1
+# CHECK: %w11 = ORRWrs %wzr, %w1, 0
+# CHECK: HINT 0, implicit %w11
Index: lib/Target/AArch64/AArch64LoadStoreOptimizer.cpp
===================================================================
--- lib/Target/AArch64/AArch64LoadStoreOptimizer.cpp
+++ lib/Target/AArch64/AArch64LoadStoreOptimizer.cpp
@@ -866,9 +866,11 @@
               .addImm(Imms);
     }
   }
-  StoreI->clearRegisterKills(StRt, TRI);
 
-  (void)BitExtMI;
+  // Clear kill flags between store and load.
+  for (MachineInstr &MI : make_range(StoreI->getIterator(),
+                                     BitExtMI->getIterator()))
+    MI.clearRegisterKills(StRt, TRI);
 
   DEBUG(dbgs() << "Promoting load by replacing :\n    ");
   DEBUG(StoreI->print(dbgs()));


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