[PATCH] D43549: [ARM] Fix issue with large xor constants.

[Dave Green via Phabricator via llvm-commits]

dmgreen created this revision.
dmgreen added reviewers: efriedma, spatel.
Herald added subscribers: kristof.beyls, javed.absar.

Fixup to https://reviews.llvm.org/rL325573 for large xor constants.

Thanks to Eli Friedman for the catch.


https://reviews.llvm.org/D43549

Files:
  lib/Target/ARM/ARMTargetTransformInfo.cpp
  test/CodeGen/Thumb/mvn.ll


Index: test/CodeGen/Thumb/mvn.ll
===================================================================
--- test/CodeGen/Thumb/mvn.ll
+++ test/CodeGen/Thumb/mvn.ll
@@ -191,3 +191,32 @@
   ret void
 }
 
+
+define void @test128(i128* %a) {
+; CHECK-LABEL: test128:
+; CHECK:         ldr r1, [r0, #4]
+; CHECK-NEXT:    ldr r2, .LCPI8_0
+; CHECK-NEXT:    eors r2, r1
+; CHECK-NEXT:    str r2, [r0, #4]
+; CHECK-NEXT:    ldr r1, [r0]
+; CHECK-NEXT:    ldr r2, .LCPI8_1
+; CHECK-NEXT:    eors r2, r1
+; CHECK-NEXT:    str r2, [r0]
+; CHECK-NEXT:    ldr r1, [r0, #8]
+; CHECK-NEXT:    ldr r2, .LCPI8_2
+; CHECK-NEXT:    eors r2, r1
+; CHECK-NEXT:    str r2, [r0, #8]
+; CHECK-NEXT:    bx lr
+; CHECK-NEXT:    .p2align 2
+; CHECK-NEXT:  .LCPI8_0:
+; CHECK-NEXT:    .long 4075008415
+; CHECK-NEXT:  .LCPI8_1:
+; CHECK-NEXT:    .long 2080661269
+; CHECK-NEXT:  .LCPI8_2:
+; CHECK-NEXT:    .long 6692605
+  %x = load i128, i128* %a
+  %xn = xor i128 %x, 123456789123456789123456789
+  store i128 %xn, i128* %a
+  ret void
+}
+
Index: lib/Target/ARM/ARMTargetTransformInfo.cpp
===================================================================
--- lib/Target/ARM/ARMTargetTransformInfo.cpp
+++ lib/Target/ARM/ARMTargetTransformInfo.cpp
@@ -127,11 +127,8 @@
   }
 
   // xor a, -1 can always be folded to MVN
-  if (Opcode == Instruction::Xor) {
-    int64_t NegImm = Imm.getSExtValue();
-    if (NegImm == -1)
-      return 0;
-  }
+  if (Opcode == Instruction::Xor && Imm.isAllOnesValue())
+    return 0;
 
   return getIntImmCost(Imm, Ty);
 }


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