Revert "[AArch64] Fix isLegalAddImmediate() to return true for valid negative...

    Revert r262248 in an attempt to fix the clang-native-aarch64-full
    bot and to investigate a performance regression in
    SingleSource/Benchmarks/CoyoteBench/huffbench

llvm-svn: 262388

diff --git a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
index 1b73654..faff086 100644 (file)
--- a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -7276,14 +7276,14 @@ EVT AArch64TargetLowering::getOptimalMemOpType(uint64_t Size, unsigned DstAlign,
 
 // 12-bit optionally shifted immediates are legal for adds.
 bool AArch64TargetLowering::isLegalAddImmediate(int64_t Immed) const {
-  // Same encoding for add/sub, just flip the sign.
-  Immed = std::abs(Immed);
   return ((Immed >> 12) == 0 || ((Immed & 0xfff) == 0 && Immed >> 24 == 0));
 }
 
 // Integer comparisons are implemented with ADDS/SUBS, so the range of valid
 // immediates is the same as for an add or a sub.
 bool AArch64TargetLowering::isLegalICmpImmediate(int64_t Immed) const {
+  if (Immed < 0)
+    Immed *= -1;
   return isLegalAddImmediate(Immed);
 }
 

diff --git a/llvm/test/CodeGen/AArch64/neg-imm.ll b/llvm/test/CodeGen/AArch64/neg-imm.ll
deleted file mode 100644 (file)
index 3ef0392..0000000
--- a/llvm/test/CodeGen/AArch64/neg-imm.ll
+++ /dev/null
@@ -1,46 +0,0 @@
-; RUN: llc -mtriple=aarch64-linux-gnu -verify-machineinstrs -o - %s | FileCheck %s
-; LSR used to pick a sub-optimal solution due to the target responding
-; conservatively to isLegalAddImmediate for negative values.
-
-declare void @foo(i32)
-
-define void @test(i32 %px) {
-; CHECK-LABEL: test:
-; CHECK: // %entry
-; CHECK: subs
-; CHECK-NEXT: csel
-entry:
-  %sub = add nsw i32 %px, -1
-  %cmp = icmp slt i32 %px, 1
-  %.sub = select i1 %cmp, i32 0, i32 %sub
-  br label %for.body
-
-for.body:
-; CHECK: // %for.body
-; CHECK:  cmp
-; CHECK-NEXT:  b.eq
-; CHECK: // %if.then3
-  %x.015 = phi i32 [ %inc, %for.inc ], [ %.sub, %entry ]
-  %cmp2 = icmp eq i32 %x.015, %px
-  br i1 %cmp2, label %for.inc, label %if.then3
-
-if.then3:
-  tail call void @foo(i32 %x.015)
-  br label %for.inc
-
-for.inc:
-; CHECK: // %for.inc
-; CHECK:  add
-; CHECK-NEXT:  cmp
-; CHECK:  b.le
-; CHECK: // %for.cond.cleanup
-  %inc = add nsw i32 %x.015, 1
-  %cmp1 = icmp sgt i32 %x.015, %px
-  br i1 %cmp1, label %for.cond.cleanup.loopexit, label %for.body
-
-for.cond.cleanup.loopexit:
-  br label %for.cond.cleanup
-
-for.cond.cleanup:
-  ret void
-}