[llvm] 5531180 - Allow bitwidth difference when checking for isOneOrOneSplat.

[Adrian Tong via llvm-commits]

Author: Adrian Tong
Date: 2022-06-16T16:04:20Z
New Revision: 55311801f06d33a71deae80209dd5640d5e7463e

URL: https://github.com/llvm/llvm-project/commit/55311801f06d33a71deae80209dd5640d5e7463e
DIFF: https://github.com/llvm/llvm-project/commit/55311801f06d33a71deae80209dd5640d5e7463e.diff

LOG: Allow bitwidth difference when checking for isOneOrOneSplat.

This helps handling a case where the BUILD_VECTOR has i16 element type
and i32 constant operands

t2: v8i16 = setcc t8, t17, setult:ch
t3: v8i16 = BUILD_VECTOR Constant:i32<1>, ...
   t4: v8i16 = and t2, t3
      t5: v8i16 = add t8, t4

This can be turned into t5: v8i16 = sub t8, t2, and allows us to remove
t3 and t4 from the DAG.

Differential Revision: https://reviews.llvm.org/D127354

Added: 
    

Modified: 
    llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
    llvm/test/CodeGen/AArch64/add-negative.ll
    llvm/test/CodeGen/AArch64/minmax.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index bf222a77cbcc8..598f0c5f1247f 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -10666,10 +10666,9 @@ bool llvm::isNullOrNullSplat(SDValue N, bool AllowUndefs) {
 }
 
 bool llvm::isOneOrOneSplat(SDValue N, bool AllowUndefs) {
-  // TODO: may want to use peekThroughBitcast() here.
-  unsigned BitWidth = N.getScalarValueSizeInBits();
-  ConstantSDNode *C = isConstOrConstSplat(N, AllowUndefs);
-  return C && C->isOne() && C->getValueSizeInBits(0) == BitWidth;
+  ConstantSDNode *C =
+      isConstOrConstSplat(N, AllowUndefs, /*AllowTruncation*/ true);
+  return C && C->isOne();
 }
 
 bool llvm::isAllOnesOrAllOnesSplat(SDValue N, bool AllowUndefs) {

diff  --git a/llvm/test/CodeGen/AArch64/add-negative.ll b/llvm/test/CodeGen/AArch64/add-negative.ll
index e62c3e421a477..ec24d2187b75e 100644
--- a/llvm/test/CodeGen/AArch64/add-negative.ll
+++ b/llvm/test/CodeGen/AArch64/add-negative.ll
@@ -1,17 +1,14 @@
 ; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
 ; RUN: llc -verify-machineinstrs -o - %s -mtriple=aarch64-linux-gnu | FileCheck %s
 
-; FIXME: D127354
 define <8 x i16> @add_to_sub(<8 x i16> %0, <8 x i16> %1) {
 ; CHECK-LABEL: add_to_sub:
 ; CHECK:       // %bb.0:
 ; CHECK-NEXT:    adrp x8, .LCPI0_0
-; CHECK-NEXT:    movi v3.8h, #1
 ; CHECK-NEXT:    ldr q2, [x8, :lo12:.LCPI0_0]
-; CHECK-NEXT:    cmhi v1.8h, v2.8h, v1.8h
 ; CHECK-NEXT:    cmhi v0.8h, v2.8h, v0.8h
-; CHECK-NEXT:    and v1.16b, v1.16b, v3.16b
-; CHECK-NEXT:    add v0.8h, v1.8h, v0.8h
+; CHECK-NEXT:    cmhi v1.8h, v2.8h, v1.8h
+; CHECK-NEXT:    sub v0.8h, v0.8h, v1.8h
 ; CHECK-NEXT:    ret
   %3 = icmp ult <8 x i16> %0, <i16 1, i16 2, i16 3, i16 4, i16 5, i16 6, i16 7, i16 8>
   %4 = sext <8 x i1> %3 to <8 x i16>

diff  --git a/llvm/test/CodeGen/AArch64/minmax.ll b/llvm/test/CodeGen/AArch64/minmax.ll
index 59faf0efc35dd..be9f45e6eea44 100644
--- a/llvm/test/CodeGen/AArch64/minmax.ll
+++ b/llvm/test/CodeGen/AArch64/minmax.ll
@@ -123,10 +123,8 @@ define <16 x i8> @t12(<16 x i8> %a, <16 x i8> %b) {
 ; CHECK-LABEL: t12:
 ; CHECK:       // %bb.0:
 ; CHECK-NEXT:    cmhi v2.16b, v1.16b, v0.16b
-; CHECK-NEXT:    movi v3.16b, #1
 ; CHECK-NEXT:    bif v0.16b, v1.16b, v2.16b
-; CHECK-NEXT:    and v1.16b, v2.16b, v3.16b
-; CHECK-NEXT:    add v0.16b, v1.16b, v0.16b
+; CHECK-NEXT:    sub v0.16b, v0.16b, v2.16b
 ; CHECK-NEXT:    ret
   %t1 = icmp ugt <16 x i8> %b, %a
   %t2 = select <16 x i1> %t1, <16 x i8> %a, <16 x i8> %b