[llvm] [DAGCombiner] Avoid the pre-truncate of BUILD_VECTOR sources. (PR #75792)
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Mon Dec 18 05:33:53 PST 2023
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-backend-aarch64
Author: Rin (Rin18)
<details>
<summary>Changes</summary>
Avoid the pre-truncate of BUILD_VECTOR sources when there is more than one use. This can avoid using unnecessary movs later down the instruction selection pipeline.
---
Full diff: https://github.com/llvm/llvm-project/pull/75792.diff
2 Files Affected:
- (modified) llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp (+1)
- (added) llvm/test/CodeGen/AArch64/avoid-pre-trunc.ll (+89)
``````````diff
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 1d4bfa6fde0352..02d2bb41b051db 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -14759,6 +14759,7 @@ SDValue DAGCombiner::visitTRUNCATE(SDNode *N) {
// Attempt to pre-truncate BUILD_VECTOR sources.
if (N0.getOpcode() == ISD::BUILD_VECTOR && !LegalOperations &&
+ N0.hasOneUse() &&
TLI.isTruncateFree(SrcVT.getScalarType(), VT.getScalarType()) &&
// Avoid creating illegal types if running after type legalizer.
(!LegalTypes || TLI.isTypeLegal(VT.getScalarType()))) {
diff --git a/llvm/test/CodeGen/AArch64/avoid-pre-trunc.ll b/llvm/test/CodeGen/AArch64/avoid-pre-trunc.ll
new file mode 100644
index 00000000000000..072694b36549cb
--- /dev/null
+++ b/llvm/test/CodeGen/AArch64/avoid-pre-trunc.ll
@@ -0,0 +1,89 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 4
+; RUN: llc -mtriple=aarch64 < %s | FileCheck %s
+
+define i32 @lower_lshr(<4 x i32> %a, <4 x i32> %b, <4 x i32> %c, <4 x i32> %d, <4 x i32> %e, <4 x i32> %f, <4 x i32> %g, <4 x i32> %h) local_unnamed_addr #0 {
+; CHECK-LABEL: lower_lshr:
+; CHECK: // %bb.0:
+; CHECK-NEXT: addv s0, v0.4s
+; CHECK-NEXT: addv s1, v1.4s
+; CHECK-NEXT: addv s4, v4.4s
+; CHECK-NEXT: addv s5, v5.4s
+; CHECK-NEXT: addv s2, v2.4s
+; CHECK-NEXT: addv s6, v6.4s
+; CHECK-NEXT: mov v0.s[1], v1.s[0]
+; CHECK-NEXT: addv s1, v3.4s
+; CHECK-NEXT: addv s3, v7.4s
+; CHECK-NEXT: mov v4.s[1], v5.s[0]
+; CHECK-NEXT: mov v0.s[2], v2.s[0]
+; CHECK-NEXT: mov v4.s[2], v6.s[0]
+; CHECK-NEXT: mov v0.s[3], v1.s[0]
+; CHECK-NEXT: mov v4.s[3], v3.s[0]
+; CHECK-NEXT: xtn v2.4h, v0.4s
+; CHECK-NEXT: shrn v0.4h, v0.4s, #16
+; CHECK-NEXT: xtn v1.4h, v4.4s
+; CHECK-NEXT: shrn v3.4h, v4.4s, #16
+; CHECK-NEXT: uhadd v0.4h, v2.4h, v0.4h
+; CHECK-NEXT: uhadd v1.4h, v1.4h, v3.4h
+; CHECK-NEXT: uaddl v0.4s, v0.4h, v1.4h
+; CHECK-NEXT: addv s0, v0.4s
+; CHECK-NEXT: fmov w0, s0
+; CHECK-NEXT: ret
+ %l87 = tail call i32 @llvm.vector.reduce.add.v4i32(<4 x i32> %a)
+ %l174 = tail call i32 @llvm.vector.reduce.add.v4i32(<4 x i32> %b)
+ %l257 = tail call i32 @llvm.vector.reduce.add.v4i32(<4 x i32> %c)
+ %l340 = tail call i32 @llvm.vector.reduce.add.v4i32(<4 x i32> %d)
+ %l427 = tail call i32 @llvm.vector.reduce.add.v4i32(<4 x i32> %e)
+ %l514 = tail call i32 @llvm.vector.reduce.add.v4i32(<4 x i32> %f)
+ %l597 = tail call i32 @llvm.vector.reduce.add.v4i32(<4 x i32> %g)
+ %l680 = tail call i32 @llvm.vector.reduce.add.v4i32(<4 x i32> %h)
+ %l681 = insertelement <8 x i32> poison, i32 %l87, i32 0
+ %l682 = insertelement <8 x i32> %l681, i32 %l174, i32 1
+ %l683 = insertelement <8 x i32> %l682, i32 %l257, i32 2
+ %l684 = insertelement <8 x i32> %l683, i32 %l340, i32 3
+ %l685 = insertelement <8 x i32> %l684, i32 %l427, i32 4
+ %l686 = insertelement <8 x i32> %l685, i32 %l514, i32 5
+ %l687 = insertelement <8 x i32> %l686, i32 %l597, i32 6
+ %l688 = insertelement <8 x i32> %l687, i32 %l680, i32 7
+ %l689 = and <8 x i32> %l688, <i32 65535, i32 65535, i32 65535, i32 65535, i32 65535, i32 65535, i32 65535, i32 65535>
+ %l690 = lshr <8 x i32> %l688, <i32 16, i32 16, i32 16, i32 16, i32 16, i32 16, i32 16, i32 16>
+ %l691 = add nuw nsw <8 x i32> %l689, %l690
+ %l692 = lshr <8 x i32> %l691, <i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1>
+ %l693 = call i32 @llvm.vector.reduce.add.v8i32(<8 x i32> %l692)
+ ret i32 %l693
+}
+
+define <8 x i16> @lower_trunc(i32 %a, i32 %b, i32 %c, i32 %d, i32 %e, i32 %f, i32 %g, i32 %h) local_unnamed_addr #0 {
+; CHECK-LABEL: lower_trunc:
+; CHECK: // %bb.0:
+; CHECK-NEXT: fmov s0, w4
+; CHECK-NEXT: fmov s1, w0
+; CHECK-NEXT: mov v0.s[1], w5
+; CHECK-NEXT: mov v1.s[1], w1
+; CHECK-NEXT: mov v0.s[2], w6
+; CHECK-NEXT: mov v1.s[2], w2
+; CHECK-NEXT: mov v0.s[3], w7
+; CHECK-NEXT: mov v1.s[3], w3
+; CHECK-NEXT: add v2.4s, v0.4s, v0.4s
+; CHECK-NEXT: add v3.4s, v1.4s, v1.4s
+; CHECK-NEXT: uzp1 v0.8h, v1.8h, v0.8h
+; CHECK-NEXT: uzp1 v1.8h, v3.8h, v2.8h
+; CHECK-NEXT: eor v0.16b, v0.16b, v1.16b
+; CHECK-NEXT: ret
+ %a1 = insertelement <8 x i32> poison, i32 %a, i32 0
+ %b1 = insertelement <8 x i32> %a1, i32 %b, i32 1
+ %c1 = insertelement <8 x i32> %b1, i32 %c, i32 2
+ %d1 = insertelement <8 x i32> %c1, i32 %d, i32 3
+ %e1 = insertelement <8 x i32> %d1, i32 %e, i32 4
+ %f1 = insertelement <8 x i32> %e1, i32 %f, i32 5
+ %g1 = insertelement <8 x i32> %f1, i32 %g, i32 6
+ %h1 = insertelement <8 x i32> %g1, i32 %h, i32 7
+ %t = trunc <8 x i32> %h1 to <8 x i16>
+ %s = add <8 x i32> %h1, %h1
+ %t2 = trunc <8 x i32> %s to <8 x i16>
+ %o = xor <8 x i16> %t, %t2
+ ret <8 x i16> %o
+}
+
+declare i32 @llvm.vector.reduce.add.v4i32(<4 x i32>)
+declare i32 @llvm.vector.reduce.add.v8i32(<8 x i32>)
+declare i32 @llvm.vector.reduce.add.v32i32(<32 x i32>)
``````````
</details>
https://github.com/llvm/llvm-project/pull/75792
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