[llvm] [ConstantHoisting] Don't attempt to hoist ConstantInt vectors. (PR #85416)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-transforms

Author: Paul Walker (paulwalker-arm)

<details>
<summary>Changes</summary>

The pass uses the TTI hook getIntImmCostIntrin that only supports scalar integer types. Whilst hoisting expensive vector constant is likely worthwhile, this is new behaviour and so I've followed the path taken by the GEP variant of collectConstantCandidates and simply bail for vector types.

---
Full diff: https://github.com/llvm/llvm-project/pull/85416.diff


2 Files Affected:

- (modified) llvm/lib/Transforms/Scalar/ConstantHoisting.cpp (+3) 
- (modified) llvm/test/Transforms/ConstantHoisting/AArch64/large-immediate.ll (+31-6) 


``````````diff
diff --git a/llvm/lib/Transforms/Scalar/ConstantHoisting.cpp b/llvm/lib/Transforms/Scalar/ConstantHoisting.cpp
index 49f8761a139232..c12dc281b0e3c4 100644
--- a/llvm/lib/Transforms/Scalar/ConstantHoisting.cpp
+++ b/llvm/lib/Transforms/Scalar/ConstantHoisting.cpp
@@ -363,6 +363,9 @@ SetVector<Instruction *> ConstantHoistingPass::findConstantInsertionPoint(
 void ConstantHoistingPass::collectConstantCandidates(
     ConstCandMapType &ConstCandMap, Instruction *Inst, unsigned Idx,
     ConstantInt *ConstInt) {
+  if (ConstInt->getType()->isVectorTy())
+    return;
+
   InstructionCost Cost;
   // Ask the target about the cost of materializing the constant for the given
   // instruction and operand index.
diff --git a/llvm/test/Transforms/ConstantHoisting/AArch64/large-immediate.ll b/llvm/test/Transforms/ConstantHoisting/AArch64/large-immediate.ll
index 196a104adc0233..6d8890d71e2be9 100644
--- a/llvm/test/Transforms/ConstantHoisting/AArch64/large-immediate.ll
+++ b/llvm/test/Transforms/ConstantHoisting/AArch64/large-immediate.ll
@@ -1,5 +1,6 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 3
-; RUN: opt -mtriple=arm64-darwin-unknown -S -passes=consthoist < %s | FileCheck %s
+; RUN: opt -mtriple=arm64-darwin-unknown -S -passes=consthoist < %s | FileCheck %s --check-prefixes=CHECK,CV
+; RUN: opt -mtriple=arm64-darwin-unknown -S -passes=consthoist -use-constant-int-for-fixed-length-splat -use-constant-int-for-scalable-splat < %s | FileCheck %s --check-prefixes=CHECK,CI
 
 define i128 @test1(i128 %a) {
 ; CHECK-LABEL: define i128 @test1(
@@ -122,13 +123,37 @@ define i64 @sdiv_minsize(i64 %a) minsize {
 }
 
 define <2 x i64> @sdiv_v2i64(<2 x i64> %a) {
-; CHECK-LABEL: define <2 x i64> @sdiv_v2i64(
-; CHECK-SAME: <2 x i64> [[A:%.*]]) {
-; CHECK-NEXT:    [[TMP1:%.*]] = sdiv <2 x i64> [[A]], <i64 4294967087, i64 4294967087>
-; CHECK-NEXT:    [[TMP2:%.*]] = add <2 x i64> [[TMP1]], <i64 4294967087, i64 4294967087>
-; CHECK-NEXT:    ret <2 x i64> [[TMP2]]
+; CV-LABEL: define <2 x i64> @sdiv_v2i64(
+; CV-SAME: <2 x i64> [[A:%.*]]) {
+; CV-NEXT:    [[TMP1:%.*]] = sdiv <2 x i64> [[A]], <i64 4294967087, i64 4294967087>
+; CV-NEXT:    [[TMP2:%.*]] = add <2 x i64> [[TMP1]], <i64 4294967087, i64 4294967087>
+; CV-NEXT:    ret <2 x i64> [[TMP2]]
+;
+; CI-LABEL: define <2 x i64> @sdiv_v2i64(
+; CI-SAME: <2 x i64> [[A:%.*]]) {
+; CI-NEXT:    [[TMP1:%.*]] = sdiv <2 x i64> [[A]], splat (i64 4294967087)
+; CI-NEXT:    [[TMP2:%.*]] = add <2 x i64> [[TMP1]], splat (i64 4294967087)
+; CI-NEXT:    ret <2 x i64> [[TMP2]]
 ;
   %1 = sdiv <2 x i64> %a, <i64 4294967087, i64 4294967087>
   %2 = add <2 x i64> %1, <i64 4294967087, i64 4294967087>
   ret <2 x i64> %2
 }
+
+define <vscale x 2 x i64> @sdiv_nxv2i64(<vscale x 2 x i64> %a) {
+; CV-LABEL: define <vscale x 2 x i64> @sdiv_nxv2i64(
+; CV-SAME: <vscale x 2 x i64> [[A:%.*]]) {
+; CV-NEXT:    [[TMP1:%.*]] = sdiv <vscale x 2 x i64> [[A]], shufflevector (<vscale x 2 x i64> insertelement (<vscale x 2 x i64> poison, i64 4294967087, i64 0), <vscale x 2 x i64> poison, <vscale x 2 x i32> zeroinitializer)
+; CV-NEXT:    [[TMP2:%.*]] = add <vscale x 2 x i64> [[TMP1]], shufflevector (<vscale x 2 x i64> insertelement (<vscale x 2 x i64> poison, i64 4294967087, i64 0), <vscale x 2 x i64> poison, <vscale x 2 x i32> zeroinitializer)
+; CV-NEXT:    ret <vscale x 2 x i64> [[TMP2]]
+;
+; CI-LABEL: define <vscale x 2 x i64> @sdiv_nxv2i64(
+; CI-SAME: <vscale x 2 x i64> [[A:%.*]]) {
+; CI-NEXT:    [[TMP1:%.*]] = sdiv <vscale x 2 x i64> [[A]], splat (i64 4294967087)
+; CI-NEXT:    [[TMP2:%.*]] = add <vscale x 2 x i64> [[TMP1]], splat (i64 4294967087)
+; CI-NEXT:    ret <vscale x 2 x i64> [[TMP2]]
+;
+  %1 = sdiv <vscale x 2 x i64> %a, splat (i64 4294967087)
+  %2 = add <vscale x 2 x i64> %1, splat (i64 4294967087)
+  ret <vscale x 2 x i64> %2
+}

``````````

</details>


https://github.com/llvm/llvm-project/pull/85416