[PATCH] D106850: [InstCombine] Simplify llvm.vscale when vscale_range attribute exists

[JunMa via Phabricator via llvm-commits]

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Reduce llvm.vscale to constant based on vscale_range attribute.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D106850

Files:
  llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
  llvm/test/Transforms/InstCombine/fold-vscale.ll


Index: llvm/test/Transforms/InstCombine/fold-vscale.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/InstCombine/fold-vscale.ll
@@ -0,0 +1,44 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -instcombine -S | FileCheck %s
+
+define i64 @vscale_i64() #1 {
+; CHECK-LABEL: @vscale_i64(
+; CHECK-NEXT:    ret i64 16
+;
+  %1 = call i64 @llvm.vscale.i64()
+  %out = shl i64 %1, 4
+  ret i64 %out
+}
+
+define i32 @vscale_i32() #2 {
+; CHECK-LABEL: @vscale_i32(
+; CHECK-NEXT:    ret i32 8
+;
+  %1 = call i32 @llvm.vscale.i32()
+  %out = shl i32 %1, 2
+  ret i32 %out
+}
+
+define i64 @vscale_i64_diff() #3 {
+; CHECK-LABEL: @vscale_i64_diff(
+; CHECK-NEXT:    [[TMP1:%.*]] = call i64 @llvm.vscale.i64()
+; CHECK-NEXT:    [[OUT:%.*]] = shl i64 [[TMP1]], 4
+; CHECK-NEXT:    ret i64 [[OUT]]
+;
+  %1 = call i64 @llvm.vscale.i64()
+  %out = shl i64 %1, 4
+  ret i64 %out
+}
+
+; Function Attrs: nofree nosync nounwind readnone willreturn
+declare i64 @llvm.vscale.i64() #0
+
+; Function Attrs: nofree nosync nounwind readnone willreturn
+declare i32 @llvm.vscale.i32() #0
+
+attributes #0 = { nofree nosync nounwind readnone willreturn }
+attributes #1 = { mustprogress nofree nosync nounwind uwtable vscale_range(1,1) }
+attributes #2 = { mustprogress nofree nosync nounwind uwtable vscale_range(2,2) }
+attributes #3 = { mustprogress nofree nosync nounwind uwtable vscale_range(2,4) }
+
+
Index: llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -2056,6 +2056,17 @@
     }
     break;
   }
+  case Intrinsic::vscale: {
+    auto Attr = II->getFunction()->getFnAttribute(Attribute::VScaleRange);
+    if (!Attr.isValid())
+      break;
+    unsigned MinSVEVectorSize, MaxSVEVectorSize;
+    std::tie(MinSVEVectorSize, MaxSVEVectorSize) = Attr.getVScaleRangeArgs();
+    if (MinSVEVectorSize == MaxSVEVectorSize && MaxSVEVectorSize != 0)
+      return replaceInstUsesWith(
+          CI, ConstantInt::get(II->getType(), MinSVEVectorSize));
+    break;
+  }
   default: {
     // Handle target specific intrinsics
     Optional<Instruction *> V = targetInstCombineIntrinsic(*II);


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