[PATCH] D107453: [SVE] Add folds for truncation of vscale

[Dylan Fleming via Phabricator via llvm-commits]

DylanFleming-arm created this revision.
Herald added subscribers: psnobl, hiraditya, tschuett.
Herald added a reviewer: efriedma.
DylanFleming-arm requested review of this revision.
Herald added a project: LLVM.
Herald added a subscriber: llvm-commits.

Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D107453

Files:
  llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
  llvm/test/Transforms/InstCombine/vscale_trunc.ll


Index: llvm/test/Transforms/InstCombine/vscale_trunc.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/InstCombine/vscale_trunc.ll
@@ -0,0 +1,42 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -instcombine -S | FileCheck %s
+
+define i32 @vscale_trunc_i64toi32() #0 {
+; CHECK-LABEL: @vscale_trunc_i64toi32(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[TMP0:%.*]] = call i32 @llvm.vscale.i32()
+; CHECK-NEXT:    ret i32 [[TMP0]]
+entry:
+  %0 = call i64 @llvm.vscale.i64()
+  %1 = trunc i64 %0 to i32
+  ret i32 %1
+}
+
+define i8 @vscale_SExt_i32toi8() #0 {
+; CHECK-LABEL: @vscale_SExt_i32toi8(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[TMP0:%.*]] = call i8 @llvm.vscale.i8()
+; CHECK-NEXT:    ret i8 [[TMP0]]
+entry:
+  %0 = call i32 @llvm.vscale.i32()
+  %1 = trunc i32 %0 to i8
+  ret i8 %1
+}
+
+
+define i8 @vscale_SExt_i32toi8_poison() vscale_range(0, 1024) {
+; CHECK-LABEL: @vscale_SExt_i32toi8_poison(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[TMP0:%.*]] = call i32 @llvm.vscale.i32()
+; CHECK-NEXT:    [[TMP1:%.*]] = trunc i32 [[TMP0]] to i8
+; CHECK-NEXT:    ret i8 [[TMP1]]
+  entry:
+  %0 = call i32 @llvm.vscale.i32()
+  %1 = trunc i32 %0 to i8
+  ret i8 %1
+}
+
+attributes #0 = { vscale_range(0, 16) }
+
+declare i32 @llvm.vscale.i32()
+declare i64 @llvm.vscale.i64()
Index: llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
@@ -961,6 +961,20 @@
       return BinaryOperator::CreateAdd(NarrowCtlz, WidthDiff);
     }
   }
+
+  if (match(Src, m_VScale(DL))) {
+    if (Trunc.getFunction()->hasFnAttribute(Attribute::VScaleRange)) {
+      unsigned MaxVScale = Trunc.getFunction()
+                               ->getFnAttribute(Attribute::VScaleRange)
+                               .getVScaleRangeArgs()
+                               .second;
+      if (Log2_32(MaxVScale) < DestWidth) {
+        Value *VScale = Builder.CreateVScale(ConstantInt::get(DestTy, 1));
+        return replaceInstUsesWith(Trunc, VScale);
+      }
+    }
+  }
+
   return nullptr;
 }
 


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