[PATCH] D124967: [SROA] Avoid postponing rewriting load/store by ignoring lifetime intrinsics in partition's promotability checking

[Dmitry Vassiliev via Phabricator via llvm-commits]

slydiman updated this revision to Diff 427652.

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D124967/new/

https://reviews.llvm.org/D124967

Files:
  llvm/lib/Transforms/Scalar/SROA.cpp
  llvm/test/Transforms/SROA/lifetime-intrinsic.ll


Index: llvm/test/Transforms/SROA/lifetime-intrinsic.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/SROA/lifetime-intrinsic.ll
@@ -0,0 +1,40 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -passes=sroa -S | FileCheck %s
+
+%i32x2 = type { [2 x i32] }
+
+; Note %arr is the union
+; union {
+;   int i[2];
+;   short s[4];
+; };
+
+define i16 @foo(i32 %a, i32 %b) #0 {
+; CHECK-LABEL: @foo(
+; CHECK-NEXT:    [[ARR_SROA_0_0_EXTRACT_TRUNC:%.*]] = trunc i32 [[A:%.*]] to i16
+; CHECK-NEXT:    [[ARR_SROA_4_4_EXTRACT_TRUNC:%.*]] = trunc i32 [[B:%.*]] to i16
+; CHECK-NEXT:    [[RET:%.*]] = add i16 [[ARR_SROA_0_0_EXTRACT_TRUNC]], [[ARR_SROA_4_4_EXTRACT_TRUNC]]
+; CHECK-NEXT:    ret i16 [[RET]]
+;
+  %arr = alloca %i32x2, align 4
+  %p = bitcast %i32x2* %arr to i8*
+  call void @llvm.lifetime.start.p0i8(i64 8, i8* %p)
+  %p0 = getelementptr inbounds %i32x2, %i32x2* %arr, i64 0, i32 0, i32 0
+  %p1 = getelementptr inbounds %i32x2, %i32x2* %arr, i64 0, i32 0, i32 1
+  store i32 %a, i32* %p0, align 4
+  store i32 %b, i32* %p1, align 4
+  %p0_i16 = bitcast %i32x2* %arr to i16*
+  %s0 = load i16, i16* %p0_i16, align 4
+  %p1_i16 = bitcast i32* %p1 to i16*
+  %s2 = load i16, i16* %p1_i16, align 4
+  %ret = add i16 %s0, %s2
+  call void @llvm.lifetime.end.p0i8(i64 8, i8* %p)
+  ret i16 %ret
+}
+
+declare void @llvm.lifetime.start.p0i8(i64, i8* nocapture) #1
+
+declare void @llvm.lifetime.end.p0i8(i64, i8* nocapture) #1
+
+attributes #0 = { alwaysinline nounwind }
+attributes #1 = { argmemonly nounwind }
Index: llvm/lib/Transforms/Scalar/SROA.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/SROA.cpp
+++ llvm/lib/Transforms/Scalar/SROA.cpp
@@ -1983,6 +1983,15 @@
   uint64_t RelBegin = S.beginOffset() - AllocBeginOffset;
   uint64_t RelEnd = S.endOffset() - AllocBeginOffset;
 
+  // Lifetime intrinsics operate over the whole alloca whose sizes are usually
+  // larger than other load/store slices (RelEnd > Size). But lifetime are
+  // always promotable and should not impact other slices' promotability of the
+  // partition.
+  if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(S.getUse()->getUser())) {
+    if (II->isLifetimeStartOrEnd())
+      return true;
+  }
+
   // We can't reasonably handle cases where the load or store extends past
   // the end of the alloca's type and into its padding.
   if (RelEnd > Size)


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