[DeadStoreElimination] Introduce test for #63473 (NFC)

[antoniofrighetto]

Preliminary tests addition.

[llvmbot]

@llvm/pr-subscribers-llvm-transforms

Author: Antonio Frighetto (antoniofrighetto)

Changes

Preliminary tests addition.

---

Full diff: https://github.com/llvm/llvm-project/pull/98737.diff

1 Files Affected:

• (added) llvm/test/Transforms/DeadStoreElimination/dependencies-cross-iterations.ll (+126)

diff --git a/llvm/test/Transforms/DeadStoreElimination/dependencies-cross-iterations.ll b/llvm/test/Transforms/DeadStoreElimination/dependencies-cross-iterations.ll
new file mode 100644
index 0000000000000..d446ebc6d2bd4
--- /dev/null
+++ b/llvm/test/Transforms/DeadStoreElimination/dependencies-cross-iterations.ll
@@ -0,0 +1,126 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -passes=dse -S %s | FileCheck %s
+
+; No final read after clobbering.
+define void @test1(i64 %arg) #0 {
+; CHECK-LABEL: @test1(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[ARRAY:%.*]] = alloca [20 x i64], align 16
+; CHECK-NEXT:    br label [[LOOP:%.*]]
+; CHECK:       loop:
+; CHECK-NEXT:    [[IV:%.*]] = phi i64 [ 0, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[LOOP]] ]
+; CHECK-NEXT:    [[PTR_1:%.*]] = getelementptr inbounds [20 x i64], ptr [[ARRAY]], i64 0, i64 [[IV]]
+; CHECK-NEXT:    store i64 0, ptr [[PTR_1]], align 8
+; CHECK-NEXT:    [[VAL:%.*]] = load i64, ptr [[PTR_1]], align 8
+; CHECK-NEXT:    [[ADD:%.*]] = add nsw i64 [[VAL]], [[ARG:%.*]]
+; CHECK-NEXT:    store i64 [[ADD]], ptr [[PTR_1]], align 8
+; CHECK-NEXT:    [[IV_NEXT]] = add nuw nsw i64 [[IV]], 1
+; CHECK-NEXT:    [[COND:%.*]] = icmp ult i64 [[IV]], 4
+; CHECK-NEXT:    br i1 [[COND]], label [[LOOP]], label [[EXIT:%.*]]
+; CHECK:       exit:
+; CHECK-NEXT:    ret void
+;
+entry:
+  %array = alloca [20 x i64], align 16
+  br label %loop
+
+loop:                                                ; preds = %loop, %entry
+  %iv = phi i64 [ 0, %entry ], [ %iv.next, %loop ]
+  %ptr.1 = getelementptr inbounds [20 x i64], ptr %array, i64 0, i64 %iv
+  store i64 0, ptr %ptr.1, align 8
+  %val = load i64, ptr %ptr.1, align 8
+  %add = add nsw i64 %val, %arg
+  store i64 %add, ptr %ptr.1, align 8
+  %iv.next = add nuw nsw i64 %iv, 1
+  %cond = icmp ult i64 %iv, 4
+  br i1 %cond, label %loop, label %exit
+
+exit:                                                ; preds = %loop
+  ret void
+}
+
+; Unused final read of %ptr.1 after clobbering it.
+define void @test2(i64 %arg) #0 {
+; CHECK-LABEL: @test2(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[ARRAY:%.*]] = alloca [20 x i64], align 16
+; CHECK-NEXT:    br label [[LOOP:%.*]]
+; CHECK:       loop:
+; CHECK-NEXT:    [[IV:%.*]] = phi i64 [ 0, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[LOOP]] ]
+; CHECK-NEXT:    [[PTR_1:%.*]] = getelementptr inbounds [20 x i64], ptr [[ARRAY]], i64 0, i64 [[IV]]
+; CHECK-NEXT:    store i64 0, ptr [[PTR_1]], align 8
+; CHECK-NEXT:    [[VAL:%.*]] = load i64, ptr [[PTR_1]], align 8
+; CHECK-NEXT:    [[ADD:%.*]] = add nsw i64 [[VAL]], [[ARG:%.*]]
+; CHECK-NEXT:    store i64 [[ADD]], ptr [[PTR_1]], align 8
+; CHECK-NEXT:    [[IV_NEXT]] = add nuw nsw i64 [[IV]], 1
+; CHECK-NEXT:    [[COND:%.*]] = icmp ult i64 [[IV]], 4
+; CHECK-NEXT:    br i1 [[COND]], label [[LOOP]], label [[EXIT:%.*]]
+; CHECK:       exit:
+; CHECK-NEXT:    [[PTR_FIRST_ELEM:%.*]] = getelementptr inbounds [20 x i64], ptr [[ARRAY]], i64 0, i64 0
+; CHECK-NEXT:    [[UNUSED_RV:%.*]] = load i64, ptr [[PTR_FIRST_ELEM]], align 8
+; CHECK-NEXT:    ret void
+;
+entry:
+  %array = alloca [20 x i64], align 16
+  br label %loop
+
+loop:                                                ; preds = %loop, %entry
+  %iv = phi i64 [ 0, %entry ], [ %iv.next, %loop ]
+  %ptr.1 = getelementptr inbounds [20 x i64], ptr %array, i64 0, i64 %iv
+  store i64 0, ptr %ptr.1, align 8
+  %val = load i64, ptr %ptr.1, align 8
+  %add = add nsw i64 %val, %arg
+  store i64 %add, ptr %ptr.1, align 8
+  %iv.next = add nuw nsw i64 %iv, 1
+  %cond = icmp ult i64 %iv, 4
+  br i1 %cond, label %loop, label %exit
+
+exit:                                                ; preds = %loop
+  %ptr.first.elem = getelementptr inbounds [20 x i64], ptr %array, i64 0, i64 0
+  %unused_rv = load i64, ptr %ptr.first.elem, align 8
+  ret void
+}
+
+; Used final read after clobbering %ptr.1.
+define i64 @test3(i64 %arg) #0 {
+; CHECK-LABEL: @test3(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[ARRAY:%.*]] = alloca [20 x i64], align 16
+; CHECK-NEXT:    br label [[LOOP:%.*]]
+; CHECK:       loop:
+; CHECK-NEXT:    [[IV:%.*]] = phi i64 [ 0, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[LOOP]] ]
+; CHECK-NEXT:    [[PTR_1:%.*]] = getelementptr inbounds [20 x i64], ptr [[ARRAY]], i64 0, i64 [[IV]]
+; CHECK-NEXT:    store i64 0, ptr [[PTR_1]], align 8
+; CHECK-NEXT:    [[VAL:%.*]] = load i64, ptr [[PTR_1]], align 8
+; CHECK-NEXT:    [[ADD:%.*]] = add nsw i64 [[VAL]], [[ARG:%.*]]
+; CHECK-NEXT:    store i64 [[ADD]], ptr [[PTR_1]], align 8
+; CHECK-NEXT:    [[IV_NEXT]] = add nuw nsw i64 [[IV]], 1
+; CHECK-NEXT:    [[COND:%.*]] = icmp ult i64 [[IV]], 4
+; CHECK-NEXT:    br i1 [[COND]], label [[LOOP]], label [[EXIT:%.*]]
+; CHECK:       exit:
+; CHECK-NEXT:    [[PTR_FIRST_ELEM:%.*]] = getelementptr inbounds [20 x i64], ptr [[ARRAY]], i64 0, i64 0
+; CHECK-NEXT:    [[RV:%.*]] = load i64, ptr [[PTR_FIRST_ELEM]], align 8
+; CHECK-NEXT:    ret i64 [[RV]]
+;
+entry:
+  %array = alloca [20 x i64], align 16
+  br label %loop
+
+loop:                                                ; preds = %loop, %entry
+  %iv = phi i64 [ 0, %entry ], [ %iv.next, %loop ]
+  %ptr.1 = getelementptr inbounds [20 x i64], ptr %array, i64 0, i64 %iv
+  store i64 0, ptr %ptr.1, align 8
+  %val = load i64, ptr %ptr.1, align 8
+  %add = add nsw i64 %val, %arg
+  store i64 %add, ptr %ptr.1, align 8
+  %iv.next = add nuw nsw i64 %iv, 1
+  %cond = icmp ult i64 %iv, 4
+  br i1 %cond, label %loop, label %exit
+
+exit:                                                ; preds = %loop
+  %ptr.first.elem = getelementptr inbounds [20 x i64], ptr %array, i64 0, i64 0
+  %rv = load i64, ptr %ptr.first.elem, align 8
+  ret i64 %rv
+}
+
+attributes #0 = { mustprogress }

[fhahn]

Would be good to also add a test case with cross-iteration dependencies in the loops?

[fhahn]

Can define this outside?

[antoniofrighetto]

test4 has been moved in read-clobber-after-overwrite.ll. I'm not exactly sure how the test would benefit from defining this outside the loop. The idea is to show that the final load (MemoryUse(2)) reads memory from the PN (2 = MemoryPhi({entry,liveOnEntry},{loop,1})), and not directly from the store (1 = MemoryDef(2)), to which it is still constrained though.

[antoniofrighetto]

Would be good to also add a test case with cross-iteration dependencies in the loops?

Reorganized the tests a bit, moved the read after clobbering out in read-clobber-after-overwrite.ll, added a few actual cross-iteration dependencies tests; thanks!