[llvm] [SandboxVectorizer] New class to actually collect and manage seeds (PR #112979)

[via llvm-commits]

================
@@ -268,3 +268,171 @@ define void @foo(ptr %ptrA, float %val, ptr %ptrB) {
   }
   EXPECT_EQ(Cnt, 0u);
 }
+
+TEST_F(SeedBundleTest, ConsecutiveStores) {
+  // Where "Consecutive" means the stores address consecutive locations in
+  // memory, but not in program order. Check to see that the collector puts them
+  // in the proper order for vectorization.
+  parseIR(C, R"IR(
+define void @foo(ptr noalias %ptr, float %val) {
+bb:
+  %ptr0 = getelementptr float, ptr %ptr, i32 0
+  %ptr1 = getelementptr float, ptr %ptr, i32 1
+  %ptr2 = getelementptr float, ptr %ptr, i32 2
+  %ptr3 = getelementptr float, ptr %ptr, i32 3
+  store float %val, ptr %ptr0
+  store float %val, ptr %ptr2
+  store float %val, ptr %ptr1
+  store float %val, ptr %ptr3
+  ret void
+}
+)IR");
+  Function &LLVMF = *M->getFunction("foo");
+  DominatorTree DT(LLVMF);
+  TargetLibraryInfoImpl TLII;
+  TargetLibraryInfo TLI(TLII);
+  DataLayout DL(M->getDataLayout());
+  LoopInfo LI(DT);
+  AssumptionCache AC(LLVMF);
+  ScalarEvolution SE(LLVMF, TLI, AC, DT, LI);
+
+  sandboxir::Context Ctx(C);
+  auto &F = *Ctx.createFunction(&LLVMF);
+  auto BB = F.begin();
+  sandboxir::SeedCollector SC(&*BB, SE);
+
+  // Find the stores
+  auto It = std::next(BB->begin(), 4);
+  // StX with X as the order by offset in memory
+  auto *St0 = &*It++;
+  auto *St2 = &*It++;
+  auto *St1 = &*It++;
+  auto *St3 = &*It++;
+
+  auto StoreSeedsRange = SC.getStoreSeeds();
+  auto &SB = *StoreSeedsRange.begin();
+  // Expect just one vector of store seeds
+  EXPECT_TRUE(std::next(StoreSeedsRange.begin()) == StoreSeedsRange.end());
+  EXPECT_THAT(SB, testing::ElementsAre(St0, St1, St2, St3));
+}
+
+TEST_F(SeedBundleTest, StoresWithGaps) {
+  parseIR(C, R"IR(
+define void @foo(ptr noalias %ptr, float %val) {
+bb:
+  %ptr0 = getelementptr float, ptr %ptr, i32 0
+  %ptr1 = getelementptr float, ptr %ptr, i32 3
+  %ptr2 = getelementptr float, ptr %ptr, i32 5
+  %ptr3 = getelementptr float, ptr %ptr, i32 7
+  store float %val, ptr %ptr0
+  store float %val, ptr %ptr2
+  store float %val, ptr %ptr1
+  store float %val, ptr %ptr3
+  ret void
+}
+)IR");
+  Function &LLVMF = *M->getFunction("foo");
+  DominatorTree DT(LLVMF);
+  TargetLibraryInfoImpl TLII;
+  TargetLibraryInfo TLI(TLII);
+  DataLayout DL(M->getDataLayout());
+  LoopInfo LI(DT);
+  AssumptionCache AC(LLVMF);
+  ScalarEvolution SE(LLVMF, TLI, AC, DT, LI);
+
+  sandboxir::Context Ctx(C);
+  auto &F = *Ctx.createFunction(&LLVMF);
+  auto BB = F.begin();
+  sandboxir::SeedCollector SC(&*BB, SE);
+
+  // Find the stores
+  auto It = std::next(BB->begin(), 4);
+  // StX with X as the order by offset in memory
+  auto *St0 = &*It++;
+  auto *St2 = &*It++;
+  auto *St1 = &*It++;
+  auto *St3 = &*It++;
+
+  auto StoreSeedsRange = SC.getStoreSeeds();
+  auto &SB = *StoreSeedsRange.begin();
+  // Expect just one vector of store seeds
----------------
Sterling-Augustine wrote:

Bundles contain stores in increasing offsets from a symbol, but those offsets may or may not be consecutive in memory.  If instructions A and B are consecutive in the bundle but are not consecutive in memory, then there there is no instruction C in the bundle that is consecutive in memory with A.

We can't check for consecutiveness until after all seeds have been collected. A series of program-consecutive stores might not be in memory-consecutive order, but still store to a contiguous block of memory.

We can either have "getSlice" check for in memory consecutiveness, or leave that as part of the additional legality checking that will also need to be done.

I'm not sure which is better.

https://github.com/llvm/llvm-project/pull/112979