[llvm] [SROA] Use tree-structure merge to remove alloca (PR #152793)

[via llvm-commits]

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@@ -0,0 +1,222 @@
+; REQUIRES: asserts
+; RUN: opt < %s -passes='sroa<preserve-cfg>' -disable-output -debug-only=sroa 2>&1 | FileCheck %s
+; RUN: opt < %s -passes='sroa<modify-cfg>' -disable-output -debug-only=sroa 2>&1 | FileCheck %s
+
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-n8:16:32:64"
+
+; CHECK-NOT: Tree structured merge rewrite
+define i32 @test_alloca_not_fixed_vector() {
+entry:
+  %alloca = alloca [4 x float]
+
+  %ptr0 = getelementptr inbounds [4 x float], ptr %alloca, i32 0, i32 0
+  store float 1.0, ptr %ptr0
+
+  %ptr1 = getelementptr inbounds [4 x float], ptr %alloca, i32 0, i32 1
+  store float 2.0, ptr %ptr1
+
+  %result = load i32, ptr %alloca
+  ret i32 %result
+}
+
+define <4 x float> @test_more_than_one_load(<2 x float> %a, <2 x float> %b) {
+entry:
+  %alloca = alloca [4 x float]
+
+  %ptr0 = getelementptr inbounds [4 x float], ptr %alloca, i32 0, i32 0
+  store <2 x float> %a, ptr %ptr0
+
+  %ptr1 = getelementptr inbounds [4 x float], ptr %alloca, i32 0, i32 2
+  store <2 x float> %b, ptr %ptr1
+
+  %result1 = load <4 x float>, ptr %alloca
+  %result2 = load <4 x float>, ptr %alloca
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Chengjunp wrote:

The major reason is that this is not a very common pattern, and it will make the checks become more complicated. So, in this change, I do not have the support for this.

https://github.com/llvm/llvm-project/pull/152793