[llvm] [LV] Vectorize conditional scalar assignments (PR #158088)

[Florian Hahn via llvm-commits]

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@@ -0,0 +1,77 @@
+; RUN: opt -passes=loop-vectorize -debug-only=loop-vectorize \
+; RUN: -force-vector-width=4 -disable-output 2>&1 < %s | FileCheck %s
+
+
+; This function is derived from the following C program:
+; int simple_csa_int_select(int N, int *data, int a) {
+;   int t = -1;
+;   for (int i = 0; i < N; i++) {
+;     if (a < data[i])
+;       t = data[i];
+;   }
+;   return t;
+; }
+define i32 @simple_csa_int_select(i64 %N, ptr %data, i32 %a) {
+entry:
+  br label %loop
+
+loop:
+  %iv = phi i64 [ 0, %entry ], [ %iv.next, %loop ]
+  %data.phi = phi i32 [ -1, %entry ], [ %select.data, %loop ]
+  %ld.addr = getelementptr inbounds i32, ptr %data, i64 %iv
+  %ld = load i32, ptr %ld.addr, align 4
+  %select.cmp = icmp slt i32 %a, %ld
+  %select.data = select i1 %select.cmp, i32 %ld, i32 %data.phi
+  %iv.next = add nuw nsw i64 %iv, 1
+  %exit.cmp = icmp eq i64 %iv.next, %N
+  br i1 %exit.cmp, label %exit, label %loop
+
+exit:
+  ret i32 %select.data
+}
+
+; CHECK: VPlan 'Initial VPlan for VF={4},UF>=1' {
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fhahn wrote:

nit: move before the test for consitency

https://github.com/llvm/llvm-project/pull/158088