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

[Florian Hahn via llvm-commits]

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@@ -0,0 +1,123 @@
+; RUN: opt -passes=loop-vectorize -debug-only=loop-vectorize \
+; RUN:   -scalable-vectorization=on -force-target-supports-scalable-vectors \
+; RUN:   -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={vscale x 1},UF>=1' {
+; CHECK-NEXT: Live-in vp<%0> = VF
+; CHECK-NEXT: Live-in vp<%1> = VF * UF
+; CHECK-NEXT: Live-in vp<%2> = vector-trip-count
+; CHECK-NEXT: Live-in ir<%N> = original trip-count
+; CHECK-EMPTY:
+; CHECK-NEXT: ir-bb<entry>:
+; CHECK-NEXT: Successor(s): scalar.ph, vector.ph
+; CHECK-EMPTY:
+; CHECK-NEXT: vector.ph:
+; CHECK-NEXT: Successor(s): vector loop
+; CHECK-EMPTY:
+; CHECK-NEXT: <x1> vector loop: {
+; CHECK-NEXT:   vector.body:
+; CHECK-NEXT:     EMIT vp<%3> = CANONICAL-INDUCTION ir<0>, vp<%index.next>
+; CHECK-NEXT:     WIDEN-REDUCTION-PHI ir<%data.phi> = phi ir<-1>, vp<%9>
+; CHECK-NEXT:     LAST-ACTIVE-MASK-PHI vp<%4> = phi ir<false>, vp<%8>
+; CHECK-NEXT:     vp<%5> = SCALAR-STEPS vp<%3>, ir<1>, vp<%0>
+; CHECK-NEXT:     CLONE ir<%ld.addr> = getelementptr inbounds ir<%data>, vp<%5>
+; CHECK-NEXT:     vp<%6> = vector-pointer ir<%ld.addr>
+; CHECK-NEXT:     WIDEN ir<%ld> = load vp<%6>
+; CHECK-NEXT:     WIDEN ir<%select.cmp> = icmp slt ir<%a>, ir<%ld>
+; CHECK-NEXT:     EMIT vp<%7> = any-of ir<%select.cmp>
+; CHECK-NEXT:     EMIT vp<%8> = select vp<%7>, ir<%select.cmp>, vp<%4>
+; CHECK-NEXT:     EMIT vp<%9> = select vp<%7>, ir<%ld>, ir<%data.phi>
----------------
fhahn wrote:

Please use patterns for the unnamed vpvalues throughout

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