[llvm] [LV] Add initial legality checks for loops with unbound loads. (PR #152422)

[David Sherwood via llvm-commits]

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@@ -0,0 +1,89 @@
+; REQUIRES: asserts
+; RUN: opt -passes=loop-vectorize -debug-only=loop-vectorize -disable-output 2>&1 -mtriple=riscv64 -mattr=+v -S %s | FileCheck %s
+
+define ptr @two_unbound_access(ptr %first, ptr %last, ptr %addr2) {
+; CHECK-LABEL: LV: Checking a loop in 'two_unbound_access'
+; CHECK:       LV: Not vectorizing: Loop contains more than one unbound access.
+entry:
+  %cond = icmp eq ptr %first, %last
+  br i1 %cond, label %return, label %for.body
+
+for.body:
+  %first.addr = phi ptr [ %first, %entry], [ %first.next, %for.inc ]
+  %match.addr = phi ptr [ %addr2, %entry ], [ %match.next, %for.inc ]
+  %1 = load i32, ptr %first.addr, align 4
+  %match.value = load i32, ptr %match.addr, align 4
+  %cmp1 = icmp eq i32 %1, %match.value
+  br i1 %cmp1, label %early.exit, label %for.inc
+
+for.inc:
+  %match.next = getelementptr inbounds nuw i8, ptr %match.addr, i64 4
+  %first.next = getelementptr inbounds i8, ptr %first.addr, i64 4
+  %exit = icmp eq ptr %first.next, %last
+  br i1 %exit, label %main.exit, label %for.body
+
+early.exit:
+  br label %return
+
+main.exit:
+  br label %return
+
+return:
+  %retval = phi ptr [ %first, %entry ], [ %last, %main.exit ], [ %first.addr, %early.exit ]
+  ret ptr %retval
+}
+
+define ptr @unbound_strided_access(ptr %first, ptr %last, i32 %value) {
+; CHECK-LABEL: LV: Checking a loop in 'unbound_strided_access'
+; CHECK:       LV: Not vectorizing: Loop contains strided unbound access.
+entry:
+  %cond = icmp eq ptr %first, %last
+  br i1 %cond, label %return, label %for.body
+
+for.body:
+  %first.addr = phi ptr [ %first, %entry ], [ %first.next, %for.inc ]
+  %1 = load i32, ptr %first.addr, align 4
+  %cond2 = icmp eq i32 %1, %value
+  br i1 %cond2, label %for.end, label %for.inc
+
+for.inc:
+  %first.next = getelementptr inbounds i32, ptr %first.addr, i64 2
+  %cond3 = icmp eq ptr %first.next, %last
+  br i1 %cond3, label %for.end, label %for.body
+
+for.end:
+  %retval.ph = phi ptr [ %first.addr, %for.body ], [ %last, %for.inc ]
+  br label %return
+
+return:
+  %retval = phi ptr [ %first, %entry ], [ %retval.ph, %for.end ]
+  ret ptr %retval
+}
+
+define ptr @single_unbound_access(ptr %first, ptr %last, i32 %value) {
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david-arm wrote:

Worth adding a test for things that targets probably won't support, such as first-faulting loads of 128-bit types, fp128, etc. Not sure what range of types is supported for RISCV.

https://github.com/llvm/llvm-project/pull/152422