[LV] Add a test for register pressure estimation. NFC

[yrouban]

Summary

The test shows that the interleave count is limited even if there is no local users other than one induction variable.

This test will be changed in the subsequent change D147434.

[yrouban]

Updated the test to use opaque pointers as suggested by @fhahn.

[fhahn]

llvm/test/Transforms/LoopVectorize/X86/interleave-count.ll

8

please add a comment indicating what this is testing. Might also e good to have. amore descriptive test file name,

26

is this needed?

35

Is the branch weight needed?

[yrouban]

addressed comments.

llvm/test/Transforms/LoopVectorize/X86/interleave-count.ll

+; REQUIRES: asserts
+;
+; RUN: opt -S -passes=loop-vectorize -debug-only=loop-vectorize \
+; RUN:     -mtriple=x86_64-pc_linux -mcpu=cascadelake \
+; RUN:     -force-target-max-vector-interleave=16 -force-target-num-vector-regs=16 \
+; RUN:     %s 2>&1 | FileCheck %s
+
+define void @test(ptr %dst, i64 %len) {
+; CHECK-LABEL: LV: Checking a loop in 'test'
+; CHECK:       LV: IC is 8
+;
+; CHECK-LABEL: define void @test
+;
+; Number of @llvm.masked.scatter() calls is 8.
+; CHECK:         call void @llvm.masked.scatter.v4f64.v4p0(<4 x double>
+; CHECK-NEXT:    call void @llvm.masked.scatter.v4f64.v4p0(<4 x double>
+; CHECK-NEXT:    call void @llvm.masked.scatter.v4f64.v4p0(<4 x double>
+; CHECK-NEXT:    call void @llvm.masked.scatter.v4f64.v4p0(<4 x double>
+; CHECK-NEXT:    call void @llvm.masked.scatter.v4f64.v4p0(<4 x double>
+; CHECK-NEXT:    call void @llvm.masked.scatter.v4f64.v4p0(<4 x double>
+; CHECK-NEXT:    call void @llvm.masked.scatter.v4f64.v4p0(<4 x double>
+; CHECK-NEXT:    call void @llvm.masked.scatter.v4f64.v4p0(<4 x double>
+; CHECK-NOT:     call void @llvm.masked.scatter.v4f64.v4p0(<4 x double>
+;
+entry:
+  %size = shl i64 %len, 3
+  %p.end = getelementptr inbounds double, ptr %dst, i64 %size
+  br label %loop
+
+loop:
+  %p = phi ptr [%dst, %entry], [%p.next, %loop]
+  store double -1.000000e+00, ptr %p, align 8
+  %p.next = getelementptr inbounds double, ptr %p, i64 8
+  %done = icmp eq ptr %p.next, %p.end
+  br i1 %done, label %exit, label %loop, !prof !{!"branch_weights", i32 1, i32 1000000}
+
+exit:
+  ret void
+}