[llvm] [LAA] rewrite a test to be less nonsensical (PR #93197)

[Ramkumar Ramachandra via llvm-commits]

https://github.com/artagnon updated https://github.com/llvm/llvm-project/pull/93197

>From 6515c6e2827e6e379aae1f02cf27fd268f62dae9 Mon Sep 17 00:00:00 2001
From: Ramkumar Ramachandra <r at artagnon.com>
Date: Thu, 23 May 2024 15:06:11 +0100
Subject: [PATCH 1/2] [LAA] rewrite a test to be less nonsensical

The test select-dependence.ll can be eliminated completely by dce, as it
returns a constant, and doesn't write any arguments. Lift out the local
allocas into arguments, so that it is less nonsensical. While at it,
rename the variables for greater readability, and regenerate the test
with UpdateTestChecks.
---
 .../LoopAccessAnalysis/select-dependence.ll   | 55 +++++++++++--------
 1 file changed, 33 insertions(+), 22 deletions(-)

diff --git a/llvm/test/Analysis/LoopAccessAnalysis/select-dependence.ll b/llvm/test/Analysis/LoopAccessAnalysis/select-dependence.ll
index 07e32f443554b..ed3e96a6ce2e3 100644
--- a/llvm/test/Analysis/LoopAccessAnalysis/select-dependence.ll
+++ b/llvm/test/Analysis/LoopAccessAnalysis/select-dependence.ll
@@ -1,30 +1,41 @@
+; NOTE: Assertions have been autogenerated by utils/update_analyze_test_checks.py UTC_ARGS: --version 5
 ; RUN: opt -passes='print<access-info>' -disable-output 2>&1 < %s | FileCheck %s
 
-; CHECK: Dependences:
-; CHECK-NEXT: Unknown:
-; CHECK-NEXT: %t63 = load double, ptr %t62, align 8 ->
-; CHECK-NEXT: store double %t63, ptr %t64, align 8
-
-define i32 @test() {
-   %a1 = alloca [128 x double], align 8
-   %a2 = alloca [128 x double], align 8
-   %a3 = alloca [128 x double], align 8
-   %t30 = getelementptr double, ptr %a2, i64 -32
+define void @test(ptr %x, ptr %y, ptr %z) {
+; CHECK-LABEL: 'test'
+; CHECK-NEXT:    loop:
+; CHECK-NEXT:      Report: unsafe dependent memory operations in loop. Use #pragma clang loop distribute(enable) to allow loop distribution to attempt to isolate the offending operations into a separate loop
+; CHECK-NEXT:  Unknown data dependence.
+; CHECK-NEXT:      Dependences:
+; CHECK-NEXT:        Unknown:
+; CHECK-NEXT:            %load = load double, ptr %gep.sel, align 8 ->
+; CHECK-NEXT:            store double %load, ptr %gep.sel2, align 8
+; CHECK-EMPTY:
+; CHECK-NEXT:      Run-time memory checks:
+; CHECK-NEXT:      Grouped accesses:
+; CHECK-EMPTY:
+; CHECK-NEXT:      Non vectorizable stores to invariant address were not found in loop.
+; CHECK-NEXT:      SCEV assumptions:
+; CHECK-EMPTY:
+; CHECK-NEXT:      Expressions re-written:
+;
+entry:
+   %gep.y = getelementptr double, ptr %y, i64 -32
    br label %loop
 
 loop:
-   %t58 = phi i64 [ %t65, %loop ], [ 0, %0 ]
-   %t59 = icmp ule i64 %t58, 32
-   %t60 = select i1 %t59, ptr %a1, ptr %t30
-   %t62 = getelementptr inbounds double, ptr %t60, i64 %t58
-   %t63 = load double, ptr %t62, align 8
-   %t61 = select i1 %t59, ptr %a2, ptr %a3
-   %t64 = getelementptr inbounds double, ptr %t61, i64 %t58
-   store double %t63, ptr %t64, align 8
-   %t65 = add nuw nsw i64 %t58, 1
-   %t66 = icmp eq i64 %t65, 94
-   br i1 %t66, label %exit, label %loop
+   %iv = phi i64 [ %iv.next, %loop ], [ 0, %entry ]
+   %icmp = icmp ule i64 %iv, 32
+   %sel = select i1 %icmp, ptr %x, ptr %gep.y
+   %gep.sel = getelementptr inbounds double, ptr %sel, i64 %iv
+   %load = load double, ptr %gep.sel, align 8
+   %sel2 = select i1 %icmp, ptr %y, ptr %z
+   %gep.sel2 = getelementptr inbounds double, ptr %sel2, i64 %iv
+   store double %load, ptr %gep.sel2, align 8
+   %iv.next = add nuw nsw i64 %iv, 1
+   %exit.cond = icmp eq i64 %iv, 94
+   br i1 %exit.cond, label %exit, label %loop
 
 exit:
-   ret i32 0
+   ret void
 }

>From 7042c2df71df110fe6cfd2de3b60df217edf509a Mon Sep 17 00:00:00 2001
From: Ramkumar Ramachandra <r at artagnon.com>
Date: Fri, 24 May 2024 16:07:59 +0100
Subject: [PATCH 2/2] Use suggestion from review

Co-authored-by: Nikita Popov <github at npopov.com>
---
 llvm/test/Analysis/LoopAccessAnalysis/select-dependence.ll | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/llvm/test/Analysis/LoopAccessAnalysis/select-dependence.ll b/llvm/test/Analysis/LoopAccessAnalysis/select-dependence.ll
index ed3e96a6ce2e3..60fe8b4fcbed4 100644
--- a/llvm/test/Analysis/LoopAccessAnalysis/select-dependence.ll
+++ b/llvm/test/Analysis/LoopAccessAnalysis/select-dependence.ll
@@ -1,7 +1,7 @@
 ; NOTE: Assertions have been autogenerated by utils/update_analyze_test_checks.py UTC_ARGS: --version 5
 ; RUN: opt -passes='print<access-info>' -disable-output 2>&1 < %s | FileCheck %s
 
-define void @test(ptr %x, ptr %y, ptr %z) {
+define void @test(ptr noalias %x, ptr noalias %y, ptr noalias %z) {
 ; CHECK-LABEL: 'test'
 ; CHECK-NEXT:    loop:
 ; CHECK-NEXT:      Report: unsafe dependent memory operations in loop. Use #pragma clang loop distribute(enable) to allow loop distribution to attempt to isolate the offending operations into a separate loop