[llvm] [LoopInterchange] Add test for floating point math flags (PR #149090)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-transforms

Author: Madhur Amilkanthwar (madhur13490)

<details>
<summary>Changes</summary>

Adding a test where both `ninf` and `reassoc` flags are present on the instruction. We don't know yet if it is legal to interchange. Prima facie, it does not look like it should be legal but more analysis is needed.

---
Full diff: https://github.com/llvm/llvm-project/pull/149090.diff


1 Files Affected:

- (modified) llvm/test/Transforms/LoopInterchange/reductions-non-wrapped-operations.ll (+38) 


``````````diff
diff --git a/llvm/test/Transforms/LoopInterchange/reductions-non-wrapped-operations.ll b/llvm/test/Transforms/LoopInterchange/reductions-non-wrapped-operations.ll
index 3ed69485bc8f2..0eb6fe98b8bb7 100644
--- a/llvm/test/Transforms/LoopInterchange/reductions-non-wrapped-operations.ll
+++ b/llvm/test/Transforms/LoopInterchange/reductions-non-wrapped-operations.ll
@@ -411,6 +411,44 @@ exit:
   ret void
 }
 
+; FIXME: Is it really legal to interchange the loops when
+; both reassoc and ninf are set?
+; Check that the interchange is legal if the floating-point addition is marked
+; as reassoc.
+;
+; CHECK:      --- !Pass
+; CHECK-NEXT: Pass:            loop-interchange
+; CHECK-NEXT: Name:            Interchanged
+; CHECK-NEXT: Function:        reduction_reassoc_ninf_fadd
+define void @reduction_reassoc_ninf_fadd(ptr %A) {
+entry:
+  br label %for.i.header
+
+for.i.header:
+  %i = phi i32 [ 0, %entry ], [ %i.inc, %for.i.latch ]
+  %sum.i = phi float [ 0.0, %entry ], [ %sum.i.lcssa, %for.i.latch ]
+  br label %for.j
+
+for.j:
+  %j = phi i32 [ 0, %for.i.header ], [ %j.inc, %for.j ]
+  %sum.j = phi float [ %sum.i, %for.i.header ], [ %sum.j.next, %for.j ]
+  %idx = getelementptr inbounds [2 x [2 x i32]], ptr %A, i32 0, i32 %j, i32 %i
+  %a = load float, ptr %idx, align 4
+  %sum.j.next = fadd reassoc ninf float %sum.j, %a
+  %j.inc = add i32 %j, 1
+  %cmp.j = icmp slt i32 %j.inc, 2
+  br i1 %cmp.j, label %for.j, label %for.i.latch
+
+for.i.latch:
+  %sum.i.lcssa = phi float [ %sum.j.next, %for.j ]
+  %i.inc = add i32 %i, 1
+  %cmp.i = icmp slt i32 %i.inc, 2
+  br i1 %cmp.i, label %for.i.header, label %exit
+
+exit:
+  ret void
+}
+
 ; Check that the loops aren't exchanged if there is a reduction of
 ; non-reassociative floating-point multiplication.
 ;

``````````

</details>


https://github.com/llvm/llvm-project/pull/149090