[llvm] [SCEV] Urem identification from X - C*X/uC (PR #210778)

[Florian Hahn via llvm-commits]

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@@ -0,0 +1,26 @@
+; RUN: opt -passes='print<scalar-evolution>' -disable-output %s 2>&1 | FileCheck %s
+
+; X - C*(X u/ C) folds to (X u% C) for power-of-two C, surfacing range [0, C-1].
+
+; CHECK-LABEL: 'pow2_matches'
+; CHECK:        %r = sub i32 %x, %m
+; CHECK-NEXT:   -->  (zext i2 (trunc i32 %x to i2) to i32) U: [0,4)
+define i32 @pow2_matches(i32 %x) {
+  %d = udiv i32 %x, 4
+  %m = mul i32 %d, 4
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fhahn wrote:

can you also add a test with negative constant

https://github.com/llvm/llvm-project/pull/210778