[LICM] Introduce test for PR92655 (NFC)

Author: antoniofrighetto

llvm/test/Transforms/LICM/update-scev-after-hoist.ll

@@ -0,0 +1,24 @@
+; RUN: opt -S -passes='loop-unroll,loop-mssa(licm),print<scalar-evolution>' -unroll-count=4 -disable-output < %s 2>&1 | FileCheck %s --check-prefix=SCEV-EXPR
+
+define i16 @main() {
+; SCEV-EXPR:      Classifying expressions for: @main
+; SCEV-EXPR-NEXT:  %mul = phi i16 [ 1, %entry ], [ %mul.n.3, %loop ]
+; SCEV-EXPR-NEXT:  -->  %mul U: full-set S: [-32768,32753)		Exits: 4096		LoopDispositions: { %loop: Variant }
+; SCEV-EXPR-NEXT:  %div = phi i16 [ 32767, %entry ], [ %div.n.3, %loop ]
+; SCEV-EXPR-NEXT:  -->  %div U: [-2048,-32768) S: [-2048,-32768)		Exits: 7		LoopDispositions: { %loop: Variant }
+; SCEV-EXPR-NEXT:  %mul.n = mul i16 %mul, 8
+; SCEV-EXPR-NEXT:  -->  (2 * %mul) U: [0,-1) S: [-32768,32767)		Exits: 8192		LoopDispositions: { %loop: Variant }
+entry:
+  br label %loop
+
+loop:
+  %mul = phi i16 [ 1, %entry ], [ %mul.n, %loop ]
+  %div = phi i16 [ 32767, %entry ], [ %div.n, %loop ]
+  %mul.n = mul i16 %mul, 2
+  %div.n = sdiv i16 %div, 2
+  %cmp = icmp sgt i16 %div, 0
+  br i1 %cmp, label %loop, label %end
+
+end:
+  ret i16 %mul
+}