[clang] [llvm] [Instcombine] use zext's nneg flag for icmp folding (PR #70845)

[Léonard Oest O'Leary via cfe-commits]

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@@ -0,0 +1,112 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 3
+; RUN: opt < %s -O3 -S | FileCheck %s
+; See issue #55013 and PR #70845 for more details.
+; This test comes from the following C program, compiled with clang
+;
+;; short vecreduce_smin_v2i16(int n, short* v)
+;; {
+;;   short p = 0;
+;;   for (int i = 0; i < n; ++i)
+;;     p = p > v[i] ? v[i] : p;
+;;   return p;
+;; }
+;
+;; short vecreduce_smax_v2i16(int n, short* v)
+;; {
+;;   short p = 0;
+;;   for (int i = 0; i < n; ++i)
+;;     p = p < v[i] ? v[i] : p;
+;;   return p;
+;; }
+
+define i16 @vecreduce_smin_v2i16(i32 %n, ptr %v) {
+; CHECK-LABEL: define i16 @vecreduce_smin_v2i16(
+; CHECK:    @llvm.smin.v2i16
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leo-ard wrote:

I didn't keep all the checks generated by `llvm/utils/update_test_checks.py` as in this tests, we only want to know if the intrinsics @llvm.smin.v2i16 has been generated or not. Let me know if you think I should leave all the checks 

https://github.com/llvm/llvm-project/pull/70845