[llvm] [ValueTracking] Pre-Commit Tests (PR #127218)

[via llvm-commits]

https://github.com/vortex73 created https://github.com/llvm/llvm-project/pull/127218

Closes #87624

>From dcb49a088ad6b34071a181923acdb142e281e7a4 Mon Sep 17 00:00:00 2001
From: Narayan Sreekumar <nsreekumar6 at gmail.com>
Date: Fri, 14 Feb 2025 21:17:15 +0530
Subject: [PATCH] [ValueTracking] Pre-Commit Tests

---
 .../InstCombine/compute-sign-bits-bitcast.ll  | 35 +++++++++++++++++++
 1 file changed, 35 insertions(+)
 create mode 100644 llvm/test/Transforms/InstCombine/compute-sign-bits-bitcast.ll

diff --git a/llvm/test/Transforms/InstCombine/compute-sign-bits-bitcast.ll b/llvm/test/Transforms/InstCombine/compute-sign-bits-bitcast.ll
new file mode 100644
index 0000000000000..887720000477a
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/compute-sign-bits-bitcast.ll
@@ -0,0 +1,35 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -passes=instcombine -S < %s | FileCheck %s
+
+define i32 @test_compute_sign_bits() {
+; CHECK-LABEL: define i32 @test_compute_sign_bits() {
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    ret i32 -1
+;
+entry:
+  %a = add i8 -1, 0
+  %b = bitcast i8 %a to <4 x i2>
+  %c = ashr <4 x i2> %b, <i2 1, i2 1, i2 1, i2 1>
+  %d = bitcast <4 x i2> %c to i8
+  %e = sext i8 %d to i32
+  ret i32 %e
+}
+
+; Test with sign extension to ensure proper sign bit tracking
+define <4 x i2> @test_sext_bitcast(<1 x i8> %a0, <1 x i8> %a1) {
+; CHECK-LABEL: define <4 x i2> @test_sext_bitcast(
+; CHECK-SAME: <1 x i8> [[A0:%.*]], <1 x i8> [[A1:%.*]]) {
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    [[CMP:%.*]] = icmp sgt <1 x i8> [[A0]], [[A1]]
+; CHECK-NEXT:    [[EXT:%.*]] = sext <1 x i1> [[CMP]] to <1 x i8>
+; CHECK-NEXT:    [[SUB:%.*]] = bitcast <1 x i8> [[EXT]] to <4 x i2>
+; CHECK-NEXT:    [[RESULT:%.*]] = ashr <4 x i2> [[SUB]], splat (i2 1)
+; CHECK-NEXT:    ret <4 x i2> [[RESULT]]
+;
+entry:
+  %cmp = icmp sgt <1 x i8> %a0, %a1
+  %ext = sext <1 x i1> %cmp to <1 x i8>
+  %sub = bitcast <1 x i8> %ext to <4 x i2>
+  %result = ashr <4 x i2> %sub, <i2 1, i2 1, i2 1, i2 1>
+  ret <4 x i2> %result
+}