[llvm] [llvm][lto] Precommit test for libcalls (PR #135705)

[Paul Kirth via llvm-commits]

https://github.com/ilovepi created https://github.com/llvm/llvm-project/pull/135705

None

>From 9dddbf97980006c9cc039436bba452396944b10d Mon Sep 17 00:00:00 2001
From: Paul Kirth <paulkirth at google.com>
Date: Mon, 14 Apr 2025 11:15:51 -0700
Subject: [PATCH] [llvm][lto] Precommit test for libcalls

---
 .../test/LTO/Resolution/RISCV/bcmp-libcall.ll | 37 +++++++++++++++++++
 1 file changed, 37 insertions(+)
 create mode 100644 llvm/test/LTO/Resolution/RISCV/bcmp-libcall.ll

diff --git a/llvm/test/LTO/Resolution/RISCV/bcmp-libcall.ll b/llvm/test/LTO/Resolution/RISCV/bcmp-libcall.ll
new file mode 100644
index 0000000000000..4c6bebf69a074
--- /dev/null
+++ b/llvm/test/LTO/Resolution/RISCV/bcmp-libcall.ll
@@ -0,0 +1,37 @@
+;; This test comes from a real world scenario in LTO, where the
+;; definition of bcmp is deleted because it has no uses, but later instcombine
+;; re-introduces a call to bcmp() as part of SimplifyLibCalls.
+
+; RUN: opt %s -o %t -module-summary -mtriple riscv32-unknown-linux-musl
+; RUN: llvm-lto2 run -o %t2 \
+; RUN:   -r %t,foo,plx \
+; RUN:   -r %t,memcmp,x \
+; RUN:   -r %t,bcmp,pl %t -save-temps
+; RUN: llvm-dis %t2.1.2.internalize.bc -o - \
+; RUN:   | FileCheck %s --check-prefix=INTERNALIZE
+; RUN: opt %t2.1.2.internalize.bc -passes=instcombine -o - -S \
+; RUN:   | FileCheck %s --check-prefix=OPTIMIZE
+
+define i1 @foo(ptr %0, [2 x i32] %1) {
+  ; OPTIMIZE-LABEL: define{{.*}}i1 @foo
+  ; OPTIMIZE-NEXT: %size = extractvalue [2 x i32] %1, 1
+  ; OPTIMIZE-NEXT: %bcmp = {{.*}}call i32 @bcmp
+  ; OPTIMIZE-NEXT: %eq = icmp eq i32 %bcmp, 0
+  ; OPTIMIZE-NEXT: ret i1 %eq
+
+  %size = extractvalue [2 x i32] %1, 1
+  %cmp = call i32 @memcmp(ptr %0, ptr null, i32 %size)
+  %eq = icmp eq i32 %cmp, 0
+  ret i1 %eq
+}
+
+; INTERNALIZE: declare i32 @memcmp(ptr, ptr, i32)
+declare i32 @memcmp(ptr, ptr, i32)
+
+;; Ensure bcmp is removed from module. Follow up patches can address this.
+; INTERNALIZE-NOT: declare{{.*}}i32 @bcmp
+; INTERNALIZE-NOT: define{{.*}}i32 @bcmp
+define i32 @bcmp(ptr %0, ptr %1, i32 %2) {
+  ret i32 0
+}
+