Auto merge of #133984 - DaniPopes:scmp-ucmp, r=scottmcm

Lower BinOp::Cmp to llvm.{s,u}cmp.* intrinsics

Lowers `mir::BinOp::Cmp` (`three_way_compare` intrinsic) to the corresponding LLVM `llvm.{s,u}cmp.i8.*` intrinsics.

These are the intrinsics mentioned in https://github.com/rust-lang/rust/pull/118310, which are now available in LLVM 19.

I couldn't find any follow-up PRs/discussions about this, please let me know if I missed something.

r? `@scottmcm`

1 files changed, 32 insertions, 3 deletions

diff --git a/tests/codegen/integer-cmp.rs b/tests/codegen/integer-cmp.rs
index 9bbf243946d..812fa8e4a42 100644
--- a/tests/codegen/integer-cmp.rs
+++ b/tests/codegen/integer-cmp.rs
@@ -4,7 +4,7 @@
 //@ revisions: llvm-pre-20 llvm-20
 //@ [llvm-20] min-llvm-version: 20
 //@ [llvm-pre-20] max-llvm-major-version: 19
-//@ compile-flags: -C opt-level=3
+//@ compile-flags: -C opt-level=3 -Zmerge-functions=disabled
 
 #![crate_type = "lib"]
 
@@ -13,7 +13,7 @@ use std::cmp::Ordering;
 // CHECK-LABEL: @cmp_signed
 #[no_mangle]
 pub fn cmp_signed(a: i64, b: i64) -> Ordering {
-    // llvm-20: @llvm.scmp.i8.i64
+    // llvm-20: call{{.*}} i8 @llvm.scmp.i8.i64
     // llvm-pre-20: icmp slt
     // llvm-pre-20: icmp ne
     // llvm-pre-20: zext i1
@@ -24,10 +24,39 @@ pub fn cmp_signed(a: i64, b: i64) -> Ordering {
 // CHECK-LABEL: @cmp_unsigned
 #[no_mangle]
 pub fn cmp_unsigned(a: u32, b: u32) -> Ordering {
-    // llvm-20: @llvm.ucmp.i8.i32
+    // llvm-20: call{{.*}} i8 @llvm.ucmp.i8.i32
     // llvm-pre-20: icmp ult
     // llvm-pre-20: icmp ne
     // llvm-pre-20: zext i1
     // llvm-pre-20: select i1
     a.cmp(&b)
 }
+
+// CHECK-LABEL: @cmp_char
+#[no_mangle]
+pub fn cmp_char(a: char, b: char) -> Ordering {
+    // llvm-20: call{{.*}} i8 @llvm.ucmp.i8.i32
+    // llvm-pre-20: icmp ult
+    // llvm-pre-20: icmp ne
+    // llvm-pre-20: zext i1
+    // llvm-pre-20: select i1
+    a.cmp(&b)
+}
+
+// CHECK-LABEL: @cmp_tuple
+#[no_mangle]
+pub fn cmp_tuple(a: (i16, u16), b: (i16, u16)) -> Ordering {
+    // llvm-20-DAG: call{{.*}} i8 @llvm.ucmp.i8.i16
+    // llvm-20-DAG: call{{.*}} i8 @llvm.scmp.i8.i16
+    // llvm-20: ret i8
+    // llvm-pre-20: icmp slt
+    // llvm-pre-20: icmp ne
+    // llvm-pre-20: zext i1
+    // llvm-pre-20: select i1
+    // llvm-pre-20: icmp ult
+    // llvm-pre-20: icmp ne
+    // llvm-pre-20: zext i1
+    // llvm-pre-20: select i1
+    // llvm-pre-20: select i1
+    a.cmp(&b)
+}