Don't `alloca` just to look at a discriminant

Today we're making LLVM do a bunch of extra work for every enum you match on, even trivial stuff like `Option<bool>`.  Let's not.

4 files changed, 30 insertions, 28 deletions

diff --git a/tests/codegen/enum/enum-two-variants-match.rs b/tests/codegen/enum/enum-two-variants-match.rs
index e5978bfc761..c1f208d7909 100644
--- a/tests/codegen/enum/enum-two-variants-match.rs
+++ b/tests/codegen/enum/enum-two-variants-match.rs
@@ -7,19 +7,22 @@
 // CHECK-LABEL: @option_match
 #[no_mangle]
 pub fn option_match(x: Option<i32>) -> u16 {
-    // CHECK: %x = alloca [8 x i8]
-    // CHECK: store i32 %0, ptr %x
-    // CHECK: %[[TAG:.+]] = load i32, ptr %x
-    // CHECK-SAME: !range ![[ZERO_ONE_32:[0-9]+]]
-    // CHECK: %[[DISCR:.+]] = zext i32 %[[TAG]] to i64
+    // CHECK-NOT: %x = alloca
+    // CHECK: %[[OUT:.+]] = alloca [2 x i8]
+    // CHECK-NOT: %x = alloca
+
+    // CHECK: %[[DISCR:.+]] = zext i32 %x.0 to i64
     // CHECK: %[[COND:.+]] = trunc nuw i64 %[[DISCR]] to i1
     // CHECK: br i1 %[[COND]], label %[[TRUE:[a-z0-9]+]], label %[[FALSE:[a-z0-9]+]]
 
     // CHECK: [[TRUE]]:
-    // CHECK: store i16 13
+    // CHECK: store i16 13, ptr %[[OUT]]
 
     // CHECK: [[FALSE]]:
-    // CHECK: store i16 42
+    // CHECK: store i16 42, ptr %[[OUT]]
+
+    // CHECK: %[[RET:.+]] = load i16, ptr %[[OUT]]
+    // CHECK: ret i16 %[[RET]]
     match x {
         Some(_) => 13,
         None => 42,
@@ -29,23 +32,23 @@ pub fn option_match(x: Option<i32>) -> u16 {
 // CHECK-LABEL: @result_match
 #[no_mangle]
 pub fn result_match(x: Result<u64, i64>) -> u16 {
-    // CHECK: %x = alloca [16 x i8]
-    // CHECK: store i64 %0, ptr %x
-    // CHECK: %[[DISCR:.+]] = load i64, ptr %x
-    // CHECK-SAME: !range ![[ZERO_ONE_64:[0-9]+]]
-    // CHECK: %[[COND:.+]] = trunc nuw i64 %[[DISCR]] to i1
+    // CHECK-NOT: %x = alloca
+    // CHECK: %[[OUT:.+]] = alloca [2 x i8]
+    // CHECK-NOT: %x = alloca
+
+    // CHECK: %[[COND:.+]] = trunc nuw i64 %x.0 to i1
     // CHECK: br i1 %[[COND]], label %[[TRUE:[a-z0-9]+]], label %[[FALSE:[a-z0-9]+]]
 
     // CHECK: [[TRUE]]:
-    // CHECK: store i16 13
+    // CHECK: store i16 13, ptr %[[OUT]]
 
     // CHECK: [[FALSE]]:
-    // CHECK: store i16 42
+    // CHECK: store i16 42, ptr %[[OUT]]
+
+    // CHECK: %[[RET:.+]] = load i16, ptr %[[OUT]]
+    // CHECK: ret i16 %[[RET]]
     match x {
         Err(_) => 13,
         Ok(_) => 42,
     }
 }
-
-// CHECK: ![[ZERO_ONE_32]] = !{i32 0, i32 2}
-// CHECK: ![[ZERO_ONE_64]] = !{i64 0, i64 2}
diff --git a/tests/codegen/intrinsics/cold_path2.rs b/tests/codegen/intrinsics/cold_path2.rs
index 54ee473e620..0891c878fd9 100644
--- a/tests/codegen/intrinsics/cold_path2.rs
+++ b/tests/codegen/intrinsics/cold_path2.rs
@@ -25,8 +25,8 @@ pub fn test(x: Option<bool>) {
         path_b();
     }
 
-    // CHECK-LABEL: @test(
-    // CHECK: %[[IS_NONE:.+]] = icmp eq i8 %0, 2
+    // CHECK-LABEL: void @test(i8{{.+}}%x)
+    // CHECK: %[[IS_NONE:.+]] = icmp eq i8 %x, 2
     // CHECK: br i1 %[[IS_NONE]], label %bb2, label %bb1, !prof ![[NUM:[0-9]+]]
     // CHECK: bb1:
     // CHECK: path_a
diff --git a/tests/codegen/match-optimizes-away.rs b/tests/codegen/match-optimizes-away.rs
index 8a70d993423..5e9be72a09f 100644
--- a/tests/codegen/match-optimizes-away.rs
+++ b/tests/codegen/match-optimizes-away.rs
@@ -1,5 +1,4 @@
-//
-//@ compile-flags: -Copt-level=3
+//@ compile-flags: -Copt-level=3 -Zmerge-functions=disabled
 #![crate_type = "lib"]
 
 pub enum Three {
@@ -18,9 +17,9 @@ pub enum Four {
 
 #[no_mangle]
 pub fn three_valued(x: Three) -> Three {
-    // CHECK-LABEL: @three_valued
+    // CHECK-LABEL: i8 @three_valued(i8{{.+}}%x)
     // CHECK-NEXT: {{^.*:$}}
-    // CHECK-NEXT: ret i8 %0
+    // CHECK-NEXT: ret i8 %x
     match x {
         Three::A => Three::A,
         Three::B => Three::B,
@@ -30,9 +29,9 @@ pub fn three_valued(x: Three) -> Three {
 
 #[no_mangle]
 pub fn four_valued(x: Four) -> Four {
-    // CHECK-LABEL: @four_valued
+    // CHECK-LABEL: i16 @four_valued(i16{{.+}}%x)
     // CHECK-NEXT: {{^.*:$}}
-    // CHECK-NEXT: ret i16 %0
+    // CHECK-NEXT: ret i16 %x
     match x {
         Four::A => Four::A,
         Four::B => Four::B,
diff --git a/tests/codegen/try_question_mark_nop.rs b/tests/codegen/try_question_mark_nop.rs
index ca15e510173..23a084c51f4 100644
--- a/tests/codegen/try_question_mark_nop.rs
+++ b/tests/codegen/try_question_mark_nop.rs
@@ -17,10 +17,10 @@ use std::ptr::NonNull;
 pub fn option_nop_match_32(x: Option<u32>) -> Option<u32> {
     // CHECK: start:
     // TWENTY-NEXT: %[[IS_SOME:.+]] = trunc nuw i32 %0 to i1
-    // TWENTY-NEXT: %.2 = select i1 %[[IS_SOME]], i32 %1, i32 undef
+    // TWENTY-NEXT: %[[PAYLOAD:.+]] = select i1 %[[IS_SOME]], i32 %1, i32 undef
     // CHECK-NEXT: [[REG1:%.*]] = insertvalue { i32, i32 } poison, i32 %0, 0
     // NINETEEN-NEXT: [[REG2:%.*]] = insertvalue { i32, i32 } [[REG1]], i32 %1, 1
-    // TWENTY-NEXT: [[REG2:%.*]] = insertvalue { i32, i32 } [[REG1]], i32 %.2, 1
+    // TWENTY-NEXT: [[REG2:%.*]] = insertvalue { i32, i32 } [[REG1]], i32 %[[PAYLOAD]], 1
     // CHECK-NEXT: ret { i32, i32 } [[REG2]]
     match x {
         Some(x) => Some(x),
@@ -33,7 +33,7 @@ pub fn option_nop_match_32(x: Option<u32>) -> Option<u32> {
 pub fn option_nop_traits_32(x: Option<u32>) -> Option<u32> {
     // CHECK: start:
     // TWENTY-NEXT: %[[IS_SOME:.+]] = trunc nuw i32 %0 to i1
-    // TWENTY-NEXT: %.1 = select i1 %[[IS_SOME]], i32 %1, i32 undef
+    // TWENTY-NEXT: select i1 %[[IS_SOME]], i32 %1, i32 undef
     // CHECK-NEXT: insertvalue { i32, i32 }
     // CHECK-NEXT: insertvalue { i32, i32 }
     // CHECK-NEXT: ret { i32, i32 }