Auto merge of #76071 - khyperia:configurable_to_immediate, r=eddyb

Make to_immediate/from_immediate configurable by backends

`librustc_codegen_ssa` has the concept of an immediate vs. memory type, and `librustc_codegen_llvm` uses this distinction to implement `bool`s being `i8` in memory, and `i1` in immediate contexts. However, some of that implementation leaked into `codegen_ssa` when converting to/from immediate values. So, move those methods into builder traits, so that behavior can be configured by backends.

This is useful if a backend is able to keep bools as bools, or, needs to do more trickery than just bools to bytes.

(Note that there's already a large amount of things abstracted with "immediate types" - this is just bringing this particular thing in line to be abstracted as well)

---

Pinging @eddyb since that's who I was talking about this change with when they suggested I submit a PR.

2 files changed, 18 insertions, 5 deletions

diff --git a/compiler/rustc_codegen_llvm/src/builder.rs b/compiler/rustc_codegen_llvm/src/builder.rs
index 4ece08f6293..89c3e21632e 100644
--- a/compiler/rustc_codegen_llvm/src/builder.rs
+++ b/compiler/rustc_codegen_llvm/src/builder.rs
@@ -6,7 +6,6 @@ use crate::type_::Type;
 use crate::type_of::LayoutLlvmExt;
 use crate::value::Value;
 use libc::{c_char, c_uint};
-use rustc_codegen_ssa::base::to_immediate;
 use rustc_codegen_ssa::common::{IntPredicate, RealPredicate, TypeKind};
 use rustc_codegen_ssa::mir::operand::{OperandRef, OperandValue};
 use rustc_codegen_ssa::mir::place::PlaceRef;
@@ -367,6 +366,20 @@ impl BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
         (self.extract_value(res, 0), self.extract_value(res, 1))
     }
 
+    fn from_immediate(&mut self, val: Self::Value) -> Self::Value {
+        if self.cx().val_ty(val) == self.cx().type_i1() {
+            self.zext(val, self.cx().type_i8())
+        } else {
+            val
+        }
+    }
+    fn to_immediate_scalar(&mut self, val: Self::Value, scalar: &abi::Scalar) -> Self::Value {
+        if scalar.is_bool() {
+            return self.trunc(val, self.cx().type_i1());
+        }
+        val
+    }
+
     fn alloca(&mut self, ty: &'ll Type, align: Align) -> &'ll Value {
         let mut bx = Builder::with_cx(self.cx);
         bx.position_at_start(unsafe { llvm::LLVMGetFirstBasicBlock(self.llfn()) });
@@ -471,7 +484,7 @@ impl BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
                 }
                 load
             });
-            OperandValue::Immediate(to_immediate(self, llval, place.layout))
+            OperandValue::Immediate(self.to_immediate(llval, place.layout))
         } else if let abi::Abi::ScalarPair(ref a, ref b) = place.layout.abi {
             let b_offset = a.value.size(self).align_to(b.value.align(self).abi);
 
@@ -479,7 +492,7 @@ impl BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
                 let llptr = self.struct_gep(place.llval, i as u64);
                 let load = self.load(llptr, align);
                 scalar_load_metadata(self, load, scalar);
-                if scalar.is_bool() { self.trunc(load, self.type_i1()) } else { load }
+                self.to_immediate_scalar(load, scalar)
             };
 
             OperandValue::Pair(
diff --git a/compiler/rustc_codegen_llvm/src/intrinsic.rs b/compiler/rustc_codegen_llvm/src/intrinsic.rs
index c1dfb83b135..951b9928cc9 100644
--- a/compiler/rustc_codegen_llvm/src/intrinsic.rs
+++ b/compiler/rustc_codegen_llvm/src/intrinsic.rs
@@ -8,7 +8,7 @@ use crate::va_arg::emit_va_arg;
 use crate::value::Value;
 
 use rustc_ast as ast;
-use rustc_codegen_ssa::base::{compare_simd_types, to_immediate, wants_msvc_seh};
+use rustc_codegen_ssa::base::{compare_simd_types, wants_msvc_seh};
 use rustc_codegen_ssa::common::span_invalid_monomorphization_error;
 use rustc_codegen_ssa::common::{IntPredicate, TypeKind};
 use rustc_codegen_ssa::glue;
@@ -301,7 +301,7 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
                 unsafe {
                     llvm::LLVMSetAlignment(load, align);
                 }
-                to_immediate(self, load, self.layout_of(tp_ty))
+                self.to_immediate(load, self.layout_of(tp_ty))
             }
             sym::volatile_store => {
                 let dst = args[0].deref(self.cx());