From 3113fef3a357ab8b39672be85951763a26261fd4 Mon Sep 17 00:00:00 2001
From: Ralf Jung <post@ralfj.de>
Date: Mon, 11 Sep 2023 09:52:45 +0200
Subject: [PATCH] move required_consts check to general post-mono-check
 function

---
 src/base.rs       | 22 ++++++++++++++++------
 src/constant.rs   | 36 +++++++-----------------------------
 src/inline_asm.rs |  3 +--
 3 files changed, 24 insertions(+), 37 deletions(-)

diff --git a/src/base.rs b/src/base.rs
index 54f82dcc8ae..e41c6b31e9c 100644
--- a/src/base.rs
+++ b/src/base.rs
@@ -2,6 +2,7 @@
 
 use rustc_ast::InlineAsmOptions;
 use rustc_index::IndexVec;
+use rustc_middle::mir::interpret::ErrorHandled;
 use rustc_middle::ty::adjustment::PointerCoercion;
 use rustc_middle::ty::layout::FnAbiOf;
 use rustc_middle::ty::print::with_no_trimmed_paths;
@@ -250,12 +251,21 @@ pub(crate) fn verify_func(
 }
 
 fn codegen_fn_body(fx: &mut FunctionCx<'_, '_, '_>, start_block: Block) {
-    if !crate::constant::check_constants(fx) {
-        fx.bcx.append_block_params_for_function_params(fx.block_map[START_BLOCK]);
-        fx.bcx.switch_to_block(fx.block_map[START_BLOCK]);
-        // compilation should have been aborted
-        fx.bcx.ins().trap(TrapCode::UnreachableCodeReached);
-        return;
+    match fx.mir.post_mono_checks(fx.tcx, ty::ParamEnv::reveal_all(), |c| Ok(fx.monomorphize(c))) {
+        Ok(()) => {}
+        Err(ErrorHandled::TooGeneric(span)) => {
+            span_bug!(span, "codegen encountered polymorphic constant");
+        }
+        Err(ErrorHandled::Reported(info, span)) => {
+            if !info.is_tainted_by_errors() {
+                fx.tcx.sess.span_err(span, "erroneous constant encountered");
+            }
+            fx.bcx.append_block_params_for_function_params(fx.block_map[START_BLOCK]);
+            fx.bcx.switch_to_block(fx.block_map[START_BLOCK]);
+            // compilation should have been aborted
+            fx.bcx.ins().trap(TrapCode::UnreachableCodeReached);
+            return;
+        }
     }
 
     let arg_uninhabited = fx
diff --git a/src/constant.rs b/src/constant.rs
index 8c67760a0b9..0d9bd3cf240 100644
--- a/src/constant.rs
+++ b/src/constant.rs
@@ -2,9 +2,7 @@
 
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
-use rustc_middle::mir::interpret::{
-    read_target_uint, AllocId, ConstValue, ErrorHandled, GlobalAlloc, Scalar,
-};
+use rustc_middle::mir::interpret::{read_target_uint, AllocId, ConstValue, GlobalAlloc, Scalar};
 
 use cranelift_module::*;
 
@@ -33,16 +31,6 @@ pub(crate) fn finalize(mut self, tcx: TyCtxt<'_>, module: &mut dyn Module) {
     }
 }
 
-pub(crate) fn check_constants(fx: &mut FunctionCx<'_, '_, '_>) -> bool {
-    let mut all_constants_ok = true;
-    for constant in &fx.mir.required_consts {
-        if eval_mir_constant(fx, constant).is_none() {
-            all_constants_ok = false;
-        }
-    }
-    all_constants_ok
-}
-
 pub(crate) fn codegen_static(tcx: TyCtxt<'_>, module: &mut dyn Module, def_id: DefId) {
     let mut constants_cx = ConstantCx::new();
     constants_cx.todo.push(TodoItem::Static(def_id));
@@ -76,30 +64,20 @@ pub(crate) fn codegen_tls_ref<'tcx>(
 pub(crate) fn eval_mir_constant<'tcx>(
     fx: &FunctionCx<'_, '_, 'tcx>,
     constant: &Constant<'tcx>,
-) -> Option<(ConstValue<'tcx>, Ty<'tcx>)> {
+) -> (ConstValue<'tcx>, Ty<'tcx>) {
     let cv = fx.monomorphize(constant.literal);
+    // This cannot fail because we checked all required_consts in advance.
     let val = cv
         .eval(fx.tcx, ty::ParamEnv::reveal_all(), Some(constant.span))
-        .map_err(|err| match err {
-            ErrorHandled::Reported(_) => {
-                fx.tcx.sess.span_err(constant.span, "erroneous constant encountered");
-            }
-            ErrorHandled::TooGeneric => {
-                span_bug!(constant.span, "codegen encountered polymorphic constant: {:?}", err);
-            }
-        })
-        .ok();
-    val.map(|val| (val, cv.ty()))
+        .expect("erroneous constant not captured by required_consts");
+    (val, cv.ty())
 }
 
 pub(crate) fn codegen_constant_operand<'tcx>(
     fx: &mut FunctionCx<'_, '_, 'tcx>,
     constant: &Constant<'tcx>,
 ) -> CValue<'tcx> {
-    let (const_val, ty) = eval_mir_constant(fx, constant).unwrap_or_else(|| {
-        span_bug!(constant.span, "erroneous constant not captured by required_consts")
-    });
-
+    let (const_val, ty) = eval_mir_constant(fx, constant);
     codegen_const_value(fx, const_val, ty)
 }
 
@@ -459,7 +437,7 @@ pub(crate) fn mir_operand_get_const_val<'tcx>(
     operand: &Operand<'tcx>,
 ) -> Option<ConstValue<'tcx>> {
     match operand {
-        Operand::Constant(const_) => Some(eval_mir_constant(fx, const_).unwrap().0),
+        Operand::Constant(const_) => Some(eval_mir_constant(fx, const_).0),
         // FIXME(rust-lang/rust#85105): Casts like `IMM8 as u32` result in the const being stored
         // inside a temporary before being passed to the intrinsic requiring the const argument.
         // This code tries to find a single constant defining definition of the referenced local.
diff --git a/src/inline_asm.rs b/src/inline_asm.rs
index 518e3da07a4..eba90949b5e 100644
--- a/src/inline_asm.rs
+++ b/src/inline_asm.rs
@@ -242,8 +242,7 @@ pub(crate) fn codegen_inline_asm<'tcx>(
                 }
             }
             InlineAsmOperand::Const { ref value } => {
-                let (const_value, ty) = crate::constant::eval_mir_constant(fx, value)
-                    .unwrap_or_else(|| span_bug!(span, "asm const cannot be resolved"));
+                let (const_value, ty) = crate::constant::eval_mir_constant(fx, value);
                 let value = rustc_codegen_ssa::common::asm_const_to_str(
                     fx.tcx,
                     span,