Use patched LLVM

https://github.com/zkMIPS/llvm-project.git#zkm-rustc/20.1-2025-02-13

Add zkm CPU
test EnableLoopTermFold
Do not emit instruction teq if divisor is non-zero immediate value in FastISel implementation (rust-lang#135768)
Add MipsLoopReduceHiLo
MIPSr6: don't emit teq for div/mod if Divisor is not zero
Use list-burr schedule
Use K0/K1
Enable MachineCombiner

Author: qethu

.gitmodules

@@ -24,8 +24,8 @@
 	shallow = true
 [submodule "src/llvm-project"]
 	path = src/llvm-project
-	url = https://github.com/rust-lang/llvm-project.git
-	branch = rustc/20.1-2025-02-13
+	url = https://github.com/ProjectZKM/llvm-project.git
+	branch = zkm-rustc/20.1-2025-02-13
 	shallow = true
 [submodule "src/doc/embedded-book"]
 	path = src/doc/embedded-book

compiler/rustc_target/src/spec/targets/mips_zkm_zkvm_elf.rs

@@ -25,7 +25,7 @@ pub(crate) fn target() -> Target {
             max_atomic_width: Some(32),
             atomic_cas: true,
 
-            features: "+mips32r2,+soft-float,+noabicalls".into(),
+            features: "+mips32r2,+inst-same-cost,+soft-float,+noabicalls,+usek0k1".into(),
             executables: true,
             panic_strategy: PanicStrategy::Abort,
             relocation_model: RelocModel::Static,

compiler/rustc_target/src/spec/targets/mipsel_zkm_zkvm_elf.rs

@@ -25,7 +25,7 @@ pub(crate) fn target() -> Target {
             max_atomic_width: Some(32),
             atomic_cas: true,
 
-            features: "+mips32r2,+soft-float,+noabicalls".into(),
+            features: "+mips32r2,+inst-same-cost,+soft-float,+noabicalls,+usek0k1".into(),
             executables: true,
             panic_strategy: PanicStrategy::Abort,
             relocation_model: RelocModel::Static,

src/bootstrap/Cargo.lock

@@ -37,7 +37,7 @@ name = "bootstrap"
 version = "0.0.0"
 dependencies = [
  "build_helper",
- "cc",
+ "cc 1.2.23+1",
  "clap",
  "clap_complete",
  "cmake",
@@ -97,6 +97,14 @@ dependencies = [
  "shlex",
 ]
 
+[[package]]
+name = "cc"
+version = "1.2.23+1"
+source = "git+https://github.com/ProjectZKM/cc-rs.git?branch=Triple_mips-zkm-zkvm-elf#22ef49e75e2b348e666781d43f67b7648e4bd50b"
+dependencies = [
+ "shlex",
+]
+
 [[package]]
 name = "cfg-if"
 version = "1.0.0"
@@ -156,7 +164,7 @@ version = "0.1.54"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e7caa3f9de89ddbe2c607f4101924c5abec803763ae9534e4f4d7d8f84aa81f0"
 dependencies = [
- "cc",
+ "cc 1.2.23",
 ]
 
 [[package]]
@@ -410,7 +418,7 @@ version = "0.1.20"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "5fda04ab3764e6cde78b9974eec4f779acaba7c4e84b36eca3cf77c581b85d27"
 dependencies = [
- "cc",
+ "cc 1.2.23",
  "libc",
  "pkg-config",
 ]

src/bootstrap/Cargo.toml

@@ -32,7 +32,7 @@ test = false
 # Most of the time updating these dependencies requires modifications to the
 # bootstrap codebase(e.g., https://github.com/rust-lang/rust/issues/124565);
 # otherwise, some targets will fail. That's why these dependencies are explicitly pinned.
-cc = "=1.2.23"
+cc = { git = "https://github.com/ProjectZKM/cc-rs.git", branch = "Triple_mips-zkm-zkvm-elf" }
 cmake = "=0.1.54"
 
 build_helper = { path = "../build_helper" }