New ME_DSL_JIT_COMPILER envvar to select compiler backend for JIT

Author: FrancescAlted

README_DEVELOPERS.md

@@ -124,6 +124,7 @@ The public/runtime-stable DSL JIT controls remain documented in [README.md](READ
 - `ME_SIMD_MATH_BACKEND=auto|sleef|accelerate|scalar`: Force the SIMD math backend selection used by `src/functions-simd.c` for benchmarking and debugging. Default: `auto` (prefers SLEEF when available, otherwise falls back to Accelerate on macOS when enabled, then the existing scalar fallback).
 - The SIMD math benchmarks print backend-aware columns. For `accelerate` and `scalar`, do not interpret the `ME_SIMD_ULP_1` / `ME_SIMD_ULP_3_5` labels as distinct math implementations.
 - `ME_DSL_WHILE_MAX_ITERS=<n>`: Override the runtime safety cap for DSL `while` loops.
+- `ME_DSL_JIT_COMPILER=tcc|cc`: Force the DSL JIT compiler backend at compile time. When unset, the parsed DSL compiler selection is used.
 - `ME_DSL_JIT_MATH_BRIDGE=0|1`: Enable or disable runtime math-bridge lowering globally. Default: `1`.
 - `ME_DSL_JIT_SCALAR_MATH_BRIDGE=0|1`: Enable scalar math-bridge lowering for the `cc` backend. Default: `0`.
 - `ME_DSL_JIT_VEC_MATH=0|1`: Enable vector math lowering where available. Default: `1`.

src/dsl_compile_support.c

@@ -103,6 +103,23 @@ static bool dsl_source_has_fp_pragma(const char *source) {
     return false;
 }
 
+static bool dsl_env_jit_compiler_override(me_dsl_compiler *out_compiler) {
+    const char *env = getenv("ME_DSL_JIT_COMPILER");
+
+    if (!out_compiler || !env || env[0] == '\0') {
+        return false;
+    }
+    if (strcmp(env, "tcc") == 0) {
+        *out_compiler = ME_DSL_COMPILER_LIBTCC;
+        return true;
+    }
+    if (strcmp(env, "cc") == 0) {
+        *out_compiler = ME_DSL_COMPILER_CC;
+        return true;
+    }
+    return false;
+}
+
 static void dsl_compiled_block_free(me_dsl_compiled_block *block);
 
 void dsl_compiled_expr_free(me_dsl_compiled_expr *expr) {
@@ -266,6 +283,7 @@ me_dsl_compiled_program *dsl_compiled_program_alloc(const me_dsl_program *parsed
         program->fp_mode = dsl_default_fp_mode_from_env();
     }
     program->compiler = parsed->compiler;
+    (void)dsl_env_jit_compiler_override(&program->compiler);
     program->compile_ndims = compile_ndims;
     dsl_var_table_init(&program->vars);
     program->idx_ndim = -1;

tests/test_dsl_jit_ir.c

@@ -6,6 +6,7 @@
 #include <stdlib.h>
 #include <string.h>
 
+#include "../src/dsl_compile_internal.h"
 #include "../src/dsl_jit_ir.h"
 #include "../src/dsl_parser.h"
 #include "minctest.h"
@@ -437,6 +438,71 @@ static int test_parser_pragmas(void) {
     return 0;
 }
 
+static int test_env_jit_compiler_override(void) {
+    printf("\n=== JIT IR Test 6b: env compiler override ===\n");
+
+    const char *src =
+        "# me:compiler=tcc\n"
+        "def kernel(x):\n"
+        "    return x\n";
+    me_dsl_error error;
+    me_dsl_program *parsed = me_dsl_parse(src, &error);
+    me_dsl_compiled_program *compiled = NULL;
+
+    if (!parsed) {
+        printf("  FAILED: parse error for env compiler override source\n");
+        return 1;
+    }
+
+    if (setenv("ME_DSL_JIT_COMPILER", "cc", 1) != 0) {
+        printf("  FAILED: could not set ME_DSL_JIT_COMPILER=cc\n");
+        me_dsl_program_free(parsed);
+        return 1;
+    }
+    compiled = dsl_compiled_program_alloc(parsed, src, 1, NULL, 0);
+    if (!compiled) {
+        printf("  FAILED: could not allocate compiled program for cc override\n");
+        unsetenv("ME_DSL_JIT_COMPILER");
+        me_dsl_program_free(parsed);
+        return 1;
+    }
+    if (compiled->compiler != ME_DSL_COMPILER_CC) {
+        printf("  FAILED: env compiler override did not force cc backend\n");
+        dsl_compiled_program_free(compiled);
+        unsetenv("ME_DSL_JIT_COMPILER");
+        me_dsl_program_free(parsed);
+        return 1;
+    }
+    dsl_compiled_program_free(compiled);
+
+    if (setenv("ME_DSL_JIT_COMPILER", "tcc", 1) != 0) {
+        printf("  FAILED: could not set ME_DSL_JIT_COMPILER=tcc\n");
+        unsetenv("ME_DSL_JIT_COMPILER");
+        me_dsl_program_free(parsed);
+        return 1;
+    }
+    compiled = dsl_compiled_program_alloc(parsed, src, 1, NULL, 0);
+    if (!compiled) {
+        printf("  FAILED: could not allocate compiled program for tcc override\n");
+        unsetenv("ME_DSL_JIT_COMPILER");
+        me_dsl_program_free(parsed);
+        return 1;
+    }
+    if (compiled->compiler != ME_DSL_COMPILER_LIBTCC) {
+        printf("  FAILED: env compiler override did not force tcc backend\n");
+        dsl_compiled_program_free(compiled);
+        unsetenv("ME_DSL_JIT_COMPILER");
+        me_dsl_program_free(parsed);
+        return 1;
+    }
+
+    dsl_compiled_program_free(compiled);
+    unsetenv("ME_DSL_JIT_COMPILER");
+    me_dsl_program_free(parsed);
+    printf("  PASSED\n");
+    return 0;
+}
+
 static int test_ir_fingerprint_includes_fp_mode(void) {
     printf("\n=== JIT IR Test 6: fingerprint includes fp mode ===\n");
 
@@ -593,6 +659,7 @@ int main(void) {
     fail |= test_ir_rejects_unsupported_statements();
     fail |= test_ir_fingerprint_is_deterministic();
     fail |= test_parser_pragmas();
+    fail |= test_env_jit_compiler_override();
     fail |= test_ir_fingerprint_includes_fp_mode();
     fail |= test_ir_accepts_while_loops();
     fail |= test_ir_accepts_reassignment_dtype_coercion();