Traverse IR blocks using a reverse post order traverse of the CFG (Fu…

…elLabs#3942)

Closes FuelLabs#3815 

This change updates how IR blocks are traversed when compiling them into
assembly. Specifically, a reverse post-order traversal is used.
Following this order forces all IR values to be converted to registers
before all their uses. Even though the initial IR (out of IR gen) may
have the right order of blocks, CFG-altering passes like simplify-cfg
can change that order, so a correct traversal of the final CFG is
needed.

sway-core/src/asm_generation/fuel/functions.rs

@@ -205,8 +205,12 @@ impl<'ir> FuelAsmBuilder<'ir> {
         // Compile instructions.
         let mut warnings = Vec::new();
         let mut errors = Vec::new();
-        for block in function.block_iter(self.context) {
-            self.insert_block_label(block);
+
+        // Traverse the IR blocks in reverse post order. This guarantees that each block is
+        // processed after all its CFG predecessors have been processed.
+        let po = sway_ir::dominator::compute_post_order(self.context, &function);
+        for block in po.po_to_block.iter().rev() {
+            self.insert_block_label(*block);
             for instr_val in block.instruction_iter(self.context) {
                 check!(
                     self.compile_instruction(&instr_val, func_is_entry),

test/src/e2e_vm_tests/test_programs/should_pass/language/complex_cfg/Forc.lock

@@ -0,0 +1,13 @@
+[[package]]
+name = 'complex_cfg'
+source = 'member'
+dependencies = ['std']
+
+[[package]]
+name = 'core'
+source = 'path+from-root-8B200AD7FF2D8C10'
+
+[[package]]
+name = 'std'
+source = 'path+from-root-8B200AD7FF2D8C10'
+dependencies = ['core']

test/src/e2e_vm_tests/test_programs/should_pass/language/complex_cfg/Forc.toml

@@ -0,0 +1,8 @@
+[project]
+authors = ["Fuel Labs <[email protected]>"]
+entry = "main.sw"
+license = "Apache-2.0"
+name = "complex_cfg"
+
+[dependencies]
+std = { path = "../../../../../../../sway-lib-std" }

test/src/e2e_vm_tests/test_programs/should_pass/language/complex_cfg/src/main.sw

@@ -0,0 +1,16 @@
+script;
+
+use std::u128::U128;
+
+pub enum Error {
+    Overflow: (),
+}
+
+fn main() {
+    let x = U128 {
+        upper: 0,
+        lower: 0,
+    };
+    let cond = false;
+    require(cond || (x < U128::from((1, 1)) || x == U128::from((1, 1))), Error::Overflow);
+}

test/src/e2e_vm_tests/test_programs/should_pass/language/complex_cfg/test.toml

@@ -0,0 +1,3 @@
+category = "run"
+expected_result = { action = "return", value = 0 }
+validate_abi = false

test/src/e2e_vm_tests/test_programs/should_pass/language/configurable_consts/json_abi_oracle.json

@@ -7,7 +7,7 @@
         "typeArguments": null
       },
       "name": "C0",
-      "offset": 3268
+      "offset": 3244
     },
     {
       "configurableType": {
@@ -16,7 +16,7 @@
         "typeArguments": null
       },
       "name": "C1",
-      "offset": 3276
+      "offset": 3252
     },
     {
       "configurableType": {
@@ -25,7 +25,7 @@
         "typeArguments": null
       },
       "name": "C2",
-      "offset": 3292
+      "offset": 3268
     },
     {
       "configurableType": {
@@ -34,7 +34,7 @@
         "typeArguments": []
       },
       "name": "C3",
-      "offset": 3356
+      "offset": 3332
     },
     {
       "configurableType": {
@@ -43,7 +43,7 @@
         "typeArguments": []
       },
       "name": "C4",
-      "offset": 3372
+      "offset": 3348
     },
     {
       "configurableType": {
@@ -52,7 +52,7 @@
         "typeArguments": []
       },
       "name": "C5",
-      "offset": 3388
+      "offset": 3364
     },
     {
       "configurableType": {
@@ -61,7 +61,7 @@
         "typeArguments": null
       },
       "name": "C6",
-      "offset": 3436
+      "offset": 3412
     },
     {
       "configurableType": {
@@ -70,7 +70,7 @@
         "typeArguments": null
       },
       "name": "C7",
-      "offset": 3460
+      "offset": 3436
     }
   ],
   "functions": [

test/src/e2e_vm_tests/test_programs/should_pass/require_contract_deployment/call_basic_storage/src/main.sw

@@ -2,7 +2,7 @@ script;
 use basic_storage_abi::{BasicStorage, Quad};
 
 fn main() -> u64 {
-    let addr = abi(BasicStorage, 0x1664598d277f39504d86fd45604e20eb3547bd4cea6b22f17854fbd6f690f53e);
+    let addr = abi(BasicStorage, 0xd0897bfc4fd711f847986c1a22444c23da58a9458133c5e99519afab57ccd242);
     let key = 0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff;
     let value = 4242;