Add wasmtime hot-blocks subcommand (#13077)

* Add `Component::{text,address_map,functions}` methods

These are similar to the methods with the same names on `Module`.

Also publicly export `ModuleFunction`, since it is returned by
`Module::functions` (and now also `Component::functions`).

Also publicly re-export `StaticModuleIndex` and `FuncIndex`, since they appear
inside `ModuleFunction`.

* Add `wasmtime hot-blocks` subcommand

This commit adds a new `wasmtime hot-blocks` subcommand that profiles Wasm
execution using `perf` and identifies the hottest basic blocks in the compiled
Wasm code.

Example output:

```
$ cargo run -- hot-blocks -F 999 -p 100 tests/all/cli_tests/fib.wat
`fib` :: block 0x16 :: 81.62% total samples

 [Samples]   [Assembly]                 [CLIF]                       [Wasm]
    14.07%   add     esi, 1             -                            -
    21.29%   lea     ecx, [rax + rdi]   v14 = iadd.i32 v13, v12      i32.add
    13.29%   mov     rdi, rax           "                            "
    17.64%   mov     rax, rcx           "                            "
    15.33%   jmp     0xe                jump block3(v18, v13, v14)   br $loop

`fib` :: block 0x0 :: 18.33% total samples

 [Samples]   [Assembly]         [CLIF]                     [Wasm]
    18.33%   cmp     esi, edx   brif v11, block2, block5   br_if $break
             jae     0x2a       "                          "

`wasm[0]::function[1]` :: block 0x37 :: 0.04% total samples

 [Samples]   [Assembly]       [CLIF]             [Wasm]
     0.04%   add     ebx, 1   -                  -
             jmp     0x6b     jump block3(v14)   br $loop
```

* Use RunCommon helpers and forward run flags in hot-blocks

Replace direct CommonOptions usage with RunCommon, using its load_module
helper and RunTarget enum to deserialize the compiled cwasm. This avoids
duplicating the module/component detection and deserialization logic.

Forward --dir, --env, -Wunknown-imports-trap, and -Wunknown-imports-default
flags through to the nested `perf record` subprocess so the profiled
execution honors WASI directory preopens, environment variables, and unknown
import handling.

* Fix `hot_blocks_fib` test on CI

* Address review feedback

* Fix clippy

* Don't bother running `wasmtime hot-blocks` unit tests under MIRI

Author: fitzgen

Cargo.lock

@@ -77,6 +77,7 @@ tempfile = { workspace = true, optional = true }
 object = { workspace = true, optional = true }
 cranelift-codegen = { workspace = true, optional = true, features = ['disas'] }
 capstone = { workspace = true, optional = true }
+wasmprinter = { workspace = true, optional = true }
 termcolor = { workspace = true, optional = true }
 gimli = { workspace = true, optional = true }
 pulley-interpreter = { workspace = true, optional = true }
@@ -478,6 +479,7 @@ default = [
   "config",
   "completion",
   "objdump",
+  "hot-blocks",
   "wizer",
 
   # On-by-default WASI features
@@ -620,6 +622,11 @@ objdump = [
   'dep:gimli',
   'pulley-interpreter/disas',
 ]
+hot-blocks = [
+  'dep:capstone',
+  'dep:tempfile',
+  'dep:wasmprinter',
+]
 wizer = [
   "wasmtime-wizer",
   "dep:wasmtime-wasi",

Cargo.toml

@@ -90,6 +90,10 @@ enum Subcommand {
     #[cfg(feature = "objdump")]
     Objdump(wasmtime_cli::commands::ObjdumpCommand),
 
+    /// Profile a Wasm module's execution and print the hottest basic blocks.
+    #[cfg(all(feature = "hot-blocks", target_os = "linux"))]
+    HotBlocks(wasmtime_cli::commands::HotBlocksCommand),
+
     #[cfg(feature = "wizer")]
     Wizer(wasmtime_cli::commands::WizerCommand),
 }
@@ -130,6 +134,9 @@ impl Wasmtime {
             #[cfg(feature = "objdump")]
             Subcommand::Objdump(c) => c.execute(),
 
+            #[cfg(all(feature = "hot-blocks", target_os = "linux"))]
+            Subcommand::HotBlocks(c) => c.execute(),
+
             #[cfg(feature = "wizer")]
             Subcommand::Wizer(c) => c.execute(),
         }

src/bin/wasmtime.rs

@@ -40,6 +40,11 @@ mod objdump;
 #[cfg(feature = "objdump")]
 pub use self::objdump::*;
 
+#[cfg(all(feature = "hot-blocks", target_os = "linux"))]
+mod hot_blocks;
+#[cfg(all(feature = "hot-blocks", target_os = "linux"))]
+pub use self::hot_blocks::*;
+
 #[cfg(feature = "wizer")]
 mod wizer;
 #[cfg(feature = "wizer")]