Set clobbers_flags to False for urm_noflags_abcd.

`urm_noflags` is a variant of `urm` which doesn't clobber the flags, and
`urm_noflags_abcd` is a further variant for ABCD registers, so it also
doesn't clobber the flags.

cranelift/docs/testing.rst

@@ -342,6 +342,14 @@ Test the DCE pass.
 The DCE pass is run on each function, and then results are run
 through filecheck.
 
+`test shrink`
+-----------------
+
+Test the instruction shrinking pass.
+
+The shrink pass is run on each function, and then results are run
+through filecheck.
+
 `test preopt`
 -----------------
 

lib/codegen/meta/isa/x86/recipes.py

@@ -389,6 +389,7 @@ urm_noflags = TailRecipe(
 urm_noflags_abcd = TailRecipe(
         'urm_noflags_abcd', Unary, size=1, ins=ABCD, outs=GPR,
         when_prefixed=urm_noflags,
+        clobbers_flags=False,
         emit='''
         PUT_OP(bits, rex2(in_reg0, out_reg0), sink);
         modrm_rr(in_reg0, out_reg0, sink);

lib/filetests/src/lib.rs

@@ -45,6 +45,7 @@ mod test_postopt;
 mod test_preopt;
 mod test_print_cfg;
 mod test_regalloc;
+mod test_shrink;
 mod test_simple_gvn;
 mod test_verifier;
 
@@ -92,6 +93,7 @@ fn new_subtest(parsed: &TestCommand) -> subtest::SubtestResult<Box<subtest::SubT
         "preopt" => test_preopt::subtest(parsed),
         "print-cfg" => test_print_cfg::subtest(parsed),
         "regalloc" => test_regalloc::subtest(parsed),
+        "shrink" => test_shrink::subtest(parsed),
         "simple-gvn" => test_simple_gvn::subtest(parsed),
         "verifier" => test_verifier::subtest(parsed),
         _ => Err(format!("unknown test command '{}'", parsed.command)),

lib/filetests/src/test_shrink.rs

@@ -0,0 +1,46 @@
+//! Test command for testing the Shrink pass.
+//!
+//! The `shrink` test command runs each function through the Shrink pass after ensuring
+//! that all instructions are legal for the target.
+//!
+//! The resulting function is sent to `filecheck`.
+
+use cretonne_codegen;
+use cretonne_codegen::ir::Function;
+use cretonne_codegen::print_errors::pretty_error;
+use cretonne_reader::TestCommand;
+use std::borrow::Cow;
+use subtest::{run_filecheck, Context, SubTest, SubtestResult};
+
+struct TestShrink;
+
+pub fn subtest(parsed: &TestCommand) -> SubtestResult<Box<SubTest>> {
+    assert_eq!(parsed.command, "shrink");
+    if !parsed.options.is_empty() {
+        Err(format!("No options allowed on {}", parsed))
+    } else {
+        Ok(Box::new(TestShrink))
+    }
+}
+
+impl SubTest for TestShrink {
+    fn name(&self) -> &'static str {
+        "shrink"
+    }
+
+    fn is_mutating(&self) -> bool {
+        true
+    }
+
+    fn run(&self, func: Cow<Function>, context: &Context) -> SubtestResult<()> {
+        let isa = context.isa.expect("shrink needs an ISA");
+        let mut comp_ctx = cretonne_codegen::Context::for_function(func.into_owned());
+
+        comp_ctx
+            .shrink_instructions(isa)
+            .map_err(|e| pretty_error(&comp_ctx.func, context.isa, Into::into(e)))?;
+
+        let text = comp_ctx.func.to_string();
+        run_filecheck(&text, context)
+    }
+}