YJIT: implement missing `asm.jg` instruction in backend (#8130)

YJIT: implement missing jg instruction in backend

While trying to implement a specialize integer left shift, I ran
into a problem where we have no way to do a greater-than comparison
at the moment. Surprising we went this far without ever needing it.

3 files changed, 17 insertions, 0 deletions

diff --git a/yjit/src/backend/arm64/mod.rs b/yjit/src/backend/arm64/mod.rs
index 9787b1a4e9..a74e5cf0ff 100644
--- a/yjit/src/backend/arm64/mod.rs
+++ b/yjit/src/backend/arm64/mod.rs
@@ -1079,6 +1079,9 @@ impl Assembler
                 Insn::Jl(target) => {
                     emit_conditional_jump::<{Condition::LT}>(cb, compile_side_exit(*target, self, ocb));
                 },
+                Insn::Jg(target) => {
+                    emit_conditional_jump::<{Condition::GT}>(cb, compile_side_exit(*target, self, ocb));
+                },
                 Insn::Jbe(target) => {
                     emit_conditional_jump::<{Condition::LS}>(cb, compile_side_exit(*target, self, ocb));
                 },
diff --git a/yjit/src/backend/ir.rs b/yjit/src/backend/ir.rs
index a28c833e89..72a4bc711b 100644
--- a/yjit/src/backend/ir.rs
+++ b/yjit/src/backend/ir.rs
@@ -432,6 +432,9 @@ pub enum Insn {
     /// Jump if lower
     Jl(Target),
 
+    /// Jump if greater
+    Jg(Target),
+
     // Unconditional jump to a branch target
     Jmp(Target),
 
@@ -578,6 +581,7 @@ impl Insn {
             Insn::Jbe(_) => "Jbe",
             Insn::Je(_) => "Je",
             Insn::Jl(_) => "Jl",
+            Insn::Jg(_) => "Jg",
             Insn::Jmp(_) => "Jmp",
             Insn::JmpOpnd(_) => "JmpOpnd",
             Insn::Jne(_) => "Jne",
@@ -725,6 +729,7 @@ impl<'a> Iterator for InsnOpndIterator<'a> {
             Insn::Jbe(_) |
             Insn::Je(_) |
             Insn::Jl(_) |
+            Insn::Jg(_) |
             Insn::Jmp(_) |
             Insn::Jne(_) |
             Insn::Jnz(_) |
@@ -822,6 +827,7 @@ impl<'a> InsnOpndMutIterator<'a> {
             Insn::Jbe(_) |
             Insn::Je(_) |
             Insn::Jl(_) |
+            Insn::Jg(_) |
             Insn::Jmp(_) |
             Insn::Jne(_) |
             Insn::Jnz(_) |
diff --git a/yjit/src/backend/x86_64/mod.rs b/yjit/src/backend/x86_64/mod.rs
index b40d8b2382..0cc276fca1 100644
--- a/yjit/src/backend/x86_64/mod.rs
+++ b/yjit/src/backend/x86_64/mod.rs
@@ -673,6 +673,14 @@ impl Assembler
                     }
                 },
 
+                Insn::Jg(target) => {
+                    match compile_side_exit(*target, self, ocb) {
+                        Target::CodePtr(code_ptr) | Target::SideExitPtr(code_ptr) => jg_ptr(cb, code_ptr),
+                        Target::Label(label_idx) => jg_label(cb, label_idx),
+                        Target::SideExit { .. } => unreachable!("Target::SideExit should have been compiled by compile_side_exit"),
+                    }
+                },
+
                 Insn::Jbe(target) => {
                     match compile_side_exit(*target, self, ocb) {
                         Target::CodePtr(code_ptr) | Target::SideExitPtr(code_ptr) => jbe_ptr(cb, code_ptr),