cranelift: Remove brz and brnz (#5630)

Remove the brz and brnz instructions, as their behavior is now redundant with brif.

cranelift/codegen/src/ir/instructions.rs

@@ -270,7 +270,6 @@ impl InstructionData {
     pub fn analyze_branch(&self) -> BranchInfo {
         match *self {
             Self::Jump { destination, .. } => BranchInfo::SingleDest(destination),
-            Self::Branch { destination, .. } => BranchInfo::SingleDest(destination),
             Self::Brif {
                 blocks: [block_then, block_else],
                 ..
@@ -292,9 +291,6 @@ impl InstructionData {
         match self {
             Self::Jump {
                 ref destination, ..
-            }
-            | Self::Branch {
-                ref destination, ..
             } => std::slice::from_ref(destination),
             Self::Brif { blocks, .. } => blocks,
             Self::BranchTable { .. } => &[],
@@ -313,10 +309,6 @@ impl InstructionData {
             Self::Jump {
                 ref mut destination,
                 ..
-            }
-            | Self::Branch {
-                ref mut destination,
-                ..
             } => std::slice::from_mut(destination),
             Self::Brif { blocks, .. } => blocks,
             Self::BranchTable { .. } => &mut [],

cranelift/codegen/src/ir/layout.rs

@@ -4,7 +4,6 @@
 //! determined by the `Layout` data structure defined in this module.
 
 use crate::entity::SecondaryMap;
-use crate::ir::dfg::DataFlowGraph;
 use crate::ir::progpoint::{ExpandedProgramPoint, ProgramOrder};
 use crate::ir::{Block, Inst};
 use crate::packed_option::PackedOption;
@@ -594,19 +593,6 @@ impl Layout {
         self.insts[inst].prev.expand()
     }
 
-    /// Fetch the first instruction in a block's terminal branch group.
-    pub fn canonical_branch_inst(&self, dfg: &DataFlowGraph, block: Block) -> Option<Inst> {
-        // Basic blocks permit at most two terminal branch instructions.
-        // If two, the former is conditional and the latter is unconditional.
-        let last = self.last_inst(block)?;
-        if let Some(prev) = self.prev_inst(last) {
-            if dfg.insts[prev].opcode().is_branch() {
-                return Some(prev);
-            }
-        }
-        Some(last)
-    }
-
     /// Insert `inst` before the instruction `before` in the same block.
     pub fn insert_inst(&mut self, inst: Inst, before: Inst) {
         debug_assert_eq!(self.inst_block(inst), None);
@@ -662,24 +648,6 @@ impl Layout {
         }
     }
 
-    /// Iterate over a limited set of instruction which are likely the branches of `block` in layout
-    /// order. Any instruction not visited by this iterator is not a branch, but an instruction visited by this may not be a branch.
-    pub fn block_likely_branches(&self, block: Block) -> Insts {
-        // Note: Checking whether an instruction is a branch or not while walking backward might add
-        // extra overhead. However, we know that the number of branches is limited to 2 at the end of
-        // each block, and therefore we can just iterate over the last 2 instructions.
-        let mut iter = self.block_insts(block);
-        let head = iter.head;
-        let tail = iter.tail;
-        iter.next_back();
-        let head = iter.next_back().or(head);
-        Insts {
-            layout: self,
-            head,
-            tail,
-        }
-    }
-
     /// Split the block containing `before` in two.
     ///
     /// Insert `new_block` after the old block and move `before` and the following instructions to