Mass rename Ebb and relatives to Block (#1365)

* Manually rename BasicBlock to BlockPredecessor

BasicBlock is a pair of (Ebb, Inst) that is used to represent the
basic block subcomponent of an Ebb that is a predecessor to an Ebb.

Eventually we will be able to remove this struct, but for now it
makes sense to give it a non-conflicting name so that we can start
to transition Ebb to represent a basic block.

I have not updated any comments that refer to BasicBlock, as
eventually we will remove BlockPredecessor and replace with Block,
which is a basic block, so the comments will become correct.

* Manually rename SSABuilder block types to avoid conflict

SSABuilder has its own Block and BlockData types. These along with
associated identifier will cause conflicts in a later commit, so
they are renamed to be more verbose here.

* Automatically rename 'Ebb' to 'Block' in *.rs

* Automatically rename 'EBB' to 'block' in *.rs

* Automatically rename 'ebb' to 'block' in *.rs

* Automatically rename 'extended basic block' to 'basic block' in *.rs

* Automatically rename 'an basic block' to 'a basic block' in *.rs

* Manually update comment for `Block`

`Block`'s wikipedia article required an update.

* Automatically rename 'an `Block`' to 'a `Block`' in *.rs

* Automatically rename 'extended_basic_block' to 'basic_block' in *.rs

* Automatically rename 'ebb' to 'block' in *.clif

* Manually rename clif constant that contains 'ebb' as substring to avoid conflict

* Automatically rename filecheck uses of 'EBB' to 'BB'

'regex: EBB' -> 'regex: BB'
'$EBB' -> '$BB'

* Automatically rename 'EBB' 'Ebb' to 'block' in *.clif

* Automatically rename 'an block' to 'a block' in *.clif

* Fix broken testcase when function name length increases

Test function names are limited to 16 characters. This causes
the new longer name to be truncated and fail a filecheck test. An
outdated comment was also fixed.

cranelift/filetests/filetests/preopt/branch.clif

@@ -2,78 +2,78 @@ test preopt
 target x86_64
 
 function %brz_fold() -> i32 {
-ebb0:
+block0:
     v0 = bconst.b1 false
-    brz v0, ebb2
-    jump ebb1
-ebb1:
+    brz v0, block2
+    jump block1
+block1:
     v1 = iconst.i32 42
     return v1
-ebb2:
+block2:
     v2 = iconst.i32 24
     return v2
 }
 ; sameln: function %brz_fold
-; nextln: ebb0:
+; nextln: block0:
 ; nextln:     v0 = bconst.b1 false
-; nextln:     jump ebb2
+; nextln:     jump block2
 ; nextln: 
-; nextln: ebb1:
+; nextln: block1:
 ; nextln:     v1 = iconst.i32 42
 ; nextln:     return v1
 ; nextln: 
-; nextln: ebb2:
+; nextln: block2:
 ; nextln:     v2 = iconst.i32 24
 ; nextln:     return v2
 ; nextln: }
 
 function %brnz_fold() -> i32 {
-ebb0:
+block0:
     v0 = bconst.b1 true
-    brnz v0, ebb2
-    jump ebb1
-ebb1:
+    brnz v0, block2
+    jump block1
+block1:
     v1 = iconst.i32 42
     return v1
-ebb2:
+block2:
     v2 = iconst.i32 24
     return v2
 }
 ; sameln: function %brnz_fold
-; nextln: ebb0:
+; nextln: block0:
 ; nextln:     v0 = bconst.b1 true
-; nextln:     jump ebb2
+; nextln:     jump block2
 ; nextln: 
-; nextln: ebb1:
+; nextln: block1:
 ; nextln:     v1 = iconst.i32 42
 ; nextln:     return v1
 ; nextln: 
-; nextln: ebb2:
+; nextln: block2:
 ; nextln:     v2 = iconst.i32 24
 ; nextln:     return v2
 ; nextln: }
 
 function %brz_fold_param(b1) -> i32 {
-ebb0(v0: b1):
-    brz v0, ebb2
-    jump ebb1
-ebb1:
+block0(v0: b1):
+    brz v0, block2
+    jump block1
+block1:
     v1 = iconst.i32 42
     return v1
-ebb2:
+block2:
     v2 = iconst.i32 24
     return v2
 }
 ; sameln: function %brz_fold_param(b1) -> i32 fast {
-; nextln: ebb0(v0: b1):
-; nextln:     brz v0, ebb2
-; nextln:     jump ebb1
+; nextln: block0(v0: b1):
+; nextln:     brz v0, block2
+; nextln:     jump block1
 ; nextln: 
-; nextln: ebb1:
+; nextln: block1:
 ; nextln:     v1 = iconst.i32 42
 ; nextln:     return v1
 ; nextln: 
-; nextln: ebb2:
+; nextln: block2:
 ; nextln:     v2 = iconst.i32 24
 ; nextln:     return v2
 ; nextln: }

cranelift/filetests/filetests/preopt/constant_fold.clif

@@ -2,7 +2,7 @@ test preopt
 target x86_64
 
 function %constant_fold(f64) -> f64 {
-ebb0(v0: f64):
+block0(v0: f64):
     v1 = f64const 0x1.0000000000000p0
     v2 = f64const 0x1.0000000000000p1
     v3 = fadd v1, v2
@@ -10,7 +10,7 @@ ebb0(v0: f64):
     return v4
 }
 ; sameln: function %constant_fold(f64) -> f64 fast {
-; nextln: ebb0(v0: f64):
+; nextln: block0(v0: f64):
 ; nextln:     v1 = f64const 0x1.0000000000000p0
 ; nextln:     v2 = f64const 0x1.0000000000000p1
 ; nextln:     v3 = f64const 0x1.8000000000000p1

cranelift/filetests/filetests/preopt/numerical.clif

@@ -2,7 +2,7 @@ test preopt
 target x86_64
 
 function %iadd_fold() -> i32 {
-ebb0:
+block0:
     v0 = iconst.i32 37
     v1 = iconst.i32 5
     v2 = iadd v0, v1
@@ -11,7 +11,7 @@ ebb0:
     return v4
 }
 ; sameln: function %iadd_fold
-; nextln: ebb0:
+; nextln: block0:
 ; nextln:     v0 = iconst.i32 37
 ; nextln:     v1 = iconst.i32 5
 ; nextln:     v2 = iconst.i32 42
@@ -21,14 +21,14 @@ ebb0:
 ; nextln: }
 
 function %isub_fold() -> i32 {
-ebb0:
+block0:
     v0 = iconst.i32 42
     v1 = iconst.i32 1
     v2 = isub v0, v1
     return v2
 }
 ; sameln: function %isub_fold
-; nextln: ebb0:
+; nextln: block0:
 ; nextln:     v0 = iconst.i32 42
 ; nextln:     v1 = iconst.i32 1
 ; nextln:     v2 = iconst.i32 41